Quantitative Precipitation Forecast
Issued by NWS

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696
FOUS30 KWBC 210726
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
325 AM EDT SUN MAY 21 2017

...VALID 12Z SUN MAY 21 2017 - 12Z MON MAY 22 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NE KOPM 35 WNW KOPM 15 WNW EBG 55 ENE MMMY 20 NW MMAN
50 SSE MMMV 40 SW MMMV 65 WNW MMMV 85 WNW MMMV 115 SSW 6R6
65 SSW 6R6 15 SSE 6R6 45 SSW E29 30 W ERV 30 ESE T82 HYI
45 ENE CXO 20 S ESF 25 ENE MCB 15 SSE NMM 15 E 8A0 20 SW JKL
25 SW UNI 10 W UNI 20 ESE 4I3 15 W BJJ 15 SE BKL 10 WSW ERI
15 SW DKK 15 NE DKK CYSN 30 NE IAG 20 NW ROC 20 NE ROC
15 SSE ROC 15 S ELZ FIG 10 E JST 30 S AOO 15 NNW MRB 10 ENE MRB
HEF 25 N FVX 30 SE LYH 15 NNW SOP 10 NNE MMT 30 NNE JYL
10 WSW LHW 35 NW VQQ 25 SSW CTY 15 SSW CTY 85 SE AAF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ESE HTS 20 E 3I2 30 NNE PKB 15 N HLG 10 W AGC 10 ENE CKB
25 NNE LWB HSP 25 SSE HSP 25 SE ROA 15 NE INT UZA 40 NE DBN
10 SSW MLJ 25 WNW MLJ 15 WSW GVL 25 NNE 47A 10 SSE TYS 25 NE TYS
25 NW LNP 15 ESE HTS.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 WSW DRT 20 WSW DRT 25 SE DLF 25 NNE MMPG 20 SSE HDO
40 SSE SSF 30 N ALI 15 WSW ALI 15 E HBV 20 S HBV 35 SW HBV
30 S MMNL 50 SW MMNL 60 WSW MMNL.


SOUTHERN TO CENTRAL APPALACHIANS

ANOTHER FORECAST PERIOD WITH A VERY BROAD MARGINAL AND SLIGHT RISK
AREAS AHEAD OF THE SURFACE FRONTAL BOUNDARY PUSHING SLOWLY
EASTWARD THROUGH THE OH AND TN VALLEYS INTO THE APPALACHIANS.  THE
OVERALL PATTERN REMAINS FAVORABLE FOR WIDESPREAD HEAVY RAINFALL
POTENTIAL IN THE VERY DIFFLUENT UPPER FLOW AND AXIS OF ANOMALOUS
PW VALUES---1.5-2+ STANDARD DEVIATIONS ABOVE THE MEAN---ALONG AND
AHEAD OF THE ABOVE MENTIONED COLD FRONT.  SIMILAR TO THE PAST FEW
FORECAST CYCLES---CONFIDENCE IN THE SHORTER TERM DETAILS OF THE
MODELS IS LOW---BUT OVERALL CONFIDENCE IS HIGH FOR POTENTIAL FOR
WIDESPREAD HEAVY TOTALS AND ISOLATED RUNOFF ISSUES AHEAD OF THE
FRONT.  CHANGES TO THE PREVIOUS OUTLOOK AREA WAS TO TRIM THE
SOUTHERN EDGE OF THE SLIGHT RISK AREA FROM THE FL PANHANDLE INTO
SOUTHWEST GA.  ONGOING CONVECTION ACROSS THESE AREAS WILL LIKELY
NOT BE A FACTOR AFTER 1200 UTC.  EMPHASIS FOR HEAVIEST PRECIP
SHOULD BE SHIFTING FARTHER NORTHWARD INTO THE SOUTHERN TO CENTRAL
APPALACHIANS.   MODEL CONSENSUS FOR MAX AMOUNTS IN THE 2-4"+ RANGE
ARE FROM FAR NORTHERN GA---UPSTATE OF SC---WESTERN NC.  THE SLIGHT
RISK OUTLINED THESE AREAS AND EXTENDED FARTHER NORTH INTO
NORTHEAST TN---FAR EASTERN KY---SOUTHWEST VA AND WESTERN TO
CENTRAL WV WHERE FFG VALUES ARE LOWER---BUT STILL POTENTIAL FOR
LOCALLY HEAVY RAINS.

SOUTH TX

CONCERN FOR HEAVY TO LOCALLY EXCESSIVE RAINFALL AMOUNTS ARE ALSO
ACROSS SOUTH TX ASSOCIATED WITH SOUTHERN STREAM SHORTWAVE ENERGY
EXPECTED TO PUSH EASTWARD ACROSS NORTHERN MEXICO AND INTO SOUTH TX
SUNDAY AFTERNOON-INTO SUNDAY NIGHT/EARLY MONDAY.  THERE IS A GOOD
CHANCE OF ORGANIZED CONVECTION AHEAD OF THESE HEIGHT FALLS
AFFECTING THE U.S./MEXICAN BORDER REGION FROM NORTHEAST
CHIHUAHUA---NORTHERN COAHUILA---NORTHERN NUEVO LEON AND INTO SOUTH
TX TO IN THE VICINITY OF 30N.  THERE ARE NUMEROUS MODEL QPF
DIFFERENCES ACROSS THESE AREAS BUT A CLEAR MODEL SIGNAL FOR
POTENTIAL FOR HEAVY PRECIP TOTALS AND ISOLATED RUNOFF ISSUES WHERE
CONVECTION MAXIMIZES.

ORAVEC
$$





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