May 2017: Memorial Day/End Of May Outlook

[srainhoutx]

NWS Houston/Galveston will be heading out today to Sealy and Simonton to survey the damage from yesterday's storms. Jeff has some impressive damage pictures via his morning update, if someone want's to upload those photos.

[srainhoutx]

Update from Jeff this morning regarding the storm damage:

Clusters of severe thunderstorms with large hail and damaging winds moved across SE TX Tuesday afternoon and evening producing large swaths of damage.

Grapeland, Houston: Quarter size hail reported on CR 1705

Giddings, Lee: widespread winds of 70-75mph across the city with numerous trees and powerlines down. Some signs blown out.

6 NW Sealy, Austin: Tree limbs and fences down. Dime size hail

12 N Columbus, Colorado: Part of FM 109 in Frelsburg blocked by downed tree

Rosenberg, Fort Bend: 61mph measured at mesonet observation site

Rosenberg, Fort Bend: 1.75 inch diameter hail

Sealy, Austin: widespread significant wind damage. 18-wheeler overturned on I-10. Portions of the roof of Sealy HS blown off and car windows blown out. Widespread trees and power lines downed over much of the city. Portions of buildings blown off with numerous metal buildings damaged or destroyed. Local bar with 20 people inside had roof torn off. Winds estimated at 75-90mph per radar velocity data. Given widespread damage and the damage patterns with much of the debris laid in the same direction suggest straight line winds.

Damage suggestive of straight line winds…all debris and broken trees limbs pointing toward the same direction

Damage suggestive of straight line winds (all damage to one side of the structure)

Needville, Fort Bend: numerous large trees down

Beasley, Fort Bend: trees down and trampoline wrapped around a light pole

Simonton/Valley Lodge, Fort Bend: numerous trees and fences down. Portions of roofs damaged and power lines down across roads

San Leon, Galveston: 41mph recorded at Eagle Point Weatherflow tower

Platform 538, 47 SE of Palacios: 47mph recorded

Matagorda Bay Entrance, Matagorda: 40mph recorded by Weatherflow tower

[tireman4]

844
FXUS64 KHGX 241728
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1228 PM CDT Wed May 24 2017

.AVIATION...
VFR conds expected for the next 24 hours. Fcst soundings look dry.
LAV guidance suggest some wind gusts this aftn. Winds will turn
around to the south overnight. The pressure gradient will tighten
significantly on Thursday and stronger winds are expected with
gusts again possible tomorrow aftn. 43

&&

.PREV DISCUSSION... /ISSUED 1045 AM CDT Wed May 24 2017/

UPDATE...
Very tranquil morning with the only mentionable adjustment to the
dew point temperature field...increased into the average middle
50s with a mix out into the upper 40s to lower 50s later today.
Combine this regional air moisture...with an evaporating wet ground
...to ambient temperatures in the lower 80s and this equates to
relative humidities in the 30 percentile. Thus...a dry sunny spring
like day with below normal afternoon and Thursday morning temperatures.
Upper ridging passes overhead tomorrow making Thursday feel much like
today but with warmer afternoon temperatures closer to seasonable
middle to upper 80 readings. Today`s northwest winds will transition
to moderate onshore tomorrow as lower Rio Grande Valley surface
high pressure advances east into the central Gulf. 31

[DoctorMu]

Rather chilly up here in NW Harris County this morning. The weather station is showing 56F!. Enjoy the next few days of cool and drier weather with low dewpoints. It's been a while since we've seen morning lows this cool in late May.

Low of 55°F in Conroe and College Station this am. DP is now 44°F! Today is a Chamber of Commerce day for certain.

[srainhoutx]

Looking ahead to Memorial Day and through at least mid next week, the overnight guidance suggests a return flow off the Gulf will resume Saturday with moisture levels increasing Sunday. A frontal boundary is expected to stall near the Coast with a series of upper level disturbances moving across Texas and the Southern Plains in mean zonal flow. There are some indications that additional disturbances may ripple across Mexico from the Eastern Pacific bringing daily chances of showers and storms mainly across S Central/Central Texas Memorial Day and possibly continuing through at least Wednesday. At this time the greatest threat for heavier rainfall appears to be North of Metro Houston. There is still a lot of uncertainty regarding the sensible weather forecast for the Hill Country and SE Texas, so I urge those with travel plans and outdoor Holiday activities to check back in from time to time as we enter the busy Memorial Day Holiday Weekend.

[tireman4]

000
FXUS64 KHGX 251714
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1214 PM CDT Thu May 25 2017

.AVIATION...
VFR conds expected through 06z. MVFR cigs expected to develop as
low level moisture increases beneath a strong capping inversion.
HRRR is showing IFR cigs developing west of Houston by 08z.
Confidence is low with regard to IFR development. Fcst soundings
keep MVFR cigs in place for much of Friday with cigs mixing out
between 18-20z. Winds will remain gusty this afternoon and drop
slightly overnight but never fully decouple with gusty winds
expected again on Friday. 43

&&

.PREV DISCUSSION... /ISSUED 1102 AM CDT Thu May 25 2017/

UPDATE...
Another gorgeous morning under sunny skies and a brisk southwest
to south wind, upper 70 regional temperatures. Moisture will
return through the day, increasing cloudiness from the west during
the overnight early Friday morning hours. Increased cloud cover
and winds staying up at around 10 mph should provide enough
insulation and mixing, respectively, to regulate Friday minTs to
the lower to middle 70s. Very low rain chances Saturday will begin
to reach chance categories Sunday. The target window for the area
receiving rainfall will be from Sunday evening through Memorial
Day. A shortwave trough passage with the best upper level support
occurs early Monday. As of now, QPF values are low with the
highest QPF of around half of an inch to an inch being focused
across the northern third of the CWA through early Tuesday. A
slow-moving surface boundary sagging into a southeastern Texas
near 2 inch pwat air mass Monday is certainly a situation that
needs to be monitored for the potential for high rainfall going
into the weekend. 31

PREV DISCUSSION... /ISSUED 439 AM CDT Thu May 25 2017/

DISCUSSION...
Cool/quiet conditions across SE TX this morning. As the surface
high moves off to the east...we should see onshore winds return
through this afternoon. Warmer temps expected the next few days
along with increasing moisture levels (as S/SE winds strengthen
in response to a low pressure moving into the Southern Plains).
Highs in the lower 90s with lows in the 70s should prevail.

No real forecast issues are expected for SE TX until the latter
part of the upcoming weekend. The system moving into the Southern
Plains will help to drag a cold front into the state on Sat and
the boundary should eventually make its way into the northern
portions of our CWFA by Sun night. The flattened upper flow will
likely keep the front over the area which will then act as a focus
for wet/active weather for perhaps much of next week. PWs are
progged to around 2" as a series of shortwaves approach from the
west. Extended models have been fairly consistent with this
scenario these last few days, so will continue to keep elevated
POPS in for this time frame. 41

MARINE...
Onshore winds will quickly strengthen during the day today as the
pressure gradient tightens in response to developing low pressure in
the lee of the Rockies. A moderate onshore flow will prevail through
the weekend with low pressure over West Texas and high pressure over
the eastern Gulf of Mexico. A SCEC will likely be required at times
through the weekend, with SCA conditions possible overnight tonight
into Friday morning. A weak cold front will approach SE TX Sunday
night but is not forecast to make it off the coast. Lighter onshore
flow is forecast for the beginning of next week. 11

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 72 91 76 92 / 0 0 10 10 10
Houston (IAH) 88 74 89 78 91 / 0 0 10 10 10
Galveston (GLS) 84 78 85 80 85 / 0 0 10 10 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 7 PM CDT this evening
for the following zones: Coastal waters from Freeport to
the Matagorda Ship Channel out 20 NM...Coastal waters from
High Island to Freeport out 20 NM...Galveston Bay...
Matagorda Bay...Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.

&&

$$

Discussion...31
Aviation/Marine...43

[srainhoutx]

Happy Memorial Day Weekend as we honor our Fallen Military Hero's that sacrificed their lives to keep our Nation Free! We honor them and their families and will never forget their sacrifice.

In the weather department, change do appear to be brewing regarding our sensible weather forecast beginning Saturday and continuing possibly through the end of May. A rather potent upper level storm system is diving S out of Idaho into the Great Basin and will eventually emerge into the Southern Plains sending a slow moving frontal boundary into Texas. In addition, deep tropical moisture is moving into the NW Caribbean associated with a weak tropical wave that appears to begin pooling moisture in the Western Gulf. To further add to the mix, a tropical disturbance in the Eastern Pacific near the Central American Coast is festering this morning and the sub tropical jet has become rather noisy with embedded mid and upper level disturbances rippling East from the Central Pacific into Mexico.



The fly in the ointment is the frontal boundary that is expected to move across Central Texas early Sunday morning and pull up stationary somewhere near the I-10 Corridor to the Coastal Texas. The overnight reliable computer guidance is still attempting to resolve exactly where the front will stall and exactly where the greatest chance of training showers and storms attempt to organize along and behind the stall boundary. To further complicate matters, most of the guidance suggest that frontal boundary may linger across the Region possibly into late next week. In addition, another tropical wave is nearing the Windward Islands and may continue moving West into the W/NW Caribbean Sea by the middle to next week timeframe.



Rainfall amounts and thunderstorm development will be mesoscale driven throughout the weekend into Memorial and beyond. As we know, those subtle mesoscale features are poorly forecasted beyond 4-6 hour at times lending to challenges of knowing where the heaviest rainfall amount may occur. For those heading to the Hill Country Lakes and Rivers for the Holiday Weekend, pay close attention to the sky and have a means to get warnings for the NWS.

[tireman4]

Alluding to Steve's forecast.....the NWS agrees..


000
FXUS64 KHGX 260909
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
409 AM CDT Fri May 26 2017

.DISCUSSION...
Hot and humid conditions are expected to settle in across
Southeast Texas over the next few days. 00Z upper air analysis
showed mid-level ridging building into Texas from Mexico with a
shortwave trough lifting across Kansas and Nebraska. As a surface
cyclone ejects across the Southern Plains today in response to the
Kansas/Nebraska shortwave, associated breezy 10-20 MPH southerly
winds will draw Gulf moisture back into the region. CIRA Layer
Precipitable Water satellite estimates show a tongue of 1.2-1.3
inch precipitable water air jutting into the Texas Coastal Bend
early this morning, with this moisture expected to rapidly
surge inland through the day.

Stout capping in place around 890 mb (also evident by the
anomalous propagation evident over the Gulf this morning) should
prevent any rain chances today and will play a critical role in
cloud cover, which will affect afternoon high temperatures. NAM
and GFS Bufr soundings show moisture remaining trapped beneath
this inversion through the day (leading to persistent cloud cover
and lower high temperatures), but with elevated near-surface winds
and daytime heating providing some turbulent mixing should see
some scattering this afternoon. This would allow for high
temperatures to again climb back to near 90 degrees inland today.

Mostly dry conditions are expected tonight through Sunday morning
as ridging over Texas amplifies as an upper level disturbance
over southern Idaho on early morning water vapor imagery slides
southeast. Increasing heights aloft associated with this ridging
will result in high temperatures climbing into the low to mid 90s
on Saturday, with peak heat index values climbing into the 100-105
degree range. While this is technically below Heat Advisory
criteria, early season heat is incredibly dangerous as people are
not acclimatized to it and anyone participating in Memorial Day
Weekend activities are urged to drink plenty of water and make
sure they have a cool place to go to if they become overheated.
Also of note will be the very warm (near to record) morning lows
on Saturday and Sunday. Cannot rule out speed convergence may
produce an isolated shower or two along the coast both Saturday
and Sunday mornings with the northern counties possibly being
grazed by a decaying thunderstorm complex moving out of North
Texas Saturday night, but rain chances during this time are 20
percent or less.

By Sunday, the disturbance now near Idaho reaches the Southern
Plains and sends a cold front into the region as it swings towards
the east. Loss of upper level forcing with the departure of this
disturbance is expected to result in the cold front stalling
somewhere near (or within) the region by Monday morning. There`s
still some uncertainty on where exactly this frontal boundary will
stall as it outruns its upper level support, but 00Z model
guidance has been fairly consistent with the boundary reaching
somewhere between the Interstate 10 corridor and the coast by
Monday. A few even show the cold front pushing just off the coast
before lifting inland as a warm front. Regardless, periods of
showers and thunderstorms are expected from late Sunday through
the middle of next week, first along the approaching frontal
boundary and then along it wherever it stalls as disturbances
override it in the weak southwest to west flow aloft.

While the severe weather threat does not appear to be
particularly high during this time given the weak flow, will have
to monitor for at least an isolated heavy rain threat as
precipitable water values peak between 1.6-1.9 inches at times in
a weakly forced environment. This would offer very little in terms
of overall storm motions, with rain chances (and highest rain
totals) focusing along either the remnant frontal boundary or
other mesoscale boundaries that develop from previous showers or
thunderstorms. Interestingly, CIPS Analog guidance shows a signal
for widespread rainfall exceeding one inch in the Monday/Tuesday
timeframe with another signal for even higher rainfall amounts
late next week. The main takeaway here is that several rounds of
rainfall will be possible throughout the next week, but will
likely be driven by features that are too far out in the forecast
to resolve at this time.

Huffman

&&

.MARINE...
Moderate to strong onshore flow this morning. Winds 15-20kts int
he far waters and increase to 20-25 in the nearshore and lower
bays. Wind profile showing the S25-30 knots at 1000ft this
morning. Expect that winds in the bays and nearshore should
gradually diminish between 7-10am to a more manageable 15-20
knots. SCA all waters through 10 am then can probably dialed back
to SCEC. The persistent moderate WAA continues through Saturday
night into Sunday morning before relaxing. A weak cold front moves
into SETX Sunday night but may be preceded by a prefrontal trough
that further relaxes winds in the bays and nearshore by Monday
morning. Frontal boundary gets diffuse and will likely be driven
by mesoscale rain events Monday possibly pushing an outflow into
nearshore waters Monday or Monday night. Showers and thunderstorm
chances increasing Sunday and Monday across the coastal waters. By
Tuesday afternoon winds should be more consistently southeasterly
and continue so through Thursday. May be experiencing some light
sea haze again Sunday through Thursday.

Tide levels on the increase with the WAA pattern and stronger
winds today and Saturday which will lead to increasing rip tide
strength and elevate levels to Gulf facing areas. May flirt with
2.5-3ft by this afternoon and again Saturday afternoon. Lighter
winds Sunday afternoon and Monday should scale back tide levels
but rip tides may be slower to improve.
45

&&

.AVIATION...
MVFR deck spreading eastward across the area and should fill in
to the east fairly quickly in the next few hours. 1200-2500ft deck
should scatter out this afternoon with winds on the increase by
15z. LLJ lined up from SW to NE across the region this morning and
afternoon and strengthens which should help boost winds by late
morning pushing gusts in the 18-28kt range. Overnight expect ST
deck to return and likely earlier than it did given slightly
richer moisture streaming in from the Gulf.
45

&&

.CLIMATE...
Near to record high minimum temperatures are possible at all of
the first order climate sites on Saturday and Sunday mornings. A
listing of the current records is provided below.

May 27
LOCATION RECORD HIGH MINIMUM YEAR
City of Houston 80 1996
Houston Hobby 78 1996
College Station 77 1924
Galveston 80 2000

May 28
LOCATION RECORD HIGH MINIMUM YEAR
City of Houston 81 1996
Houston Hobby 79 1996
College Station 77 1996
Galveston 81 1996

Huffman

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 91 76 94 76 90 / 10 10 10 20 30
Houston (IAH) 90 78 93 78 90 / 10 10 10 10 20
Galveston (GLS) 85 80 87 80 85 / 10 10 10 10 20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 10 AM CDT this morning for the
following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM...Galveston Bay...Matagorda
Bay...Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.

&&

$$

Discussion/Climate...14
Aviation/Marine...45

[tireman4]

From Joe Bastardi's tweet:

@BigJoeBastardi: I do not like this pattern in Texas.Front pushing into state next week could reach gulf,feedback Has several precedents I am
looking at

[DoctorMu]

Props to GFS for sniffing this out over a week ago.

Should be a wide disparity in the amount of rain each locale gets. Impulses and MCV-related downpours are noisy.

Sprinklers set on stun. Kirk out.

[srainhoutx]

Complicated Holiday Weekend into next week forecast setting up for our Region. The afternoon guidance suggests the stalled boundary along with several other features to our West and South will impact our sensible weather throughout the next 7 Days. We will need to monitor trends into the weekend and Monday for potential changes regard the shower and storm chances and just who and where will see the "best" chances for some beneficial rainfall total.

[srainhoutx]

I am closely watching the ECMWF in the Medium range as it is suggesting a wave of lower pressure attempting to organize next weekend in the NW Gulf near Corpus Christi and moving NE along the Texas and SW Louisiana Coasts. While it way too soon to speculate our sensible weather possibilities beyond 3 to 5 days, the ECMWF has shown some consistency suggesting this scenario may be possible. Keep weather aware tomorrow and throughout the coming week for updates.

Late Friday evening update from Jeff:

Prolonged period of wet weather expected Memorial Day through all of next week.

Several interesting features showing up in model runs today for next week, any one of which could result in heavy rainfall over the region. An upper level trough will move out of the SW US on Saturday and into the southern plains on Sunday helping to force a surface cold front southward into TX. Extremely moist low level air mass has already returned to the TX coast with afternoon heat index values today reaching near 108 across the coastal bend and 98-102 over SE TX. Low level moisture may mix out better on Saturday, but it will be incredibly humid outside. Since this is the first “real” heat of the summer the combined rapid onset effects on the body will be more than if it were July or August.

Surface front arrives into SE TX late Sunday night into Monday morning and will likely stall somewhere south of I-10 toward the coast. PWS pool to near 2.0 inches with broad divergent upper air winds over the area and likely some short wave activity moving out of MX. This all points to increasing rain chances Sunday night into Monday and the potential for slow moving heavy rainfall along or near the frontal boundary. As with so many similar events in the recent past, it is impossible to determine where the greatest rainfall may occur and just how large some of the totals could be, but parameters certainly will be in place to produce some isolated very heavy rainfall. We are still outside the range of the meso scale models but some the of the globals are keying in along the US 59 corridor from around Victoria to about Wharton Monday morning for some sort of slow moving MCS.

Tuesday onward…

A very unsettle pattern will reside over TX with the stalled frontal boundary eventually washing out into a low pressure trough. Short waves will continue to ride NE out of MX and across SE TX during this period helping to keep rain chances alive nearly every day next week. Somewhat interesting in some of the global guidance is the position of the surface trough across the NW/W Gulf of Mexico by the middle of next week. While this could shift the focus for heavy rainfall and thunderstorms toward the Gulf waters Tuesday and Wednesday there is some evidence that the surface trough attempts to close off a surface low off the lower TX coast by the latter part of next week. The CMC is the most aggressive with this trend showing a 1009 closed system, maybe some sort of hybrid low, over the NW Gulf moving inland over SE TX…this seems pretty far fetched at this point. Additionally large convective complexes across the Rio Grande plains into SC TX will have to be watched for meso vortex development that could become warm core in the extremely moist and generally weak shear environment across the southern half of TX. Such systems are notorious for producing some very large amounts of rainfall in a very short period of time, but are nearly impossible to predict at this time range.

[srainhoutx]

The afternoon guidance continues to advertise a wet and unsettled Sunday afternoon throughout the end of May into early June. A quick glance at the 12Z ECMWF suggest it is continuing its theme along with the Canadian model of a wave of low pressure emerging out of the Bay of Campeche and attempting to close off a surface low in the NW Gulf near Corpus next weekend. As we are nearing the end of May and June right around the corner, perhaps someone will start a new June Topic as we start the 2017 Hurricane Season.

[srainhoutx]

Sunday morning briefing from Jeff:

Highly active weather pattern will reside across much of TX for the next several days resulting in several periods of thunderstorms.

Upper level trough is edging deeper into TX this morning helping slowly drive a weak cold front southward over the state. Front is currently along line from NW of Dallas to SW TX and slowly moving SE while an outflow boundary from storms over AR/N OK overnight is progressing SW into SE TX from the NE. Air mass remains pretty capped this morning, but this cap will lift and erode this afternoon with peak heating and arrival of a short wave out of MX. Air mass will become very unstable with forecasted CAPE of 4000 J/kg and LI’s around -8 late this afternoon N of HWY 105 where high resolution models set off strong to severe thunderstorms. There will be a large hail and damaging wind threat with these storms late this afternoon and into the evening hours mainly north of I-10 along with a heavy rainfall threat especially since storm motions will be slowing.

The front or storm outflows will progress southward overnight and high resolution models have differing ideas on how things will play out with some moving a line of storms southward from the north across the area while another complex approaches from the SW with another short wave out of MX while others show very little along the front across the central portions of the area and then blow up numerous storms south of I-10 toward the coast early Monday morning. Given the meso scale nature of the events either one of these solutions seems possible.

Rainfall amounts will likely average 1-2 inches with isolated totals of 3-5 inches possible where storms cluster or train. Focusing on two main areas…1...north of Columbus to Cleveland and….2…south of I-10 toward the coast. High hourly rainfall rates will be possible with totals of 2-3 inches possible leading to rapid street flooding. Overall think much of the area can handle 2-3 inches of rainfall if spread out over time enough…a few hours…as grounds remain somewhat dry.

Bigger concern with flooding will be onward into the week as additional disturbances move across the area and trigger more storm complexes. Grounds will become increasingly saturated and run-off will increase so flooding will be a much greater concern Tuesday onward all the way into next weekend and possibly even the following week.

Today (Severe Weather Outlook):

[srainhoutx]

Mesoscale Discussion 0901 NWS Storm Prediction Center Norman OK 0134 PM CDT Sun May 28 2017 Areas affected...Central Texas Concerning...Severe potential...Watch likely Valid 281834Z - 281930Z Probability of Watch Issuance...80 percent SUMMARY...A severe weather watch seems probable at some point late this afternoon and evening, perhaps as early as 20-21Z. DISCUSSION...Objective analysis indicates that insolation within a boundary layer characterized by high moisture content (lower/mid 70s F surface dew points) is contributing to strong/extreme CAPE on the order of 4000+ J/kg across much of the region, including the Interstate 35 corridor between San Antonio and Waco. Mid-level inhibition beneath warm elevated mixed layer air does still appear considerable, particularly given weak, or at least unclear, mid/upper forcing for ascent. An area of enhanced ascent contributing to deepening mid-level based convection near the Interstate 20 corridor, west of the Dallas/Fort Worth metroplex, may remain displaced to the north of an area of sustained enhanced low-level convergence near the Waco area. This is near the intersection of a surface front that extends southwestward into the Rio Grande Valley, to the west of Del Rio, and the western flank of composite outflow from extensive overnight convection, now advancing into the north central Gulf Coast. However, the latest Rapid Refresh suggests that additional surface heating, coupled with subtle mid-level height falls on the southern fringe of the westerlies, may be sufficient to support the initiation of thunderstorms as early as 20-21Z. Once this does occur, intensification likely will be very rapid, and deep layer shear appears sufficient for the evolution of supercell structures with large hail and perhaps an isolated tornado, in addition to strong downbursts accompanied by potentially damaging surface gusts. ..Kerr/Hart.. 05/28/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...HGX...FWD...EWX...SJT...

[Katdaddy]

And so it begins. A Severe Thunderstorm Watch just issued for Central and SE TX until 10PM.

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 293
NWS Storm Prediction Center Norman OK
310 PM CDT Sun May 28 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
Central and Southeast Texas

* Effective this Sunday afternoon and evening from 310 PM until
1000 PM CDT.

* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible

SUMMARY...Thunderstorms are expected to rapidly develop over the
watch area this afternoon, spreading slowly eastward this evening.
Damaging winds and hail will be possible in the strongest cells.

The severe thunderstorm watch area is approximately along and 60
statute miles either side of a line from 35 miles south southeast of
Del Rio TX to 65 miles north of Huntsville TX. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

[srainhoutx]

The Storm Prediction Center has issues a Severe Thunderstorm Watch across portions of Central, S Central and SE Texas until 10:00 PM CDT. HGX is monitoring the trends closely as aircraft data in and out of Bush and Hobby suggest the cap is eroding and Harris and Liberty Counties may need to be added to the Watch, depending on the trends a bit later in the afternoon/evening.

[texoz]

Between 4-4:45pm, the area about 50 miles south of Junction, TX is getting copious amounts of rain with stationary storms. Looks like similar system of storms are forming along a line from just north of Uvalde to Waco. Could be a rough afternoon/evening Hill Country area if these storms don't move.

[DoctorMu]

Between 4-4:45pm, the area about 50 miles south of Junction, TX is getting copious amounts of rain with stationary storms. Looks like similar system of storms are forming along a line from just north of Uvalde to Waco. Could be a rough afternoon/evening Hill Country area if these storms don't move.

Yep - a broken line of showers (that is filling in) is forming just south of Waco stretch from De Rio to Longview...starting to sag SE

[srainhoutx]

MESOSCALE PRECIPITATION DISCUSSION 0281
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
539 PM EDT SUN MAY 28 2017

AREAS AFFECTED...CENTRAL TX...NORTHEAST TX...EXTREME SW AR...NW LA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 282138Z - 290138Z

OVERVIEW...STRONG THUNDERSTORMS DEVELOPING FROM JUST EAST OF BIG
BEND TX ALONG A LINE TO NORTHEAST TX WILL INCREASE DURING THE NEXT
FEW HOURS. THESE STORMS COULD RESULT IN LOCAL FLASH FLOODING.

DISCUSSION...STRONG THUNDERSTORMS ARE DEVELOPING ALONG A FRONTAL
BOUNDARY THAT EXTENDS NORTHEAST FROM NEAR DEL RIO TO JUST SOUTH OF
TEXARKANA. THESE STORMS ARE PRODUCING LOCAL HOURLY RAIN RATES OF
1-3". RADAR INDICATES THAT LOCAL RAINFALL TOTALS OF 3" HAVE
ALREADY FALLEN WHERE THE STRONGEST STORMS ARE OCCURRING
CURRENTLY... ALONG THE SOUTHWEST AND NORTHEAST PORTIONS OF THE
FRONTAL BOUNDARY ACROSS TX.

SURFACE DEW POINTS ARE MAINLY 70 DEGREES F AND HIGHER ACROSS THE
REGION...WITH PRECIPITABLE WATER AROUND 1.5-2.0" LOW LEVEL
SOUTHERLY FLOW OF 15-20 KT WILL CONTINUE TO FEED MOISTURE INTO THE
REGION. SPC MESOANALYSES SHOW A VERY UNSTABLE ENVIRONMENT WITH
MUCAPE IN THE RANGE OF 4000-6000 J/KG. IN ADDITION CIN THAT WAS
ACROSS THE REGION EARLIER HAS MOSTLY ERODED DURING THE LAST 3
HOURS.

SO CONDITIONS ARE FAVORABLE FOR CONVECTION TO CONTINUE...AND IT
WILL PROBABLY FILL IN ALONG MUCH OF THE BOUNDARY DURING THE NEXT
COUPLE HOURS. WITH THE MOVEMENT OF THE STORMS ALONG THE
BOUNDARY...AND ADDITIONAL CONVECTION DEVELOPING JUST TO THE
SOUTHWEST IN THE STATE OF COAHUILA MEXICO...THERE IS GOOD
POTENTIAL FOR TRAINING AND REPEAT STORMS. OVER THE NEXT FOUR HOURS
THE EASTERN END OF THE COMPLEX COULD EXTEND INTO EXTREME SE AR AND
NORTHEAST LA...SO THEY HAVE BEEN INCLUDED IN THE MPD AS WELL.

HIRES MODELS AGREE RATHER WELL ON THE POTENTIAL FOR HEAVY RAIN
ACROSS THE AREA. THE HRRR...NAM...NAM CONEST...ARW...AND NSSL WRF
ALL SHOW LOCAL AREAS OF 4" TOTAL RAINFALL. SOME OF THE MODELS SHOW
LOCAL TOTALS AS HIGH AS 6". THE 3 HOUR FLASH FLOOD GUIDANCE ACROSS
THE THREAT AREA IS GENERALLY 3-5"...SO LOCALIZED FLASH FLOODING IS
POSSIBLE.

MCDONNAL

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...SJT...