Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 5

[Srain]

The overnight medium/long range guidance is beginning to advertise a rather strong upper low moving inland along the California Coast next week and traversing rather far S across Arizona and New Mexico toward the end of next week. With a return flow becoming established by next week across our Region and possibly some deep tropical moisture moving NW from the Western Caribbean, there may be a potential for some heavy rainfall and stronger storms developing near the 10^th, +/- a couple of days. There are indications that below normal temps will continue into the mid May time frame as that slowly moving storm system passes off to the E. We will see.

 

 

 

 

 

[Ed Lizard]

I'm trying to look for a silver lining to this miserable Spring without much rain (IMBY, anyway) and no fun-derstorms.

The cold shelf waters never really socked us in, returning airmasses never had time to get juicy enough between frontal passages.

What if cold shelf waters heading into sea breeze season, which sort of starts in a few weeks, increases the temperature contrast between the sun baked generally bone dry land, and the cool Gulf waters, and provides sharper sea breeze boundaries moving in shore.

No idea if it works like that, actually, but I can't help my naturally optimistic nature.

[wxmx]

Even Monterrey should see lows in the upper 40s (9°C).

 

Advection is hitting hard as temps continue their day-long slide in CLL.  Impressive wind gusts to 35-40 mph.

Bottomed at 12C (54F)...impressive for May, but a few degrees above forecasted...and no low record.

[DoctorMu]

Bottomed at 12C (54F)...impressive for May, but a few degrees above forecasted...and no low record.

 

Despite a plummeting dewpoint we got stuck in the mid-40s during the dead of night and never reached the upper 30s as it could have if the wind had died down just a little.  43°F was the official low.  About 42°F tonight, although outlying areas, Conroe and NW Harris could see some upper 30s...breaking a few records.

[DoctorMu]

Conroe hit a nadir of 35°F last night.  We tied the record in CLL...and IAH set a record of 42°F.  

 

SW winds are bringing a rapid turnaround in temps.

[Srain]

The cool and pleasant weather of this weekend will begin to transition to that of warmer temps and E to SE winds off the Gulf by Tuesday. Increasing moisture will be the theme during the second half of the week as a slow moving storm system moves across Mexico and into Texas by next weekend bringing increased rain and storm chances for the second weekend of May.

 

 

 

[Ed Lizard]

GFS and Euro seem to agree less boring weather late week into weekend, with 0Z GFS somewhat happier for SETX.

[Srain]

Morning e-mail from Jeff:

 

Record cold for the last 4 days is ending. All time May monthly low temperature record was established Saturday morning at BUSH IAH of 42 degrees breaking the old record of 44. The 42 is the coldest low temperature ever recorded in the month of May. Surface high pressure responsible for the record cold is starting to shift eastward and this will allow winds to gradually veer around to the ESE and SE today. Very dry air mass in place will begin to moisten by the middle of the week as SE winds bring Gulf moisture into the state. Blocky pattern aloft currently with a large upper level storm over the SE US and the other off the CA coast will break down allowing the CA system to move inland and into the SW US.

 

This pattern will result in an increasingly SW flow aloft over the state by Thursday. Disturbances in the SW flow aloft along with increasing Gulf and Pacific moisture will result in slight rain chance son Thursday especially west of I-45 where moisture will be greatest. Ingredients appears to be coming together for a fairly active period of weather Friday-Saturday night. Slow moving cold front will be entering into central TX late Thursday and expect widespread convection along this boundary possibly entering into portions of SE TX on Friday. Continued moistening and heating of the air mass on Friday ahead of the slow moving cool front and approaching upper level disturbances from the SW spell a round of wet weather. Air mass will become increasingly unstable during the day with weak cap likely being removed by early to mid afternoon suggesting storms developing in the afternoon hours.

 

Cool front and continued disturbances crossing the area into Saturday with fairly high rain chances. Will have to see how Friday afternoon/evening weather plays out and this may have a somewhat big impact on Saturday storm development. Current model projections indicate this as a slow moving weather system with multiple rounds of strong to severe storms possible with heavy rainfall. Not favoring any area over another with respect to heavy rainfall potential at this point given the highly meso scale nature of the upcoming events. Think the frontal boundary will act as a decent focus for storms. Widespread amounts of 1-2 inches appear likely from late Thursday through early Sunday, but some significantly higher totals will be possible under any areas where cell training develops.

 

Cold front should move off the coast on Sunday with drier air filtering in from the north, but this air mass is not anywhere close to the intensity of the pass several fronts and do not see records lows behind this front…maybe summer is finally on its way!     

 

 

 

[Srain]

Morning e-mail from Jeff:

 

Moisture is on the increase across the region ahead of the next slow moving storm system currently over the SW US.

 

Blocky upper air pattern over the US is starting to break down with storm systems on both coasts and high pressure through the center of the nation. The pattern has broken and shifted enough to allow Gulf moisture to begin to return to the state of TX as clearly noted by the increase in surface dewpoints (into the 60’s) compared to the past several days in the 30’s and 40’s. Large upper level storm over the SW US will only slowly move eastward and then stop over the weekend and possibly drift back W late in the weekend as upper level ridging builds over the top of the low across the northern Rockies. The position of the upper level storm has increased the SW flow aloft over TX and upstream water vapor images show a plume of mid and high level moisture advancing toward Baja from the Pacific. It is likely that this plume of moisture also represents a few disturbances aloft that will cross MX and enter TX over the next 24-48 hours.

 

Ingredients are slowly coming together for a fairly active period of weather from late Thursday through potentially late Saturday. Will be clear up front that while the upper level pattern is slow moving, the meso scale influences will play a big part in the weather over the next several days. Air mass will continue to moisten with PWS rising to near 1.5 inches by late Thursday and the upper level jet splitting over S TX as the sub-tropical jet cores into the region. Heating over SW and C TX on Thursday along with a disturbance or two pulling out of MX and across the dryline will help to focus thunderstorm activity along the dryline and approaching frontal boundary over the Hill Country Thursday afternoon and evening. Shorter term models which barely reach this time period suggest a complex of storms developing between Midland and DFW and tracking ESE into SE TX overnight before weakening. Depending on how far south and how strong these storms are will help determine what happens on Friday. Heating of the unstable air mass on Friday should result in the development of numerous thunderstorms both along outflow boundaries from previous day storms, the frontal boundary sagging into the region from the north, and disturbances moving out of MX. PWS rise to near 1.5-1.7 inches on Friday and this will support a heavy rainfall threat especially along any slow moving boundaries or within locations of cell training. There will also be a severe weather threat with a fairly unstable air mass and modest shear. Main threats will be wind damage and large hail.

 

Expect Friday afternoon/evening convection to work over the air mass and deplete local moisture requiring air mass recovery on Saturday. Frontal boundary will be slowly moving across the region on Saturday and if the area can heat and recover from the previous day storms, may see another round on Saturday afternoon. Current thinking is that this round may be focused more near the coast or even offshore, but way too hard at this point to try and determine such fine scale details.

 

Looking at a promising 1-2 inches of rainfall from late Thursday through early Sunday across the region. Factors will be in place to support heavy rainfall including high moisture levels, slow moving low level boundaries, and potential cell training. Meso scale nature of the event will dictate on a short term hour by hour basis where the heaviest rains will fall, but would not be surprised to see a few locations total 3-5 inches in the time period.   

 

Very little air mass change with this weak front so the warm and muggies will be around for a while.

 

[Srain]

E-mail from Jeff:

Very active 48-72 hours expected across the state as a slow moving upper level low and cool front combine with increasing Gulf and Pacific moisture.

 

Upper level storm system over the SW US has stalled out this morning with a strong connection of sub-tropical moisture plume from the central Pacific NE across MX into C TX on the south and east flank of this system. A weak cool front is over NW TX and just ahead of this feature severe thunderstorms have developed in the last hour near Brownwood, TX. Pattern over the next few days will be highly meso scale driven with multiple storm complexes moving across the region while the upper level pattern remains nearly unchanged. With the upper level storm remaining to our west broad upper air divergence will be maintained for the next 72 hours helping to vent surface convection. Frontal boundary will only slowly move toward the coast under the help of outflow boundaries and should limp to the coast by early Sunday.

Main concerns are timing of storms, rainfall amounts, and the severe weather threat.

 

Timing:
Appears in water vapor images that a disturbance is crossing the Rio Grande currently and should progress eastward this afternoon. Short term models blow up convection over C TX and our NW counties this afternoon into the evening hours and progress it E into E TX as a linear line or MCS. I am wary of the southward trailing outflow boundary however which appears to reach toward I-10 this evening and overnight as this could support additional slow moving storm development further south. Question appears to be with the intensity of the capping along and south of I-10 and at this time it appears that the capping will hold convection over these areas in check this evening.

Numerous boundaries will likely be in place early Friday and once heating onsets, expect thunderstorms to once again fire off with the approaching frontal zone and additional disturbances out of MX. Hard to exactly pin down the best time or location for development, but will aim for the central counties roughly from Columbus to Conroe during the afternoon hours with storms then drifting into the metro area and southern area in the evening hours.

 

Saturday is even more of a wild card as the air mass begins to become worked over and boundaries near the coast. Could see heavy rains and storms focus near the coast or offshore although several models develop more convection near the lagging 850mb front further inland. A lot is going to happen between now and Saturday and the forecast for Saturday is highly dependent on the next 24-48 hours of weather.

 

Heavy Rainfall:
Moisture levels are on the increase this morning with 1.4 inch PWS over the NW Gulf moving onshore. Mid and high level moisture is also noted over MX streaming toward TX. PWS are forecast to increase into the 1.5-1.6 range on Friday which is in the 75-90 percentile for early May. Potential for slow moving and training storms along boundaries will be increasing as there will be little movement of the main upper trough and good upper level divergence over the next 72 hours. Storms will focus on the boundaries. Feel the models are likely not handling he meso scale situation overly well nor the placement of activity as this is nearly impossible to predict more than a few hours out in time. Given moisture levels, excessive rainfall rates will become increasingly likely under the stronger storms with rates approaching 2.0 inches per hour possible. Widespread amounts of 1-3 inches appear likely between this afternoon and early Sunday with isolated amounts of 4-5 inches. Some flooding is possible with this type of pattern.

 

Severe Weather:
Recent short term models have suggested an increase in the severe threat for a larger part of SE TX this afternoon. Some of this is currently being driven by the formation of severe storms over W/C TX currently. Cloud cover over the region should keep instability on the lower side today along with the mid-level warm nose however should storms to our NW form into an MCS a threat for strong winds would be possible this afternoon north of I-10. Severe threat on Friday is conditional on the events today and tonight. Little change in the air mass would seem to support a risk of additional severe storms with hail and wind being the main threats. However, if an outflow boundary undercuts the unstable surface layer this could mitigate some of the severe weather threat on Friday. Once again I stress that meso scale influence will play a big role in developments over the next 1-3 days.

 

SPC Outlooks for Today and Friday:

 

Today:

 

Friday:

 

 

[Ed Lizard]

Don't think I've had a 50 knot wind gust at my house in 4 1/2 years.

 

[DoctorMu]

AggieDome in serious jeopardy this afternoon:

 

[DoctorMu]

Pea to small marble size hail in this cell.  First truly substantial rain since April 2 (1.15 in) and March 10 (1.25 in).

[Ed Lizard]

Just sprinkles IMBY.

[andyhb]

Two tornado warnings now in effect on the supercells back in South Central TX.

[andyhb]

Fredericksburg in the path of that lead tornado warned cell.

[Srain]

E-mail update from Jeff:

A band of intense…at times…severe thunderstorms have developed over Fort Bend, southern Harris, and southern Liberty Counties as a result of overnight outflow boundary settling southward. Extensive thunderstorm complex to our N and E overnight has produced a large area of 2-5 inches of rainfall. In the last 1.5 hours HCFCD Flood Warning gages and radar indicates 2-3 inches of rainfall over SE Harris County from The Medical Center to Baytown. Significant street flooding is likely under the band of slow moving thunderstorms with several gages reporting over 1.0 inch in 15-minutes.

 Favorable low level inflow off the western Gulf of Mexico continues to supply a rich feed of moisture into the southern and western flank of this complex as it has all night long allowing the continued development of cells on the SW flank which then train ENE. An additional 1-3 inches of rainfall will be possible in the next hour along this band of storms with storm totals nearing 3-4 inches.

 Be aware of high water on streets for the morning commute.

[Srain]

Another update from Jef:

NWS has issued a Flash Flood Watch for the following counties in SE TX: Grimes, Polk, San Jacinto, and Walker through this afternoon.

 Overnight complex of training and slow moving storms from Huntsville to Lake Livingston has produced 4-6 inches of rainfall. Next well defined disturbance over SW TX has already fired off a complex of thunderstorms and this complex will be moving toward SE TX today. Short term models have been under-estimating to amount of development and rainfall amounts thus far and appear to be off on the slower timing of the next round of weather coming in from the west. With grounds saturated over our northern counties and run-off still in progress from the overnight rains, additional heavy rainfall will quickly lead to flooding and rises on area watersheds.

 Guidance and HPC progs appear way too low on the forecasted rainfall amounts as this air mass is very capable of 2-4” per hour if not more. With numerous low level boundaries in place and a frontal boundary sinking in from the north corridors of cell training and excessive rainfall seem likely this afternoon into tonight. Easily 2-3 inches of rainfall under these bands with isolated amounts up to 5-6 inches and possibly locally higher.

 This watch may be extend and expanded to include more of the area later this morning or this afternoon.

[Srain]

Update from Jeff:

Next disturbance is quickly approaching the area this morning.

Thunderstorm complex currently crossing I-35 moving E at 40mph along and ahead of the next disturbance ejecting out of the upper level low stalled over the SW US. Recently thunderstorms have begun to once again develop from Brazos County and the College Station area SW toward this complex possibly along an old outflow boundary from the overnight activity. These newly developing storms are showing slow storm motions and this is over an area that was hit hard yesterday…so it is not going to take much rainfall to cause problems.

Southward the complex along I-35 will continue east into a moist and unstable air mass over the western sections of SE TX where dewpoints are in the lower 70’s and PWS in the 1.5-1.7 inch range. Two large supercells on the southern flank of this line continue to have a large hail and wind damage threat and radar and satellite images show rotation within the main rain shield suggesting a meso low has developed with this system and is helping in the downstream lifting of the air mass. Appears our local air mass is still primed and ready to go given recent development across an area that was heavily worked over last night. This is likely due to the fact that the feed of moisture off the Gulf has yet to be disrupted by storm complexes that have remained north of I-10 and not affected the coast counties much. Feel that this complex will maintain its intensity and possibly intensify some over the next 1-3 hours as it enters our western counties. This may enhance the severe weather threat across the region late this morning.

As far as the heavy rainfall threat goes…there has been little to no change in the air mass and the concern continues to be cell training with excessive rainfall rates. Next few hours will favor areas north of a Navasota to Conroe to Livingston line and then the entire area late this morning as the next complex arrives. Forward motion with this approaching complex is 30-40mph and there does not appear to be a significant amount of cell regeneration on its SW flank so the complex is progressively passing a location and not training over the same areas. Moisture levels continue to pool highly over the region along both outflow boundaries and later today and approaching frontal boundary. Similar rainfall rates to what has been experienced seems likely with the next few rounds of storms, but it is impossible to determine where the training may set up.

Meso models have become of little use as they nor the global systems are handling the ejecting disturbances well. Models really hammer the area again tonight, but this current complex approaching may in fact finally stabilize things some and hold back development this evening/overnight. With that said, the incoming next short wave does look potent and I suspect the current complex will move more ESE and not SE allowing the persistent Gulf feed to be maintained and a quick recharging of the air mass.

[Srain]

MESOSCALE DISCUSSION 0621
   NWS STORM PREDICTION CENTER NORMAN OK
   0843 AM CDT FRI MAY 10 2013
  
   AREAS AFFECTED...MIDDLE AND UPPER TX COASTAL PLAIN
  
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
  
   VALID 101343Z - 101415Z
  
   PROBABILITY OF WATCH ISSUANCE...60 PERCENT
  
   SUMMARY...ISOLD LARGE HAIL POTENTIAL MAY AFFECT THE MIDDLE AND UPPER
   TX COASTAL PLAIN.  A SEVERE WATCH DECISION WILL LIKELY NEED TO BE
   MADE BY 14Z OR SO.
  
   DISCUSSION...RADAR MOSAIC SHOWS A DIFFUSE CLUSTER OF EWD MOVING
   STORMS FROM 20 MI E SAT TO 20 MI WSW UTS.  AN OUTFLOW BOUNDARY
   EXTENDS FROM THE TRAILING EDGE OF THE LA MCS WWD TOWARDS THE STORM
   OVER WILSON COUNTY.  THE STORMS ALONG AND N OF THE BOUNDARY ARE
   LIKELY ROOTED AT THE TOP OF THE BOUNDARY-LAYER ON THE NERN PERIPHERY
   OF AN UNCONVECTIVELY-MODIFIED EML PLUME OF VERY STEEP LAPSE RATES
   SAMPLED BY THE 12Z CRP RAOB.  ADEQUATE MID LEVEL FLOW /40 KT AT KEWX
   AND KHGX AT 6 KM AGL/ WILL ACT TO SUPPORT UPDRAFT ORGANIZATION.  AS
   SUCH...A LARGE HAIL THREAT MAY DEVELOP/INCREASE AS THE STORMS MOVE
   EWD AND IMPACT THE MIDDLE TO UPPER TX COASTAL PLAIN THROUGH THE
   MORNING HOURS.
  
   ..SMITH/CARBIN.. 05/10/2013
  
  
   ATTN...WFO...HGX...CRP...EWX...
 

 

[Srain]

[DoctorMu]

Impressive rains this am just south of CLL in a line from Navasota to Huntsville.  3.5 in IMBY so far

 

Storms may form over the same area this afternoon.

[DoctorMu]

Two tornado warnings now in effect on the supercells back in South Central TX.

 

We had some hail (marble size) and possibly slight rotation in CLL last night.  Everything was rain wrapped - no substantive observations possible.

 

The south end of CLL saw dime size hail last night.  Uprooted trees reported in Madisonville.  

[Ed Lizard]

Only 0.5 to 1" IMBY by radar, but I think there is a boundary near I-10 between SAT and HOU, stuff is trying to develop already, and SETX may not have to wait for the stuff in the Western Hill Country, which HRRR puts into I-35 corridor during the evening.

 

I think I see it on satellite.  It extends West of SAT, where I'd think instability is higher, but its getting active near and East of SAT.

 

Juicy stuff looks bottled up South of a boundary CRP to LRD.  Capping probably stonger there, but if it breaks down there in an unperturbed airmass.  Could be good times.  Deep STX outside SPC risk area, stout cap on CRP sounding, but 4620 J/Kg MUCAPE at 7 am (~2600 J/KG ML),   With 50 knots 0-6 km shear.

 

Like I said, low odds but high rewards on exciting times.

 

 

[DoctorMu]

Some severe cells lined up along I-35 heading East.

 

[Ian]

60 years since Waco: http://www.ustornadoes.com/2013/05/11/may-11-1953-waco-f5-monster-from-the-skies/

[Ed Lizard]

60 years since Waco: http://www.ustornadoes.com/2013/05/11/may-11-1953-waco-f5-monster-from-the-skies/

  Thanks, Ian.

[wxmx]

Reporting back from the land of feast or famine.

 

After having received no more than 2" of precip from Oct thru April, we are approaching 4" for today, and 5.5" since Friday. We are probably still short 1 more inch before this event is over. It will be a fun commute.

[DoctorMu]

This are firing up in W Texas along the trough...could be in the Hill Country later tonight.  Hoping for another 0.5-1 in in CLL.  Storms only have limited risk of becoming severe with maybe some hail.

 

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
837 PM CDT TUE MAY 14 2013

.UPDATE...
EVENING FORECAST UPDATE.

&&

.DISCUSSION...
SHORT WAVE TROUGH MOVING INTO W C TX WITH A LINE OF STRONG/SEVERE
STORMS SHOULD PUSH EAST THROUGH THE NIGHT. WRF-ARW AND TX TECH WRF
ARW BOTH SEEM TO BRING LINE OF STORMS FROM W C TX INTO THE HILL
COUNTRY AND TOWARDS SE TX BY 12Z WED. STORMS SEEM TO WEAKEN AS
THEY APPROACH THE CWA. OVERALL THINK POPS/WX ON TRACK BUT STILL A
LOT OF UNCERTAINTY ON HOW CONVECTION WILL EVOLVE. SOUTHERLY WINDS
SHOULD REMAIN OVERNIGHT WITH A 30-40KT LLJ. BUMPED MIN TEMPS UP A
COUPLE OF DEGREES GIVEN SFC DEWPOINT TEMPS IN MID 60S AND WINDS
REMAINING CLOSE TO 7-10KTS.

AS FOR ANY SEVERE THREAT...LOOKS LIKE INSTABILITY WILL BE RATHER
LIMITED WITH CAPE AROUND 500-1000 J/KG. WIND SHEAR WILL BE ENOUGH
FOR AT LEAST MORE ORGANIZED MULTICELLS BUT STORMS WILL LIKELY BE
PULSE STRONG STORMS GIVEN WEAK INSTABILITY. STRONGEST STORMS MAY
PRODUCE SOME SMALL HAIL AND GUSTY WINDS BUT NOT REALLY SEEING EVEN
A LOCALIZED SEVERE THREAT.

39

[Srain]

DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0734 AM CDT WED MAY 15 2013
  
   VALID 151300Z - 161200Z
  
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
   PARTS OF TX...
  
   ...SYNOPSIS...
  
   A SPLIT-FLOW PATTERN WILL PREVAIL OVER THE CONUS THROUGH THE D1
   PERIOD WITH THE PRIMARY FEATURE OF INTEREST BEING A
   SUBTROPICAL-BRANCH SHORT-WAVE TROUGH WHICH WILL EVOLVE INTO A CLOSED
   LOW OVER THE SRN PLAINS TODAY.  MEANWHILE...THE POLAR BRANCH OF
   WESTERLIES WILL REMAIN MORE ENERGETIC WITH AN EMBEDDED SHORT-WAVE
   TROUGH OVER THE UPPER GREAT LAKES AND ONTARIO ALSO EVOLVING INTO A
   CLOSED MIDLEVEL CIRCULATION OVER QUEBEC LATER IN THE PERIOD.
  
   IN THE LOW LEVELS...A SURFACE CYCLONE ASSOCIATED WITH THE LATTER
   DISTURBANCE MENTIONED ABOVE WILL DEVELOP FROM LAKE HURON INTO THE
   CANADIAN MARITIMES WHILE A TRAILING COLD FRONT SHIFTS EWD THROUGH
   THE LOWER GREAT LAKES AND NEW ENGLAND.  THIS BOUNDARY WILL STRETCH
   WWD THROUGH THE OH...MID-MS...AND LOWER-MO VALLEYS BEFORE LINKING
   WITH A LEE CYCLONE OVER THE CNTRL HIGH PLAINS.  BY THIS
   AFTERNOON...A DRYLINE OR LEE TROUGH WILL EXTEND FROM THE CNTRL
   PLAINS LEE CYCLONE SWD TO A SECONDARY LOW DEVELOPING OVER WRN TX AND
   INTO WRN PARTS OF THE EDWARDS PLATEAU. 
  
   ...SRN PLAINS THIS AFTERNOON INTO TONIGHT...
  
   LATEST MODEL GUIDANCE INDICATES A COMPLEX SITUATION TODAY WITH
   MULTIPLE TSTM REGIMES FORECAST.  ONGOING STORMS FROM THE TX HILL
   COUNTY TO THE LOWER TX COAST APPEAR TO BE ASSOCIATED WITH A COUPLE
   OF VORTICITY MAXIMA WHICH HAVE BEEN EMITTED FROM THE UPPER LOW OVER
   NRN MEXICO.  THIS ACTIVITY WILL CONTINUE EWD THIS MORNING AND LIKELY
   REMAIN SUB-SEVERE.  RENEWED TSTM DEVELOPMENT WILL BE POSSIBLE THIS
   AFTERNOON IN THE WAKE OF THESE INITIAL STORMS /MAINLY E OF THE I-35
   CORRIDOR/ WHERE INCREASED DCVA ATTENDANT TO THE UPPER TROUGH
   INTERACTS WITH A MOIST...DESTABILIZING ENVIRONMENT.  THE
   JUXTAPOSITION OF MID AND HIGH-LEVEL WIND MAXIMA WITH A 30-35 KT LLJ
   WILL RESULT IN SUFFICIENT VERTICAL SHEAR FOR ORGANIZED STORMS
   INCLUDING SUPERCELLS CAPABLE OF A COUPLE OF TORNADOES AND DAMAGING
   WINDS.  THE PRIMARY UNCERTAINTY AT THIS JUNCTURE IS THE DEGREE OF
   INSTABILITY THAT DEVELOPS OWING TO THE POTENTIAL FOR LINGERING
   CLOUDS/PRECIPITATION.  A SWD/SEWD EXTENSION OF THE CURRENT SLIGHT
   RISK AREA MAY BECOME NECESSARY WITH THE NEXT UPDATE TO THE D1
   OUTLOOK.
  
   COMPARATIVELY HIGHER CONFIDENCE EXISTS IN THE DEVELOPMENT OF
   SURFACE-BASED TSTMS LATER THIS AFTERNOON ALONG THE DRYLINE OVER NWRN
   TX.  HERE...STRONG HEATING WEST OF THE DRYLINE WILL COMBINE WITH A
   VORTICITY MAXIMUM ROTATING AROUND THE PARENT UPPER LOW TO FOSTER
   STORM DEVELOPMENT WITHIN A MODERATELY UNSTABLE AIR MASS WITH MLCAPE
   OF 1000-2500 J/KG.  FORECAST HODOGRAPHS EXHIBIT A PRONOUNCED VEERING
   OF WINDS WITH HEIGHT AND 40-45 KT OF DEEP-LAYER SHEAR WHICH WILL
   SUPPORT SUPERCELLS INITIALLY WITH A RISK FOR VERY LARGE HAIL AND
   PERHAPS A BRIEF TORNADO.  RELATIVELY WEAK ANVIL-LEVEL WINDS AND A
   MODERATELY DEEP PBL WITH SIZABLE T-TD SPREADS WILL PROMOTE COLD POOL
   GENERATION AND THE POTENTIAL FOR ORGANIZATION OF STORMS INTO A
   SEWD-MOVING MCS /BOW ECHO -- AS SUGGESTED BY SOME
   CONVECTION-ALLOWING MODEL GUIDANCE/.  DAMAGING WIND GUSTS WOULD
   BECOME THE PREDOMINANT HAZARD WITH THIS CONVECTIVE MODE TRANSITION.
  
   FINALLY...STORM INITIATION ALONG THE SERRANIAS DEL BURRO RANGE IS
   POSSIBLE THIS AFTERNOON WITHIN A MOIST...LOW-LEVEL UPSLOPE REGIME.
   SUFFICIENT INSTABILITY AND VERTICAL SHEAR WILL EXIST FOR SUPERCELLS
   WHICH COULD POTENTIALLY IMPACT PARTS OF THE EDWARDS PLATEAU AND THE
   BRUSH COUNTRY WITH A RISK FOR HAIL AND DAMAGING WINDS THIS EVENING
   INTO TONIGHT. 
  
   ...UPPER-OH VALLEY INTO MID-ATLANTIC STATES THIS AFTERNOON AND
   EVENING...
  
   STRENGTHENING WLY FLOW IN THE 700-500-MB LAYER WILL PROMOTE THE EWD
   ADVECTION OF AN EML ACROSS THE REGION TODAY...ALONG THE SRN FRINGE
   OF THE PROGRESSIVE UPPER-LEVEL SYSTEM MOVING THROUGH ERN CANADA.
   THESE LAPSE RATES WILL COINCIDE WITH A MOISTENING...PRE-FRONTAL
   BOUNDARY LAYER TO YIELD AFTERNOON MLCAPE VALUES APPROACHING 500-750
   J/KG.  CAPPING AT THE BASE OF THE EML AND THE DISPLACEMENT OF
   STRONGER MIDLEVEL HEIGHT FALLS/FORCING FOR ASCENT FROM THE SURFACE
   FRONT CAST UNCERTAINTY ON SURFACE-BASED STORM DEVELOPMENT LATER
   TODAY. 
  
   SHOULD SURFACE-BASED TSTMS DEVELOP AND BECOME SUSTAINED...THE
   COMBINATION OF THE STEEP LAPSE RATES AND VERTICALLY VEERING WIND
   PROFILES WITH 40-50+ KT OF NWLY DEEP-LAYER SHEAR WILL BE SUPPORTIVE
   OF ORGANIZED STORM MODES WITH A RISK FOR DAMAGING WINDS AND SEVERE
   HAIL.  OTHERWISE...A MARGINAL HAIL THREAT WILL EXIST WITH ELEVATED
   TSTMS MOVING ACROSS THE LOWER GREAT LAKES THIS MORNING.
  
   ...LOWER-MO/MID-MS VALLEYS THIS AFTERNOON AND EVENING...
  
   THE NRN EXTENSION OF THE WARM CONVEYOR BELT ASSOCIATED WITH THE SRN
   PLAINS UPPER LOW WILL ENHANCE THE NWD FLUX OF AN INCREASINGLY MOIST
   BOUNDARY LAYER INTO THE REGION TODAY...ALONG AND SOUTH OF THE
   STALLED SURFACE FRONT.  THIS MOISTURE WILL COMBINE WITH DAYTIME
   HEATING AND STEEP MIDLEVEL LAPSE RATES TO YIELD AFTERNOON MLCAPE
   VALUES APPROACHING 1000-2000 J/KG. WHILE LARGE-SCALE FORCING WILL
   REMAIN NEGLIGIBLE...LOW-LEVEL CONVERGENCE ALONG THE FRONT WILL BE
   SUFFICIENT TO INITIATE WIDELY SCATTERED TSTMS LATER TODAY...THE MOST
   INTENSE OF WHICH WILL BE CAPABLE OF LOCALLY STRONG WIND GUSTS AND
   PERHAPS SOME HAIL.  A MORE ROBUST SEVERE WEATHER THREAT WILL BE
   LIMITED BY WEAK VERTICAL SHEAR.
  
   ..MEAD/MOSIER.. 05/15/2013