Quantitative Precipitation Forecast
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FOUS30 KWBC 182344
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
743 PM EDT SAT APR 18 2015

...VALID 00Z SUN APR 19 2015 - 00Z MON APR 20 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
EXX 10 E MTV 10 SW ROA 10 SSW PSK 10 SSW MKJ 15 NW TNB
25 NNW AVL 10 WNW RHP 25 ENE DNN 10 NNW 47A 10 NE LZU 20 W 27A
GRD 35 SW UZA 10 E UZA EXX.


...CENTRAL/EASTERN GULF COAST...

THE LATEST GLOBAL AND HI-RES GUIDANCE ARE HANDLING THE ONGOING
CONVECTION OVER THE NORTHERN GULF OF MEXICO QUITE POORLY AND AS A
RESULT ARE LIKELY NOT ACCURATELY DEPICTING THE FORECAST CONVECTIVE
EVOLUTION OF PRECIPITATION ACROSS THE GULF COAST STATES OVERNIGHT
AND ON SUN. NEVERTHELESS...THE GUIDANCE AGAIN INDICATES THAT A
SHORTWAVE THAT IS EJECTING NORTHEAST ACROSS NORTHEAST MEXICO WILL
CROSS SOUTHEAST TX AND MOVE INTO THE LOWER MS VALLEY AND CENTRAL
GULF COAST REGION LATER TODAY AND TONIGHT. THIS SHOULD HELP
INCREASE THE SOUTHWESTERLY LOW LEVEL JET/WARM ADVECTION INTO AND
OVER A WARM FRONT THAT WILL GRADUALLY LIFT OR REDEVELOP FARTHER
NORTH AND AWAY FROM THE GULF COAST. THIS ENERGY WILL THEN LIFT
INTO THE TN VALLEY AND SOUTHERN APPALACHIANS ON SUN. THE RESULT
SHOULD BE REDEVELOPMENT AND EXPANSION OF MORE CONCENTRATED AND
ORGANIZED AREAS OF HEAVY SHOWERS AND THUNDERSTORMS. HOWEVER...THE
PRESENCE IN THE SHORT-TERM OF A CONVECTIVELY REINFORCED BOUNDARY
OVER THE NORTHERN GULF OF MEXICO MAY TEND TO IMPEDE OR DELAY SOME
OF THE CONVECTIVE REDEVELOPMENT AT LEAST FOR AREAS NEAR THE
IMMEDIATE GULF COAST. CONVECTION SHOULD BECOME BETTER FOCUSED OVER
CENTRAL/SOUTHERN AL AND INTO GA AND THE FL PANHANDLE ON SUN ONCE
STRONGER INSTABILITY AND MOISTURE TRANSPORT BECOMES ESTABLISHED.
WPC GENERALLY LEANED TOWARD THE 12Z WRF-ARW FOR THE DETAILS OF THE
CONVECTION ACROSS THIS REGION AS THIS MODEL TENDED TO HAVE THE
BEST HANDLE OF THE ONGOING ACTIVITY ACROSS THE REGION. CONFIDENCE
IS LOW ON EXACT PLACEMENT AND AMOUNTS...BUT LOCALLY 2 TO 3 INCHES
OF RAIN WITH ISOLATED HEAVIER AMOUNTS ARE POSSIBLE WHICH WILL
LIKELY FOCUS AT LEAST SOME RUNOFF PROBLEMS.


...SOUTHERN APPALACHIANS...

SOUTHERN STREAM SHORTWAVE ENERGY LIFTING NORTHEAST OUT OF THE GULF
COAST STATES WILL CROSS THE TN VALLEY AND SOUTHERN APPALACHIANS BY
LATE SUN. A SIGNIFICANT RESURGENCE OF DEEPER MOISTURE/HIGHER PWATS
OWING TO AN INCREASE IN WARM ADVECTION/LOW LEVEL JET
ENERGY...COUPLED WITH THE LARGER SCALE SHORTWAVE DYNAMICS AND THE
NORTHWARD ADVANCE OF A FRONT SHOULD HELP FOCUS HEAVIER SHOWERS
LATE TONIGHT AND SUN UP ACROSS THE INTERIOR OF THE SOUTHEAST AND
ESPECIALLY THE SOUTHERN APPALACHIANS WHERE DEVELOPING UPSLOPE FLOW
WILL SET THE STAGE FOR HEAVY RAINFALL AMOUNTS. THE GLOBAL MODELS
LED BY THE ECMWF/UKMET/NAM AND GFS ALL FOCUS HEAVY AMOUNTS ACROSS
FAR NORTHEAST GA...NORTHWEST SC AND WRN NC AND THIS IS SUPPORTED
BY THE HI-RES WRF-ARW AS WELL. RAINFALL AMOUNTS OF 2 TO 4 INCHES
WITH ISOLATED AMOUNTS IN EXCESS OF 5 INCHES WILL BE POSSIBLE. THIS
WILL FAVOR EXCESSIVE TOTALS AND AS A RESULT A SLIGHT RISK HAS BEEN
HIGHLIGHTED HERE.

ORRISON/HURLEY
$$





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