Quantitative Precipitation Forecast
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FOUS30 KWBC 251212
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
812 AM EDT TUE JUL 25 2017

...VALID 1212Z TUE JUL 25 2017 - 12Z WED JUL 26 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNW ALS 25 S SKX 10 ENE 4MY 30 NNE TCS 40 SSE DMN 90 SE DUG
20 NNE DUG 10 E SOW 35 ESE PRC 20 S PRC 55 SSE IGM 35 S EED
50 WNW EED 40 SW HND 30 S DRA 30 NNW DRA 50 N DRA 20 S TPH
50 ESE NFL 25 WNW WMC 55 WNW WMC 25 S AAT 35 WNW AAT 15 WSW LMT
40 NE MFR 70 S RDM 40 SW BNO 45 SSE BNO 25 S EUL 30 SW TWF
40 SW 77M 30 SE 77M 25 NNW U78 10 NE RXE 20 E S14 35 NW WYS
20 NE P60 55 WNW RIW 20 SW LND 15 SSE BVR 15 SSE HLD 20 SSW BFU
30 E IKA 25 ENE RCA 35 NW PIR 15 WSW 8D3 15 NE MOX 10 E BRD
10 NNE CKC 60 W CWYW 35 NNW CYGQ 50 N CYXZ 30 N ERY 10 ESE EGV
20 NNE AIG 20 ENE STE 15 SSW ISW 15 NE RST 20 E FRM 20 NW SHL
20 SSW FSD 10 NE YKN 15 NNW OFK BVN 10 ENE LXN 40 N GLD
45 ESE AKO 15 NNE AKO 15 SSW SNY 25 SE BFF 10 WNW BFF 10 SSW TOR
CYS 10 W BJC 30 NNE MYP 30 NNW ALS.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WSW JKA 15 SSE HDC 25 E ACP 25 NNE POE 15 WNW IER 35 ENE IER
35 N TVR 35 NNE HKS 55 ESE NMM 20 ESE EET 15 SSE FFC 25 NE DBN
20 NW JYL 30 ENE CHS 55 SSE HXD 40 SE VLD 30 W 40J 10 WSW AAF
10 S HRT 25 WSW JKA.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WNW MWM 20 SSE PQN 20 W FSD 35 SE MHE 35 W YKN 10 N ONL
35 E ANW 20 NE ANW 15 SW ICR 35 N VTN 45 NW ICR 25 S PIR
30 WNW HON 25 NNE HON 10 NNW DXX 10 SE BBB 10 ESE STC 25 ENE RNH
20 S EAU 10 ESE FBL 25 WNW MWM.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 ESE P68 55 SW ENV 50 WSW DPG 30 WSW PVU 40 SE FIR 40 S BIT
25 SSE RWL 25 NNE HDN 15 NW 20V 15 SE EGE 15 W GUC 20 ESE TEX
15 ENE CEZ 15 WSW 4BL 35 SE 4HV 45 SW 4HV 40 W PGA 45 ENE IGM
IGM 35 NW IFP 15 WSW HND 10 W VGT 20 NE DRA 70 NNE DRA
65 ENE TPH 30 ESE P68.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 N SGU 20 ENE SGU 55 SSE SGU 45 NNE IGM 30 ESE HND LSV
25 NNW VGT 40 ENE DRA 65 WNW SGU 35 N SGU.


...12Z SPECIAL UPDATE...

AFTER COLLABORATION WITH WFO VEF, WPC WENT AHEAD AND UPGRADED SERN
NV/NWRN AZ AND SWRN UT IN A MODERATE RISK BASED ON CURRENT BLOB OF
HEAVY RAINS WITH BACKBUILDING CAPABILITY. THE HI-RES GUIDANCE
INCLUDING THE 10Z HRRR DEPICT THIS AREA OF INTENSE RAINS TO
PERSIST BEFORE SLOWLY TRACKING OFF TO THE NORTH AND EAST. THIS IS
ALL RELATED TO THE DEEP POOLING MONSOONAL MOISTURE INTERACTING
WITH A WELL-DEFINED MID-LEVEL DISTURBANCE ROUNDING THE WESTERN
PORTION OF A 500MB RIDGE AXIS. THESE RAINS OVER THE NEXT FEW HRS
COULD PRODUCE RAPID WATER RISES WITH FLASH FLOODING NORTH AND EAST
OF LAS. WPC ALSO EXPANDED THE MARGINAL RISK IN THE SOUTH/GULF
COAST REGION TO COVER MPDS 558 AND 559 FOR LOCALLY HEAVY RAINS IN
SWRN/SOUTHERN MS AND EAST CENTRAL AL.

MUSHER


...CNTL PLAINS NEWD INTO THE UPPER MS VALLEY...

    ...SLIGHT RISK OF EXCESSIVE RAINS FROM PARTS OF CNTL/ERN
SD/EXTREME NRN NEB EWD INTO SRN MN/WRN WI...

COMPACT UPPER LOW IS FCST TO PUSH EWD ACRS SRN CANADA ON TUESDAY
HELPING TO DRAG AN ASSOCD COLD FRONT EWD INTO MN BY TUE EVENING
WITH TRAILING PORTION SLOWING ACRS WRN SD.  MSTR IS EXPECTED TO
RAPIDLY DEEPENING ALONG THE TRAILING PORTION OF THE FRONT BY LATE
TUES AFTN TO OVER 1.75 INCHES PERHAPS AS HIGH AS 2" AS
STRENGTHENING SLY FLOW ENHANCES CONVERGENCE INTO THE BNDRY.
MEANWHILE..MODELS RAPIDLY TAKE VORT MAX LIFTING INTO WRN UT MON
NIGHT NEWD INTO WY WITH SHEARING ENERGY MOVING EWD ACRS SD TUES
EVENING.  THE TIMING SUGGESTS TSTMS SHOULD RAPIDLY EXPAND EWD
ALONG THE FRONT THRU SD AND INTO MN WITH VEERING LOW LEVEL JET
TUES NIGHT..WHILE ADDITIONAL STORMS DVLPG EWD OUT OF SE CO/NE CO
INTO WRN NEB AND STRENGTHEN INTO MORE FAVORABLE INSTABILITY AND
DEEPER MSTR.  THE ORIENTATION OF THE SFC FRONT WITH THE MIDLEVEL
WLY FLOW SUGGESTS POTNL FOR TRAINING OF CELLS ESPECIALLY DURING
EARLY STAGE OF DVLPMENT ACRS PORTIONS OF SRN SD ENEWD INTO SRN MN
AND WRN WI LEADING TO SOME POTNL FLOODING ISSUES.  HEAVIER RAIN
THREAT WILL GRADUALLY EXPAND SEWD INTO NRN PORTIONS OF NEB..WITH
ISOLD STG STORMS WITH LOCALLY HEAVY RAINS EXPECTED TO WORK EWD
ACRS SW NEB TOWARD SCNTL NEB BY WED MRNG.  SOME SWD ADJUSTMENT TO
THE HEAVIER QPF AXIS WAS MADE GIVEN STRONG CONSENSUS OF THE HIER
RES MODEL GUIDANCE..WITH THE NAM CONEST/CANADIAN GEM GIVEN A BIT
MORE WEIGHT.  WITHIN THE SLIGHT RISK AREA LOCAL RAINFALL AMOUNTS
OF 2 TO 3 INCHES IN SEVERAL HOURS MAY BE PSBL WHICH COULD LEAD TO
RUNOFF ISSUES.

...SOUTHEAST/SOUTH...

WIDESPREAD SHOWER/TSTM ACTIVITY IS EXPECTED ONCE AGAIN ACRS MUCH
OF THE GULF COAST REGION INTO THE SE STATES WITH VERY HIGH
TROPICAL LIKE AIRMASS FOCUSED ALONG A BROAD UPPER SHEAR AXIS
EXTENDING FROM ERN TX EWD INTO GA/SC.  WHILE 85H WLY FLOW IS A BIT
WEAKER THAN YDA...SUFFICIENT WLY FLOW AND CONFLUENCE COULD SUPPORT
SOME ORGANIZED CLUSTERS/BANDS LEADING TO SOME LOCALIZED VERY HEAVY
RAINS. THOUGH PERHAPS NOW QUITE AS ORGANIZED AS YDA GIVEN THE
WEAKER 85H FLOW...HI RES GUIDANCE SUGGESTS SOME ISOLD RAINFALL
AMOUNTS IN EXCESS OF 3 INCHES COULD OCCUR FROM THE CNTL GULF COAST
EWD INTO SRN GA/SRN SC.  GIVEN SOME LOCALIZED VERY HEAVY RAINS
WHICH OCCURED YESTERDAY ACRS PARTS OF THE LOWER MS VALLEY...HAVE
INCLUDED MUCH OF THAT REGION EWD INTO THE SOUTHEAST COAST IN A
MARGINAL RISK OF EXCESSIVE RAINS.

...SOUTHWEST INTO GREAT BASIN...

   ...SLIGHT RISK OF EXCESSIVE RAINS FROM ERN NV EWD INTO WRN
CO...

ACRS THIS REGION...THE MORE CONCENTRATED HEAVIER RAIN THREAT WILL
CONTINUE TO LIFT NEWD EARLY IN THE PD ACRS UT INTO WRN CO/SRN WY
WITH WELL DEFINED VORT/CIRC INITIALLY OVER SW UT LIFTING NEWD
AROUND WRN PERIPHERY OF THE CNTL U.S. UPPER RIDGE AND TO THE EAST
OF UPPER TROF ALONG THE CA COAST.   THE UPPER TROF WITH CLOSED
CENTER ALONG THE NRN CA COAST IS NOT FORECAST TO MOVE MUCH THROUGH
THE PD BUT WITH PASSAGE OF VORT TO THE NE MODELS SHOW SOME GRADUAL
DRYING IS EXPECTED BY LATE AFTN INTO TUES NIGHT.  THAT
SAID..SHOULD SEE ANOTHER FAIRLY ACTIVE MONSOONAL CONVECTIVE DAY
ACROSS MUCH OF THE SOUTHWEST BUT ESPECIALLY FROM PARTS OF ERN NV
EWD THROUGH UT/WRN CO INTO SRN WY..IN CLOSER PROXIMITY TO MID
LEVEL VORT.   THREAT OF FLASH FLOODING WILL AGAIN BE PSBL ACRS
MUCH OF THE AREA GIVEN RAINS OVER THE PAST SEVERAL DAYS AND HAVE
INCLUDED AREA FROM ERN NV EWD INTO MUCH OF CNTL/SRN UT/NW AZ INTO
WRN CO IN A SLIGHT RISK OF EXCESSIVE RAINS.

SULLIVAN
$$





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