Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 110830
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
430 AM EDT FRI AUG 11 2017

...VALID 12Z FRI AUG 11 2017 - 12Z SAT AUG 12 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 E CSG 25 NW LGC 15 WSW RMG 10 NNE DNN 35 NNE 1A5 15 SW MRN
25 ESE GSP 10 NE HQU 10 W EZM 30 E CSG.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 N RQE 45 SSE DRO 20 SSW CPW 35 S MYP 30 SW FCS 25 NNE LHX
35 NE SPD 25 NW GAG 15 SSE WWR 30 E JWG 20 ENE CQB 10 NNW XNA
15 NW BPK 20 NNE BPK 30 WNW POF 25 N BYH M97 35 WNW MLU
25 ESE GGG 30 ENE CRS 20 NW NFW 30 SSW SPS CDS 45 SW AMA
60 SW TCC 50 W 4CR 15 NNE TCS 40 NW SVC 25 W SAD 20 NE DMA
30 W TUS 60 SSE GBN 35 WSW GBN 25 W LUF 50 WSW PRC 40 SE IFP
25 NNW EED 35 W LAS 25 SE DRA 40 N LSV 15 W SGU 50 NNW GCN
70 N INW 30 N RQE.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ESE INW 25 SSW GUP 25 NE GNT 30 W SKX 20 NE RTN 15 N DHT
25 W HHF 20 NNE FSI 10 E ADM 30 SE MLC 10 SE JSV 15 SE FYV
35 S HRO 25 SE RUE 15 SE M89 30 NW ELD 30 SSW TXK 15 SSW SLR
10 ENE DTO 10 SE SPS 30 NW CDS 15 WNW TCC 15 SE 4MY 50 N TCS
60 NNW SVC 50 NNE SAD 50 SW SOW 20 ESE IWA 40 SE GBN 10 SSE GYR
30 N DVT PRC 30 NNW PRC 20 ESE FLG 15 ESE INW.


MADE AN EFFORT TO TAKE INTO ACCOUNT FAVORED MODEL TRENDS AND ALSO
MAINTAIN AS MUCH WPC CONTINUITY AS FEASIBLE FOR QUITE A DIFFICULT
QPF FORECAST. ACCORDINGLY BLENDED THE LATEST HRRR/WPC CONTINUITY
INTO 18 UTC OR SO FRI AND THEN USED MORE OF A GUIDANCE COMPOSITE
ALONG WITH WPC CONTINUITY THROUGH THE REST OF DAY 1. MANUALLY
MODIFICATIED THESE BLENDS TO INCREASE AREAL COVERAGE OVER THE
SOUTHWEST AND NORTHWEST GIVEN RECENT HISTORY AND ATTEMPTED TO
ANTICIPATE CONVECTIVE AREA FOCUS/PROPAGATIONS OVER THE SRN TO SERN
US TIER STATES. FORECASTER CONFIDENCE IS BELOW NORMAL GIVEN HIGH
GUIDANCE SPREAD.

...SOUTHWEST AND CO/NM ROCKIES TO THE S-CENTRAL PLAINS/MS VALLEY...

SATELLITE DERIVED AND OBSERVED PRECIPITABLE WATER VALUES UPWARDS
OF 2 INCHES REMAIN OVER PORTIONS OF AZ AND MODELS FCST ADDITIONAL
MOISTURE ADVECTING INTO THE SOUTHWEST FROM MEXICO. VORT ENERGIES
ON THE WRN PERIPHERY OF THE RIDGE IN FAVORABLE UPPER
DIVERGENCE/UPPER JET DYNAMICS KEEPS CONVECTION ACTIVE DAY 1 ACROSS
AZ...SRN NV...AND INCREASINGLY INTO NM. THE COMBINATION OF
ENHANCED LIFT/MOISTURE LEADS TO LOCALLY HEAVY DOWNPOURS...WITH
LOCAL RUNOFF PROBLEMS. MODEL QPFS SEEMS UNDERDONE.

FAVORABLE RIGHT ENTRANCE REGION DYNAMICS WILL PERSIST WITH A
CENTRAL PLAINS TO OH VALLEY JET MAXIMA TODAY. LIFT IS AIDED BY LOW
LEVEL BOUNDARY AND MOISTURE POOLING ALONG THE BNDRY UPWARDS TO 2
STD DEVIATIONS ABOVE NORMAL. AMPLE STRONG CONVECTION CONTINUES TO
PROGRESS ESE TO A MOIST/UNSTABLE AXIS ACROSS THE S-CENTRAL
US...BUT FUTURE OUTFLOW POSITIONING AND REDEVELOPMENT REMAINS
UNCERTAIN LATER DAY 1 GIVEN MOST GUIDANCE IS NOT PROGRESSIVE
ENOUGH WITH CURRENT CONVECTION...POSSIBLY ACROSS SRN HIGH PLAINS/N
TX AND THE ARKLATEX. THERE IS A CONTINUED RISK FOR LOCALLY
EXCESSIVE RAINFALL ACROSS THIS REGION AND BACK FLOWED INTO THE SRN
HIGH PLAINS WITH ADDITIONAL IMPULSE PASSAGES OUT OVER THE SRN
ROCKIES / REBOUNDING INFLOW. THERE IS A MARGINAL TO SLIGHT RISK OF
EXCESSIVE RAINFALL ACROSS THIS REGION.

...SOUTHEAST US/SRN APPALACHIANS...

A PLUME OF MOISTURE WITHIN A LOW-MID LEVEL CONFLUENT ZONE IS
FORECAST FROM THE CENTRAL GULF COAST STATES/TN VALLEY TO THE
SOUTHEAST. WIDESPREAD/HEAVY CENTRAL GULF COAST CONVECTION
DEVELOPED TODAY WITH A FOCUSING MCV. EXPECT ACTIVITY WILL
REDEVELOP FRI INTO SAT WITH THE SLOW MOVING FEATURE AS THE PLUME
OF LEAD MOISTURE REMAINS IN PLACE AS A WEST-EAST UPPER JET MAXIMA
PUNCHES EWD ACROSS KY FRI. COUPLETS OF UPPER DIVERGENCE/LOWER
CONVERGENCE DEVELOP AND PRODUCE SHOWERS/STORMS ACROSS THE
SOUTHEAST/CENTRAL TO SRN APPALACHIANS...AND ADJACENT LEE AREAS UP
THROUGH THE CAROLINAS/MID-ATLANTIC LATER DAY1 IN ADVANCE OF THE
APPROACHING NRN STREAM COLD FRONT. BELIEVE HEAVIEST THREAT TODAY
MAY BE OVER N-CENTRAL GA/SRN APPALACHIANS/WRN CAROLINAS WITH THE
MCV/DEEPEST MOISTURE...BUT DEEP MOISTURE LINGERS ACROSS MUCH OF
THIS REGION INCLUDING AREAS WET WITH RECENT RAINFALL. THERE IS A
MARGINAL RISK OF EXCESSIVE RAINFALL.


GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

SCHICHTEL
$$





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