May 2017: Memorial Day/End Of May Outlook

[Katdaddy]

SE TX weather takes a back seat today with a very high concern for NW OK and KS. If you have family and friends in NW OK and S & S Central KS they need to be weather aware which could be the difference between life and death. This is as serious as it gets folks.

The SPC has a very rare High Risk area across NW OK and S & S Central KS. A very dangerous life-threatening event will occur later this afternoon through tonight. I can't remember ever seeing a 30% hatch for tornadoes from the SPC.

Back home, expect mostly cloudy, humid, and breezy today across SE TX. Thunderstorm chances will increase for the weekend with locally heavy rainfall possible.

[srainhoutx]

I am finally seeing some believable changes in our sensible weather pattern beginning this weekend continuing into early Next week. A rather strong cold upper trough looks to settle across the Eastern 1/2 of the US suggesting a frontal boundary will meander into SE Texas before stalling with the possibility of a Coastal wave of low pressure developing along the Middle and Upper Texas Coast late Sunday into next Monday combining this a noisy sub tropical jet with a SW flow aloft on top of a Northerly flow at the surface.

Look for rain and storm chances to increase Saturday night into Sunday with local rainfall amounts near 1 to 2 inches with isolated higher amounts possible with stronger storms and any training that may develop. There are indications that a significant cold pool aloft will settle into the Lower 48 East of the Rockies with additional upper air disturbances diving SE from the NE Pacific into Canada and nearing the Eastern half of Texas and Louisiana.

[tireman4]

Echoing what Srain alluded to in his forecast, the NWS agrees...


240
FXUS64 KHGX 181629
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1129 AM CDT Thu May 18 2017

.UPDATE...
Forecast largely on track today. Did bump up highs at coastal
sites as they were already getting distressingly close to the
previous forecast high in the late morning - looks like another
warm one there, despite the onshore flow.

As far as precip today, there is plentiful low level moisture and
strong onshore flow. But, morning soundings from LCH and CRP were
pretty heavily capped - not completely invincible, but enough to
cast doubt on initiation. Backing that up, there are some very
strong returns on radar over the Gulf - but not precipitation,
it`s sea spray (or the surface?), indicating some serious
super refraction underneath a strong cap. Anyway, long story
short (too late, I know) - after getting burned on lowering PoPs
yesterday, will leave the slight chances we have in place well
inland, but will not be upping rain chances today at all.

Luchs

&&


.PREV DISCUSSION... /ISSUED 500 AM CDT Thu May 18 2017/

DISCUSSION...
A moist and increasingly unstable resident atmosphere will support
low to slight probabilities for either a light passing shower or
an isolated thunderstorm the next couple of days. A strengthened
near 30 knot low level jet will pull up a southwest-to-northeast
Theta E ridge across southeast Texas and...with pwats in the 1.6
to 1.7 inch range (near 75th percentile for mid May)...lower to
mid layer moisture will be sufficient to maintain unstable area
profiles the next several days. An approximate 7-8H warm nose will
cap the weakly-sheared region but...with lower level 6 to 7 deg C
afternoon lapse rates (greater than 2.5 J/kg CAPE values)...scattered
warmth-of-the-day showers and elevated thunder will not be out of
the question. Occasional cloud breaks should allow an already warm
and humid morning in the upper 70s to lower 80s to reach the average
middle 80s by noon...topping out in the mean upper 80s (coastal middle
80s) with a few spots hitting the lower 90s both today and tomorrow.

The upper level low centered over Salt Lake that is introducing
late season Colorado snow and providing (SPC`s) rare high risk
for severe weather over the Plains states today will move into the
northern Plains by early Saturday. Energy diving down under the
southern periphery of the main trough/shortwave trough will swing
across the state this weekend. An associated cold front will move
into Central Texas Saturday and will be the focus for developing
precipitation. Confidence is mounting that clustering thunderstorms
will impact (north) central state through the day Saturday with
this activity slowly sagging into the area Sunday. This early week
meso-driven -TSRA behavior may introduce locally high rainfall
that could lead to weekend flooding concerns. As of now...deterministic
models are not generating high QPF so the current WPC weekend
storm total ranges between a quarter of an inch and slightly
under an inch (over our extreme northern counties). A somewhat
split look to the jet stream during Sunday...with a northern lift
of the jet core across the state...may place east Texas under a
more favorable diffulent sector Monday. Surface high pressure
moving across the Red River Valley travels more east than south so
there isn`t a real push of any lingering synoptic cold front or
residual convective cold pool and respective outflow boundaries.
Relatively lower heights/surface troughing near the coast within a
continued highly moist environment...1.8 to near 2 inch pw air
mass shunted off the west to southwest...will keep at least low
POPs in place next Monday. A secondary...slightly more pronounced
cold frontal passage Tuesday has late period rain/storm chances
increasing back up into the moderate to high chance realm next
Tuesday morning and/or afternoon. High pressure building in behind
the front will likely dry the mid-week out and warm diurnal
temperatures a few degrees. 31

MARINE...
Gradient will support onshore winds bouncing around between 15-25
knots along with elevated seas through Saturday morning. Will keep
the caution flags going this morning but upgrade areas west of
Freeport to an advisory this afternoon. This will likely need to be
expanded further east over all waters tonight. A cool front will
make its way into se Tx over the weekend and close to the coast on
Sunday. There is considerable uncertainty as to if/when this
boundary will make it all the way offshore. It may meander north and
south along the coast for a couple of days and bring some unsettled
wx into early next week. 47

AVIATION...
Mainly a fcst of persistence. MVFR ceilings this morning should
transition upward into VFR territory by mid day, then fall back down
to 1200-1800 feet during the evening hours. Winds will gradually
increase thru the day, esp west of Interstate 45 where gusts >20kt
can be expected this afternoon. There may be some iso/sct popcorn
shra n/w of Highway 59 later today, but strong capping will limit
overall growth/strength. Minimal (if any) accumulations and no impacts
are expected so will probably forgo the mention in the TAFs. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 89 74 90 73 87 / 20 10 20 20 60
Houston (IAH) 89 75 89 75 87 / 10 10 20 20 60
Galveston (GLS) 87 78 85 78 85 / 10 10 20 20 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 7 PM CDT this evening for the
following zones: Matagorda Bay.

SMALL CRAFT SHOULD EXERCISE CAUTION until 1 PM CDT this
afternoon for the following zones: Coastal waters from
Freeport to the Matagorda Ship Channel out 20 NM...
Matagorda Bay...Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM.

SMALL CRAFT SHOULD EXERCISE CAUTION until 7 PM CDT this evening
for the following zones: Coastal waters from High Island to
Freeport out 20 NM...Galveston Bay...Waters from High
Island to Freeport from 20 to 60 NM.

Small Craft Advisory until 8 AM CDT Friday for the following
zones: Coastal waters from Freeport to the Matagorda Ship
Channel out 20 NM...Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM.

Small Craft Advisory from 7 PM this evening to 8 AM CDT Friday
for the following zones: Coastal waters from High Island to
Freeport out 20 NM...Waters from High Island to Freeport
from 20 to 60 NM.

&&

$$

Discussion...25

[DoctorMu]

[Katdaddy]

A cluster of strong to severe storm are currently moving across NW TX near Abilene. Additional development will occur across the Plains later today however a much lower risk for severe weather than yesterday.

A more unsettled pattern the next 5 days for SE TX but the details will be the challenge. The combination of a meandering front stalling across the area in combination with upper level disturbances will result in well needed periods of rain and thunderstorms with a low end threat for severe weather.

[oleander]

My yard is ready for a pattern change.

[srainhoutx]

Meso features will be the main theme for the upcoming weekend regarding our sensible weather and just how much rainfall we may get. Convection is firing along the dryline this morning to our NW near Abilene. The dryline and a vortmax should meander NE today allowing a weak frontal boundary to slowly creep SE into Central Texas tomorrow. There may be a focus of heavy thunderstorms developing along and just NW of the I-35 Corridor allowing for a cold pool to develop that could assist the frontal boundary to meander into SE Texas Saturday night into Sunday, but even the shorter term meso models are not too keen on bringing much rainfall into Metro Houston.



It does look like a stronger cold front may develop Monday and push SE into our Region allowing for a better chance of some rainfall, but I will remain cautiously optimistic regarding those chances as additional data arrives today and tomorrow. Lets see if a cluster of storms develop near the Hill Country tomorrow afternoon/evening before getting are hopes up for any significant rain.

[Cromagnum]

Every single future track I've seen show that all rain fizzles out by the time it gets to Houston and especially the coast. Drought continues...

[tireman4]

000
FXUS64 KHGX 191003
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
503 AM CDT Fri May 19 2017

.DISCUSSION...
Like yday, can`t rule out some brief isolated & insignificant
shra under the cap. Otherwise, continued warm and breezy today.
May see another record or two in jeopardy at Galveston (record
high 87/2008 & record high min 78/2015).

Beyond that...forecast confidence between Sat afternoon and
Tuesday is quite low.

The upper trof currently stretching across the Rockies will make
its way into the cntl and nrn plains this weekend. Its associated
surface cool front will make its way into se Tx Saturday aftn but
gradually loose it`s support and southward momentum. It`ll eventually
stall somewhere near the coast Sunday. This boundary, or remnants
of such, will meander about the region into Tuesday and provide a
focus for precip as a series of upper disturbances embedded in
the sw flow aloft move overhead.

As to exactly where the boundary will be, timing/placement of the
disturbances, and how much rain will occur -- unfortunately
there`s a high degree of uncertainty. Much of this will be likely
be determined on a smaller scale than models can resolve this far
out.

Expect some scattered showers and tstms to develop along the
front late in the day Saturday as it pushes in. Late Saturday
night & Sunday morning, several models indicate a fairly healthy
vort moving ene from the Big Bend area and parallel to the slow
moving boundary. There is some concern for some localized heavy
rain as PW`s pool to 1.7-1.9" along the front, cap has eroded,
mean steering flow diminishes to <8kt, along with some notable
upper diffluence aloft. Most solutions, including SREF plumes show
total QPF`s into Monday morning less than 1.25" which would be
highly welcome rainfall. But, we`ve also noticed some much higher
bullseye`s pop up for several days now. They`re highly inconsistent
from model-to-model and run-to-run, but can`t completely ignore
such signals that keep showing up with a surface boundary
lingering about in May. (Also of note, is the Tx Tech WRF which
has been excellent as of late, isn`t all that impressed). Think
the main threat area for heavy rain Saturday night and Sunday, if
there ends up being one, will mainly be n/nw of HWY 59.

As mentioned above, chances of precip should continue thru the
day Tuesday until a stronger front moves into the region and off
the coast late in the day. This front should have enough upper
support to do so. 47

&&

.MARINE...
Onshore winds are continuing to decrease this morning but will keep
the SCEC/SCA up for the coastal waters through 18Z/1 PM at the very
latest. However, that being said, we could see the gradient tighten
up briefly once again late this afternoon as models try to bring a-
nother shortwave into the area from the west. These moderate/strong
wind speeds should finally start to decrease Sat/Sun as a weak cold
front moves into northern portions of SE TX. Scattered showers with
possibly strong thunderstorms will be possible Sun through Tues for
our marine locations. This activity is expected to shove out of the
area will late Tues with the passage of a cold front. Moderate off-
shore winds will develop across the bays/coastal waters in the wake
of this front by early Weds morning. Onshore winds are then progged
to return Thurs afternoon. 41

&&

.AVIATION...
Not planning on a lot of changes with the 12Z TAFS...keeping with a
mix of MVFR/overcast VFR CIGS this morning. The strong WAA in place
could help to produce an isolated SHRA through mid morning but, the
best chances for precipitation should be for our northern sites for
this afternoon/early evening with the approach of the dry line from
the west. The cap will likely hold so not going with any mention at
this time. Hazy conditions are expected down at GLS once again this
afternoon. MVFR CIGS should return tonight/early Sat morning. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 75 87 68 83 / 20 20 50 70 30
Houston (IAH) 90 75 89 72 86 / 20 10 40 50 60
Galveston (GLS) 87 79 87 77 85 / 20 10 20 30 50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 5 AM CDT early this
morning for the following zones: Galveston Bay...Matagorda
Bay.

Small Craft Advisory until 5 AM CDT early 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.

SMALL CRAFT SHOULD EXERCISE CAUTION until 1 PM CDT this
afternoon 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.

Small Craft Advisory until 1 PM CDT this afternoon for the
following zones: Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.

&&

$$

[srainhoutx]

Increasing the optimism level to about a 7 out of 10 chance this morning that we may final see some rainfall through at least Tuesday. After about of month of nothing to really talk about in the weather department for SE Texas, I believe we will probably see a general 1 to 2 inches of rainfall across our Region with some isolated totals possibly approaching 4 to 5 inches where heavier training storms organize along and behind the weak boundary that may stall along near the I-10 Corridor.

Clear a cold pool has developed across the I-35 Corridor this morning as the frontal boundary slowly meanders toward us throughout the day into tomorrow. Aircraft data just a capping inversion is still holding at IAH and Hobby, but it appears that the cap is breakable as the boundary nears and an embedded disturbance at the upper levels approaches the Region later today. Again, the pattern suggests the everything will been meso driven by features that cannot be reasonably forecasted beyond 4 to 6 hours.

The overnight computer guidance suggest a strong front arrives Monday night into Tuesday. The disturbance that will usher in that front can be seen clearly on water vapor imagery in the Pacific NW diving SE toward the Intermountain West and eventually the Plains.



The Weather Prediction Center places SE Texas in a Slight Risk for Excessive for the next 24 hours and again on Monday into early Tuesday.

[don]

The European Model also shows widespread rainfall amounts of 3-6 inches across the southern half of Southeast Texas fwiw

[srainhoutx]

Looking at the 13Z HRRR, the best chance of showers and storms arriving later this afternoon into the early evening hours. It is also noted via MIMIM that a strong surge of deep rich tropical moisture from the NW Caribbean is moving NW into the Gulf of Mexico suggesting more tropical juice of our Region that may coincide with the arrival of the secondary strong front on Monday into early Tuesday.

[Katdaddy]

Strong to severe thunderstorms could move into portions of SE TX later this afternoon and evening from storms over S Central and STX. A Severe Thunderstorm Watch was issued a little earlier for much of that region.

The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
South Central Texas
* Effective this Saturday morning and afternoon from 1010 AM until 500 PM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2.5 inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Strong/severe storms currently west of San Antonio are
expected to develop eastward and southeastward along an outflow
boundary into a very warm and moist air mass. The stronger storms
will be capable of producing large hail and damaging wind gusts.
The severe thunderstorm watch area is approximately along and 60
statute miles either side of a line from 90 miles west northwest of
Cotulla TX to 20 miles east northeast of Victoria TX.

[DoctorMu]

Today was off to a good start in CLL.

The secret was to run the sprinkler system last night as a "prime the pump" strategy...and sure enough, a couple of hours later and before 6am the heavens opened as the outflow boundary/meso held together.

1.2 in IMBY and the first significant rainfall in weeks.

The meso SW of San Antonio has potential later today as it eases NE along the boundary. The cap in the HOU might break in mid-afternoon. Stay tuned.

[DoctorMu]

Cap battling triggering mechanisms for showers across outflow boundaries.

The cold front has the potential to stall though before disturbances from Mexico move across the region.


Potential for Feast or Famine! - sounds like an iconic Texas forecast


Area Forecast Discussion
National Weather Service Houston/Galveston TX
1239 PM CDT Sat May 20 2017

.AVIATION...
Daytime heating could bring increasing SHRA/TSRA coverage for area TAF
sites this afternoon, so 18Z TAFs are carrying VCSH/VCTS through around
21/01Z. Hard to time disturbances moving across the state in combination
with any mesoscale boundaries are expected to bring periods of SHRA/TSRA
to the area tonight and tomorrow. Mainly MVFR ceilings are anticipated
during the overnight hours, with VFR conditions anticipated during
the day outside of the storms. We`ll also be dealing with a cold front
and associated wind shift to the north and northeast later tonight
and tomorrow. 42
&&

.PREV DISCUSSION... /ISSUED 1101 AM CDT Sat May 20 2017/

UPDATE...
The line of showers and thunderstorms that moved across the
northeastern counties earlier this morning along an outflow
boundary have cleared the region, but radar imagery shows isolated
cells developing across the northern half of the forecast area in
its wake. Visible satellite imagery shows an outflow boundary
associated with this line stretching from roughly Brenham to
Cleveland, with surface analysis revealing another outflow
boundary northwest of the region stretching from San Antonio to
Ft. Hood. Expect both of these features to serve as focusing
mechanisms for additional shower (and possibly thunderstorm
development) today as temperatures continue to rise into the 80s.


The environment across Southeast Texas today is capable of
producing thunderstorms today, but have low confidence in overall
coverage . Stabilization behind this morning`s thunderstorms may
limit development along the northwestern outflow boundary for the
next few hours as it sags across the Brazos Valley, with anvil
debris from ongoing convection near San Antonio`s area also
inhibiting better destabilization across the northern counties as
it advects to the northeast. Additional development is expected
along the southern outflow boundary, but aircraft soundings out of
Houston continue to show mid-level temperatures ranging from 10-12
degrees C and provide enough of a cap to also limit thunderstorm
development. However, morning upper air analysis showed strong
divergence across the region in response to the upper low lifting
across the Central Plains and this may be enough to overcome the
aforementioned factors. Cannot rule out a strong or severe
thunderstorm producing large hail or damaging winds given mid-
level lapse rates around 7 C/km per SPC mesoanalysis, but this is
all contingent on thunderstorm development. Brief heavy rain will
also be capable in stronger activity.

The HRRR/RAP show any activity developing today sweeping from
northwest to southeast as a cold front stretching from Presidio to
south of the D/FW Metroplex overtakes both outflow boundaries
this afternoon and evening. However, RAP VAD wind profilers show
mid level flow becoming increasingly weak/light during the
afternoon hours and consistent with the previous forecast am
concerned that this may result in the front slowing down or
stalling across the region. This would result in possibly another
round of rain this evening or tonight as subtle disturbances lift
out of Mexico.

[Cromagnum]

Gonna go ahead and call bust. Really hope I'm wrong.

[mckinne63]

Bust that cap! Just cloudy muggy and humid.

[DoctorMu]

A few scattered showers emerging along the outflow boundary this evening.

[Katdaddy]

.30" early this morning of well needed rain and more on the way. SE TX is in a Moderate Risk for flash flooding tomorrow and expect a Flash Flood Watch to be issued later today. Its been awhile since the windows have condensated from deep tropical moisture.

[Katdaddy]

Latest from Jeff Linder....
Heavy Rainfall Event becoming likely tonight-Monday night.

Flash flooding possible over the region…flash flood watch may be required later today.

Surface front is currently stalling near the coast this morning after an active night of severe thunderstorms producing large hail along and N of I-10. Area is currently in a break between upper level impulses aloft with the next disturbance currently crossing SW TX and will be arriving later this morning across the area. Expect showers and thunderstorms to develop near the stalled frontal boundary across our coastal counties from Matagorda Bay to TX/LA state line and move very slowly this afternoon. This will promote a short fused flash flood threat due to slow cell motions and high rainfall rates. Should see activity weaken and dissipate by early evening.

Tonight-Monday:

Big concern is this period as a very strong short wave trough ejects out of NE MX and across SE TX late tonight and on Monday. Stalled front will remain across the region and PWS climb to extremely high values of 1.9-2.2 inches during this period which is concerning. Upper level winds become strongly divergent (split) aloft helping to vent convection. Parameters are pointing toward an increasing flash flood threat on Monday. Main question will be the exact location of the surface frontal boundary as this will determine where the maximum rainfall occurs. Models are keying in on the US 59 corridor to just offshore for this boundary and this area will likely be at the most threat which also happens to be where storms may develop today and wet the grounds. Should storms develop near the coast or offshore most of the inland locations would be robbed on moisture and rainfall amounts would be fairly low.
With PWS getting up and even above 2.0 inches on Monday the threat for intense short duration rainfall rates of 2-4 inches per hour is threat. Slow storm motions and potential for cell training or cell anchoring will be increasing which will increase help to promote areas where training occurs under intense rainfall rates at a flash flood risk. Patterns like this in the past have certainly produced flooding over the region and some impressive rainfall totals (ie Danbury in April with nearly 11 inches in about 3 hrs).

While grounds remain generally dry across the region, expected rainfall intensities will likely exceed short duration flash flood guidance resulting in run-off which is why WPC has increased the flash flood threat to moderate through Monday night.

Widespread rainfall amounts of 2-3 inches appear likely with much higher totals (8+inches) under any cell training or anchoring. The spatial coverage of the maximum amounts should be small which will help to mitigate the flooding concerns to just those areas.

Tuesday:

Area should get a break at some point Monday night, but a couple of short waves dropping SE in the NW flow aloft on Tuesday will likely spark a thunderstorms complex over NW TX Monday evening which may arrive in some fashion across SE TX on Tuesday. This could bring additional heavy rainfall to the region along with potential severe weather if in fact it makes it this far SE.