March-2017: Active Spring WX Pattern Ahead

[srainhoutx]

The overnight guidance is advertising a potentially active weather pattern developing Friday and again next Wednesday into Thursday. The storm system next week may be a bit more energetic and further South suggesting the potential for better dynamics across Texas and closer to home. It is still too far out in the future to worry about the finer details, but we will continue to monitor.

[BlueJay]

Whew! I thought Spring would never get here... Happy Spring to all!

[Katdaddy]

Near record to record high temps possible across SE TX today and Wednesday as it will feel more like mid-May than Mid-March as a very warm 2017 continues. The severe weather potential is still on track to increase across the S Plains and SE US Friday into Saturday which will include portions of SE TX and NTX.

[srainhoutx]

Tuesday morning briefing from Jeff:

Near record to record highs possible today-Thursday.

Upper level ridge of high pressure continues to dominant the southern plains with record highs falling at several locations across TX on Monday and more will fall today and into the rest of the week. SSW low level flow is a warm wind direction for SE TX and with very dry air above 850mb to mix down this morning it would seem mid 80’s would be reachable today. Could see a couple of 90 degree readings on Wednesday or Thursday over the area.

A storm system will approach the southern plains late this week with both SPC and historical CIPS analogs suggesting strong to severe thunderstorms possible Friday afternoon and evening over at least the northern portions of SE TX. Track of the upper level system supports mid level flow becoming SW ahead of the cold front which usually caps off the local air mass. Additionally, instability looks marginal with CAPE values around 1000 J/kg, but wind energy is impressive, much will depend on the cap intensity and the amount of instability on where if any severe thunderstorms may occur Friday evening.

It is starting to look questionable now if the front will actually move off the coast and this could impact the Saturday forecast if any sort of surface boundary is left to linger over the region. For now will keep rain chances low, but may need to bump up rain chances over the next few days as convective evolution and surface boundary positions become better defined.

[Katdaddy]

Areas of fog across SE TX with mild temps in the upper 60s to low 70s. The fog will lift later this morning giving way to mostly sunny skies and low 80s. Thursday will be another 80F and mostly sunny day before clouds and increasing thunderstorm chances arrive Friday afternoon and night. The potential will exist from some strong to severe storms with the SPC having a slight risk area N of I-10.

Beginning tomorrow the severe weather potential will ramp up across the S Plains into the SE US through Sunday with NTX seeing 2 rounds of severe weather on Friday and again Sunday.

[srainhoutx]

Wednesday morning briefing from Jeff:

A spring storm system will bring severe weather to the southern plains Thursday-Friday

Upper level ridging over TX will begin to break down and move eastward as a storm system approaches from the west and will usher in an active period of weather over the southern plains and TX for the next week or so. Moisture remains shallow across the region this morning and areas of fog will lift and burn off quickly as dry air aloft mixes to the surface. Expect another day of near record highs in the mid 80’s across the region. Changes begin on Thursday as flow off the Gulf of Mexico increases and subsidence from the ridge aloft is lessened allowing much more significant moisture return into the region.

Storm system approaches on Friday with strong mid level flow of 60-80kts across a central TX dryline by early afternoon. Moisture advection east of the dryline brings PWS of 1.5 inches into SE TX by mid afternoon on Friday. Air mass just east of the surface dryline over C/N TX is uncapped by early afternoon and expect thunderstorms to rapidly develop as the dryline begins to progress eastward on the southern flank of the upper air system over OK. Strong linear forcing along the dryline will support a line of strong to severe thunderstorms across E TX by mid afternoon which will move eastward during the evening and overnight hours. Main questions at this time are how far south will these storms extend and will SE TX experience any severe weather. Much of this answer will be found within the intensity of the capping inversion which will develop across SC TX on Friday into at least the SW 1/3rd of SE TX. Northern extent of the cap will likely define the southern extent of the line of strong to severe thunderstorms. Model forecast soundings show this capping layer extending to roughly I-10 Friday afternoon and Day 3 SPC threat probabilities keep the slight risk outline along and N of I-10. Determining where and how strong of a capping inversion may be in place this far in advance is difficult and many times forecast models are weaker than reality with the cap.

Given current model projections expect a squall line to approach SE TX from the WNW Friday late afternoon and move across at least the northern ½ of the region Friday evening. A threat of damaging winds will be possible with this line with the highest threat north of HWY 105. Actual surface front may stall across the area on Saturday, but forecast models have backed away from any lingering activity.

Another short wave arrives into TX on Sunday and profiles across NC/N TX look favorable for severe weather and we will have to see if any of this activity can evolve into our area by Monday.

Another potentially potent storm system may arrive into the state by the middle to end of next week with severe weather and heavy rainfall chances.

Upcoming pattern looks very active for the southern plains and TX for the next week and it is the time of year where severe weather (large hail, damaging winds, and tornadoes) occur.

Day 3 (Friday) Severe Weather Outlook:

03222017 Jeff 1 untitled.png

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[DoctorMu]

Dry line approaching Friday.

Pretty modest CAPE



Heavier rain still N and E. Something to keep our eye on.

[DoctorMu]

Dry line approaching Friday.

Pretty modest CAPE



Heavier rain still N and E. Something to keep our eye on. (Long range: unsettled weather in early April?)

[srainhoutx]

Thursday morning briefing from Jeff:

Strong to severe thunderstorms possible across the northern half of SE TX Friday afternoon.

Low level moistening of the air mass is already underway this morning on increasing southerly winds as surface low pressure begins to develop over the high plains. Upper level system over the western US will move eastward and into the plains helping to deepen the surface low and dragging a dryline across TX on Friday. Onset of 35kt low level jet this evening will pump higher moisture values off the western Gulf of Mexico into eastern TX by early Friday. Dryline will march eastward on Friday with the local air mass slowly destabilizing with modest low level heating through a mostly cloudy sky. Areas north of a line from Columbus to Lake Livingston should be able to realize CAPE values of 1500-2500 J/kg by early to mid afternoon which is plenty for thunderstorm formation.

Main question remains the intensity and position of the northern edge of a mid level capping inversion (layer of warm stable air about 5000 ft off the ground which will prevent thunderstorm formation). Latest models show the capping inversion holding stout for areas SW of a line from Galveston to Houston to Columbus with very little to any activity. Forecast soundings show mid level winds SW at 30-35kts early Friday which is a favorable capping wind direction even though models want to lift and erode the inversion. North of this line a broken line of thunderstorms remains possible which also matches well with the forecasted greater values of instability. Incoming 110kt upper level jet and 80kt mid level jet will help support thunderstorm formation and organization into a fast eastward moving squall line across the northern portions of the area.

Main severe weather threat north of I-10 will be damaging winds of 60mph+ as the line moves quickly across this area during the afternoon and early evening hours. Hail and tornadoes will be a secondary lesser threat. Greatest potential for severe weather will be north of HWY 105 where the capping inversion will be weakest. It is certainly possible that areas south of I-10 will see little to no rainfall with this system.

Surface front will stall near the coast on Saturday, but dry westerly flow should negate any thunderstorm potential with the boundary. A fast moving southern stream disturbance rapidly approaches TX Sunday into Monday sending another weak front into our area which also looks to stall near the coast. Moisture levels may be high enough to support scattered showers and thunderstorms over the southern portions of the area on Monday.

Long range models show a fairly strong system currently out over the northern Pacific aimed at the southern plains for the middle of next week with the potential for widespread showers and thunderstorms by next Wednesday/Thursday.

SPC Day 2 (Friday) Severe Weather Outlook:

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[srainhoutx]

I continue to see strong signals indicating a rather active and potentially stormy weather pattern developing as we end March and head into April. Today, the strongest storms appear to impact areas from Lufkin on North and East into the Shreveport area. There is a possibility of a skinny line of showers and storms this afternoon and evening North of I-10, but the better dynamics are locate well NE of Metro Houston. The next in a series of fast moving bowling ball upper air disturbances arrives Sunday with another to follow mid next week.



A rather impressive Pacific jet streak combined with embedded disturbances moving inland along the West Coast and the Eastern Pacific suggest to me that after a quiet weather pattern, changes are brewing. Looking at the Western Gulf Sea Surface Temperature Anomalies, the Gulf is running above normal that adds fuel and Gulf moisture to these upper air systems as they cross our Region.

The morning updated 7 Day Quantitative Precipitation Forecast suggest increasing rainfall chances and the possibility of strong to severe storms and a threat of some heavy rainfall. We will continue monitor the sensible weather expected in the days ahead and update accordingly.

[mcheer23]

Seems like all these storm systems just want to go just to the north of here.

[Cromagnum]

Looks like a coin flip on rain for Houston to me. Might get an inch of rain, but could just as easily get zero again.

[DoctorMu]

The dry line is pretty broken up. This one's a bust. We'll see what happens Sunday and Monday. Hope the warm and dry pattern doesn't continue...dire consequences paid in the summer.

[tireman4]

00
FXUS64 KHGX 241855
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
155 PM CDT Fri Mar 24 2017

...MESOSCALE/SEVERE WEATHER DISCUSSION...

.DISCUSSION...
This discussion pertains to the severe weather potential for
mainly areas north and east of a Brenham to Houston line this
afternoon and tonight. SPC outlook has increased the threat over
Houston, Trinity and Polk counties with an enhanced risk and
assigned a 10 percent tornado probability for these areas. Even
the 5 percent tornado probability extends from east of College
Station towards Liberty.

Surface analysis at some composite mapping shows low level
moisture axis coming up from the middle Texas coast through
eastern portions of central Texas. Latest radar imagery shows
shower activity in this moisture axis where a few showers have
become enhanced but not able to break the cap. Capping from the
elevated mixed layer is a concern and seems to be holding since
cloud cover has held temperatures in the upper 70s to near 80F
instead of mid 80s. ML CAPE within the moisture axis looks to be
on the low side under 1000 J/kg due to this. AMDAR soundings
continue to show capping at 800-700mb but AMDAR soundings over
central Texas show that cap eroding. Water vapor imagery shows the
approaching trough axis so cooling aloft is expected with the
height falls later this afternoon. At this point look for the cap
to be stronger along the coast but farther north into the higher
risk areas, the cap should be weaker. Confidence in the cap
breaking would be higher if shower activity continue to increase
and one or two of those can be sustainable. Best PVA and height
falls are not expected to occur until closer to 00Z this evening
so still time to monitor the evolution of convection through the
moisture axis as the trough axis approaches.

Should the cap break, severe weather potential will depend upon
instability. Should CAPE reach more than 1000 J/kg then chances of
severe weather will be higher. Still there will be more than
enough shear that even 500-1000 J/kg of CAPE may yield an
organized storm. Deep layer shear continues to increase towards 60
kts at 0-6km with 0-1km shear near 20-25kts especially in the
moisture axis. Based on HRRR model soundings, 0-1km SRH could
reach around 200-300 m2/s2 late this evening in the
slight/enhanced risk areas. These shear values support rotating
storms and a tornado/wind threat. HRRR/WRF model runs continue to
show more of a broken line of storms which if updrafts can sustain
themselves would likely rotate. HRRR updraft helicity also shows
indication of rotating storms.

Bottom line is that we will continue to be monitoring for cap
breaking due to cooling aloft with the approaching trough. Should
surface based convection develop breaking the cap, severe weather
probabilities are warranted. SPC did issue a mesoscale discussion
which outline their thinking for a possible watch this evening.

Overpeck

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 57 81 58 86 66 / 30 10 10 10 20
Houston (IAH) 66 83 61 85 68 / 60 10 10 10 10
Galveston (GLS) 71 80 69 81 72 / 50 20 10 10 0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 4 PM CDT this afternoon for the following
zones: Austin...Brazoria...Brazos...Burleson...Colorado...
Fort Bend...Jackson...Matagorda...Waller...Washington...
Wharton.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 PM CDT this evening
for the following zones: Galveston Bay...Matagorda Bay.

Small Craft Advisory until 10 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...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...39

[srainhoutx]

Mesoscale Discussion 0317
NWS Storm Prediction Center Norman OK
0148 PM CDT Fri Mar 24 2017

Areas affected...Portions of central and eastern Texas

Concerning...Severe potential...Watch possible

Valid 241848Z - 242115Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms will gradually strengthen this afternoon
across central/eastern Texas, with an attendant threat for strong
wind gusts and a few instances of severe hail. Towards mid/late
evening, the tornado threat will likely increase as storms approach
the Sabine Valley. As such, a watch could be needed in the next 1-2
hours, with a tornado watch more likely this evening.

DISCUSSION...Recent radar mosaic data depict slowly organizing bands
of convection near/east of the I-35 corridor early this afternoon.
Convective intensity at present is quite marginal, as considerable
cloud cover has limited surface heating/destabilization. However,
stronger forcing for ascent will overspread richer moisture farther
east (evident in low-level cloud streets in visible imagery) over
the next several hours. As mid-level lapse rates steepen, this
thermodynamic profile should support around 1000-1500 J/kg of MLCAPE
across parts of the discussion area. In turn, convection is forecast
to intensify through the afternoon and into the evening hours.

Considerable large-scale ascent and more meridional flow aloft with
northward extent may maintain more of a linear structure, favoring
primarily damaging winds initially. In turn, convective trends are
being monitored for a possible watch this afternoon, with the
probability of issuance around 60%. By mid evening, low-level
storm-relative helicity should increase substantially, in response
to a strengthening low-level jet across east Texas. Moreover, richer
low-level moisture will continue to stream north, with surface dew
points reaching the mid/upper 60s. This low-level
thermodynamic/kinematic environment will favor an increasing tornado
threat with any line-embedded and/or semi-discrete cells.
Additionally, more discrete convection will be capable of severe
hail, considering favorable mid-level shear and sufficient buoyancy.
A Tornado Watch will likely be needed across this region by
early/mid evening.

..Picca/Guyer.. 03/24/2017


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

[CrashTestDummy]

Wow, the center of that low that's moving eastward, currently right along the state line between OK and the Texas panhandle looks impressive! Kind of reminds me of tropical stuff! Luckily, it's not that strong.

[Katdaddy]

Watching the trends this and enjoying some gusts to TS force. The earlier Mesoscale Discussion expired and no Tornado Watch issued for SE TX. Radar shows some storms beginning to fire between Houston and San Antonio which are depicted well on satellite. The SPC (Storm Prediction Center) still has a slight risk area just N of Houston metro.

[Cromagnum]

Complete bust. Zero rain for all.

[Katdaddy]

Tornado Watch until 12:00AM for SE TX.

[Katdaddy]

Would not be surprised to see a Tornado Warning issued for the cell in Colorado County very soon. Also watching the little cell moving into Wharton County. An active weather evening across SE TX.