Flash Flood in Texas, February 27, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
200 PM CST TUE FEB 27 2001

THE POTENTIAL FOR FLASH FLOODING AND RIVER FLOODING HEADLINES THIS
FORECAST THROUGHOUT MUCH OF THE WEEK AS THE UPPER FLOW PATTERN ACROSS
THE SOUTHERN PLAINS CHANGES LITTLE THROUGH AT LEAST THURSDAY.

MODEL DISCREPANCIES ARE HAMPERING AN ALREADY DIFFICULT FORECAST IN THE
MAKING AS THEY CONTINUE TO HAVE PROBLEMS WITH WEAK SUBTROPICAL SHORTWAVES
EJECTING INTO THE LOWER MISS VALLEY. WHILE MODELS INITIALIZED WELL THIS
MORNING WITH THE HEAVY RAINFALL ALONG AND NORTH OF THE I-20 CORRIDOR...ALL
DIVERGE OVERNIGHT WITH AREAS OF MID LEVEL LIFT AND ASSOCIATED DIVERGENCE.
ONE THING MODELS DO AGREE WITH IS SOME DRIER AIR ADVECTING NORTHWARD OUT
OF CENTRAL/SE TX OVERNIGHT. THIS SUPPORTED WITH THE 12Z SOUNDING AT CRP
AND LACK OF CONVECTION ACROSS THIS REGION DURING THE DAY. THIS COULD
ENHANCE THE SEVERE WEATHER THREAT THIS EVENING/TNGT WHERE DESCENT HEATING
THIS AFTN HAS LED TO A HIGHLY UNSTABLE ATMOSHPERE.

AT THE SURFACE...NEARLY STATIONARY COLD FRONT SHOULD GET A PUSH SOUTH
OVERNIGHT WITH THE MESOETA SHOWING IT NEAR A LFK...SHV...MLU LINE BY
MIDNIGHT. WARM FRONT MAKING GOOD PROGRESS NORTH THIS AFTERNOON WILL MEET
UP WITH COLD FRONT TONIGHT. GOOD THETA-E CONVERGENCE AND PACKING NOTED
ALONG THESE BOUNDARIES COMBINED WITH HIGH PRECIPITABLE WATER VALUES AND
700-300MB Q-VECTOR CONVERGENCE MAXIMUM ACROSS E TX OVERNIGHT WILL SUPPORT
A CONTINUED HEAVY RAINFALL THREAT. GOOD THETA-E CONVERGENCE ASSOCIATED
WITH 850MB TROUGH DIVING SOUTH OUT OF CENTRAL OK WILL RESULT IN A
CONTINUED OVERRUNNING CONVECTIVE RAINFALL THREAT ACROSS THE NORTHERN
THIRD OVERNIGHT. RAIN MAY TAPER OFF OVERNIGHT ACROSS THE EAST BUT WILL
LIKELY SEE REDEVELOP ACROSS CENTRAL TEXAS...MOVING EAST INTO WATCH AREA
AFTER MIDNIGHT. WHILE MODELS SUGGEST THAT HEAVY RAINFALL MAY NOT MAKE IT
INTO CENTRAL LOUISIANA UNTIL SECOND PERIOD TIME FRAME...A COMBINATION OF
LOW CONFIDENCE IN MODEL PERFORMANCE AND HEAVY RAINFALL ACROSS THIS REGION
ON MONDAY WILL RESULT IN THIS AREA REMAINING IN THE WATCH.

AXIS OF HEAVIEST RAINFALL SHOULD SHIFT WELL NORTH OF THE FRONT INTO THE
MIDDLE RED VALLEY OF NE TX/SE OK/SW AR ON WED AS RATHER POTENT PIECE OF
ENERGY EJECTS OUT OF NORTH TX/S OK. HOWEVER...AGAIN DO TO LOW MODEL
CONFIDENCE...WILL CHOOSE TO ONLY EXPAND WATCH THROUGH TONIGHT AND ALLOW
FUTURE SHIFTS TO ADJUST OR EXPAND AS NECESSARY.

TEMPS ARE A CRAP SHOOT AS THEY OFTEN ARE WITH THIS TYPE OF SITUATION BUT
ONCE FRONT PUSHES THROUGH OVERNIGHT TONIGHT...EXPECT LITTLE DIURNAL CHANGE.
PRELIMINARY NUMBERS ARE FOR COORD PURPOSES ONLY...13

SHV 50/51/45/51 7567  MLU 50/53/45/52 I7555  TXK 45/47/41/47 8554
TYR 49/50/43/50 7567  LFK 57/58/48/55 6567

.SHV...FLASH FLOOD WATCH TONIGHT FOR ALL ZONES.