Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 212336
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
735 PM EDT SUN MAY 21 2017

...VALID 01Z MON MAY 22 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
25 SE KMIU 10 WSW MMRX 40 ESE MMMY 20 NNE MMAN 50 WNW MMNL
30 W MMPG 30 ESE 6R6 45 WNW E29 SJT 45 WSW BWD 30 N 6R9
10 NE AUS 30 NW SGR 20 NNE BPT 35 SE ESF 25 SE TVR 35 E GWO
25 W 1M4 30 WNW BHM 45 E NMM 55 N MOB 30 NW PNS 10 SSW DTS
75 SW PAM 50 ENE KIPN 30 W KIPN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WNW GMU 20 W MRN 10 WNW BCB 15 W SHD 10 NNE LKU 20 NW HNZ
HFF 35 SSE SSC 20 S OGB 20 E AGS 30 E GRD 25 E GRD 35 ESE GSP
15 ESE GSP 10 SSW GYH 20 WNW GMU.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 WSW GLW LEX 30 ESE ILN 10 ENE LPR ERI 30 WSW DUJ 30 NNE CRW
30 SE JKL 30 W 1A6 30 SW EKQ 10 WSW GLW.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 N CUB 10 NNW CAE 30 NW CAE 40 ENE GRD 35 ESE GSP 15 E GSP
GYH 15 NNW GMU 10 NNE MRN 20 NNE SVH RUQ EQY 30 N CUB.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSW MMNL 45 WSW COT 10 NNE COT 35 NW ALI 30 NW EBG
65 NE MMMY 30 SSW MMNL.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S HBG 10 SSW PQL 30 NNE KMIS 15 S KDLP 30 N KSPR 10 ENE 7R4
20 W BTR 20 SE MCB 25 S HBG.


2100 UTC UPDATE...

HAVE MADE SEVERAL ADJUSTMENTS TO THE DAY 1 ERO BASED ON
OBSERVATIONAL TRENDS (SATELLITE AND COMPOSITE RADAR
ESPECIALLY)...ALONG WITH THE MOST RECENT TRENDS IN THE MESOSCALE
GUIDANCE (ESPECIALLY THE HRRR). THE AREAS DENOTING A MORE
HIGHLIGHTED RISK ("SLIGHT") INCLUDE SOUTHWEST TX...EASTERN
LA-SOUTHERN MS...AND A SMALL PORTION OF UPSTATE SC INTO THE
PIEDMONT/FOOTHILLS OF NC....AREAS WHERE SUBTLE MCV FORCING IS
ALLOWING FOR A MORE FOCUSED AREA OF LOW-LEVEL MOISTURE FLUX
CONVERGENCE TO GO ALONG WITH A FAVORABLE THERMODYNAMIC PROFILE. OF
GREATEST CONCERN IN THE NEAR TERM (THROUGH EVENING) WILL BE ACROSS
EASTERN LA-SOUTHERN MS...GIVEN THE MODERATE DEGREE OF DEEP-LAYER
INSTABILITY (MIXED LAYER CAPES 1000-2000 J/KG) COINCIDING WITH PWS
OF 2-2.25". FOR FURTHER DETAILS REGARDING ANY ACTIVE MESOSCALE
PRECIPITATION DISCUSSIONS (MPD) WITHIN THE EXCESSIVE RAINFALL
OUTLOOK AREA...PLEASE REFER TO THE LINK ON THE WPC HOME PAGE UNDER
"WPC TOP STORIES"...OR GO DIRECTLY TO THE MPD PAGE:
WWW.WPC.NCEP.NOAA.GOV/METWATCH/METWATCH_MPD.PHP.

HURLEY


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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