TX / South Severe Threat (Sun PM through Tuesday)

[jeff]

Upper ridging over TX will break down as potent S/W off the CA coast moves into N Mexico over the next 24 hours.

Low level Gulf moisture will begin returning late Sunday across TX with enough of a surge up the Rio Grande into W TX for 500 J/kg of CAPE by late afternoon over the TX plains and E NM. Large scale ascent will spread into W TX by late afternoon with forcing and moisture sufficent for thunderstorm formation. Lack of good instability will result in only one or two hailers.

Sunday Night:

Strong WAA regime develops over C and SE TX into developing cyclone over SE CO and NE NM. 30-40kt 850mb LLJ will tranport 1.30 in PWS into C TX atop low level cool air mass in place. Strong isentropic ascent coupled with strong WAA at 850mb and increasing large scale ascent should support scattered to numerous elevated thunderstorms overnight from C into N TX. Storms will be capable of hail with some severe.

Monday:

Rapid air mass modification is forecast over SE and E TX into much of LA as surface high pushes E and strong return flow into OK cyclone develops. 30-40kts LLJ will transport PWS of 1.3-1.5 in into the region. Surface dewpoints climb into the mid to upper 60's and a surface warm front will push into EC TX and then extend back ESE toward N.O. by Monday afternoon. Warm sector will become unstable by mid afternoon supported by WAA and breaks in the OVC. Forecast ETA CAPE of 2000 J/kg and LI's in the -4 to -6 range with little capping support thunderstorm formation along and ahead of SE moving frontal boundary late Monday into Monday night. Strong large scale ascent and Q-vector convergence along with decent low level lift along the front and a 30kt low level inflow should be more than enough to develop and keep storms going.

It should be noted that degree of air mass modification may be slightly overdone within the guidance due to current cold front penetration deep into the GOM. Return flow may be modfied and re-circulated air from the SE US and not true rich Gulf air. This could limit overall instability and severe threat. However should the models be correct with near 70 degree dewpoints by late Monday evening an upgrade to a mod. risk for a portion of the slight risk area may be needed given favorbale shear profiles and long curved hodographs.

A more widespread severe threat may exists Tuesday into Wednesday across the C and E Gulf states where rapid influx of rich Gulf moisture and strong dynamics comes into play. Additional very heavy rainfall and severe weather can be expected from MS into GA during this time frame. Potential does exists for a mod. risk during this period over MS into AL given very favorable shear profiles and rich low level moisture.

Will watch with interest next few model runs across TX and LA. Typical story the last 4-6 weeks has been for an active event forecasted 1-3 days in advance only to vanish as the time draws near. Dry conditions have developed over most of TX into parts of SW and S LA where rainfall for March and April are running 1-4 inches below normal. DFW has only recorded .13 inches of rain for Apr and if this holds through this week it would become the 2nd driest Apr on record. Drought conditions are gradually developing N from deep S TX into SC and NC TX and slowly E into SE and E TX. However rainfall surpluses in Feb across most of E TX are slowing the effects of the current dry streak and most lakes E of I-35 remain near 95-100% of storage capacity with streama conditions near normal.

[gboudx]

The DFW NWS seems like they want to get excited about our rain chances tomorrow night into Monday, but they admit they've been burned the past few times. I'll report on whatever weather we experience.

[Yankeegirl]

Is that stupid cap still sitting over the Houston area? I am about to the point, when it rains and I see it, then I will believe it! lol...

[Huckster]

The event on Friday afternoon did finally bring some storms to southcentral Louisiana, although rather isolated. It began with a severe storm that moved southeasterly from central Louisiana, and it dropped 1.75 inch hail near Alexandria. Since skies were rather clear, and the storm was pretty isolated, I decided to take a ride on I-10 toward Lafayette (I am in Baton Rouge) to get a better look. It was very impressive indeed, the storm's structure. Conditions were clear around the storm, and the only clouds were basically just the storm and its anvil...nice, crip structure, sun behind it, amazing contrast...not often seen with springtime storms in this area. The storm seemed to split just before sunset, with the weaker storm going toward the east or east south east and the stronger storm going toward the south southeast. I decided not to venture any farther west since I was about to cross the Atchafalaya swamp (the "Spillway" as it is known around here), and there are not really any places to seek shelter. The interstate is completely elevated from basically Ramah, LA to just east of Lafayette. When I got home, I checked the radar and it looked like the storm probably dropped some hail in St. Martin Parish or far western Iberville Parish, so I am glad I did not continue any farther west than I did. Anyway, I said all that just to say this, as far as I can tell, these were the first really severe thunderstorms in the southcentral Louisiana area since this active pattern began in March. So, hopefully the rains will come again, and with more coverage to southern Louisiana and Texas. I am sick of droughts and floods. Can't we just go back to a healthy weather pattern?

[jeff]

Million dollar question this morning is degree and quality of Gulf moisture return into E TX and LA tonight into Monday.

Surface data shows rich moisture confined deep to the southern Gulf and BOC roughly south of a line due E of Tampico Mexico.

Strong surface cyclone will develop over SE CO ahead of potent shortwave. Cyclone will deepen and drop SE into the C Red River valley by late Monday with trailing dryline along the I-35 corridor. 30-40kt LLJ will transport Gulf moisture northward although it is questionable if juicy air gets into E TX. The ETA seems to be overdoing the moisture return considering winds are still NE over SE TX and SW LA.

Regardless, it is expectd for at least low to mid 60 degree dewpoints to surge into SE and E TX early Monday supporting CAPE values of 1500-2000 J/kg by mid afternoon. Capping will be maintained through the early part of the day considering SSW 800 to 750mb flow off of the hot higher elevations of Mexico. Decent heating within low level WAA should be enough to break the cap along with favorable lift and large scale ascent with approach of a jet streak by late afternoon.

NOTE: Quality of moisture return is extremely important. Low to mid level shear profiles are extremely favorable for long lived supercells and if moisture return was not in question a MOD risk would be up already. 0-1km helicity values of 150-250 are forecast from the ARLATX to near Conroe TX Monday afternoon. Low level winds will remained backed from the ESE or even E across this region due to track of surface low along the Red River. If moisture return and CAPE are realized close to the ETA solution an increased tornado threat and upgrade to MOD risk will be needed.

Simply put we must wait to see what kind of moisture return we get.

[Yankeegirl]

SO what about the "cap"? Is it still there?

[jeff]

SO what about the "cap"? Is it still there?

We will not have a good feel for the cap intensity nor the moisture profiles until at least the AM soundings. Given the winds are just now starting to come around to the SE along the coastal bend and the 60 degree dewpoint line is well south of Brownsville makes me think the ETA/NAM is overdoing the moisture return and the GFS may have the better handle. However moisture can return very quickly given the right setup especially with a developing low level jet.

For what it is worth the cap intensity does not look to be as big of a problem as it has been the last few events, but at the same time the best moisture and dynamics do not really phase until NE LA into MS as has been the case for the last 3-5 weeks.

[PTrackerLA]

I'm keeping my fingers crossed YankeeGirl, for the past 6+ weeks we have pretty much missed every event like this. I've recorded less than 2" of rain since February, but like Jeff said Feb. was a pretty wet month. Had february been dry we would definately be in a moderate drought by now. If we got a good 2-3" areawide with this event we'd be in pretty good shape but I don't know if it is going to happen. Seems like moisture will be an issue once again and everytime that's been an issue we've gotten screwed.

[PTrackerLA]

The latest AFD sounds promising and there definately appears to be a severe weather threat Monday/Tuesday over here.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
415 PM CDT SUN APR 24 2005

.DISCUSSION...H20 SAT PICS/UPPER AIR ANALYSIS THIS AFT SHOWED UPPER
RIDGING OVER THE CENTRAL CONUS...W/ LOW SPINNING TWD THE 4 CORNERS
REGION...AND ANOTHER VORT LOBE DIVING SOUTH THROUGH THE
SASKATCHEWAN/MANITOBA PROVINCES OF CENTRAL CANADA.

PIECE OF ENERGY FROM SHEARING OUT 4 CORNERS LOW WILL TRANSLATE EAST
ACROSS THE REGION TONIGHT. VIS SAT/SFC OBS SHOW PLENTY OF MID LEVEL
CLOUDS ACROSS CENTRAL/NORTHERN TX IN ASSOCIATIONN WITH THIS FEATURE...
AND RETURNS SHOWING UP ON 88D RADAR MOSAIC. REALLY THINK LOW LEVELS ARE
FAR TOO DRY FOR ANYTHING OF SIGNIFICANCE TO REACH THE GROUND...BUT
WILL CARRY A SLGT POP OVER EAST TX ZONES WHERE AN EARLIER ONSET OF
MOISTURE RETURN IS EXPECTED.

OTHERWISE...MAIN CONCERN FOR THIS FORECAST IS CONVECTIVE CHANCES AND
SEVERE POTENTIAL MONDAY/MONDAY NIGHT. 0-6KM SHEAR/HODOGRAPHS FROM
FORECAST SOUNDINGS OMINOUS TO SAY THE LEAST...BUT REAL QUESTION IS
DEGREE OF MOISTURE RETURN/AVAILABLE ENERGY. GFS SHOWS LITTLE TO
NOTHING...WHILE THE NAM IS MORE ROBUST. SVR WORDING ALREADY INSERTED
IN ZONES...AND WHILE I THINK THE NAM IS OVERDONE...WILL LEAVE AS IS
WITH THOSE KIND OF SHEAR PARAMETERS.

TUESDAY LOOKING MORE PROMISING WITH VERY STEEP LAPSE RATES/MUCH BETTER
CAPE PROGS. 0-6KM SHEAR STILL PROGGED >50KTS...THOUGH BY THIS TIME IS
NEARLY UNIDIRECTIONAL...WHICH WOULD MITIGATE TORNADO POTENTIAL AND POINT
TO A BETTER HAIL/WIND THREAT.

BEYOND TUESDAY...DRY AND SEASONAL ON TAP THROUGH THE REST OF THE WEEK...
WITH RAIN CHANCES RETURNING TO THE FORECAST FOR THE WEEKEND AMID AN
ACTIVE SOUTHERN STREAM.

[KatDaddy]

[KatDaddy]

One more try.

Looks like the severe weather will be NE of Houston again.i

[KatDaddy]

Sorry for the previous posts.

Testing out my new cell phone. Its quite cool to post from my new cell. A few little glitches to overcome.

We need some rain but I think the severe weather will be NE of the Houston area as we have seen during the last few weeks. Hoping for some rain down here in League City.

As Jeff stated it depends on the moisture return for severe weather.

We shall see.

[jeff]

Although the moisture return is important I am surprised with the amount of activity over N and EC TX currently with dewpoints in the 30's. Yes, it is reaching the ground in many places. Quite the dynamics working on very limited elevated moisture.

Also note the intense southern jet punching in from N Mexico toward SW TX. Dewpoints are up to 58 at Rockport and 45 at Galveston with surface pressures falling through the 29.90's. Continued pressure falls over New Mexico should increase the SE onshore flow tonight although it is still questionable as to the quality of moisture return as late afternoon visible images are just starting to show low clouds over the SW Gulf heading NNW.

[jeff]

Evening soundings from KCRP and KLCH show much work is needed to prime the area for deep moist convection. KLCH is very dry below 600mb where most of the 19.4mm of PW is found.

KCRP is more moist with 31.0mm of PW and less of a dry layer. Both soundings show a strong inversion around 875 to 750mb. KCRP sounding may be somewhat affected by a seabreeze boundary as well as Rockport Td temp. compared with surrounding obs where Td's are more in the low to mid 50's along the coast.

[Yankeegirl]

I see alotta stuff well to the north of Houston.... Storms, Come On Down!!!!!

[Yankeegirl]

Hazardous Weather Outlook

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
700 AM CDT MON APR 25 2005

TXZ163-164-176>179-195>200-210>214-226-227-235>238-261200-
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-GALVESTON-
GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-MADISON-MATAGORDA-MONTGOMERY-
POLK-SAN JACINTO-TRINITY-WALKER-WALLER-WASHINGTON-WHARTON-
700 AM CDT MON APR 25 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

...SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND TONIGHT
ACROSS SOUTHEAST TEXAS...

.DAY ONE...TODAY AND TONIGHT.
LOW-LEVEL MOISTURE WILL CONTINUE TO GRADUALLY INCREASE OVER THE AREA
TODAY AS SOUTHERLY WINDS INCREASE IN RESPONSE TO A DEVELOPING
STORM SYSTEM CENTERED OVER THE PLAINS. A WARM FRONT IS EXPECTED TO
MOVE INLAND LATER TODAY AND AID WITH THUNDERSTORM DEVELOPMENT.
BY THIS AFTERNOON...THE WIND PROFILE OVER THE AREA IS EXPECTED TO BE
FAVORABLE FOR SEVERE THUNDERSTORMS. HOWEVER...THE DEGREE OF
DE-STABILIZATION IS STILL QUESTIONABLE. IT IS POSSIBLE THAT THE
ATMOSPHERE WILL DESTABILIZE SUFFICIENTLY TO SUPPORT SEVERE
THUNDERSTORMS AS AN UPPER LEVEL JET CORE AND MID-LEVEL DISTURBANCE AID
THE DE-STABILIZATION PROCESS...EVEN WITH LIMITED SURFACE HEATING
DUE TO EXTENSIVE CLOUD COVER.

TORNADOES...LARGE HAIL...AND DAMAGING WINDS ARE ALL POTENTIAL THREATS
WITH THE MAIN THREAT TIME PERIOD BEGINNING EARLY THIS AFTERNOON AND
ENDING DURING THE EARLY MORNING HOURS ON TUESDAY. A PACIFIC COOL FRONT
WILL MOVE ACROSS THE AREA LATE TONIGHT AND BRING AN END TO THE SEVERE
WEATHER THREAT FROM WEST TO EAST.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.
NO HAZARDOUS WEATHER IS ANTICIPATED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS POSSIBLE THIS AFTERNOON AND TONIGHT.

[jeff]

Showers and thunderstorms are increasing over SE TX this morning on
nose of low level jet and shortwave lifting crossing the area.

Moisture levels this morning fit the GFS solution the best instead of
the ETA. However, even with less moisture than the ETA we are seeing
plenty of elevated rainfall from dynamical forcing and elevated
moisture return.

Surface warm front over the WC Gulf of Mexico will move northward
today and ashore this afternoon bringing mid 60 degree dewpoints
inland. Air mass recovery will be slowed by scattered convection
throughout the day and this should limit instability. However given
expected dewpoints in the low to mid 60's by afternoon CAPE of 1000-
1500 J/kg wil be possible E of the C TX dryline. Degree of heating is
in question across the dryline area of C TX, but given strong large
scale forcing by early evening thunderstorms should develop.

Favorable shear and backed low level winds favor storm organization,
however limited instability should preclude a significant tornado
threat. Main severe modes will be large hail and damaging winds.

Even with a smaller severe threat the region should see a welcomed
soaking with basin averages of .5 to 1.5 inches through tonight.

[vbhoutex]

We have had a few passing showers already this morning. A good soaking would be quite welcome.

[Johnny]

Conroe is registering a 55 degree dewpoint reading and Galveston Island is registering a 60 degree dewpoint reading. As Jeff has said, as the day goes on moisture levels will increase. If you take a look at radar there are some nice showers and some decent storms around as of now. This is with dewpoints a little on the low side. With an increase in moisture throughout the day we could see some pretty healthy thunderstorms. If they are not severe, they will be strong bringing us some good solid rain...which we could use.

[JenBayles]

<does rain dance around office praying for a miracle>