Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 170731
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
331 AM EDT TUE OCT 17 2017

...VALID 12Z TUE OCT 17 2017 - 12Z WED OCT 18 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 ENE VRB 35 E SUA 15 SE SUA 15 W FPR 10 E LEE 20 SSE SGJ
50 E SGJ 70 ENE DAB.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 E TTS 25 E COF MLB 15 E ORL 20 WSW DAB 20 N DAB 40 NE DAB
60 ENE DAB.


...EAST-CENTRAL FLORIDA...

THE SOUTHERN PERIPHERY OF AN UPPER LEVEL SHORTWAVE TROUGH ACROSS
THE FL PANHANDLE AND EASTERN GULF EARLY TODAY WILL PUSH SLOWLY
EASTWARD ACROSS THE FL PENINSULA BY EARLY WED. AT THE SURFACE...IN
LIGHT OF THE SLOW MOVING UPPER SHORTWAVE AND WEAK WESTERLY FLOW
ALOFT...THE FRONT IS EXPECTED BECOME STATIONARY ACROSS SOUTH FL
LATER TUE AND TUE NIGHT. WHILE THE BULK OF POST-FRONTAL
INSTABILITY IS EXPECTED TO REMAIN OFF THE EAST COAST OF
FL...SUFFICIENT MUCAPES WILL BE PRESENT DURING THE DAY 1 PERIOD
ALONG THE EAST COAST OF CENTRAL-SOUTH FL (1000-1500 J/KG DURING
THE DAY TUE...500-1000 J/KG TUE NIGHT). MEANWHILE...ROBUST
POST-FRONTAL LOW-LEVEL E-NE FLOW (25-30+ KTS AT 850 MB) IS ALSO
NOTED...WHICH IS HELPING TO MAINTAIN HEALTHY LOW-LEVEL MOISTURE
TRANSPORT DURING THE PERIOD AS 850 MB MOISTURE FLUX ANOMALIES
AROUND +1.5-2.0 PERSIST THROUGH TUE NIGHT. THE FAVORABLE MOISTURE
PROFILE AT BOTH LOWER LEVELS AND ALOFT (WITH THE SW FLOW) WILL
MAINTAIN THE ANOMALOUS PW VALUES OF 1.75-2.0 INCHES (WITH LAYER
PWs OF  AROUND 0.25" BETWEEN 500-300 MB).

IN LIGHT OF THESE FAVORABLE THERMODYNAMIC PARAMETERS...ALONG WITH
THE SUBTLE YET PROLONGED RIGHT-ENTRANCE REGION UPPER JET FORCING
(UPPER DIVERGENCE...LOW-MID LAYER FRONTOGENESIS)...THE LATEST
MODEL GUIDANCE (ESPECIALLY HIGH-RES CAMs) CONTINUE TO INDICATE
HEAVY RAINFALL TOTALS ALONG THE EAST COAST OF FL BETWEEN PALM
COAST AND VERO BEACH. UTILIZING A MULTI-MODEL BLEND WITH THE
QPF...PARTICULARLY WITH THE HIGH-RES CAMs...HIGHEST AREAL-AVERAGE
TOTALS OF 1.5-3.0+ INCHES WERE NOTED (HEAVIEST NORTH OF THE CAPE).
THE 27KM ECMWF AND GFS OUTPUT WERE NOTABLY MORE CONSERVATIVE WITH
AMOUNTS...ESPECIALLY INLAND...LIKELY OWING TO THE PROGGED
INSTABILITY GRADIENT ALONG AND EAST OF THE COAST. FOR NOW HAVE
LEANED TOWARD THE HIGH-RES MEANS GIVEN THE STRONG LOW-LEVEL
ONSHORE FLOW AND THETA-E TRANSPORT...WHICH RESULTED IN LITTLE
CHANGE FROM THE PREVIOUS FORECAST (CONTINUITY) OUTSIDE OF A SLIGHT
SOUTHWARD SHIFT OF THE MAX AMOUNTS. AS A RESULT...MINIMAL CHANGES
WERE MADE TO THE EXCESSIVE RAINFALL OUTLOOK INHERITED FROM
YESTERDAY`s DAY 2 ERO (MARGINAL AND SLIGHT RISK AREAS ACROSS EAST
CENTRAL FL)...SUPPORTED BY THE LATEST SSEO 40KM NEIGHBORHOOD
PROBABILITIES OF QPF>FFG EXCEEDANCE (INCLUDING 30-70% PROBS WITHIN
THE SLIGHT RISK AREA BETWEEN 15-00Z).

HURLEY
$$





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