Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 190101
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
800 PM EST SAT NOV 18 2017

...VALID 01Z SUN NOV 19 2017 - 12Z SUN NOV 19 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNE CRW 3I2 20 WNW HTS 20 NNE LOZ 10 N CSV 20 NE MDQ
15 NE MSL 45 NW MSL 40 ENE MKL 20 NNW HOP 40 SSE BMG 20 NE GEZ
20 WNW AOH 20 S CXPT 20 NW ERI 15 NW JHW 25 ENE ELZ 25 NE IPT
15 ESE SEG 30 ENE AOO 20 NNE 2G4 15 S EKN LWB 25 ESE CRW
20 NNE CRW.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 E LHQ 10 NNE ILN 20 NW WMO 30 NW DAY 10 S FDY 20 W LPR
15 NE CGF 10 NNW GKJ 25 SSE JHW 20 NNE DUJ 15 NNE IDI 15 SE AGC
15 SW AFJ 20 E LHQ.


...OH/TN VALLEYS INTO THE NORTHERN MID-ATLANTIC...

A LONGWAVE TROUGH CONTINUES TO ADVANCE EAST THIS EVENING TOWARD
THE APPALACHIANS AND IS DRIVING A STRONG COLD FRONT ACROSS THE
OH/TN VALLEYS TO THE SOUTH OF A 986 MB LOW SITUATED OVER CENTRAL
LAKE ERIE AS OF 00Z. THERE CONTINUES TO BE A LINE OF CONVECTION
ALONG AND AHEAD OF THE COLD FRONT ACROSS PARTS OF EASTERN
OH/WESTERN PA AND STRETCHING SOUTH DOWN THROUGH EASTERN
KY...EASTERN TN AND NORTHERN AL. A SOUTH-SOUTHWEST LOW LEVEL JET
OF NEAR 50 KTS CONTINUES AHEAD OF THE COLD FRONT WHICH IS
FOSTERING A NOSE OF 1.25+ INCH PWATS ACROSS THE REGION...BUT THE
BEST INSTABILITY AT THIS TIME IS WELL SOUTH DOWN ACROSS AREAS OF
THE GULF COAST STATES AT THIS TIME...WITH MUCH OF THE OH/TN VALLEY
REGION SEEING MUCAPE VALUES OF ONLY 100 TO 200 J/KG GIVEN THE LOSS
OF DIURNAL HEATING.  THE CONVECTION IN PARTICULAR ACROSS THE OH
VALLEY HAS BEEN WEAKENING SUBSTANTIALLY OVER THE LAST FEW HOURS
AND THIS TREND WILL CONTINUE OVERNIGHT AS DECREASING INSTABILITY
WILL ALLOW CONVECTION TO DAMPEN FURTHER. FLASH FLOOD GUIDANCE
VALUES REMAIN RATHER LOW OVER FAR EASTERN OH AND WESTERN PA...BUT
WITH RAINFALL RATES DECREASING AND THE CONVECTION ENCOUNTERING AN
INCREASINGLY STABLE BOUNDARY LAYER...THE THREAT FOR FLASH FLOODING
IS DECREASING. AS SUCH...THE SLIGHT RISK AREA IS BEING REMOVED AT
THIS TIME. THE MARGINAL RISK AREA WILL REMAIN IN EFFECT TO ACCOUNT
FOR THE CURRENT CONVECTION.

ORRISON
$$





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