Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 141436
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1036 AM EDT MON AUG 14 2017

...VALID 15Z MON AUG 14 2017 - 12Z TUE AUG 15 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 SW BNA 30 SSE GLW 10 SSE 1A6 25 WSW I16 10 SSE W22 10 S W99
25 ENE HSP 15 S ROA 20 NE GSO 15 SW LHZ 15 NW ECG 30 SSE EDE
20 WNW EWN CPC 45J 20 S EHO 30 W CEU 15 S RMG TCL 40 N TVR
15 S ELD 10 ESE LBR ADM 15 W CQB 15 E GCM 15 SE HRO 20 ESE M19
10 SSE NQA 55 SW BNA.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 SE SAD 30 ESE DUG 45 S DUG 65 SSE OLS 15 W OLS 20 NNW DMA
35 ENE IWA 45 ESE PRC 40 S FLG 20 SW INW 25 WNW SJN 70 WNW TCS
40 WNW TCS 45 E SAD 55 SE SAD.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW LRJ 15 ESE CIN 20 SE MIW 15 ENE EFT 15 SSE BUU 25 NW C75
30 SSE OTM 15 SE ICL 20 SSW LNK 15 E HDE 15 S BBW 20 ENE ONL
20 WSW LRJ.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 W 2GL 20 SSE ARA 10 W CWF ACP 20 NW HDC 25 E NBG 15 W 2GL.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SE MMCS 30 E LRU 45 NNW HMN 30 W 4CR 35 NNW ROW 30 NNE CNM
30 NNW E38 40 SW MRF 20 SE MMCS.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 ENE SGT 35 NNE TUP 10 E MDQ 15 W BHM 30 SE GWO 20 NNW ELD
15 WSW DEQ 20 SE MLC MKO 35 SSW HRO 30 ENE SGT.


15 UTC UPDATE...

...EASTERN OK/RED RIVER REGION EASTWARD THROUGH THE TN VALLEY INTO
THE SOUTH/CENTRAL APPALACHIANS AND CENTRAL NC...

EXTENDED THE MARGINAL RISK EASTWARD ACROSS THIS REGION TO
ENCOMPASS MUCH OF THE TN VALLEY INTO THE SOUTHERN AND CENTRAL
APPALACHIANS...AS WELL AS PORTIONS OF CENTRAL NC.   ALSO EXTENDED
THE SLIGHT RISK FURTHER EAST...WITH A SMALL ADJUSTMENT FURTHER TO
THE SOUTH AS WELL.  WESTERLY FLOW IS EXPECTED TO CONTINUE TO MOVE
DEEP MOISTURE AND MID LEVEL ENERGY PARALLEL TO A STATIONARY
BOUNDARY EXTENDING FROM THE COASTAL CAROLINAS BACK INTO OK.  THE
11 UTC RAP SHOWS PWS AT OR ABOVE 2 INCHES SPREADING EAST FROM
CENTRAL OK AND THE RED RIVER REGION EASTWARD ACROSS THE TN VALLEY
INTO PORTIONS OF THE SOUTHERN APPALACHIANS.  THIS DEEP MOISTURE IS
EXPECTED TO SUPPORT EFFICIENT RAINFALL PRODUCERS...WHILE DEEP
WESTERLY FLOW PARALLEL TO THE BOUNDARY MAY ENCOURAGE CELL
TRAINING.  INCREASING SOUTHERLY FLOW AHEAD OF A WAVE MOVING ACROSS
THE TN VALLEY THIS AFTERNOON IS EXPECTED TO DRAW SOME OF THIS
DEEPER MOISTURE FURTHER TO THE NORTH INTO THE CENTRAL
APPALACHIANS...INCREASING THE POTENTIAL FOR LOCALLY HEAVY RAINS
THERE AS WELL DURING THE AFTERNOON/EVENING HOURS.  DEEPER MOISTURE
WILL ALSO BE DRAWN NORTH TO THE EAST OF THE MOUNTAINS ACROSS
WESTERN AND CENTRAL NC...INCLUDING PORTIONS WESTERN NC WHERE THE
LATEST 3 HR FLASH FLOOD GUIDANCE IS AN INCH OR LESS.  REFER TO WPC
MPD #0688 (VALID THROUGH 1950 UTC) FOR THE ONGOING HEAVY
RAINFALL/FLASH FLOODING THREAT ACROSS  PORTIONS OF SOUTHERN
AR...NORTHERN MS AND NORTHERN AL.

...SOUTHERN LA...

12 UTC SOUNDINGS AT LIX AND LCH SHOWED PWS OVER 2 INCHES ACROSS
THE REGION.  EXPECT LOW LEVEL SOUTHERLY WINDS TO FORTIFY THIS
ALREADY MOIST AIRMASS...SUPPORTING AFTERNOON CONVECTION ACROSS THE
AREA.  WHILE WEAK RIDGING ALOFT MAY HAMPER DEVELOPMENT...STORMS
THAT DO FORM WILL LIKELY BE SLOW MOVING GIVEN WEAK FLOW ALOFT.
AND GIVEN THE AMPLE MOISTURE...THEY ARE EXPECTED TO BE EFFICIENT
RAINFALL PRODUCERS AS WELL.

...SOUTHERN NM/WEST TEXAS...

SOUTHEASTERLY WINDS ARE EXPECTED TO INCREASE LATER
TODAY...MAINTAINING SOME ANOMALOUS MOISTURE ACROSS PORTIONS OF
WEST TX AND SOUTHEASTERN NM.  THIS MOISTURE ALONG WITH LOW-MID
LEVEL TROUGHING MAY SUPPORT AFTERNOON AND EVENING CONVECTION.
RELATIVELY LOW FLASH FLOOD GUIDANCE VALUES SUGGEST THAT ANY HEAVY
RAINS THAT DO DEVELOP MAY RESULT IN LOCALIZED FLASH FLOODING
CONCERNS.

ELSEWHERE...MORE MINOR ADJUSTMENTS WERE MADE BASED UPON RECENT
OBSERVATION TRENDS AND THE LATEST RUNS OF THE HI-RES GUIDANCE.

PREVIOUS DISCUSSION...

...BLENDED THE 04 UTC NBM WITH WPC CONTINUITY AS STARTING POINT
FOR MANUAL CORRECTIONS BASED ON LATEST RADAR TRENDS...

...AZ/NM...

MODELS AGREE THAT A MID-UPPER LEVEL TROUGH PUSH TO THE SOUTHWEST
WILL CONTINUE A DECREASING MOISTURE TREND.
ACCORDINGLY...CONVECTION MAY FOCUS TODAY FROM THE MOGOLLON RIM TO
SE AZ/SRN NM IN THE LEAD AXIS OF MAX LINGERING MOISTURE AND
INSTABILITY. EVEN THOUGH DAY1 QPF DOES NOT OFFER HEAVY AREAL AVG
QPF AMOUNTS...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL AND
ASSOCIATED LOCAL RUNOFF ISSUES.

...NE TX/SE OK ...CENTRAL/SRN AR...AND NRN LA/MS...

DIGGING IMPULSE ENERGIES THROUGH AN S-CENTRAL HIGH PLAINS HAS
FIRED ORGANIZED CONVECTION CAPABLE OF PRODUCING MODERATE TO
LOCALLY HEAVY RAINFALL WITHIN AN AXIS OF ENHANCED INSTABILITY OVER
NRN TX/SW OK. MODELS HAVE BEEN TOO SLOW WITH DEVELOPMENT...BUT
LATEST TRENDS SUGGEST CONTINUED ACTIVITY WILL FOCUS/REFOCUS DAY 1
IN THE WAVY FRONTAL ZONE AS ENHANCED IN ADVANCE OF THE
MCV/OUTFLOW. CONFIDENCE IS NOT HIGH WITH MODEL SPECIFICS AND LEAD
IN MASS FIELDS...BUT HAVE FOCUSED HEAVIEST QPF POTENTIALS DAY1
DOWNSTREAM ACROSS NERN TX/SERN OK IN A REGION OF BEST SUSPECTED
INFLOW/INSTABILITY/LIFT. THIS AREA HAS RECEIVED VERY HEAVY RECENT
RAINS SO ADDITIONAL RAINS ARE PROBLEMATIC. ENHANCED LEAD THETAE
ADVECTION SHOULD MEANWHILE ALSO LEAD TO SLOW MOVING/TRAINING OF
CELLS DOWNSTREAM OVER AR AND NRN LA/MS. WPC ALSO JUST ISSUED
MESOSCALE PRECIPITATION DISCUSSION #687 THAT ADDRESSES THE LEAD-IN
FLOW DETAILS AND POTENTIALS. GIVEN RECENT HEAVY RAINFALL OVER THE
REGION AND TRAINING POTENTIAL...UPGRADED TO A SLIGHT RISK
EXCESSIVE RAINFALL AREA.

...ERN CAROLINAS...

LINGERING IMPULSE ENERGY WITHIN A SLOW TO DISLODGE CAROLINAS TO
SERN US/CENTRAL GULF COAST DEEP MOISTURE AXIS WITH PWS AOA 2
INCHES SHOULD AGAIN FIRE CLUSTERS OF ENHANCED CONVECTION DAY1 IN A
REGION OF FAVORABLE RIGHT ENTRANCE REGION UPPER JET LIFT AND
INSTABILITY ALONG THE SAGGED/WAVY FRONTAL ZONE. PREDICTABILITY OF
SPECIFICS OF CONVECTIVE FOCUS IS AT OR SOMEWHAT BELOW AVERAGE.
EVEN THOUGH DAY1 QPF DOES NOT OFFER HEAVY AREAL AVERAGE QPF...A
MARGINAL RISK OF EXCESSIVE RAINFALL AND SPOTTY ASSOCIATED LOCAL
RUNOFF ISSUES IS POSSIBLE WITHIN THE DEEP MOISTURE AXIS.

...N-CENTRAL PLAINS/UPPER MIDWEST...

IMPULSE PASSAGE WITHIN A NRN STREAM TROUGH AND UPPER JET SUPPORT
FAVORS ASCENT AND INCREASED INSTABILITY. LOWER LEVEL SOUTHERLY
RETURN FLOW IS ADVECTING MOISTURE NORTH INTO THE REGION WITH AN
AXIS OF ENHANCING PW VALUES INCREASING TO THE 1.25-1.5 INCH RANGE
OVER THE ERN PLAINS/UPPER MIDWEST. THIS IS FUELING INCREASED
COVERAGE OF SHOWERS AND THUNDERSTORMS. ACTIVITY RECOUPS LATER PD
OVER THE HIGH PLAINS WITH UPSTREAM SYSTEM APPROACH AND FRONTAL
ZONE LIFT. THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL AND
ASSOCIATED LOCAL RUNOFF ISSUES MONDAY.

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

SCHICHTEL
$$





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