Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 240035
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
835 PM EDT TUE MAY 23 2017

...VALID 01Z WED MAY 24 2017 - 12Z WED MAY 24 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 E KIKT 20 SW JKA 15 ESE GZH 30 N ABY 10 WNW TBR 20 NE FLO
PGV 15 SSE 9W7 50 ESE MQI 35 E HSE 50 SE MRH 60 S SUT 45 ESE HXD
40 E NRB 20 W OCF 80 NW PIE 120 S AAF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNW 27A 25 ESE ATL 30 SE ANB ANB RMG 30 ENE DNN 10 NNW 27A.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SSW PAM 25 N AAF 20 SW VLD 10 SW SSI NRB 20 WNW GNV
45 SSW CTY 75 SE AAF.


24/0100 UTC UPDATE...

A SIGNIFICANT REDUCTION TO THE SLIGHT RISK AREA WAS MADE FOR THE
00Z UPDATE PACKAGE AS STRONGER CONVECTION ALONG THE CAROLINA
COASTS CONTINUES TO PUSH EWD WITH THE DEEPER MOISTURE AND
INSTABILITY AXES.  A REALIGNMENT OF THE SLIGHT RISK AREA TOWARD
NORTHERN FL WAS MADE WITH A MULTI-MODEL SIGNAL FOR HEAVIER RAIN
FOCUS FOR THE REMAINDER OF THE OVERNIGHT PD AS WSWLY LOW LEVEL JET
AND STGEST MSTR FLUX BECOMES FOCUSED ACRS THAT REGION OVERNIGHT.
THIS COULD LEAD TO THE POTNL OF SEVERAL ROUNDS OF CONVECTION AND
PSBL TRAINING OF CELLS ACRS THE REGION OVERNIGHT AS THE LOW LEVEL
JET MOVES LITTLE OVERNIGHT AND MAINTAINS 1.75 TO 2" PWS ACRS THE
AREA.  THOUGH FFG VALUES ACRS NRN FL ARE RATHER HI..THE POTNL FOR
TRAINING OF CELLS ALONG WITH HIGH RAINFALL RATES COULD LEAD TO
RAINFALL AMOUNTS APCH OR LOCALLY EXCEEDING THE 1 HOUR FF GUIDANCE
VALUES.  MAIN FLY IN THE OINTMENT IS WHETHER CURRENT OFFSHORE
CONVECTION WELL TO THE WEST OF THE PENINSULA HOLDS TOGETHER AND
ROBS THE BETTER INFLOW/MSTR TO ITS ENE AS ONE OF THE LATEST HRRR
RUNS HAS INDICATED.  SULLIVAN


15 UTC UPDATE...

OVERALL NO LARGE-SCALE CHANGES WERE MADE TO THE PREVIOUS
OUTLOOK...JUST SMALLER ADJUSTMENTS BASED ON RECENT RADAR/SATELLITE
TRENDS AND RECENT RUNS OF THE HI-RES GUIDANCE.  THESE ADJUSTMENTS
INCLUDED A SLIGHT NORTHWARD EXPANSION OF THE OUTLOOK AREAS ACROSS
CENTRAL AL AND NORTHERN/CENTRAL GA.  THE ONGOING HEAVY RAIN THREAT
IS EXPECTED TO CONTINUE THROUGH THE REMAINDER OF THE MORNING INTO
THE AFTERNOON...WITH THE LATEST RUNS OF THE OPERATIONAL AND
EXPERIMENTAL HRRR SHOWING A STRIPE OF MODERATE TO HEAVY
ACCUMULATIONS.  REFER TO WPC MPD #0265 FOR ADDITIONAL DETAILS ON
THIS ONGOING THREAT.  TO THE NORTH...INCLUDED THE REMAINDER OF
CENTRAL NC IN THE SLIGHT RISK AREA.  THE LATEST HI-RES
ENSEMBLES...IN ADDITION TO THE LATEST RUNS OF THE OPERATIONAL AND
EXPERIMENTAL HRRR...SHOW THE POTENTIAL FOR REDEVELOPING MODERATE
TO HEAVY RAINS ACROSS THE REGION LATER TODAY...WITH LOCALLY HEAVY
TO EXCESSIVE ACCUMULATIONS POSSIBLE.


PREVIOUS DISCUSSION...

FL PANHANDLE/NORTH FLORIDA INTO THE SOUTHEAST AND SOUTHERN MID
ATLANTIC

A BROAD MARGINAL AND SLIGHT RISK AREA WAS MAINTAINED IN THE
VICINITY OF THE STATIONARY FRONTAL BOUNDARY FORECAST TO STRETCH
FROM THE CENTRAL GULF COAST---NORTHEASTWARD INTO THE SOUTHEAST AND
SOUTHERN MID ATLANTIC THIS PERIOD.   A WELL DEFINED IMPULSE IN THE
BROAD WEST SOUTHWEST MID TO UPPER LEVEL FLOW DOWNSTREAM OF THE
AMPLIFYING UPPER TROF ACROSS THE PLAINS/MS VALLEY REGION WILL PUSH
THROUGH THE SOUTHEAST INTO THE SOUTHERN MID
ATLANTIC---ACCENTUATING LIFT IN THE VICINITY OF THE FRONT AND THE
ANOMALOUS PW AXIS THAT WILL PERSIST IN THE VICINITY OF THE
BOUNDARY.   THIS WILL SUPPORT A BROAD SWATH OF POTENTIALLY HEAVY
RAINS ACROSS THESE REGIONS THIS PERIOD---WITH POTENTIAL FOR
TRAINING OF CELLS IN WEST SOUTHWEST TO EAST NORTHEASTERLY
DIRECTION PARALLEL TO THE FRONTAL ZONE.  IN AREAS OF
TRAINING---HOURLY RAINFALL TOTALS OF 1-1.5"+ AND TOTALS OF 2-4"+
ARE POSSIBLE.  RECENT VERIFICATION HAS SHOWN A LOT OF MODEL ERROR
IN QPF DETAILS---WITH OFTEN THE BEST PERFORMING GUIDANCE BEING
THESE HI RES ARW AND NMMB MODELS.   THESE MODELS WERE FOLLOWED
MORE CLOSELY THIS PERIOD FOR QPF DETAILS.

PEREIRA/ORAVEC

$$





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