Severe Thunderstorm Warning 298, NWS Midland/Odessa, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX
658 PM CDT WED JUL 29 2009

.DISCUSSION...
SEE AVIATION DISCUSSION BELOW.

&&

.AVIATION...
SHOWERS AND THUNDERSTORMS ARE APPROACHING THE KCNM TERMINAL AND
WILL TEMPO THAT LOCATION FOR MVFR CONDITIONS THROUGH 04Z. A COMPLEX
OF THUNDERSTORMS CURRENTLY ACROSS EASTERN NEW MEXICO IS EXPECTED
TO TRACK SOUTHEAST AND IMPACT KHOB BY 04Z OR 05Z AND KMAF BY 07Z
WITH TEMPO MVFR CONDITIONS. OTHERWISE A STRONG COLD FRONT WILL PUSH
SOUTH AND RESULT IN A WIND SHIFT THURSDAY AFTERNOON WITH INCREASING
CHANCES FOR THUNDERSTORMS ONCE AGAIN. FOR NOW HAVE PUT IN A PROB
30 GROUP FOR MVFR CONDITIONS FROM 18Z TO 24Z FOR THE TERMINALS.

12

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.PREV DISCUSSION... /ISSUED 317 PM CDT WED JUL 29 2009/

DISCUSSION...
SIGNIFICANT HYDROMETEOROLOGICAL IMPACTS OVER THE NEXT 48 HOURS ARE
THE POTENTIAL FOR SEVERE WINDS AND HEAVY RAINFALL DURING THE LATE
NIGHT AND EARLY MORNING HOURS.

CONVECTION IS ONCE AGAIN FIRING OVER THE MOUNTAINS AND ADJACENT
PLAINS OF EASTERN NEW MEXICO. SUFFICIENT BUOYANCY AND SHEAR
APPEARS TO BE IN PLACE FOR UPSCALE DEVELOPMENT INTO ONE OR MORE
FORWARD PROPAGATING MCSS. PRECISE PLACEMENT OF THESE MCSS IS
PROBLEMATIC AT THIS TIME...HOWEVER...THIS SITUATION LOOKS SOMEWHAT
SIMILAR TO LAST NIGHT...WITH AN AXIS OF HIGHER LOW LEVEL THETAE
AIR ROUGHLY ALONG AN AXIS EXTENDING FROM AMARILLO SOUTH ACROSS THE
TEXAS SOUTH PLAINS TO THE LOWER TRANS PECOS. OUR CONCEPTUAL MODEL
IS THUS SIMILAR TO WHAT HAPPENED LAST NIGHT...WITH THE GREATEST
POPS DRAWN OVER SOUTHEASTERN NEW MEXICO EAST ACROSS THE NORTHERN
PERMIAN BASIN. WITH DRIER MIDTROPOSPHERIC AIR NOTED...STRONGER
COLD POOLS SHOULD BE GENERATED...WHICH NOT ONLY IMPLIES A GREATER
THREAT OF SEVERE OUTFLOW WINDS BETWEEN 9 PM CDT AND 3 AM CDT...BUT
ALSO THE POTENTIAL FOR BOUNDARY INTERACTIONS AND SUBSEQUENT CELL
REGENERATION. LOCALLY HEAVY RAINFALL IS ALSO INDICATED WITH
PRECIPITABLE WATER VALUES IN EXCESS OF 3 CM NOTED ACROSS MUCH OF
THE CWA OVERNIGHT. THIS WILL IN TURN IMPLY A THREAT OF FLASH
FLOODING...PARTICULARLY IN AREAS THAT RECEIVED SIGNIFICANT RAINS
LAST NIGHT.

THE MCSS WILL TRANSLATE EAST SOUTHEAST OVERNIGHT AND OUTFLOW FROM
THESE SYSTEMS WILL SERVE TO REINFORCE A SURFACE BOUNDARY THAT
SHOULD EXTEND MORE OR LESS ALONG THE PECOS RIVER BY THURSDAY
AFTERNOON. AN APPROACHING SHORTWAVE TROUGH EMBEDDED WITHIN
NORTHWESTERLY FLOW ALOFT WILL PROVIDE SUFFICIENT BACKGROUND DEEP
LAYER LIFT AND INSTABILITY...AND WITH SUFFICIENT LOW LAYER UPSLOPE
FLOW BEHIND THE FRONT ADVECTING MOIST AIR OVER THE REGION...RAIN
CHANCES LOOK PRETTY GOOD THURSDAY AFTERNOON AND THURSDAY EVENING...
ESPECIALLY FROM THE DAVIS MOUNTAINS NORTHEAST ACROSS THE PERMIAN
BASIN. STORM TOTAL RAINS WELL OVER AN INCH ARE NOT OUT OF THE
QUESTION...AND GIVEN ANTECEDENT CONDITIONS A FLASH FLOOD WATCH MAY
BE NEEDED FOR AREAS OF THE CWA THURSDAY NIGHT.

THEREAFTER...THE STRONG UPPER LEVEL HIGH EXPANDS TO THE EAST AS
THE PERSISTENT AND ANOMALOUSLY DEEP UPPER TROUGH OVER EASTERN NOAM
WEAKENS A BIT. THIS WILL SERVE TO DIMINISH THE POTENTIAL FOR
THUNDERSTORMS INTO THE WEEKEND WITH THE EXCEPTION OF THE
MOUNTAINS...WHERE HEATING AND RESIDUAL MOISTURE SHOULD BE ENOUGH
TO GIN UP SOME ISOLATED AFTERNOON AND EVENING THUNDERSTORMS.

IN CLOSE...THE GFS WAS PRETTY MUCH USELESS GIVEN ITS PROPENSITY
FOR CONVECTIVE FEEDBACK...AND INSTEAD WE OPTED TO FOCUS ON THE
NAM12 WITH INPUT FROM 4KM NAM-ARW MODEL GUIDANCE. QPF AND POPS
WERE DRAWN TO THE EXPECTED EVOLUTION OF TONIGHTS MCS ACTIVITY...
THEN TOWARD THE HPC SOLUTION FOR THURSDAY AND THURSDAY NIGHT. HAVE
UNDERCUT GUIDANCE HIGH TEMPERATURES TOMORROW THROUGH SATURDAY
GIVEN PRECIP...LOWERED INSOLATION...AND ACCOUNTING FOR
EVAPOTRANSPIRATION...THEN NUDGED HIGHS TOWARD THE GEFS SOLUTION.
MORNING LOWS ARE EXPECTED TO STAY CLOSE TO CLIMATOLOGY...AND THIS
IS REFLECTED IN A BLEND OF NUMERICAL GUIDANCE.

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.MAF WATCHES/WARNINGS/ADVISORIES...
NM...NONE.
TX...NONE.

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