Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 4

[Srain]

MESOSCALE DISCUSSION 0572

NWS STORM PREDICTION CENTER NORMAN OK

0130 PM CDT FRI APR 20 2012

AREAS AFFECTED...PORTIONS DEEP S TX...LOWER RIO GRANDE VALLEY

REGION...COASTAL PLAIN SW OF WW 184.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 201830Z - 202030Z

SVR POTENTIAL FCST TO INCREASE THROUGH LATE AFTERNOON OVER

DISCUSSION AREA...INCLUDING CONDITIONAL POTENTIAL FOR A FEW

SUPERCELLS. MAIN CONCERN WILL BE LARGE/DAMAGING HAIL. SVR

DOWNDRAFT GUSTS ALSO ARE POSSIBLE...RELATED BOTH TO PRECIP LOADING

AND POTENTIAL FOR EVENTUAL UPSCALE COLD-POOL GROWTH. TORNADO THREAT

IS MORE CONDITIONAL ON BOUNDARY INTERACTIONS AND STORM-SCALE

PROCESSES...BUT A TORNADO OR TWO IS POSSIBLE.

SFC MESOANALYSIS SHOWED COLD FRONT FROM NE TX SWWD ACROSS SAT AREA

TO JUST W COT. PREFRONTAL WIND SHIFT WAS DRAWN JUST E OF I-35

BETWEEN SAT-LRD THEN SSWWD TO MMMY. FRONT IS FCST TO MOVE SEWD

THROUGH AFTERNOON...OVERTAKING WIND SHIFT AND MOVING INTO

DESTABILIZING AIR MASS WITH WEAKENING CINH. MODIFIED RAOBS AND FCST

SOUNDINGS SUGGEST MLCAPE INCREASING TO 2000-3000 J/KG RANGE WITH SFC

DEW POINTS REMAINING MID-60S F...AND CONTINUED STG INSOLATION.

BOUNDARY-LAYER FLOW IS NOT PARTICULARLY STG...LIMITING EFFECTIVE

SRH. HOWEVER...SUBSTANTIAL DIRECTIONAL VEERING WITH HEIGHT SHOULD

BE MAINTAINED THROUGH AT LEAST LATE AFTERNOON. 850 MB WINDS HAVE

VEERED FARTHER N ACROSS CRP AREA...APPARENTLY IN RESPONSE TO

SEWD-MOVING...MESOBETA-SCALE PERTURBATION ACCOMPANYING

EARLIER/WEAKENING PLUME OF CLOUDS/PRECIP. HOWEVER...SFC FLOW THAT

VEERED LAST HOUR IN THAT AREA...HAS BACKED AGAIN. AS MID-UPPER

TROUGH PASSING ACROSS NRN PORTIONS OF THIS AREA ENHANCES HEIGHT

GRADIENT...MIDLEVEL WINDS AND THUS DEEP-LAYER SHEAR WILL

STRENGTHEN...ESPECIALLY WHERE LOW-LEVEL WINDS REMAIN RELATIVELY

BACKED. RESULT SHOULD BE 40-50 KT EFFECTIVE SHEAR MAGNITUDES...AND

ELONGATED...SOMEWHAT HOOK-SHAPED LOW-LEVEL HODOGRAPHS DEVELOPING

THAT MOST FAVOR SUPERCELLS FOR ANY DISCRETE TSTMS EXHIBITING

STRONGLY DEVIANT/SWD MOTIONS.

..EDWARDS.. 04/20/2012

ATTN...WFO...CRP...BRO...

[Srain]

[JoMo]

Tornado Warning for the Corpus Christi area.

[Ellinwood]

Haven't seen anything other than weak rotation on radar... wouldn't be surprised if Texas ended up with 0 tornadoes. The warning issued by the Brownsville NWS might have been legitimate, but I've been scratching my head a little WRT the warnings coming out of CRP.

[Ellinwood]

Galveston: http://abclocal.go.c...enow?id=7292434

4:42pm CDT:

[Srain]

CRP NWS employee reported some weak rotation. The line has produced a lot of hail. I had penny to nickle size here in NW Harris County with winds gusting to 50 mph.

Edit to add: Strongest rotation was near CC NAS a moment ago via CRP

[Srain]

MESOSCALE DISCUSSION 0574

NWS STORM PREDICTION CENTER NORMAN OK

0448 PM CDT FRI APR 20 2012

AREAS AFFECTED...DEEP S TX

CONCERNING...SEVERE THUNDERSTORM WATCH 185...

VALID 202148Z - 202245Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 185

CONTINUES.

A LARGE TO VERY LARGE HAIL THREAT...IN ADDITION TO DMGG WINDS AND AN

ISOLD TORNADO RISK...WILL CONTINUE UNTIL THE STORMS OVER THE AREA

MOVE SEWD AND OFFSHORE INTO THE WRN GULF.

RADAR MOSAIC/SURFACE CHART ANALYSIS SHOWS AN EXTENSIVE SQUALL LINE

EXTENDING FROM THE MIDDLE TX COAST NEWD THROUGH THE HOUSTON METRO

VICINITY WITH A BROKEN LINE/CLUSTER OF QUASI-DISCRETE SUPERCELLS

DEVELOPING FARTHER SW OVER DEEP S TX FROM CRP TO 40 MI NNW MFE. THE

AIRMASS IMMEDIATELY AHEAD OF THE ESEWD MOVING CONVECTIVE COMPLEX HAS

WARMED INTO THE UPPER 80S WITH MID-UPPER 60S DEWPOINTS. THIS

POTENTIALLY UNSTABLE BOUNDARY LAYER RESIDES UNDERNEATH A STOUT CAP

/PER 18Z BRO RAOB/ WITH VERY STEEP H7-H5 LAPSE RATES /NEAR 9 DEG C

PER KM/. HOWEVER...LARGE SCALE FORCING FOR ASCENT DUE TO AN

EQUATORWARD DIGGING UPPER TROUGH OVER TX AND LOW LEVEL LIFT OWING TO

A COLD FRONT MOVING THROUGH THE AREA WILL CONTINUE TO STRONGLY FAVOR

FURTHER STORM DEVELOPMENT. STRONG UPPER TROPOSPHERIC FLOW SAMPLED

BY AREA 88D VAD/S AND RAOB DATA WILL SUPPORT ROTATION WITH THE

STRONGER UPDRAFTS. THIS WILL LEND TO THE POSSIBILITY OF HAIL OF

BEING GOLFBALL SIZE OR LARGER WITH THE MOST INTENSE STORMS...OWING

TO LARGE CAPE IN THE -10 TO -30 DEG C LAYER. AN ISOLD TORNADO RISK

CANNOT BE RULED OUT DESPITE WEAK LOW LEVEL FLOW...DUE TO VEERING LOW

LEVEL WINDS WITH HEIGHT AND SUPERCELLULAR STORM MODE.

..SMITH.. 04/20/2012

ATTN...WFO...CRP...BRO...

[Ellinwood]

By the way... does anyone know why CRP isn't cancelling old warnings? The storms moved out of the tornado warning 20 minutes ago and the warning doesn't expire for another 10 minutes. Not enough staff to issue the severe warnings and cancel old ones?

EDIT: I've been informed of server issues.

[Ellinwood]

I guess I'll have to take back my earlier statement about no tornadoes... not too long after I said that this happened:

2245 ... 1 SE Raymondville ... Willacy ... TX

Brief touchdown and lift up. No damage reported.

The two scans before the report (which was at 2245... around the same time they expired the warning):

[JoMo]

Tornado warning down near Brownsville, multiple funnel clouds reported. (Edit: And cancelled)

[Ed Lizard]

Official NWS forecast high at San Angelo, TX is 101ºF. May can't be far behind.

[Ed Lizard]

In main forum tropical thread, 12Z Crazy Uncle brings a very weak but trackable 850 mb feature with a hint of a surface low Northwest across the Gulf to rain on Louisiana mid-week.

Nothing like that on the more reliable GFS, but we get close to getting South of the 700 mb ridge axis at the end of the month for a couple of days before we get back into SW low-mid-level flow.

[Ed Lizard]

Still immensely boring locally, but SPS area in a hatched hail risk area, and mid-week, GFS seems a bit on the Canadian train with a barely perceptible disturbance from the East enhancing rain chances in Louisana.

[Quixotic1]

Seeing lightning here in Collin Co but not a thing on the radar.

[Srain]

...SERN TX TODAY...

A WELL-DEFINED MCV SE OF AUS WILL CONTINUE EWD TODAY...LIKELY

SERVING AS THE FOCUS FOR DIURNALLY ENHANCED TSTM DEVELOPMENT.

MODIFICATION OF 12Z CRP SOUNDING FOR FORECAST AFTERNOON SURFACE

CONDITIONS SUGGESTS AIR MASS WILL BECOME MODERATELY UNSTABLE WITH

MLCAPE OF 1500-2000 J/KG. MOREOVER...CURRENT CRP VWP SHOWS THE

PRESENCE OF MODESTLY STRONG LOW-LEVEL SHEAR WHICH MAY PROMOTE A FEW

ROTATING STORMS WITH AN ATTENDANT RISK FOR HAIL...LOCALLY DAMAGING

WINDS AND PERHAPS A TORNADO.

[DoctorMu]

Yeah, this weather starts to drive me bonkers. Increasing hot, high dewpoints, nothing in the tropics, heavy cloud but no rain.

12 zzzzzzzzzzzz models

Then it gets worse...

[Srain]

While we are in the midst of a quiet pattern where the capping has been rather stout and rain has been almost non existent, there is a change beginning to show up via guidance for next week. A push of deep rich tropical moisture will be working its way W and a trough/frontal boundary digs SE across the Plains and could set the stage for several days of sorely needed rainfall across the Lone Star State with ‘cooler temps’ as well. There is even a hint of a tropical disturbance in the longer range working its way NW from the Caribbean. My hunch is the doldrums in the weather department may begin to ease as we head into the second week of May. We will see.

[Ed Lizard]

Got to disagree with SRain about anything remotely tropical. Only hope is very positively tilted trough in a week as seen on North American ensembles ejecting hard to forecast little disturbances in the SW flow aloft. Operational 0Z GFS hints at this, but it is a week away. Operational Euro may show one such disturbance crossing over SETX Tuesday evening. Deep SE surface flow on models suggests ample low level moisture and may also reduce tendency for capping to be an issue. Surface gradient may also weaken enough to allow seabreeze boundaries to develop.

Next few days, glass 1/64 empty, not very optimistic, next week, glass half full optimistic on needed rain for the lawn, glass quarter full on a surprise on a sea breeze boundary storm.

(I saw hail once, not much bigger than peas, smaller than dimes, but hail, in Spring 1990, in Austin, on early evening storms that had travelled all the way in from the coast (and AUS is not near the coast) on a sea breeze boundary.)

What I really love, could actually sea it sometimes when I worked nearshore Gulf of Mexico, was late night early morning land breeze, with tall cu and even a few showers, reverse course and head inland as a sea breeze by mid to late morning. And, of course, I love watching the little hint of a sea breeze coming off the Gulf and the little hint off Galveston Bay, as seen on HGX 88D, especially where they sometimes merge and trigger a storm.

[Srain]

Morning e-mail from Jeff:

Quite upper air pattern remains over the state prolonging the current dry period.

Water vapor images and upper air analysis this morning showing ridging over the western Gulf of Mexico and off the SE US coast with a trough axis from the Mississippi Valley into the SE Gulf of Mexico with active thunderstorms. An upper level low is starting to eject NE out of the Baja region toward the SW US along the NW side of the western Gulf of Mexico ridge. Dryline remains anchored well west of our region over far west TX and this is where it will remain for the next several days. Air mass over the region is moist at the surface and fairly dry in the mid and upper levels compared with points to our east where deep tropical moisture has surged inland. Lack of a surface focus, dry air aloft, and mid level capping will keep rain chances low for the next 3-5 days.

Ridge over the western Gulf of Mexico will build NE into TX and along much of the Gulf coast over the next few days allowing heights to increase and then a resultant increase in surface temperatures. BUSH IAH broke 90 degrees yesterday for the first time in 2012 (91) and suspect that additional 90 degree days will occur today-Sunday with increased heights and temperatures aloft. Combination of warm afternoon temperatures and high dewpoints will result in hot and humid afternoons and sticky mornings through the weekend. A couple of isolated light showers may be possible at any time under the mid level cap moving inland off the Gulf of Mexico…but this chance is remote and measurable rainfall is not likely.

Extended finally does feature a pattern change to a potentially more wetter and slightly cooler period. A deep upper level trough will move out of the western US late this weekend toward the Midwest by the middle of next week and this system appears strong enough to push a cool front southward into TX by the middle to end of next week as ridging over the area weakens. At the same time another low is forecast to develop in the region of Baja and potentially approach the region from the SW. Timing of both of these features remains in question along with how far south the potential surface front will get…it is starting to get late for cool fronts this far south…and we are talking over a week out so there will be some changes in the forecast, but at this point rain chances appear to be possibly increasing for this period of time.

Note: The 91 yesterday at IAH is right about on average for the first 90 degree day (May 7 is average). Last year we hit 90 by April 8, so while we have been warm for the last several months, we are not nearly as warm as last year thanks mainly to a moist ground and “green” vegetataion.

[Srain]

It still appears rain chances will increase beginning late Sunday extending into the middle part of next week as a deep cut upper low drops into the Four Corners Region that meanders E and stalled Pacific boundary drapes across the Lone Star State. The sub tropical jet looks to become active with multiple short wave impulses riding along the upper SW flow from the Eastern Pacific that could provide for several days of showers/storms to develop. As I mentioned several days ago, some deep tropical moisture from the Caribbean will begin to enter the Gulf later next week as well, so our quiet benign weather pattern may be trending to that of a bit wetter scenario. We will see.

[bubba hotep]

FWD bringing the knowledge :

AREA FORECAST DISCUSSION...UPDATED

NATIONAL WEATHER SERVICE FORT WORTH TX

124 PM CDT FRI MAY 4 2012

.UPDATE...

...MESOSCALE FORECAST UPDATE...

REGARDING THUNDERSTORM CHANCES THIS AFTERNOON AND EVENING ACROSS

NORTH TEXAS.

12Z UPPER AIR ANALYSIS INDICATED RICH GULF MOISTURE IN PLACE OVER

THE SOUTHERN PLAINS WITH H850 DEWPOINTS OBSERVED ABOVE 10 DEG C

OVER THE ENTIRE CWA. ANALYSIS ALSO DEPICTS A LARGE PLUME OF VERY

STEEP MID LEVEL LAPSE RATES OVER THE REGION WITH AN OBSERVED H700

TO H500 TEMPERATURE DIFFERENCE IN EXCESS OF 22 DEG C. THIS EQUATES

TO NEAR DRY ADIABATIC LAPSE RATES OVER MUCH OF THE REGION

ASSOCIATED WITH A STOUT ELEVATED MIXED LAYER. WATER VAPOR IMAGERY

DEPICTS A COMPACT SHORTWAVE TROUGH NEAR A WICHITA FALLS TO

SWEETWATER LINE...GENERALLY MOVING NORTHEAST EARLY THIS AFTERNOON.

SURFACE OBSERVATIONS SEEM TO INDICATE THAT THE DRYLINE HAS BECOME

WELL ESTABLISHED OVER THE TX PANHANDLE. THE 12Z FWD UPPER AIR

SOUNDING INDICATED A NEARLY HALF INCH INCREASE IN PRECIPITABLE

WATER. AFTERNOON AIRCRAFT SOUNDINGS FROM DFW INDICATE THAT A VERY

STRONG CAP REMAINS IN PLACE FOR SURFACE BASED STORMS...WITH NEARLY

250 J/KG OF CONVECTIVE INHIBITION OBSERVED AT 1715Z.

THE TWO PRIMARY PLAYERS IN TODAYS CONVECTIVE EVOLUTION ARE THE

SHORTWAVE TROUGH AND THE DRYLINE. MOST HIGH RESOLUTION GUIDANCE

INITIATES CONVECTION ALONG THE DRYLINE LATE THIS AFTERNOON. WHILE

THIS IS A PLAUSIBLE SOLUTION...THE CURRENT POSITION OF THE DRYLINE

IS FAR TOO WEST TO HAVE ANY IMPACT ON LOCAL THUNDERSTORM

INITIATION...SO THE DRYLINE WOULD HAVE TO MIX EAST RAPIDLY HERE

OVER THE NEXT FEW HOURS FOR THIS TO COME TO FRUITION. THERE ARE

SOME SIGNS THAT THIS WILL HAPPEN...17Z SURFACE OBSERVATIONS

INDICATE SOUTHWESTERLY WINDS FROM POSSUM KINGDOM LAKE WEST THROUGH

ABILENE AND SWEETWATER. TO THE EAST WINDS REMAIN BACKED OUT OF THE

SOUTH-SOUTHEAST. ASSUMING THIS WIND SHIFT LINE IS RELEVANT...IT

MAY MARK THE EVENTUAL POSITION OF THE DRYLINE LATE THIS AFTERNOON.

WITH REGARDS TO THE SHORTWAVE TROUGH...THIS FEATURE IS EXTREMELY

IMPORTANT BECAUSE IT MAY BE THE ONLY MECHANISM THAT CAN PROVIDE

SUFFICIENT LARGE SCALE ASCENT TO LIFT THE STRONG EML CAP OBSERVED

ON THE 17Z DFW AIRCRAFT SOUNDING. THE PRIMARY FORECAST CHALLENGE

IS DETERMINING WHETHER THE LARGE SCALE FORCING ASSOCIATED WITH

THIS TROUGH WILL STILL BE PRESENT OVER NORTH TX LATE THIS

AFTERNOON WHEN THE DRYLINE MIXES EAST TOWARDS THE CWA. WITH THE

SHORTWAVE TROUGH MOVING NORTHEAST THERE IS SOME CHANCE THAT LARGE

SCALE FORCING WILL BE DISPLACED NORTH OF THE RED RIVER BEFORE THE

DRYLINE CIRCULATION CAN ATTEMPT TO INITIATE STORMS LATE THIS

AFTERNOON. IT IS VERY DIFFICULT TO DETERMINE THE EXTENT OF LARGE

SCALE FORCING ASSOCIATED WITH THE TROUGH IN CLEAR AIR. THE MOST

TELLING SIGN THAT FORCING FOR ASCENT STILL EXISTS OVER NORTH TX IS

THE DEVELOPMENT OF THE MID LEVEL CUMULUS CLOUDS JUST WEST OF FORT

WORTH...EXTENDING NORTH TOWARDS THE RED RIVER. WHILE THIS MAY NOT

MARK THE ONLY LOCATIONS RECEIVING STRONG FORCING FOR ASCENT...IT

SEEMS TO AT LEAST FAVOR MUCH STRONGER FORCING FOR THE NORTHERN CWA

FOR THIS AFTERNOON.

WITH AT LEAST MODERATE CONFIDENCE THAT LARGE SCALE FORCING WILL

PERSIST FOR THE NORTHERN HALF OF THE CWA NEAR THE DRYLINE LATE

THIS AFTERNOON...WENT AHEAD AND INCREASED POPS TO 30 FOR AREAS

NORTHWEST OF THE METROPLEX THROUGH 00Z. ALSO EXPANDED THE COVERAGE

OF 20 POPS MUCH FURTHER EAST AS THE TRUE AREAL EXTENT TO THE

FORCING ASSOCIATED WITH THE TROUGH IS UNKNOWN. ALSO...DESPITE

STRONG LARGE SCALE SUPPORT FURTHER SOUTH...MESOSCALE FORCING NEAR

THE DRYLINE CAN EASILY DOMINATE LARGE SCALE INFLUENCES...SO

THUNDERSTORM INITIATION REMAINS POSSIBLE WITHOUT THE HELP OF THE

SHORTWAVE TROUGH. AFTER 00Z MOVED THE AREA OF 30 POPS EAST TO

INCLUDE THE METROPLEX AS INITIATED CONVECTION FROM THE DRYLINE

WILL TEND TO COLLECT INTO A MULTI-CELL CLUSTER OR LINE AND THEN

MOVE EAST-NORTHEAST OFF THE DRYLINE FOR THE EVENING HOURS. EXPECT

THAT WITH THE LOSS OF DAYTIME HEATING STORMS WILL TEND TO WEAKEN

AND WILL LIKELY DISSIPATE BY MIDNIGHT ACROSS THE CWA.

RICH GULF MOISTURE BENEATH THE STEEP MID LEVEL LAPSE RATES

ASSOCIATED WITH THE EML WILL ALLOW FOR MODERATE TO STRONG

INSTABILITY BY LATE THIS AFTERNOON. FORECAST MIXED LAYER CAPE

VALUES IN EXCESS OF 3000 J/KG ARE LIKELY TO BE REALIZED. DEEP

LAYER SHEAR IS SOMEWHAT MARGINAL WITH 30 TO 35 KTS OF 0-6 KM BULK

SHEAR FORECAST FOR THIS AFTERNOON. STRONG INSTABILITY WILL

SOMEWHAT COMPENSATE FOR WEAKER DEEP LAYER SHEAR AND SHOULD STILL

SUPPORT A SUPERCELL STORM MODE. LOW LEVEL STORM RELATIVE WINDS AND

LOW LEVEL ENVIRONMENTAL SHEAR ARE BOTH EXPECTED TO BE SOMEWHAT

LOW. THIS GENERALLY DOES NOT SUPPORT A STRONG TORNADO THREAT...SO

DESPITE STRONG INSTABILITY WILL KEEP THE TORNADO PROBABILITIES

LOW. THE PRIMARY SEVERE WEATHER HAZARDS WOULD BE THE POTENTIAL FOR

VERY LARGE HAIL AND DAMAGING DOWNBURST WINDS. OF COURSE THIS IS

ALL ASSUMING STORMS ARE ABLE TO INITIATE IN THE FIRST PLACE WHICH

IS THE PRIMARY FORECAST CHALLENGE.

THE MOST LIKELY SCENARIO IS FOR STORMS TO DEVELOP SOMEWHERE NEAR A

GAINESVILLE TO MINERAL WELLS LINE JUST BEFORE 00Z THIS AFTERNOON.

IF THE SHORTWAVE TROUGH HAS SUFFICIENTLY WEAKENED THE CAP AWAY

FROM THE DRYLINE...WOULD EXPECT THESE INITIAL STORMS TO INTENSIFY

RAPIDLY INTO SUPERCELLS AND BECOME SEVERE AND MOVE EAST-NORTHEAST.

ITS POSSIBLE THAT THIS ACTIVITY WILL REMAIN NORTH OF THE

METROPLEX...BUT IN THIS SCENARIO IT WOULD BE VERY CLOSE...SO THOSE

PARTICIPATING IN OUTDOOR ACTIVITIES THIS AFTERNOON AND EVENING ARE

ENCOURAGED TO HAVE SOME METHOD TO RECEIVE WEATHER WARNINGS AND

UPDATES. IF THE SHORTWAVE TROUGH MOVES NORTHEAST TOO QUICKLY THIS

AFTERNOON...WE MAY SEE CONVECTIVE ATTEMPTS ALONG THE DRYLINE

TRANSITION INTO ORPHANED/ELEVATED SHOWERS AS THEY MOVE EAST AWAY

FROM THE BOUNDARY.

BOTTOM LINE IS THAT THERE IS A THREAT FOR SEVERE STORMS THIS

AFTERNOON. BECAUSE THE PRIMARY FORECAST CHALLENGE IS WHETHER OR

NOT STORMS WILL BE ABLE TO DEVELOP WE WILL HAVE TO WAIT TO SEE HOW

THE DRYLINE LINES UP BEFORE SUBSTANTIALLY INCREASING OR LOWERING

POPS FOR LATE THIS AFTERNOON/THIS EVENING. WILL BE UPDATING THE

FORECAST QUICKLY IF ANYTHING CHANGES SIGNIFICANTLY IN THE

MESOSCALE ENVIRONMENT.

CAVANAUGH

[DoctorMu]

That sw trough has a target again.

[DoctorMu]

Happy Cinco De Mayo caliente

We areas N of I-10 may get de-CAP-itated a bit on Tuesday with a weak PAC front. Perhaps a nascent ULT later in the week.

THE UPPER RIDGE THAT HAS BROUGHT THE UNSEASONABLY WARM

TEMPERATURES IS EXPECTED TO LOSE SOME OF ITS AMPLIFICATION OVER

THE NEXT COUPLE OF DAYS AS A SERIES OF S/WVS TRAVERSE THE TOP OF

THE RIDGE. A PACIFIC COLD FRONT WILL SLOWLY CROSS SOUTHEAST TEXAS

TUES/WEDS. MOISTURE LEVEL INCREASE TO BETWEEN 1.5 AND 1.6 INCHES

JUST AHEAD OF THE FRONT SO FEEL SCATTERED SHRA/TSRA WILL DEVELOP

ALONG THE FRONT. A CAPPING INVERSION WILL LIMIT RAINFALL POTENTIAL

OVER THE SOUTH UNTIL WEDNESDAY WHILE AREAS NORTH OF I-10 SHOULD

SEE THE CAP BEGIN TO ERODE ON TUESDAY. THERE SHOULD BE A GAP IN

PRECIP ON THURSDAY AHEAD OF AN UPPER LEVEL TROUGH THAT WILL MOVE

TOWARD THE REGION THURSDAY NIGHT AND FRIDAY. THE GFS AND ECMWF ARE

IN UNUSUALLY GOOD AGREEMENT WITH THE TIMING AND POSITION OF THE

UPPER FEATURE. THE UPPER LOW SHOULD BE LOCATED BETWEEN JUNCTION

AND ABILENE BY FRIDAY MORNING. MOISTURE LEVELS WILL DEEPEN TO

AROUND 1.8 INCHES FRIDAY MORNING. UPPER LEVEL WINDS LOOK VERY

FAVORABLE AS THE JET SPLITS AROUND THE UPPER LOW. BOTH MODELS

PRODUCE SOME MODERATE RAINFALL TOTALS LATE THURSDAY NIGHT THROUGH

FRIDAY AFTERNOON. RAISED POPS TO CHANCE FOR THURS NITE/FRI. LOWER

HEIGHTS AND CLOUD COVER SHOULD LIMIT MAX TEMPS TO AROUND 80

DEGREES FOR THU-SAT. OVERNIGHT LOWS WILL ALSO TREND COOLER TOWARD

THE END OF THE WEEK. FOR TEMPS...SPLIT THE DIFFERENCE BETWEEN

GFS/ECMWF. 43

[Ed Lizard]

Marginally severe storm in Menard and McCullogh counties, raining into the Colorado River watershed.

[Srain]

A dying MCS is approaching SE TX from the W this morning and showers are possible along and S of I-10 early in the day. The 06Z WRF/NMM model is suggesting a breakable cap later this afternoon if skies can clear out a bit allowing temps to reach 90F and new storms fire in a 'cold pool' aloft across areas along and N of the I-10 Corridor. Those with afternoon outdoor plans may need to keep and eye to the sky for another round of heavy storms with frequent lightening near the Houston Metro should the cap break.

Looking ahead to Tuesday-Wednesday, a Pacific boundary drops into our area suggesting an increase in showers/storms, some possibly severe. The slow meandering cut off upper low will near the region from the W late Thursday with a increase of moisture and a return flow from the Gulf suggesting late week strong storms once again before we clear out and cool down rather significantly. Some guidance is even suggesting night time lows in the upper 50's for next weekend bring a rather big change temp wise. We'll monitor those trends as the week ahead progresses and we enter a more active weather pattern.

[bubba hotep]

FWD is noting a few heatburst and I think one of those would be cool to experience.

From the

DISCUSSION... /ISSUED 438 AM CDT SUN MAY 6 2012/

...AND WE HAVE EVEN NOTED A FEW HEATBURST EVENTS EARLIER.

and another interesting comment:

DIFFICULT FORECAST DUE TO THE ONGOING CONVECTION OVER THE HILL

COUNTRY WHICH...ACCORDING TO ALL MODEL GUIDANCE...SHOULD NOT BE

THERE.

Anyway, looks like the potential is there for a wild evening across the northern DFW burbs.

[Srain]

The over night guidance is rather good agreement for the week ahead and suggests plentiful rainfall for parts of the Lone Star State and particularly for those areas that are still in a severe drought situation in W Texas. The guidance has also trended a tad further N with the slow moving upper low ejecting from Old Mexico later in the week and may bring rain chances further inland as the week progresses for Friday into Saturday morning before shearing out and heading E. We will see if that late week trend continues.

[Srain]

Morning e-mail from Jeff:

Chances for showers and thunderstorms will be on the increase from this afternoon through the end of the week.

Quite upper level pattern for the past several weeks dominated by high pressure aloft has been transitioning to a more active pattern since last Friday. Ridging over SE TX is losing ground with the thermal profile improving aloft as the mid level capping which has kept convection at bay for the past several weeks weakens.

At the surface a fairly chaotic pattern is in play with numerous outflow boundaries from overnight thunderstorm complexes to our northwest moving toward/into the area. Additionally, there is likely a few boundaries leftover from the late afternoon storms yesterday over the northern portions of our area and the water vapor and IR images show a series of gravity waves moving SSW to S across central and SC TX this morning. On top of all of this, there is a moderately defined meso vorticity center (MVC) located upstream of the area over N TX from the overnight storm complex and a cold front over NW TX moving SE. Air mass across the region will become very unstable by mid afternoon due to surface heating with SB CAPE pushing into the 3000-3500 J/kg range and LI’s falling into the -2 to -4 range. Convective trigger temperatures have decreased from the 89-92 degree range yesterday into the 86-89 degree range for today based on the forecasted soundings for late this afternoon at College Station and IAH. Once trigger temperatures are achieved, expect thunderstorms to begin to develop along old boundaries and ahead/near SE moving N TX MVC. Lowest trigger temperatures and best chances for storms will be along and north of I-10 although short term rapid refresh guidance is suggesting southward moving activity late this afternoon could make it into the metro area before running against slightly more unfavorable capping south of I-10.

Forecasted soundings show the potential for a few severe thunderstorms this afternoon/evening where activity develops with wind damage being the main threat. General feeling is that the threat is too isolated for a regional slight risk outlook from SPC, but a few reports of strong/severe winds or hail will be possible.

Tues-Wed:

Upstream frontal boundary over NW TX currently, will progress southward and eventually off the TX coast by late Wednesday. Expect strong heating today along this boundary coupled with upslope ESE flow off the western Gulf toward the high terrain of NE MX to set off early evening severe thunderstorms. Models are in decent agreement with activity over both the Hill Country and NE MX this evening merging and growing upscale into a large thunderstorm complex (MCS). Favorable low level inflow off the western Gulf coupled with strong moisture convergence will likely maintain this complex well into the night and into Tuesday morning. Expect activity in some form to approach our western counties by early Tuesday morning, and either the complex itself or its outflow boundaries/MVC will arrive into the area on Tuesday sparking more widespread storms. Additionally the frontal boundary itself will move into the region adding an additional focus. With such an environment driven by the meso (small scale) features, there is plenty of room for the forecast models to either under or over estimate the amount of rainfall coverage. Forecasting will be highly driven by previous day events and small scale features nearly impossible to predict more than 12 hours in advance.

Thurs:

Brief break in the active weather on Thursday as drier air seeps into the area from the NE and the frontal boundary slips into the NW Gulf. I am very wary of the active SW flow pulling up our of MX and for any potential weak impulses that models are not seeing this far out…hence rain chances could be added to Thursday as we more through the week.

Fri-Sat:

Strong upper level storm system which will dig down into the Baja region today and Tuesday will eject ENE across N MX and toward TX Fri-Sat. Frontal boundary over the NW Gulf will begin to surge back north late Thursday as strong system nears the Mexican border. Suspect returning warm front may spark a round of thunderstorms Thursday night followed by the main event Friday-Friday night as the upper low moves across central TX. Fairly slow storm motion by the main system and tremendous moisture advection ahead of the feature is raising the red flags for heavy rainfall and potential flooding, especially given the several days of “wetting” rainfall that will be possible today-Wed. Severe weather will also be possible with this system, but it is still too far out to talk about the details just yet.

Rainfall:

Widespread rainfall amounts of 1-2 inches appear likely by late Wednesday aver the region, with some areas likely seeing much higher totals up to 4 inches possible. Grounds have dried over the past several weeks with the lack of rainfall and high temperatures, and much of the rainfall will go into saturating the soil although some local run-off problems may be possible especially under the higher totals. End of the week event is more concerning as totals begin to stack up and grounds become soggy saturated with time. Not overly confident at the moment on the placement of the heavy rainfall axis Fri-Sat with both the GFS and HPC showing most offshore with the ECMWF more inland. Think the inland solution is likely on the more correct track, but this is still 4 days away!

[wxmx]

Very similar pattern to the one in winter....good for W and S TX and Nern MX.

* Was going to change the thread subtitle, but I see Steve already did the job

[Srain]

FLOOD ADVISORY

NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX

651 PM CDT MON MAY 7 2012

TXC171-080200-

/O.NEW.KEWX.FA.Y.0043.120507T2351Z-120508T0200Z/

/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

GILLESPIE-

651 PM CDT MON MAY 7 2012

THE NATIONAL WEATHER SERVICE IN AUSTIN SAN ANTONIO HAS ISSUED AN

* URBAN AND SMALL STREAM FLOOD ADVISORY FOR...

EASTERN GILLESPIE COUNTY...

* UNTIL 900 PM CDT

* AT 648 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS HAVE

DETECTED THUNDERSTORMS WITH HEAVY RAINFALL ACROSS THE ADVISORY

AREA. DOPPLER RADAR ESTIMATED THAT 1 TO 3 INCHES OF RAINFALL HAS

OCCURRED OVER THE LAST TWO HOURS ACROSS THE EASTERN HALF OF

GILLESPIE COUNTY. AN ADDITIONAL INCH OF RAIN CAN BE EXPECTED

OVER THE NEXT ONE TO TWO HOURS.

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE MINOR FLOODING TO

OCCUR...ESPECIALLY ALONG SMALL STREAMS AND NEAR LOW WATER

CROSSINGS. SOME LOCATIONS THAT WILL EXPERIENCE MINOR FLOODING

INCLUDE...FREDERICKSBURG...ALBERT...BLUMENTHAL...CAIN CITY...

CRABAPPLE...ECKERT...GRAPETOWN...LBJ STATE PARK...LUCKENBACH AND

ROCKY HILL.