Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 181859
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT MON AUG 18 2014

...VALID 18Z MON AUG 18 2014 - 00Z WED AUG 20 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNE CHA 15 SSW RHP 10 N GVL LZU ATL 20 ENE ALX 20 SE EET
10 N TCL 30 SSW 1M4 MSL 25 NW MSL 20 SSE MKL 25 WSW MKL
25 NE NQA 15 SE HKA 15 SE DYR 35 NE MKL 55 SSW CKV 25 S MQY
25 NNE CHA.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 S LSE 15 NNE TOB 15 ENE FBL FCM 8Y2 PNM 10 SW JMR 15 NE JMR
CDD 15 NNE CDD DLH 25 SSE TWM 20 SW ASX 15 ESE HYR 10 N RCX
20 SSE RCX 10 SW MDZ 10 SE CWA 10 NW OSH 10 SSW SBM 30 NE MWC
15 NE RAC 10 W BUU 20 N OVS 15 S LSE.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 E 40G 25 WNW SOW 25 NE SAD 45 NE DUG 35 ESE DUG 65 SSE DUG
85 S DUG 75 NNE MMHO 80 N MMHO 75 SW OLS 100 W OLS 90 SSW GBN
75 SE YUM 55 S NYL 50 SSW NYL 50 S IPL 40 S NJK 20 WSW NJK
20 NE TRM 45 NW BLH 45 WNW EED 30 SW HND 20 W VGT 40 NE DRA
95 S ELY 50 WNW MLF 15 NNE U24 30 WNW PUC 15 SW PUC 40 W 4HV
25 NE GCN 40 E 40G.


SOUTHEAST VIRGINIA INTO NORTHEAST NORTH CAROLINA

A SLIGHT RISK AREA WAS MAINTAINED AHEAD OF THE WELL DEFINED VORT
MOVING EASTWARD ACROSS SOUTHERN VIRGINIA INTO NORTHEAST NORTH
CAROLINA THIS AFTERNOON. CONVECTION SHOULD CONTINUE TO BE WELL
DEFINED AHEAD OF THIS FEATURE THIS AFTERNOON--WITH CONTINUED
INTENSIFICATION OF ACTIVITY POSSIBLE IN THE WELL DEFINED UPPER
DIFFLUENCE AXIS.  ABOVE AVERAGE PW VALUES-- 1 TO 2 STANDARD
DEVIATIONS ABOVE THE MEAN---IN THIS DIFFLUENCE MAX WILL SUPPORT
HEAVY TO ISOLATED EXCESSIVE RAINFALL POTENTIAL.  AT THE
MOMENT--ACTIVITY IS REMAINING PROGRESSIVE---KEEPING SHORT TERM
PRECIPITATION TOTALS IN THE 1-1.5"+ RANGE.  STILL SOME CONCERN FOR
RUNOFF ISSUES IF ACTIVITY CONTINUES TO ENHANCE AS IT APPROACHES
THE MORE URBANIZED AREAS OF SOUTHEAST VIRGINIA.

UPPER TN VALLEY

THE PREVIOUS SLIGHT RISK AREA OVER THE TN VALLEY WAS EXPANDED
SLIGHTLY NORTHWARD INTO SOUTHERN TN AND DECREASED IN SIZE ON THE
SOUTHERN END.  ENHANCING CONVECTION AHEAD OF THIS MCV IS MOVING
OVER AREAS OF TN WHERE FFG VALUES HAVE LOWERED FROM EARLIER HEAVY
RAINS.  WESTERLY LOW LEVEL FLOW MAY SUPPORT TRAINING AND/OR BACK
BUILDING OF CELLS ACROSS THESE REGIONS---WITH ISOLATED 1-2"
AMOUNTS IN AN HOUR WHERE TRAINING OCCURS.  FARTHER TO THE
SOUTH---CONVECTION IS MORE PROGRESSIVE AND FFG VALUES ARE HIGHER.
FOR THESE REASONS---THE PREVIOUS SLIGHT RISK AREA WAS TRIMMED ON
THE SOUTHERN END.

NORTH CENTRAL TX

AN UPPER LEVEL CIRCULATION IS EXPECTED TO MOVE LITTLE THIS PERIOD
OVER NORTH CENTRAL TX---TRAPPED BETWEEN THE UPPER RIDGE OVER THE
SOUTHERN ROCKIES AND AN UPPER RIDGE OVER THE GULF OF MEXICO.  VERY
HEAVY RAINFALL AMOUNTS HAVE FALLEN IN THE VICINITY OF THIS
VORT---WITH POTENTIAL FOR ADDITIONAL LOCALLY VERY HEAVY TO
EXCESSIVE AMOUNTS.  CONFIDENCE RATHER LOW WITH QPF DETAILS---BUT
WITH THE EXPECTED SLOW MOVEMENT--CONFIDENCE HIGHER THAT THERE MAY
BE ADDITIONAL HEAVY TO LOCALLY EXCESSIVE AMOUNTS.

SOUTHWEST INTO THE GREAT BASIN

ABOVE AVERAGE PW VALUES--- 1 TO 2 STANDARD DEVIATIONS ABOVE THE
MEAN---WILL CONTINUE TO BE FUNNELED NORTH AND NORTHEASTWARD THIS
PERIOD ACROSS THE SOUTHWEST INTO THE GREAT BASIN BETWEEN THE
CLOSED LOW DIVING SOUTHWARD INTO NORTHERN TO CENTRAL CALIFORNIA
AND THE UPPER HIGH OVER THE SOUTHERN ROCKIES.  VERY DIFFLUENT
UPPER FLOW EXPECTED AHEAD OF THIS CLOSED LOW AND WELL DEFINED
VORTS MOVING NORTH NORTHEASTWARD IN THE HIGH PW AXIS.  THIS WILL
SUPPORT WIDESPREAD CONVECTIVE ACTIVITY THIS PERIOD FROM THE
SOUTHWEST INTO THE GREAT BASIN---WITH MODEL CONSENSUS FOR
POTENTIAL OF WIDESPREAD MODERATE TO HEAVY PRECIPITATION
TOTALS---ALONG WITH POTENTIAL FOR FLASH FLOODING.  THE HI RES ARW
AND IN HOUSE PSEUDO BIAS CORRECTED ENSEMBLE MEAN USED FOR QPF
DETAILS THIS PERIOD.

MID TO UPPER MS VALLEY INTO THE WESTERN LAKES


MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE EAST SOUTHEASTWARD
PUSH OF NORTHERN STREAM HEIGHT FALLS FROM THE UPPER MS VALLEY INTO
THE UPPER LAKES REGION THIS AFTERNOON INTO TUESDAY.  DIFFLUENT
UPPER FLOW AHEAD OF THESE HEIGHT FALLS IN AN AXIS OF ABOVE AVERAGE
PW VALUES---1 TO 1.5+ STANDARD DEVIATIONS ABOVE THE MEAN---WILL
SUPPORT WIDESPREAD SCATTERED CONVECTION FROM THE UPPER MS
VALLEY---INTO THE UPPER LAKES AND EVENTUALLY SOUTHWARD ALONG THE
TRAILING COLD FRONT INTO THE MID MS VALLEY.  CONFIDENCE NOT GREAT
WITH DETAILS---BUT CONFIDENCE HIGHER THAT THERE WILL BE MODERATE
TO LOCALLY HEAVY PRECIPITATION TOTALS GIVEN THE ABOVE
DYNAMICS/MOISTURE.  THE HI RES---NSSL WRF AND NAM CONEST WERE USED
PRIMARILY FOR QPF DETAILS---WITH THEIR FAIRLY SIMILAR MAX AXES IN
THE VICINITY OF THE WARM FRONTAL BOUNDARY USED TO DEPICT THE
GREATEST RISK OF RUNOFF ISSUES.  PRECIPITATION TOTALS IN THIS AXIS
OF 2-4"+ POSSIBLE.


ORAVEC
$$





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