Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 241321
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
921 AM EDT WED MAY 24 2017

...VALID 15Z WED MAY 24 2017 - 12Z THU MAY 25 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
CAE 15 ENE MLJ 10 SSE LZU 35 NNE 1A5 20 NE TYS 20 WSW OQT
20 S CSV 30 W CSV 35 NNE GLW 30 NNE LOU 35 WNW WMO 15 NW DAY
50 SSE ILN 25 NNW HTS 25 NE 3I2 30 ENE PKB 10 NE EKN 25 W OKV
20 SW JYO RMN 25 NW PTB 20 SE HBI CAE.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SSW HRT 20 WNW MAI 40 SSW WRB 20 E DBN 30 NNE JYL 15 ENE HXD
50 ENE DAB 30 ESE COF 10 SSE FPR 25 SE APF 70 NW KEY.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSW MKJ 15 WSW PSK 10 WNW PSK 20 S LWB HSP 25 NE HSP
15 SSW SHD 25 NW FVX 25 SSW LYH 10 WNW DAN GSO RUQ 10 SW SVH
10 SSE TNB TNB 20 WNW GEV 10 SSW MKJ.


SOUTHERN TO CENTRAL APPALACHIANS INTO THE OH VALLEY/FLORIDA

ADDITIONAL HEIGHT FALLS WILL BE DIVING INTO THE BASE OF THE UPPER
TROF THROUGH THE OH---TN---VALLEYS---SOUTHERN APPALACHIANS AND
SOUTHEAST.  THE LOW TO MID LEVEL FLOW WILL BE BACKING IN RESPONSE
TO THIS AMPLIFYING UPPER TROF FROM THE UPPER TN VALLEY---SOUTHERN
TO CENTRAL APPALACHIANS---MID ATLANTIC AND INTO THE OH VALLEY.
THIS WILL SUPPORT A FEW ORGANIZED AREA OF PRECIPITATION...THE
FIRST OF WHICH IS IN THE VICINITY OF THE UPPER LOW OVER PORTIONS
OF THE UPPER OH VALLEY WHERE THE ASSOCIATED COMMA HEAD/DEFORMATION
PRECIPITATION BAND MAY PIVOT THIS AFTERNOON AND EVENING.  THE
STORM SCALE ENSEMBLE MEAN SHOWS RAINFALL TOTALS OF 1-2 INCHES
ACROSS THE REGION.    ANOTHER MAX AREA POSSIBLE ACROSS THE
SOUTHERN TO CENTRAL APPALACHIANS WHERE THE SOUTH SOUTHEASTERLY LOW
LEVEL FLOW WILL ENHANCE UVVS IN THE EASTERN UPSLOPE SIDE FROM
WESTERN NC INTO SOUTHWEST TO WESTERN VA AND EASTERN WV.  WHILE HI
RES GUIDANCE IS NOT IN AGREEMENT WITH LOCATION---THE MEAN SHOWS
1.2.5 INCHES OF RAIN IN SOUTHWEST VA TO THE NC BORDER. A SLIGHT
RISK REMAINS OVER FAR SOUTHERN WV INTO ADJACENT SOUTHWEST VIRGINIA
AND FAR NW NC WHERE THE 1 HOURLY FFG VALUES ARE BETWEEN .50-1".

FINALLY...HEAVY SHOWERS AND STORMS ARE FORECAST TO MOVE ONSHORE
FROM THE GULF OF MEXICO ACROSS THE NORTHERN AND CENTRAL FL
PENINSULA...WITH THE RAP AND ECMWF BOTH SHOW 850 MB INFLOW NEAR 50
KT. CONFLUENT FLOW WITH UPPER DIVERGENCE/LOWER CONVERGENCE
COUPLETS COMBINES WITH RAP/ECMWF FORECAST 2 INCHES OF AVAILABLE
PRECIPITABLE WATER TO LEAD TO NUMEROUS SHOWERS/STORMS.  STORMS
WILL PRODUCE OUTFLOWS INTERACTING WITH SEA AND LAKE BREEZES SO
DIURNAL DESTABILIZATION ALLOWS STORMS TO FORM FURTHER SOUTH INTO
CENTRAL FL THIS AFTERNOON AND SOUTH CENTRAL FLORIDA LATE THIS
AFTERNOON AND TONIGHT. THE HIGH FLASH FLOOD GUIDANCE FOLLOWING
RECENT DRY CONDITIONS LEAVES THE RISK AS MARGINAL IN SPITE OF THE
STORM SCALE MEAN RAINFALL OF 2-3 INCHES ACROSS MUCH OF THE
NORTHERN PENINSULA OF FL.

FINALLY...DIFFERENTIAL HEATING OCCURS IN CENTRAL AND SOUTHERN GA
WITH THE 12Z HIGH RES RAPID REFRESH SHOWING MIXED LAYER CAPES TO
2000 J/KG BY MID AFTERNOON.  SHOWERS/STORMS INITIATE IN THE AREA
WHERE PRIOR SHOWERS HAD NOT OCCURRED WITH A FEW OF THE HIGH RES
ENSEMBLE MEMBERS SHOWING BANDS OF SHOWERS/STORMS DEVELOPING.
BRIEFLY TRAINING CELLS COULD RESULT IN 1-2 INCHES OF RAIN BEFORE
THE BANDS PROGRESS FURTHER EAST NORTHEAST.

PETERSEN

$$





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