Quantitative Precipitation Forecast
Issued by NWS

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065
FOUS30 KWBC 160853
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
453 AM EDT SUN JUL 16 2017

...VALID 12Z SUN JUL 16 2017 - 12Z MON JUL 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
70 ENE SGJ 25 SE SGJ 25 NE VVG 30 WSW GNV 20 E 40J 25 WSW TLH
10 SSE PNS 20 ESE NBG 10 ENE GSM 30 E KXIH 20 S KMZG NGP
20 NW VCT 15 NNW UTS 40 NNE IER 20 E TVR 35 WNW CHA 30 N AVL
30 NNW FQD 10 ENE EXX 25 NNE PHF 110 ESE WAL 175 E FFA
205 ESE HSE 200 SE HSE 185 SE MRH.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
130 SSW GBN 40 SE YUM 35 NNE YUM 30 NE IGM 30 NNW GCN 60 N INW
55 NNW RQE 30 W TEX 20 ENE MTJ 15 N MYP 40 W FCS 10 E APA
35 SSW IBM 25 NNE OGA 30 S HDE 30 WSW HYS 35 NW LBL 25 N CAO
50 NW TCC 20 ENE CQC 10 NW AEG 55 NNW TCS 15 ENE DMN 95 SW MMCS
145 ENE MMHO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SSE HXD 40 S AYS 20 SW ABY 25 SSE LSF 15 ESE OPN 10 ENE DNL
10 SSE CTZ 15 NNE EDE 30 ENE FFA 105 E HSE 100 SE HSE.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
105 WSW OLS 50 WSW GBN 60 WNW LUF 35 WNW PRC 25 SSW 40G
25 ESE FLG 25 SE INW 15 NW SJN 10 NNW SJN 35 ESE SJN 35 NW SVC
70 E DUG 80 SSE DUG 95 S DUG.


...GEORGIA AND THE EASTERN CAROLINAS...

SOUTHEAST GEORGIA AND THE COASTAL CAROLINAS SIT IN A FAVORABLE
POSITION FOR ENHANCED COVERAGE OF AFTERNOON CONVECTION PRODUCING
HEAVY RAIN. EASTERN U.S. TROUGHING WILL UNDERGO SLIGHT
AMPLIFICATION TODAY WITH THE MEAN TROUGH AXIS BACK ACROSS WESTERN
GEORGIA AND ALABAMA. THIS PLACES THE SOUTHERN ATLANTIC COAST
BENEATH SLIGHTLY DIFLUENT UPPER FLOW WHICH WILL AIDE THUNDERSTORM
GROWTH...INTENSITY...AND LONGEVITY...AS STORMS INITIATE NEAR THE
COASTAL CONVERGENCE ZONE / SEA BREEZE AND ALSO WITHIN THE MOIST
AND STRONGLY HEATED ENVIRONMENT FARTHER INLAND TOWARD A SLOWLY
SAGGING FRONTAL BOUNDARY. IN THE ABSENCE OF A WELL DEFINED UPPER
SHORTWAVE...AND WITH MODEST DEEP LAYER WIND SPEEDS AND SHEAR...IT
WILL BE DIFFICULT TO ANTICIPATE EXACTLY WHERE CONVECTION WILL
BECOME MORE ORGANIZED...BUT THE MODEL QPF SOLUTIONS ARE
INCREASINGLY CONFIDENT IN AN AXIS OF ORGANIZED HEAVY RAINFALL FROM
SOUTH OF MACON OVER TOWARD SAVANNAH AND CHARLESTON...AND
CONTINUING UP THE COAST INTO THE OUTER BANKS. WITH PRECIPITABLE
WATER AROUND 2 INCHES...THERE WILL BE VERY HEAVY RAIN RATES IN THE
STRONGEST CELLS...WITH POTENTIAL FOR ISOLATED 4-PLUS INCH AMOUNTS
WHEREVER CELL MERGERS OR TRAINING OCCURS.


...ARIZONA AND WESTERN NEW MEXICO...

THE PAST FEW DAYS HAVE BEEN ACTIVE FROM THE MOGOLLON RIM
SOUTHWARD...AND AS MOISTURE DEPTH CONTINUES TO CREEP WEST THROUGH
THE DESERTS WE SAW AN ENVIRONMENT ON SATURDAY THAT SUPPORTED
CONVECTION SURVIVING DOWN INTO THE VALLEYS AND DESERT AREAS OF
SOUTHERN ARIZONA. SUNDAY SHOULD BE SIMILAR AS STEERING FLOW
REMAINS NORTHEAST TO SOUTHWEST...WITH THE RIDGE POSITION OVER THE
NV/UT BORDER. CONSENSUS QPF AND THE WPC MANUAL FORECAST HIGHLIGHT
CENTRAL ARIZONA WITH SOME ROBUST AREAL AVERAGE PRECIPITATION. THE
SETUP IS NOT OVERLY FAVORABLE FOR CELL TRAINING...BUT THERE IS
USUALLY SOME SLOW MOVEMENT IN THE EARLY STAGES BEFORE A LARGER
COLD POOL IS BUILT. ONE OF THE CONCERNS TODAY...IS THAT ALL OF THE
HEAVY RAIN PARAMETERS CONTINUE TO INCREASE JUST AHEAD OF AN
EASTERLY WAVE COMING THROUGH MEXICO. PRECIPITABLE WATER VALUES
SPIKE AT 2.0 TO 2.5 STANDARD DEVIATIONS ABOVE AVERAGE OVER CENTRAL
TO SOUTHERN ARIZONA...AND THE HI-RES MODELS PREDICT AFTERNOON
DEWPOINTS HOLDING UP IN THE 60S...WITH LARGE CAPE VALUES.
THUS...EVEN WITHOUT MUCH TRAINING THE SHORT TERM HEAVY RAIN RATES
MAY BE ON THE EXCEPTIONAL SIDE ON LOCAL SCALES...CAUSING AN
INCREASE TO THE NUMBER OF INSTANCES OF FLASH FLOODING COMPARED TO
RECENT DAYS. AFTER COORDINATING WITH LOCAL FORECAST OFFICES WE
UPGRADED THIS REGION TO A SLIGHT RISK OF EXCESSIVE RAINFALL.
THANKS WFO FGZ...PSR...TWC...EPZ...ABQ.


...NORTHERN NEW MEXICO THROUGH WESTERN KANSAS...

THE SMALL VORTICITY MAXIMUM OVER COLORADO...EMBEDDED IN MEAN
RIDGING...HAD BECOME MORE PRODUCTIVE WITH LARGER SCALE CONVECTION
ON SATURDAY. STILL...ITS RADIUS OF INFLUENCE IS FAIRLY
SMALL...WITH WEAK WIND FIELDS SURROUNDING IT. THE FEATURE WILL
OPEN UP A BIT AND BECOME STRETCHED NORTH TO SOUTH WHILE ALSO
BEGINNING TO LIFT NORTHWARD LATE SUNDAY...UNDER THE ENCOURAGEMENT
OF NORTHERN STREAM FLOW PICKING UP ACROSS THE ROCKIES. THIS SETS
UP AN AXIS OF MODERATE AND LOCALLY HEAVY RAINFALL ALONG THE KS/CO
BORDER AND EXTENDING BACK ALONG THE TRAILING TROUGH AXIS INTO
NORTHERN NEW MEXICO. VERY WEAK STEERING FLOW WILL LEAD TO SLOW
MOVING CELLS...INCREASING THE LIKELIHOOD OF LOCALLY EXCESSIVE
RAINFALL. THIS COULD PROVE PROBLEMATIC IN THE MOUNTAINOUS
TERRAIN...AND ALSO OUT ACROSS THE HIGH PLAINS WHERE SOMEWHAT
STRONGER LOW LEVEL INFLOW COULD SUSTAIN LOCAL POCKETS OF
CONVECTION.


...WESTERN GULF COAST...

BACK WEST...WPC WAS FAIRLY GENEROUS WITH THE AREAL COVERAGE OF
HYDROLOGICALLY SIGNIFICANT PRECIPITATION AT LEAST A QUARTER INCH
OR MORE WITHIN A ZONE OF FAVORABLE MID LEVEL MOISTURE...WHICH WILL
ENHANCE RAINFALL EFFICIENCY FROM SOUTHERN ALABAMA TOWARD THE UPPER
TEXAS COAST. ANYWHERE IN THIS ZONE PW WILL AVERAGE 2
INCHES...LEADING TO THE POTENTIAL FOR RAPID MULTI-INCH RAINFALL
ACCUMULATIONS AND LOCAL FLASH FLOODING. WE WILL ALSO HAVE TO WATCH
THE TX GULF COAST CAREFULLY. HI-RES MODELS ARE INDICATIVE OF VERY
HEAVY RAIN ASSOCIATED WITH A MID LEVEL CIRCULATION NEAR COASTAL
TEXAS...ALTHOUGH THE HEAVIEST MAY TEND TO OCCUR JUST OFFSHORE.

BURKE
$$





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