Flash Flood Warning 39, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
810 PM CDT FRI JUN 8 2001

...A DANGEROUS FLASH FLOOD THREAT PERSISTS ACROSS SOUTHEAST TEXAS
TONIGHT...

NO SIGNIFICANT CHANGES PLANNED IN 9 PM UPDATE...

THE REMNANTS OF TROPICAL DEPRESSION ALLISON, STILL PROBABLY EASIEST
TO TRACK WITH THE RUC 700MB CIRCULATION, CONTINUES TO PLAGUE THE
REGION WITH HEAVY RAINS. AT 7 PM, THE CENTER OF THIS CIRCULATION WAS
CENTERED ROUGHLY BETWEEN COLUMBUS AND SEALY, AND CONTINUED TO BECOME
MORE ELLIPTICAL WITH A NORTHEAST-SOUTHWEST AXIS.  SEVERAL FACTORS
ARE COMBINING TO FOCUS PRECIP ALONG THE SOUTHEAST SIDE AND NORTHEAST
END OF THIS CIRCULATION, ONE ITEM BEING THE STRONGER BAROCLINICITY
AT THE NORTHERN END WHERE THERE IS STILL A COOL CORE AT 700 MB, THE
OTHER BEING THE SIMILAR ELLIPTICAL STRETCHING OF THE SURFACE LOW
WITH EAST WINDS ACROSS THE NORTHERN TIER OF COUNTIES BEING MET BY
THE SOUTHEASTERLY INFLOW FROM FREEPORT TO BEAUMONT.  THIS IS
PROVIDING A NEARLY STATIC SURFACE CONVERGENCE ALONG WHICH CONVECTION
CONTINUES TO FIRE FROM PALACIOS TO PEARLAND, AND THIS CONVECTION IS
SWEEPING CYCLONICALLY ABOUT THE UPPER CIRCULATION TRACKING WITH THE
700 MB FLOW.  THIS IS CAUSING HEAVY RAINS TO TRAIN OVER PARTS OF
FORT BEND, BRAZORIA, HARRIS, MONTGOMERY, AND WALKER COUNTIES.
INCIDENTALLY, THE CURRENT RUC VALUES OF 1000MB MOISTURE FLUX
DIVERGENCE (-50) TO THE SOUTHEAST OF THE 700 MB CYCLONE CENTER ARE
THE HIGHEST I HAVE SEEN IN THE 4 DAYS I'VE WORKED THIS SYSTEM, AND
CONVECTION CONTINUES TO FIRE AGGRESSIVELY IN THIS REGION,
COMPOUNDING THE ALREADY-ONGOING FLASH FLOOD SITUATION.   AND THE
FOREGOING MAINLY ADDRESSES THE ISSUE OF THE *HEAVY* RAINS.
ELSEWHERE ACROSS THE FORECAST AREA, PRECIPITATION OF SOME SORT WAS
ACTIVE IN ALL 23 COUNTIES AT 730 PM.

AS YOU MAY HAVE GUESSED FROM THE FOREGOING, WILL BE KEEPING THE
FLASH FLOOD WATCH IN PLACE TONIGHT FOR THE ENTIRE CWA, AND EXPECT IT
WILL PROBABLY HAVE TO BE EXTENDED INTO AT LEAST SATURDAY IF NOT
BEYOND.

SO MUCH FOR THE VERY SHORT TERM.  WITH THE SLOW SOUTHWARD DRIFT OF
THE UPPER ELLIPTICAL CIRCULATION AND CONTINUED ELONGATION OF THE
SURFACE LOW, THE RESULT SATURDAY SHOULD BE A NEARLY STATIONARY
SURFACE TROUGH EXTENDING FROM BEAUMONT TO PALACIOS, WITH DECREASING
STEERING FLOW FOR CONVECTION IN THE UPPER LEVELS, RESULTING IN THE
POTENTIAL FOR A (CONTINUING) HEAVY RAIN EVENT, ESPECIALLY ALONG AND
JUST NORTH OF THE SURFACE TROUGH AXIS.  ON SATURDAY, THIS AXIS WILL
LIKELY BE ALONG AND NORTH OF A LINE FROM COLUMBUS TO LIBERTY,
SLIPPING GRADUALLY SOUTHWARD DURING THE DAY, HOPEFULLY DRAGGING
HEAVIEST PRECIP OFFSHORE SATURDAY NIGHT INTO SUNDAY.

STILL, THE MUCH OF THE REGION IS IN FOR SERIOUS FLOODING PROBLEMS IN
THE SHORT TERM.

BY SUNDAY NIGHT AND MONDAY, UPPER CYCLONE SHOULD FILL A FEW METERS,
BECOME AN OPEN WAVE, AND SHIFT INTO THE NORTHERN GULF, DECREASING
PRECIP POTENTIAL FOR A MUCH-SOAKED SOUTHEAST TEXAS.

STILL, WILL LEAVE THE CURRENTLY HIGH POP FORECAST THROUGH SUNDAY,
AND NO CHANGES TO EXTENDED FORECAST.

38/36/30/41/35/48

.HGX...FLASH FLOOD WATCH ALL OF SO2UTHEAST TEXAS THROUGH TONIGHT.
       EXPECT TO RETAIN SCEC 0-60 NM WATERS.

PRELIMS...
CLL TT 071/082 071/082 071 +95
IAH TT 072/084 072/085 072 +97
GLS TT 075/084 075/084 075 +97