Texas Spring-2015

[Brent]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
1102 AM CDT FRI APR 24 2015

.UPDATE...

...NORTH TEXAS MESOSCALE FORECAST UPDATE...

WATER VAPOR SATELLITE IMAGERY SHOWS A STRONG SHORTWAVE TROUGH
OVER FAR WEST TEXAS...MOVING NORTHEAST OVER EASTERN NEW MEXICO.
THIS TROUGH IS EXPECTED TO CONTINUE NORTHEAST THROUGHOUT THE DAY
TODAY...SPREADING RELATIVELY STRONG LARGE SCALE FORCING FOR ASCENT
OVER THE REGION. 12Z UPPER AIR ANALYSIS SHOWED A PLUME OF DEEP
MOISTURE IN PLACE OVER THE SOUTHERN PLAINS WITH STRONG SPEED AND
DIRECTIONAL SHEAR FROM THE SURFACE TO 500 MB. AT THE 850 MB LEVEL
A RELATIVELY STRONG TROUGH WAS ANALYZED OVER THE HIGH
PLAINS...DOWNSTREAM OF THE SHORTWAVE TROUGH MOVING NORTHEAST OVER
THE REGION. AT THE SURFACE...ONGOING THUNDERSTORM ACTIVITY LEFT A
SOMEWHAT MESSY ANALYSIS IN PLACE...BUT BASED ON THE 15Z ANALYSIS
THERE WAS A WARM FRONT LOCATED JUST SOUTH OF THE INTERSTATE 20
CORRIDOR ACROSS THE DFW AREA...MORE OR LESS ATTACHED TO A SURFACE
LOW LOCATED IN SOUTHERN PALO PINTO COUNTY.

15Z REGIONAL RADARS SHOWED SCATTERED CONVECTION NEAR THE SURFACE
LOW...AND ALL ALONG AND NORTH OF THE WARM FRONT. VISIBLE SATELLITE
IMAGERY SHOWED THAT THE THICK MORNING CLOUD COVER WAS BEGINNING TO
CLEAR OUT FROM CLEBURNE SOUTHWEST TO GOLDTHWAITE...AND SOUTH ALONG
THE INTERSTATE 35/35W CORRIDORS. FROM GRANBURY TO CLEBURNE
SOUTHWEST TOWARDS HAMILTON...LOCALLY CALCULATED CONVECTIVE
PARAMETERS WERE HIGHLIGHTING A LOCAL MAXIMA OF LOW-LEVEL (0-3 KM)
CAPE OF AROUND 100 TO 150 J/KG...AND A LOW-LEVEL EHI OF JUST UNDER
2. BOTH OF THESE PARAMETERS FAVOR THE POTENTIAL FOR STRONG LOW-
LEVEL UPDRAFTS AND THE POTENTIAL TO TILT LOW-LEVEL HORIZONTAL
VORTICITY INTO THE VERTICAL. THE PRIMARY MISSING INGREDIENT TO
ACCOMPLISH THIS THUS FAR HAS BEEN WELL ORGANIZED CONVECTION/STRONG
UPDRAFTS.

WHILE DEEP MOISTURE WAS ANALYZED ON THE 12Z UPPER AIR MAPS...THERE
WERE NO STRONG OR STEEP MID-LEVEL LAPSE RATES ANALYZED UPSTREAM OF
NORTH AND CENTRAL TEXAS. WHILE DEEP MOISTURE VALUES APPEAR TO BE
AT NEAR RECORD LEVELS FOR THIS TIME OF YEAR...THIS DEEP MOISTURE
ALSO INDICATES THAT THERE IS NO STRONG THETA-E CHANGE WITH
HEIGHT...LEADING TO A THERMODYNAMIC PROFILE CHARACTERIZED BY TALL
AND SKINNY CAPE. WHILE THIS IS A VERY FAVORABLE PROFILE FOR
THUNDERSTORM CHANCES AND EFFICIENT RAINFALL IN GENERAL...IT COULD
LIMIT THE STRENGTH OF INITIAL UPDRAFTS TODAY. IF STORMS CAN
MAINTAIN UPDRAFTS LONG ENOUGH TO INGEST SOME OF THE RELATIVELY
STRONG HORIZONTAL VORTICITY INDICATED BY CALCULATED PARAMETERS...
SUPERCELLS WILL BECOME MORE LIKELY. IF A SUPERCELL CAN BECOME
ESTABLISHED...THE INTERNAL DYNAMICS OF THE SUPERCELL WILL PROMOTE
A MUCH STRONGER UPDRAFT THAN WHAT WOULD BE SUPPORTED BY
THERMODYNAMICS ALONE.

WITH STRONG FORCING UPSTREAM...DEEP MOISTURE IN PLACE...AND ALMOST
NO CAPPING INVERSION IN PLACE...THUNDERSTORMS ARE VERY LIKELY
TODAY...AND WILL LIKELY CONTINUE INTO THE AFTERNOON HOURS OF THE
DAY. COPIOUS AMOUNTS OF MORNING CONVECTION CAN OFTEN STABILIZE THE
ENVIRONMENT MAKING IT LESS FAVORABLE FOR STORMS LATER ON. THAT
DOES NOT APPEAR TO BE THE CASE TODAY AS THE LACK OF A STRONG
THETA-E DIFFERENCE WITH HEIGHT NOT ONLY LIMITS UPDRAFT
STRENGTH...BUT IT ALSO LIMITS THE STRENGTH OF RAIN COOLED AIR...
I.E. THE RAIN IS NOT VERY COLD BECAUSE THERE IS NOT MUCH DRY AIR
ALOFT TODAY. THE PRIMARY FORECAST CHALLENGE IN DETERMINING STORM
MODE AND THEN THE ASSOCIATED HAZARDS. HERES WHAT WE`RE WATCHING
CLOSELY:

IN GENERAL...THE KINEMATIC OR WIND SHEAR AND FORCING ENVIRONMENT
ARE FAVORABLE FOR SUPERCELL THUNDERSTORMS AND TORNADOES TODAY. THE
THERMODYNAMIC ENVIRONMENT IS MORE QUESTIONABLE. WE CERTAINLY HAVE
AMPLE MOISTURE IN PLACE TO SUPPORT ANY STORM MODE...BUT LAPSE
RATES ALOFT ARE SOMEWHAT MARGINAL...LIMITING UPDRAFT STRENGTH FROM
AIR BEING LIFTED ABOVE ITS LEVEL OF FREE CONVECTION. IT LOOKS LIKE
THE MORE SUNSHINE WE GET THROUGH THIS AFTERNOON...THE MORE LIKELY
WE ARE TO SEE SUPERCELL THUNDERSTORMS. THE MORE CLOUD COVER WE
HANG ON TO...THE MORE LIKELY WE ARE TO SEE NUMEROUS...SOMEWHAT
WEAKER STORMS...THAT POSE MORE OF A HEAVY RAINFALL AND FLOODING
THREAT THAN A LARGE HAIL...DAMAGING WIND AND TORNADO THREAT.

IF WE MAINTAIN THE CLEARING SOUTH-SOUTHWEST OF THE DFW AREA FOR A
FEW HOURS HEADED INTO THIS AFTERNOON...OUR CHANCES OF SEEING A
SUPERCELL STORM MODE INCREASE QUITE A BIT. LOW-LEVEL HEATING WILL
HELP MORE OR LESS MAKE UP FOR THE MARGINAL MID-LEVEL LAPSE RATES
AND INCREASE UPDRAFT SPEED TO THE POINT THAT SUPERCELLS DOMINATE
THE INITIAL STORM MODE. IF WE GET STORMS QUICKLY...OR SIMPLY CLOUD
UP HERE AGAIN BEFORE NOON...A MORE WIDESPREAD STORM COVERAGE MAY
OCCUR WITH WEAKER STORMS IN GENERAL.

IN EITHER CASE...MOST MODEL GUIDANCE FAVORS THUNDERSTORMS GROWING
UPSCALE INTO A SQUALL LINE AND MOVING EAST ACROSS NORTH AND
CENTRAL TEXAS BY LATE THIS AFTERNOON. WITH A NEAR RECORD
PRECIPITABLE WATER VALUE OBSERVED ON THE 12Z FWD
SOUNDING...FLOODING IS ALSO A MAJOR CONCERN TODAY. ONCE DEEP
CONVECTION INITIATES...ANY TRAINING OF STORMS WILL LIKELY RESULT
IN ENOUGH LOCALLY HEAVY RAINFALL TO RESULT IN FLOODING. RAINFALL
RATES OF 2 INCHES PER HOUR ARE VERY LIKELY... AND REALLY THE ONLY
LIMITING FACTOR FOR FLOODING IS THE EXPECTED SPEED OF STORMS.
STORMS ARE EXPECTED TO MOVE EAST OR NORTHEAST AT 35 TO 40 MPH
TODAY...MAKING ANY ONE STORM UNLIKELY TO PRODUCE FLOODING.

WE WILL BE KEEPING A CLOSE EYE ON ALL OF THESE FACTORS HEADED INTO
THE AFTERNOON HOURS...AND WILL ISSUE THE APPROPRIATE WATCHES AS
VARIOUS THREAT LEVELS INCREASE. THERE IS A FAIR AMOUNT OF
UNCERTAINTY REGARDING STORM MODE THIS AFTERNOON...SO IT IS
ADVISABLE TO PAY CLOSE ATTENTION TO THE FORECAST THROUGHOUT THE
DAY AS CONDITIONS COULD BECOME MORE FAVORABLE FOR SUPERCELLS OR
HEAVY RAINFALL AND FLOODING QUICKLY. WE WILL PROVIDE SHORT TERM
FORECAST UPDATES AS QUICKLY AS POSSIBLE AS THESE CONDITIONS
EVOLVE.

CAVANAUGH

[Tireman4]

From HGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
948 AM CDT FRI APR 24 2015

.DISCUSSION...
LEADING IMPULSE SUPPORTING AREA OF ELEVATED MOIST CONVECTION OVER
THE NRN COUNTIES WILL CONTINUE TO QUICKLY PULL NEWD THROUGH THE
DAY...AND PULL RAIN OUT OF THE AREA BY EARLY AFTERNOON. MODEST
DIURNAL HEATING HAS ALLOWED AIRMASS TO BECOME MODERATELY UNSTABLE
FEEDING INTO THIS COMPLEX AS OF 14Z. HOWEVER...CAPPING REMAINS IN
PLACE. WITH FURTHER DIURNAL HEATING...A FEW CELLS MAY STRENGTHEN
WITH PRIMARY THREATS OF BRIEF HEAVY RAIN AND SOME HAIL. WILL
CONTINUE TO MONITOR RADAR TRENDS FOR THESE CELLS...ALTHOUGH
CURRENT THINKING IS SVR THREAT WILL REMAIN MODEST AT BEST WITH
ONGOING STORMS THROUGH THE REST OF THE MORNING WITH BRIEF HEAVY
RAINFALL.

MUCH OF THE AREA WILL ESSENTIALLY REMAIN BETWEEN SYSTEMS
TODAY...WITH LOWER POPS THIS AFTERNOON. 12Z UA ANALYSIS/SOUNDINGS
INDICATE RICH SURFACE MOISTURE FEED IS QUITE SHALLOW...WHICH WILL
LIKELY KEEP RAIN CHANCES IN THE SCATTERED RANGE AT BEST FOR THE
REST OF THE AFTERNOON AS AFTERNOON HEATING FURTHER WEAKENS CAP.
OTHER THAN MAKING NEAR TERM CHANGES ASSOCIATED WITH ONGOING
WEATHER...HAVE LEFT REST OF FORECAST THE SAME.

48

&&

.PREV DISCUSSION... /ISSUED 705 AM CDT FRI APR 24 2015/

AVIATION...
THE BIGGEST CONCERN WILL BE THE CHANCES FOR THUNDERSTORMS TODAY.
LIKED THE HRRR MODEL FOR HOW IT INITIALIZED AND CONTINUES TO
DEPICT THE THUNDERSTORMS IN THE HILL COUNTRY.

THE THUNDERSTORMS OCCURRING OVER THE HILL COUNTRY WERE APPROACHING
KCLLAT 11Z. THE HRRR BRINGS THE BEST CHANCES FOR THUNDERSTORMS
ACROSS KCLL AND KUTS THROUGH 18Z. ALTHOUGH WIDESPREAD STORMS WILL
LIKELY OCCUR TO THE NORTH...BOTH KCXO AND KIAH SHOULD SEE A WINDOW
OF HIGHEST CHANCES FROM ABOUT 15Z THROUGH 18Z.

THE HIGH PRESSURE RIDGE OVER THE GULF WAS PROVIDING A STRONGER
CAP OVER THE REMAINING SITES...ALTHOUGH THE MODELS ERODE THIS CAP
LATER THIS MORNING. BECAUSE OF THIS...KHOU AND KSGR SHOULD SEE
SHOWER OR THUNDER CHANCES AFTER 14Z. KLBX AND KGLS WILL HAVE A
MORE DIFFICULT TIME. THE BEST CHANCES WILL LIKELY BE DURING THE
MID AND LATE MORNING PERIOD AS THE REMNANTS OF A MESO-SCALE
CONVECTIVE COMPLEX THAT AFFECTED SOUTH TEXAS EARLIER THIS MORNING
MOVE UP THE COASTAL AREAS. THESE REMNANTS MAY PROVIDE ENOUGH LIFT
FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORM THROUGH MIDDAY.

[JayDT]

Looks like the NWS just issued a Flash Flood Watch for the DFW area.

[TheProfessor]

Clouds are starting to thin out here.

[TheProfessor]

Hmm. If we do end up getting super cells if any tornadoes would be rained rapped due to high moisture? If so it could make it a dangerous situation as people would be able to see the tornado.

[stephen23]

Temperatures appear to be rebounding pretty quickly in the southern part of DFW. 77 in Burleson. Shouldn't that help the severe weather chances go up?

[BrokenGlassRepublicn]

With the persistent rain over the northern counties, no doubt Lake Lavon will exceed conservation pool. As of yesterday it was < 2'.

As of Noon today, it is now less than 1.5' below full pool with Collin County under Flash Flood Warning. If I remember the drainage map, most of Collin County of sits in the Lavon watershed.

[TheProfessor]

Storms have started to pop up in West Texas, I wonder if the warm front will beat them here?

[BrokenGlassRepublicn]

And for those of you that don't live in North Texas, note that Lavon Lake is the drinking water source for most Eastplexers.

[weatherdude1108]

So happy for you guys in north Texas and your replenishing area lakes' levels!

[Texas Snowman]

Ray Roberts has also surged up from nearly eight feet below normal a few weeks ago, now only 2.5 feet low and lots on inflow coming after the big rains in its watershed over the last 24-hours. I'd bet it's full w/in the week.

[Texas Snowman]

The AC weather station has recorded 1.15 inches of rain today and is now sitting at just more than 7-inches for the month in northern Grayson County.

According to NWS radar estimates, some areas just north and northeast of my house have seen 2.5 inches of rainfall today with a few in the 3-4" range.

And another thunderstorm is about to come across us as I write this.

Wow.

[Ellsey]

TORNADO WATCH OUTLINE UPDATE FOR WT 100
NWS STORM PREDICTION CENTER NORMAN OK
210 PM CDT FRI APR 24 2015

TORNADO WATCH 100 IS IN EFFECT UNTIL 1000 PM CDT FOR THE
FOLLOWING LOCATIONS

TXC001-027-035-049-059-081-083-085-093-095-099-113-119-121-133-
139-143-145-151-161-193-207-213-217-221-223-231-235-237-251-253-
257-281-293-307-309-327-333-349-353-363-367-379-397-399-411-413-
417-425-429-431-439-441-447-451-467-497-503-250300-
/O.NEW.KWNS.TO.A.0100.150424T1910Z-150425T0300Z/

TX
. TEXAS COUNTIES INCLUDED ARE

ANDERSON BELL BOSQUE
BROWN CALLAHAN COKE
COLEMAN COLLIN COMANCHE
CONCHO CORYELL DALLAS
DELTA DENTON EASTLAND
ELLIS ERATH FALLS
FISHER FREESTONE HAMILTON
HASKELL HENDERSON HILL
HOOD HOPKINS HUNT
IRION JACK JOHNSON
JONES KAUFMAN LAMPASAS
LIMESTONE MCCULLOCH MCLENNAN
MENARD MILLS NAVARRO
NOLAN PALO PINTO PARKER
RAINS ROCKWALL RUNNELS
SAN SABA SCHLEICHER SHACKELFORD
SOMERVELL STEPHENS STERLING
TARRANT TAYLOR THROCKMORTON
TOM GREEN VAN ZANDT WISE
YOUNG
$$


ATTN...WFO...FWD...SJT...

[TarrantWx]

SEL0

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 100
NWS STORM PREDICTION CENTER NORMAN OK
210 PM CDT FRI APR 24 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF
WESTERN AND NORTH TEXAS

* EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 210 PM UNTIL
1000 PM CDT.

* PRIMARY THREATS INCLUDE...
A FEW TORNADOES LIKELY WITH A COUPLE INTENSE TORNADOES POSSIBLE
SCATTERED LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 3
INCHES IN DIAMETER LIKELY
SCATTERED DAMAGING WINDS AND ISOLATED SIGNIFICANT GUSTS TO 75
MPH POSSIBLE

SUMMARY...SCATTERED STORMS FORMING OVER THE EASTERN PERMIAN BASIN
WILL INTENSIFY THIS AFTERNOON INTO EARLY EVENING ACROSS THE BIG
COUNTRY TO NORTH-CENTRAL TEXAS. ADDITIONALLY...A FEW DISCRETE STORMS
SHOULD DEVELOP ACROSS PARTS OF CENTRAL TEXAS IN THE LATE AFTERNOON.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST OF SAN ANGELO
TEXAS TO 70 MILES NORTHEAST OF CORSICANA TEXAS. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU0).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

[Texas Snowman]

A couple of intense tornadoes possible.

Oh boy, that wouldn't be good.

[Tireman4]

More HGX AFD

000
FXUS64 KHGX 241814
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
114 PM CDT FRI APR 24 2015

.AVIATION...
MADE SOME TWEAKS TO THE TAFS FOR THIS AFTN/EVENING. FOR THE MOST
PART HAVE TAKEN THE MENTION OF PCPN OUT FOR THE REST OF THE AFTN
(SAVE FOR THE LBX WHERE THERE MIGHT BE SOME ISO DEVELOPMENT COM-
ING IN FROM THE SW). SHORT-TERM MODELS IN GENERAL AGREEMENT WITH
THE TIMING FOR THE START OF THE NEXT BATCH OF STORMS TONIGHT AOA
06Z. 41

[Texas Snowman]

Atmosphere is wound up. Storms continue to fire up even near Red River where so much rain has fallen in the last 12 hours.

[TexasStorm]

Cell down near Cleburne needs watching. It has not got its act together but keeps intensifying on each scan.

[Texas Snowman]

I was just about to mention that. Fort Worth might need to watch out for that one.

[Texas Snowman]

Storms are really firing up SW of Abilene