Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 152246
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
645 PM EDT WED OCT 15 2014

...VALID 00Z THU OCT 16 2014 - 00Z FRI OCT 17 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
BID 50 SSE HTO 95 SSE FOK 95 SE MJX 80 SE ACY 50 ESE WWD
15 SSE WWD 15 NNW DOV 20 NNW ILG 15 WSW MPO 20 WNW MSV
35 WSW SCH 15 NE SCH 25 SSW VSF 15 N AFN 10 S ASH 10 SW OWD BID.


DEEP LAYERED MOISTURE AHEAD OF A STRONG AND HIGHLY AMPLIFIED MID
LEVEL TROUGH CROSSING THE EASTERN UNITED STATES WILL FEED LOW
TOPPED CONVECTION ACROSS PORTIONS OF THE NORTHERN MID ATLANTIC
INTO NY STATE AND NEW ENGLAND DURING THE EVENING AND OVERNIGHT
HOURS. A 40 KNOT LOW LEVEL SOUTHERLY FLOW WILL CONTINUE TO PUMP
HIGH MOISTURE CONTENT AIR INTO THE REGION AHEAD OF A SURFACE FRONT
EXTENDING FROM WESTERN NY STATE THROUGH THE MID ATLANTIC STATES.
THE LATEST BLENDED TOTAL PRECIPITABLE WATER PRODUCT SHOWED A 1.90
INCH (WHICH IS BETWEEN TWO AND THREE STANDARD DEVIATIONS ABOVE
NORMAL) BULLSEYE OVER SOUTHEAST PA AND SOUTHERN NJ. AS THIS
MOISTURE SLUG MOVES NORTH...IT WILL FEED LOW TOPPED CONVECTION
SPANNING FROM SOUTHEAST PA INTO CENTRAL AND NORTHERN NY STATE.

INSTABILITY IS THE LIMITING FACTOR WITH RESPECT TO CONVECTION...
BUT THE LATEST RAP MODEL SOUNDINGS FOR THE REGION SHOWED MOIST
PROFILES THROUGH AT LEAST 16/04Z...SUGGESTING THAT THE CONVECTION
IS DOMINATED BY WARM RAIN PROCESSES. RAINFALL RATES (BASED ON
LOCAL RADAR ESTIMATES) ARE GENERALLY BETWEEN 0.50 AND 1.00
INCHES...WITH THE HIGHEST RATES ACROSS SOUTHEAST PA...WHICH APPEAR
TO BE SUPPORTED BY LOCAL MESONET OBSERVATIONS. IT IS POSSIBLE
THAT...DUE TO THE WARM RAIN PROCESSES...THAT THE RADAR ESTIMATES
COULD BE UNDERDONE...ESPECIALLY ACROSS NORTHEAST PA INTO CENTRAL
NY STATE.

THE LATEST HIGH RESOLUTION GUIDANCE (INCLUDING THE LATEST
RAP...HRRR AND NAM CONEST) ARE RUNNING A BIT BEHIND REALITY...BUT
CLOSE ENOUGH TO SUGGEST THAT 1.00 TO 2.00 INCHES OF QPF SHOULD BE
EXPECTED WITH THE LOW TOPPED CONVECTION THROUGH ABOUT 16/08Z
ACROSS PORTIONS OF NJ/SOUTHEAST NY STATE INTO WESTERN NEW ENGLAND.
BASED ON THE HIGH RESOLUTION GUIDANCE...AND THE CURRENT RADAR
TRENDS...THE SLIGHT RISK AREA WAS WAS ADJUSTED WESTWARD TO INCLUDE
MORE OF EASTERN PA AND SOUTHEAST NY STATE...WHERE SOME TRAINING IS
EXPECTED DURING THE EVENING. SINCE RAINFALL RATES SHOULD REMAIN
BELOW 1.50 INCHES IN AN HOUR...IT APPEARS AS THOUGH MOST FLOODING
ISSUES MAY BE MORE ALONG THE LINES OF FLOOD VS FLASH
FLOOD...ESPECIALLY IN URBAN AREAS.

HAYES
$$




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