Quantitative Precipitation Forecast
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FOUS30 KWBC 211500
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EDT SUN MAY 21 2017

...VALID 15Z 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 25 S MMMV 20 WNW MMMV 60 NW MMMV 130 SW 6R6 75 S E38
35 S FST 30 WNW E29 10 ENE ECU RND 11R 10 NW JAS ESF 30 E PIB
10 NNE NSE 20 NE BGE 20 WSW WRB 10 SW RMG 30 W CSV 10 SW JKL
25 W 3I2 10 W UNI 20 ESE 4I3 10 SSW BJJ 15 SE BKL 10 WSW ERI
15 SE CWPS 10 SW CWPC CYSN 30 NE IAG 20 NW ROC 20 NE ROC
15 SSE ROC 15 S ELZ FIG 10 E JST CBE 25 WNW OKV 10 NNW JYO HEF
20 SSW LKU 30 SE LYH 15 NNW SOP 30 S EQY 15 W OGB 20 N BQK
25 WNW VQQ 25 SSW CTY 15 SSW CTY 85 SE AAF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 NW I16 25 N CRW 35 SW HLG 10 SSW BTP MGW 15 SSE W22
10 ENE BLF 15 SE ROA 20 NW DAN 10 NNW GSO 10 ESE HKY 30 ESE GSP
20 NNE DNL 20 S HQU 15 N AHN 25 NNE 47A 15 NW RHP 45 ENE TYS
20 S LNP 35 NW I16.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 SSW 6R6 10 WSW 6R6 50 SW E29 20 ENE DLF 25 W UVA 30 S SSF
30 N ALI 15 WSW ALI 15 E HBV 10 S HBV 25 SW HBV 30 S MMNL
35 SSW MMNL 60 WSW MMNL.


15 UTC UPDATE...

OVERALL...NO SIGNIFICANT CHANGES WERE MADE TO THE PREVIOUS
OUTLOOK.  BASED ON RECENT RADAR/SATELLITE TRENDS AND THE MOST
RECENT HI-RES GUIDANCE...SOME MINOR ADJUSTMENTS WERE
MADE...INCLUDING REMOVING THE MARGINAL RISK ACROSS PORTIONS OF AL
INTO WESTERN GA.  IN THE WAKE OF AN OUTFLOW BOUNDARY PUSHING SOUTH
INTO THE NORTHERN GULF OF MEX AND A MID-UPPER LEVEL SHORTWAVE
LIFTING TO THE NORTHEAST...STABLE AIR IS EXPECTED TO
PREVAIL...WITH THE MAJORITY OF THE HI-RES GUIDANCE SHOWING LITTLE
TO NO ORGANIZED CONVECTIVE REDEVELOPMENT ACROSS THE REGION THROUGH
12 UTC MON.

PREVIOUS DISCUSSION...

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.

PEREIRA/ORAVEC
$$





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