March Weather Disccusion: Severe Storms Possible Tues/Wed

[svrwx0503]

Looking at some RUC model soundings over IAH, there is quite a bit of instability out there so we could see a few strong storms if the cap can be broken with hail being the main threat from any of the stronger activity. Right now, the front looks to be draped between IAH and DWH with a very slow south/southeasterly movement.

[srainhoutx]

SPC 2:43 PM Update...

THE FINAL CHANGE TO THE OUTLOOK IS TO
ADD THUNDER TO PARTS OF SE OK AND THE TX HILL COUNTRY. IN SW
TX...TOWERING CUMULUS IS EVIDENT ON SATELLITE IMAGERY AND ISOLATED
THUNDERSTORM DEVELOPMENT REMAINS POSSIBLE LATE THIS AFTERNOON.

[srainhoutx]

Frontal boundary just slipped S of my location. Temp dropped from 84 to 74 after passage.

[jasons2k]

Still watering here with sprinklers....winds from the N/NE....I think any shot of rain will be over the city and not up here.

[srainhoutx]

The good news is the rain chances for the week are looking good. It's been a while since we've had chances of a 1/4 to 3/4 inch amounts in the forecast. The beginning of April is even looking better, but that's a different Topic, I suspect.

[wxman57]

Weather wasn't TOO bad for the Bluebonnet Metric Century out of Waller yesterday. Took off, intending to do the 54 mile route. Temperature was around 70 degrees, just a bit cool. Missed the turn for the 54 mile route and found myself on the 68 mile loop. Oh well, decided to stay on that route rather than making a U-turn and riding a mile or so back to the 54 mile route. Got to Bellville and decided to make my own route due northeast to knock 2-3 miles off the route. Soon as I left Bellville heading up Hwy 159 I ran into the cold front.

It felt like a freezer door opened. Had to fight the moderate headwind, cold temps, light drizzle and a road that some call paved but it was more like a bunch of rocks glued together for about 10 miles before joining up with the folks on the 68 and 75 mile routes again. As we traveled a bit more to the east toward Hempstead, we crossed the frontal boundary back into the warmer air and the drizzle stopped. Got back to the car about 20 minutes ahead of my wife who didn't miss the 54 mile turn. She definitely noticed biking across the frontal boundary a time or two.

[wxman57]

In the SWODY2 slight tomorrow, but 15% overall and rather tame text, IMHO.

Main energy passes WELL to our north tomorrow (Kansas, northern Missouri). Maybe some light showers here late tomorrow. Even later this week, the energy passes well to our north on Thursday (OK/AR). Still doesn't look very good for much rain around here over the next week. Long range GFS indicates possibly a better chance of rain the week after next.

[srainhoutx]

In the SWODY2 slight tomorrow, but 15% overall and rather tame text, IMHO.

Main energy passes WELL to our north tomorrow (Kansas, northern Missouri). Maybe some light showers here late tomorrow. Even later this week, the energy passes well to our north on Thursday (OK/AR). Still doesn't look very good for much rain around here over the next week. Long range GFS indicates possibly a better chance of rain the week after next.

Surface low may be close enough to enhance activity along the dryline to our W. We've had little if any thunderstorm activity of late, so I'll take any rain we can get at this point.

[wxman57]

Latest GFS has no surface low except for the lee-side low that doesn't move. Just a surface trof/frontal boundary across the south. With the vorticity center passing so far north, there won't be any significant surface low in Texas.

[jasons2k]

I'll believe I'll see some rain again when I see it falling from the sky.

[srainhoutx]

SPC expands Slight Risk further W in TX...

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT MON MAR 28 2011

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS TUE AFTN AND EVE ACROSS PARTS
OF SOUTHEAST TEXAS INTO THE LWR MS VALLEY...

...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT THE PREVAILING BLOCKING PATTERN
WILL BEGIN TO WEAKEN OR BECOME LESS PROMINENT DURING THIS FORECAST
PERIOD...AS A STRONG MID-LATITUDE PACIFIC JET NOSES INLAND AROUND
THE CREST OF A RIDGE BUILDING JUST WEST OF THE PACIFIC COAST. A
REMNANT BELT OF STRONGER FLOW IS EXPECTED TO LINGER...HOWEVER...IN A
MORE OR LESS ZONAL FASHION FROM THE LEE OF THE ROCKIES THROUGH THE
MID ATLANTIC SEABOARD. WITHIN THIS REGIME...ONE SIGNIFICANT SHORT
WAVE IMPULSE IS PROGGED TO TRANSLATE EASTWARD THROUGH THE CENTRAL
PLAINS/MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS...AS ANOTHER DIGS
INTO THE CENTRAL ROCKIES. AT THE SAME TIME...WITHIN A BELT OF
STRONGER FLOW EMANATING FROM THE SUBTROPICAL EASTERN
PACIFIC...ANOTHER SHORT WAVE IMPULSE IS PROGGED TO DEVELOP EAST
NORTHEASTWARD ACROSS THE NORTHERN MEXICAN PLATEAU INTO THE
WESTERN/CENTRAL GULF COAST LATE TUESDAY AND TUESDAY NIGHT.

IN LOWER LEVELS...A LARGE COLD SURFACE RIDGE EXTENDING SOUTHEASTWARD
OUT OF CENTRAL CANADA THROUGH THE SOUTHEASTERN STATES MAY SLOWLY
BEGIN TO WEAKEN/ERODE...PARTICULARLY ALONG ITS SOUTHWESTERN
PERIPHERY ACROSS THE WESTERN AND CENTRAL GULF COAST. AS THIS
OCCURS...SUBSTANTIVE MOISTENING MAY OCCUR OFF THE WESTERN GULF OF
MEXICO...AS A FRONTAL WAVE SHIFTS FROM NORTH TEXAS INTO THE NORTH
CENTRAL GULF STATES. HOWEVER...DUE TO THE WEAK NATURE OF THIS
WAVE...LOW-LEVEL WIND FIELDS ARE PROGGED TO REMAIN GENERALLY WEAK
THROUGH THE PERIOD...AND BOUNDARY LAYER MOISTENING MAY BE CONFINED
TO PORTIONS OF SOUTHEAST TEXAS AND THE LOWER MISSISSIPPI VALLEY
THROUGH LATE TUESDAY EVENING.

...SOUTH CENTRAL STATES...
THUNDERSTORMS MAY BE ONGOING AT 12Z TUESDAY ACROSS PARTS OF THE
SOUTH CENTRAL PLAINS...AIDED BY FORCING ASSOCIATED WITH THE SHORT
WAVE IMPULSE TURNING EAST OF THE ROCKIES. HOWEVER...STRONGEST
FORCING APPEARS LIKELY TO SHIFT TOWARD THE OHIO VALLEY DURING THE
DAY...GENERALLY AWAY FROM THE FRONTAL WAVE AND TRAILING SURFACE COLD
FRONT ADVANCING SOUTHWARD INTO THE SOUTHERN PLAINS. WEAK MID-LEVEL
HEIGHT FALLS COULD STILL SUPPORT ADDITIONAL STORM DEVELOPMENT ALONG
THE FRONT ACROSS PARTS OF CENTRAL AND NORTHEAST TEXAS TUESDAY
AFTERNOON. HOWEVER...GUIDANCE IS SUGGESTIVE THAT HIGHER
THUNDERSTORM PROBABILITIES MAY EXIST SOUTH OF THE FRONT...ACROSS
PARTS OF SOUTHEAST TEXAS INTO SOUTHERN LOUISIANA...PERHAPS PARTS OF
SOUTHERN MISSISSIPPI. THIS IS WHERE DAYTIME HEATING AND SURFACE DEW
POINT INCREASES INTO THE MID 60S ...BENEATH STEEP MID-LEVEL LAPSE
RATES...MAY YIELD MIXED LAYER CAPE OF 1000-2000 J/KG.

FORCING ASSOCIATED WITH THE APPROACH OF THE SUBTROPICAL IMPULSE IS
EXPECTED TO CONTRIBUTE TO WEAKENING OF MID-LEVEL INHIBITION DURING
THE LATE AFTERNOON HOURS...ALLOWING STORMS TO INITIATE IN THE
PRESENCE OF MODERATELY STRONG DEEP LAYER SHEAR BENEATH 30-50 KT
WESTERLY 500 MB FLOW. ALTHOUGH LOW-LEVEL FLOW AND SHEAR MAY REMAIN
RATHER WEAK...MID-LEVEL UPDRAFT ROTATION SHOULD AT LEAST ENHANCE THE
RISK FOR LARGE HAIL IN STRONGER STORMS. ACTIVITY COULD CONSOLIDATE
INTO AN EXPANDING STORM CLUSTER OR TWO BY EARLY EVENING...WITH
PERHAPS SOME POTENTIAL FOR STRONG GUSTY WINDS... BEFORE INSTABILITY
WANES AND CONVECTION WEAKENS.

..KERR.. 03/28/2011

[srainhoutx]

The 18Z WRF is sniffing the impulse (shortwave) currently just W of the Baja. That model does develop some showers/storms mighty close to SE TX. We will see...

[sleetstorm]

Have any of you seen KHOU 11 News' new seven day forecast yet? I have and it looks better in my opinion.

[srainhoutx]

E-mail from Jeff:

A chance for showers and thunderstorms tonight into Wednesday.

Storm system over the Rockies will progress eastward today increasing lift over TX, while surface Gulf moisture returns northward behind a warm front currently moving north across the region. This spells an increasing rain for showers and thunderstorms late this afternoon through midday Wednesday.

Warm front is moving northward across the region this morning with dewpoints surging back into the upper 60’s on ESE winds. Capping inversion is noted above the surface moist layer, so clouds will likely be slow to break up and this will hinder surface warming and instability this afternoon. Out west over SC TX and the Rio Grande plains, clouds should break up by early afternoon allowing good surface heating and instability to develop. Enough heating combined with ripples of energy in the sub-tropical jet stream aloft look to be enough to break the capping inversion by late afternoon along a dry line feature WSW of San Antonio. Built up surface energy will be released and expect storms to go quickly severe with large hail being the main threat (this area is confined to the western part of the SPC outlook below for this afternoon or generally W of I-35).

Late this afternoon/early this evening increasing large scale lift ahead of the upper trough and cold front will come to bear across the region along with a favorable region of the sub-tropical jet stream. Expect storms out west to move ESE toward the coastal bend while additional showers and thunderstorms develop over SE TX as the mid level cap is lifted and weakened. Parameters are still not overly favorable for a big severe weather outbreak and really even thunderstorms as there is some question as to how long/if the cap will weaken enough to even allow thunderstorms to develop. 00Z 29 WRF model appears to have a fairly good handle on the situation showing a broken/multi-cell type event developing over SE TX between 600-300am. Leaning more toward the showers with isolated thunderstorms, and while SPC has the entire area outlooked for a risk of severe weather, the parameters are looking marginal at best. Main threats with any severe storms will be large hail and wind damage. Widespread rainfall amounts of .25 to .75 of an inch are likely with a few isolated amounts up to 1 inch which will greatly help with the ongoing drought conditions, but far from what is needed to end the drought.

Cold front will reach the coast early Wednesday and slow down as the main upper trough hangs back to the west. This will induce a period of overrunning moisture and possibly showers/thunderstorms to re-develop between 600am and 200pm on Wednesday. Elevated instability looks favorable for a few strong storms especially from Matagorda Bay southward where the main threat will be large hail.

Upper trough axis will clear the area early Thursday ushering in a period of very nice weather with lows in the 50’s and highs in the 80’s through the weekend.

[wxman57]

Nothing to get excited about. Hopefully we get at least enough rain to partially water the plants.

[srainhoutx]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0722 AM CDT TUE MAR 29 2011

VALID 291300Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY TO
SOUTH CENTRAL TX/LOWER RIO GRANDE VALLEY......

...SYNOPSIS..
DEVELOPMENT OF THE UNSTABLE AIR MASS WILL BE THE PRIMARY PLAYER
ACROSS TX TO LOWER MS VALLEY SUPPORTING THE SEVERE THUNDERSTORM
THREAT FOR THIS FORECAST PERIOD. THE TRANSITORY S/WV TROUGH
EMBEDDED IN THE NEARLY ZONAL FLOW CURRENTLY MOVING E OF CENTRAL
ROCKIES TO OVER THE MID MS VALLEY BY LATER TONIGHT WILL HAVE LITTLE
IN THE WAY OF SURFACE REFLECTION OTHER THAN REINFORCE THE SWD PUSH
OF POLAR AIR NOW TAKING PLACE OVER THE SRN HIGH PLAINS.

THERE IS A FLAT WAVE IN THE SUBTROPICAL STREAM NOW ACROSS NRN MEXICO
WHICH WILL AID THE HIGH LEVEL DIVERGENCE AS IT SPREADS EWD ACROSS
THE SRN PLAINS AND LOWER MS VALLEY BY THIS EVENING.

STALLED OLD FRONTAL ZONE JUST OFFSHORE NERN GULF WWD TO ALONG SRN LA
COAST TO S TX WILL RETURN NWD AS A WARM FRONT TODAY IN ADVANCE OF
NEXT POLAR SURGE OVER NRN TX.

A PRONOUNCED EML WITH MID LEVEL LAPSE RATES OF 8C/KM OR GREATER
COVERS ALL THE SRN PLAINS EWD TO MS RIVER. GULF MOISTURE MOVES
INLAND WITH THE WARM FRONT ACROSS LOWER MS VALLEY AND S TX LEADING
TO DEVELOPMENT OF A MDTLY UNSTABLE AIR MASS THIS AFTERNOON.

...ARKLATEX TO SERN TX AND LWR MS VALLEY...
NWD DEVELOPMENT OF WARM FRONT THIS AFTERNOON WILL BE AN IMPORTANT
FACTOR IN DETERMINING WHERE THE GREATEST SEVERE THUNDERSTORM THREAT
WILL BE LOCATED. FRONT COULD MAKE IT AS FAR AS N OF AN I-10 LINE IN
LA AND THEN WWD TO NEAR CLL PRIOR TO ARRIVAL OF THE POLAR FRONT.
WITH MLCAPES CLIMBING TO AOA 2000 J/KG AND CINH DISSIPATING BY MID
AFTERNOON...THUNDERSTORMS EXPECTED TO FORM VICINITY BOTH THE WARM
FRONT AND ALONG THE SEWD MOVING POLAR FRONT. WHILE LOW LEVEL SHEAR
IS EXPECTED TO BE GENERALLY LESS THAN 20KT...BRN SHEAR OF 40-50KT
ALONG WITH THE STEEP LAPSE RATES...UPPER DIVERGENCE AND INSTABILITY
SUPPORT SEVERE THUNDERSTORMS. PRIMARY THREAT WILL BE LARGE HAIL
ALONG WITH WIND DAMAGE AS STORMS EVOLVE INTO SHORT LINE SEGMENTS AS
THEY MOVE GENERALLY EWD ACROSS SERN TX/SRN HALF OF LA INTO MS.
SUPERCELLS ARE POSSIBLE...PARTICULARLY NEAR THE WARM FRONT WHERE
ENHANCED LOW LEVEL SHEAR WILL BE FOCUSED RAISING THREAT OF
TORNADOES.

THUNDERSTORMS EXPECTED TO DEVELOP UPSCALE INTO A QLCS TONIGHT AS
STORMS TAP INTO AN INCREASINGLY RICH AIR MASS MOVING INLAND CENTRAL
GULF COAST...POSSIBLY REACHING THE WRN FL PANHANDLE BY 12Z WED. THIS
WILL MAINTAIN A WIND DAMAGE THREAT ALONG WITH ISOLATED TORNADOES
OVERNIGHT.

...PARTS OF SOUTH CENTRAL TX/LOWER RIO GRANDE VALLEY...
SCATTERED TSTMS MAY DEVELOP BY LATE AFTERNOON/EARLY
EVENING ACROSS THE SWD MOVING POLAR FRONT AS IT ENCOUNTERS A
MODERATELY UNSTABLE AIR MASS. MLCAPES IN EXCESS OF 2500 J/KG AND THE
STEEP LAPSE RATES SUGGEST THAT ANY STORM THAT FORMS WILL BE CAPABLE
OF PRODUCING VERY LARGE HAIL GIVEN THE 50KT OF BULK SHEAR AND UPPER
DIVERGENCE ACROSS THE REGION. PRIMARY QUESTION IS HOW MANY
STORMS...AS THE CAP WILL NEED CONSIDERABLE WORK THROUGH HEATING TO
WEAKEN SUFFICIENTLY. HI RES MODELS SUGGEST THAT STORMS COULD
DEVELOP IN THE HOTTEST AIR NEAR THE RIO GRANDE E OF DRT TO LRD LINE
AND THEN TRACK SEWD THRU THE EVENING. ANY STORM WILL BE CAPABLE OF
VERY LARGE HAIL AS WELL AS DAMAGING DOWNBURSTS WINDS GIVEN THE
FAVORABLE THERMODYNAMICS. FAR S TX STILL EXPECTED TO REMAIN
SUFFICIENTLY CAPPED THAT SEVERE PROBABILITIES WILL BE LOW BUT
NON-ZERO.

..HALES/STOPPKOTTE.. 03/29/2011

[srainhoutx]

Watch the frontal boundary draped along Coastal TX retreat N as a warm front. That will be the focus of any storm chances as the day progresses. Although things do look marginal regarding storm chances and rainfall amounts look less than an inch area wide, we need rain and any that falls will be welcomed.



The 'trigger' (shortwave) is on the move E bound from MX. We'll see if that feature can spark some activity as we head toward the afternoon/evening hours...

[srainhoutx]

The 12Z WRF is a bit more encouraging regarding rainfall/storm chances...

[srainhoutx]

Starting to see some breaks in the clouds in NW Harris County as the ceilings lift. HGX thoughts prior to the SPC Update that should be out momentarily.

[srainhoutx]

SPC expands Slight Risk a bit N in S Central TX...

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT TUE MAR 29 2011

VALID 291630Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SOUTH-CENTRAL/SOUTHEAST
TX TO LOWER MS VALLEY/CENTRAL GULF COAST...

...SOUTH TX/TX COASTAL PLAIN TO LOWER MS VALLEY/CENTRAL GULF
COAST...
WATER VAPOR IMAGERY REFLECTS A MODESTLY AMPLIFYING LONGWAVE TROUGH
OVER THE CENTRAL CONUS...WITH AN EMBEDDED SHORTWAVE TROUGH SPREADING
EASTWARD OVER THE CENTRAL HIGH PLAINS AT MIDDAY. THERE ALSO APPEARS
TO BE ONE OR MORE SUBTLE/LOW AMPLITUDE IMPULSES EMBEDDED WITHIN A
SUBTROPICAL STREAM ACROSS NORTHERN MEXICO...WHICH IS EXPECTED TO AID
HIGHER LEVEL DIVERGENCE AS IT SPREADS EASTWARD ACROSS THE SOUTHERN
PLAINS/LOWER MS VALLEY BY THIS EVENING. AN OLD FRONTAL BOUNDARY
OFFSHORE WILL RETREAT NORTHWARD AS A WARM FRONT TODAY ACROSS
SOUTHEAST TX AND THE LOWER MS RIVER VALLEY...AHEAD OF A POLAR FRONT
CROSSING EAST/SOUTH TX.

A PRONOUNCED ELEVATED MIXED LAYER WITH MID LEVEL LAPSE RATES OF 8
C/KM OR GREATER COVERS ALL OF THE SOUTHERN PLAINS EASTWARD TO THE MS
RIVER. CURRENT CLOUD COVER ACROSS THE WARM SECTOR WILL GIVE WAY/THIN
THROUGH THE AFTERNOON...AS AMPLE HEATING COMBINED WITH SURFACE
DEWPOINTS INCREASING INTO THE UPPER 60S/LOWER 70S F CONTRIBUTES TO
MODERATE SURFACE BASED BUOYANCY THIS AFTERNOON /1500-2500 J PER KG
MLCAPE/. AT THIS TIME...IT APPEARS THE RELATIVELY STRONGEST
DESTABILIZATION WILL OCCUR ACROSS THE SOUTH-CENTRAL TX/RIO GRANDE
VICINITY...AND PERHAPS SOUTHERN LA.

IT APPEARS THAT THE AFOREMENTIONED STRONG EML/STOUT CAP WILL TEND TO
GENERALLY LIMIT WARM SECTOR DEEP CONVECTIVE DEVELOPMENT...WITH
SCATTERED TSTMS MOST LIKELY TO FORM LATE THIS AFTERNOON/EVENING IN
VICINITY OF THE SOUTHEAST ADVANCING POLAR FRONT ACROSS
SOUTH-CENTRAL/SOUTHEAST TX...AS WELL AS NEAR THE WARM FRONT ACROSS
THE LOWER MS VALLEY.

THE PRIMARY SEVERE THREATS WILL BE LARGE HAIL AND WIND DAMAGE AS
STORMS EVOLVE INTO SHORT LINE SEGMENTS AS THEY MOVE
EAST-SOUTHEASTWARD ACROSS SOUTHEAST TX AND THE SOUTHERN HALVES OF
LA/MS. SUPERCELLS ARE POSSIBLE...PARTICULARLY NEAR THE WARM FRONT
WHERE MODESTLY ENHANCED LOW LEVEL SHEAR WILL SUPPORT A RISK OF
TORNADOES. BUT OTHERWISE...RELATIVELY WEAK WIND SPEEDS IN THE LOWER
TROPOSPHERE WILL TEND TO LIMIT A TORNADO THREAT.

..GUYER/ROGERS.. 03/29/2011