Flash Flood Guidance
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000
AWUS01 KWNH 292221
FFGMPD
TXZ000-300120-

MESOSCALE PRECIPITATION DISCUSSION 0151
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
620 PM EDT FRI APR 29 2016

AREAS AFFECTED...SE TEXAS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 292220Z - 300120Z

SUMMARY...HIGHLY EFFICIENT CONVECTIVE EVENT WITH REPEAT
DEVELOPMENT AND TRAINING IS POSSIBLE.  STILL MUCH UNCERTAINTY AS
TO WHEN AND WHERE OR EVEN IF A FOCUSED EVENT WOULD SETUP.

DISCUSSION...DEPICTING A WORST CASE SCENARIO ON A LOCAL
SCALE...RAPID REFRESH HI-RES CAMS SUCH AS THE HRRR AND RAP
CONTINUE TO SUGGEST THE EVOLUTION OF A LINE OF CONVECTION ACROSS
SE TX.  A SURGE OF HIGH MOISTURE IS ANALYZED IN MULTIPLE REMOTE
SENSING PRODUCTS WITH BLENDED TPWS VALUES IN THE 2-2.25"
RANGE...SUPPORTED BY 50 KT LLJ.  ADDITIONALLY ALOFT...SUBTLE
SHORTWAVE NEAR KLRD WOULD PROVIDE MILD DPVA AND WITH INCREASED
DIFFLUENCE ALOFT BETWEEN A SPLIT JET SETUP...THE POTENTIAL FOR
REDEVELOPMENT/BACKBUILDING TO OCCUR.  AS THE POSSIBLE COMPLEX
DEVELOPS A WEAK COLD POOL AND SHIFTING NE OF SHORTWAVE ENERGY
WOULD LEAVE AN EFFECTIVE OUTFLOW BOUNDARY ORIENTED FAVORABLY TO
THE CONTINUED STRONG ONSHORE MOISTURE TRANSPORT FOR CONTINUED
STRONG CONVERGENCE AND FLUX TO MAINTAIN RAINFALL EFFICIENCIES IN
THE 3-4"/HR RANGE.
ALONG WITH THE RECENT HRRR/RAP RUNS THE 18Z GEM-REGIONAL IS ALSO
SUPPORTIVE OF THIS SETUP WITH TOTALS THROUGH 04-05Z IN THE 4-5"
RANGE.

HOWEVER...EARLIER THIS AFTERNOON A SURGE OF DRY AIR IN THE RETURN
FLOW FROM THE NORTH AND CENTRAL GULF HAS KEPT CINH RELATIVELY HIGH
 IN THE 25-75 J/KG RANGE.  THIS IS HELPING TO KEEP CONVECTIVE
DEVELOPMENT SEEN IN SRSO VIS/IR FROM GOES-14 FURTHER WEST; FROM
MATAGORDA BAY  NORTH TOWARD THE MATURING MCS ACROSS N TX...IN LINE
WITH SOME OF THE DRIER CAMS OVER SE TX SUCH AS THE WRF-ARW AND THE
HI-RES MEANS: HREF AND SSEO.

OBSERVATIONALLY...THE HIGHLY DEFINED CU FIELDS OVER THE WESTERN
GULF ARE WASHING OUT WITH SURGES IN THE MARINE LAYER SEEN MOVING
NORTH BETWEEN 94-96W THROUGH BREAKS IN THE SUBTROPICAL JET CIRRUS
SUGGESTING THE BULGE OF HIGHER TPWS SEEN IN EARLY MORNING POLAR
PASSES IS MAKING ITS WAY NORTH IN LINE WITH THE RAP ANALYSIS
FIELDS.  THIS BREEDS INCREASING CONFIDENCE TOWARD THE RAPID
REFRESHING CAMS TREND WITH THE POTENTIAL FOR LOCALLY HEAVY
RAINFALL LATER THIS EVENING BUT WITH A LARGE AMOUNT OF REMAINING
UNCERTAINTY AS TO WHERE THE EVENT WILL FOCUS.  WILL UPDATE MPD BY
0130Z.

GALLINA/BURKE

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...

LAT...LON   31369526 31219465 30779430 30139448 29779482
            29429527 29039598 29029667 29489698 30279685
            30889634



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