Quantitative Precipitation Forecast
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FOUS30 KWBC 260827
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
426 AM EDT WED APR 26 2017

...VALID 12Z WED APR 26 2017 - 12Z THU APR 27 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 E GMJ 20 NW AIZ 10 NW PPQ 30 NE GBG 15 E DLL 25 WNW MKG
15 E LWA 15 NNE HUF 20 ENE M30 10 SSE CKV 40 NNE TUP 30 WSW TUP
20 S GLH 25 SW ELD 30 SW TXK 25 WSW PRX MLC 20 E GMJ.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 NE PVC SFM AUG 25 WNW CWSS 25 NE CWSS 15 ENE CWPE CWVU.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW RSV 15 W RSV 30 N DYR 10 E MKL 25 SSE OLV PBF 10 S DEQ
45 SE MLC JSV 15 S SLG 25 NNW UNO STL 15 ENE AAA 15 SE JOT
35 S VPZ 20 NNW RSV.


...EASTERN OK INTO THE LOWER/MID MS VALLEY AND PORTIONS OF THE
OH/TN VALLEY...

AS OF 08Z CONVECTION IS ONGOING ALONG A NORTHEAST TO SOUTHWEST
ORIENTED LINE ACROSS PORTIONS OF MO...EASTERN OK AND NORTHWEST AR.
THE APPROACH OF ADDITIONAL SHORTWAVE ENERGY AND INCREASED UPPER
LEVEL DIFFERENCE SHOULD LEAD TO ADDITIONAL CONVECTIVE DEVELOPMENT
INTO EARLY MORNING ACROSS PORTIONS OF EASTERN OK INTO WESTERN AR
AND SOUTHERN MO. EXPECT THAT THERE COULD BE A PERIOD OF TRAINING
CONVECTION THIS MORNING INTO EARLY AFTERNOON ACROSS PORTIONS OF
FAR EASTERN OK INTO CENTRAL AND NORTHERN AR. IT IS HERE WHERE
THERE IS A PERIOD LATER TONIGHT INTO WEDNESDAY MORNING WHERE WE
SEE AN INCREASE IN 850 MB MOISTURE TRANSPORT CONVERGENCE...WITH
CORFIDI VECTORS GENERALLY PARALLEL TO THE ORIENTATION OF THE
CONVERGENCE AXIS. THIS SUGGEST WE COULD SEE SOME WEST TO EAST
TRAINING FOR A PERIOD INTO EARLY WEDNESDAY AFTERNOON. EXPECTING
AREAL AVERAGED RAINFALL OF 1-3" ACROSS THIS AREA...WITH LOCALIZED
3-5" AMOUNTS PROBABLE. BY EARLY TO MID AFTERNOON THE WAVE AND
FRONT BECOME MORE PROGRESSIVE ACROSS THIS REGION AND THE
ORIENTATION OF THE FRONT AND LOW LEVEL MOISTURE TRANSPORT BECOME
MORE SUGGESTIVE OF A PROGRESSIVE EASTWARD MOVING CONVECTIVE LINE.
THIS SHOULD HELP KEEP AMOUNTS FROM GETTING TOO EXTREME ACROSS
OK/AR. THIS LINE WILL MOVE INTO WESTERN TN BY THIS EVENING. THE
LINE SHOULD BE PROGRESSIVE BY THIS TIME...BUT HEAVY RAINFALL RATES
ARE STILL LIKELY WHICH COULD RESULT IN SOME LOCALIZED FLASH FLOOD
ISSUES IN MORE SUSCEPTIBLE AREAS. HAVE A SLIGHT RISK FOR LOCATIONS
THAT SHOULD SEE THE HIGHEST RAINFALL TOTALS FROM EASTERN OK INTO
CENTRAL/NORTHERN AR AND FAR WESTERN TN.


ALSO COULD SEE SOME TRAINING FROM SOUTHEAST MO INTO SOUTHERN
IL...AS THIS AREA CURRENTLY APPEARS TO BE NEAR THE PIVOT POINT OF
CONVECTION AS THE SYSTEM BECOMES MORE NEUTRAL TO NEGATIVELY TILTED
THIS AFTERNOON. THUS WOULD EXPECT A LONGER DURATION OF CONVECTIVE
ACTIVITY ACROSS THIS AREA...ALTHOUGH THE PROGRESSIVENESS OF THE
WAVE WILL EVENTUALLY PUSH THE FRONT EASTWARD AND END THE
CONVECTIVE THREAT EARLY TONIGHT. A PRETTY STRONG HIGH RES MODEL
SIGNAL FOR LOCALIZED 3-5" AMOUNTS IN THIS AREA TODAY..AND THUS
WILL EXTEND THE SLIGHT RISK TO INCLUDE THIS REGION. WILL CARRY A
MARGINAL RISK FURTHER NORTH ACROSS NORTHERN IL INTO SOUTHERN WI.
THINK THE HEAVIEST CONVECTIVE ACTIVITY WILL REMAIN SOUTHEAST OF
THIS AREA AS SUGGESTED BY ALL THE HIGH RES CAM GUIDANCE. THINK
MOST OF THE GLOBAL MODELS ARE A BIT TOO HEAVY WITH QPF AMOUNTS
ACROSS THIS AREA...LIKELY NOT PROPAGATING CONVECTION CORRECTLY OFF
TO THE EAST WITH TIME...AND THUS MOVING THE HEAVIER AMOUNTS MORE
DUE NORTH. PREFER TO LEAN OUR FORECAST MORE IN THE DIRECTION OF
THE MORE PROGRESSIVE 12Z ECMWF...0Z WRF ARW...NSSL WRF AND THE
PARALLEL NMMB (WHICH IS MORE PROGRESSIVE THAN THE OPERATIONAL
NMMB).

...SOUTHERN MAINE...

THE SLOW MOVING CLOSED LOW WILL MOVE OFF OF SOUTHERN NEW ENGLAND
TODAY. STRONG SOUTHERLY FLOW AND ANOMALOUS PRECIPITABLE WATER
VALUES APPROACHING 3 STANDARD DEVIATIONS ABOVE THE CLIMATOLOGICAL
MEAN WILL RESULT IN CONTINUED SHOWERY CONDITIONS INTO MAINE TODAY.
A LACK OF INSTABILITY WILL KEEP RAIN RATES IN CHECK (GENERALLY
BELOW 0.25" IN AN HOUR)...AND GENERALLY LOOKING AT AREAL AVERAGED
AMOUNTS AROUND 1" ALONG THE MAINE COASTLINE...WITH ISOLATED
AMOUNTS UP TO 2" POSSIBLE. NOT EXPECTING SIGNIFICANT ISSUES FROM
THIS RAINFALL...BUT COULD SEE SOME PONDING OF WATER AND OTHER
MINOR ISSUES. THUS WILL CONTINUE TO CARRY THE MARGINAL RISK OVER
FROM THE PREVIOUS DAY 2 OUTLOOK.

CHENARD

$$





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