Quantitative Precipitation Forecast
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FOUS30 KWBC 251445
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1044 AM EDT TUE JUL 25 2017

...VALID 15Z 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
20 SSW CYS 10 SW MNH 20 WNW VTP 25 NNE CPW 20 W SKX 10 ENE AEG
60 SSW ABQ 10 WNW TCS 20 NE DMN 50 SSW DMN 90 SE DUG 85 SSW DUG
10 WSW OLS 20 NNW DMA 25 E IWA 20 NNE DVT 40 WSW PRC 30 S EED
20 NE TRM 15 WNW PSP 20 S DAG 40 NE DAG 55 WSW HND 10 W DRA
55 SE TPH 40 NE BIH 60 NNE MMH 25 NE NFL 25 WNW WMC 55 WNW WMC
25 S AAT 40 W AAT 30 N O54 40 E CEC 20 ESE MFR 70 SSW RDM
60 WSW BNO 50 SW ONO 40 W MUO 30 NNE AWH 45 SW 77M 40 SW 77M
30 SE 77M 25 NNW U78 10 NE RXE 25 NE WYS 50 NNW COD 15 W COD
30 NW LND 30 SW BVR 35 WSW PAT CPR BFU 35 NW RCA 25 E RCA
40 WNW PIR 15 SE ABR AXN 15 WNW HIB 35 NW CKC 20 S CWEC
45 ESE GNA 20 E BFW 15 NW IWD 35 NW SAW 20 WSW CIU MGN 30 E AIG
15 SW ISW 25 NNW LNR 20 S DEH 20 W AEL MJQ 15 NE DNS 15 SSE LNK
15 W HJH 20 W HDE 35 N GLD 40 WNW ITR 40 NNW LIC 30 SSW SNY
25 NNE IBM 25 SW BFF 20 SSW CYS.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S HRT 40 S PQL 15 SSE HDC 25 E ACP 25 NNE POE 15 WNW IER
35 ENE IER 35 N TVR 35 NNE HKS 50 SE NMM 50 SSE TCL 25 NNW BHM
HSV 25 W CHA 20 SSW RMG 20 E FFC 25 NE DBN 20 NW JYL 30 ENE CHS
55 SSE HXD 15 W JAX 20 SW GNV 40 SW 40J 15 SW AAF 25 S HRT.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSE MKT 20 NE PQN 15 ESE MHE 15 E ONL 20 E TIF 45 N OGA
30 SSE IEN 15 S PHP 55 ENE PIR 20 NNW ATY 15 E MOX STC
20 ENE RNH 20 N LSE DEH 10 SSE MKT.

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 50 ENE PGA 15 E GCN 40 NW PRC 30 SSE IGM
EED 45 NNE NXP 30 SW HND 25 WNW 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
25 ESE IGM 20 NNW EED 35 S HND HND 10 NNW VGT 50 NNE LSV
35 W CDC 15 N CDC 30 SW BCE 60 ESE SGU 50 W 40G 25 ESE IGM.



...15Z UPDATE...

CONTINUED TO CARRY A MODERATE RISK AS CONVECTION CONTINUES TO
FLOURISH NEAR LAS AND SOUTH AND EAST OF THE METRO AREA. THE 12Z
NAM CONEST AND 13Z HRRR KEEP THIS CONVECTIVE HEAVY RAINFALL
BUILDING OFF TO THE NORTH AND EAST OVER THE NEXT 3 TO 6 HRS. THESE
INTENSE CONVECTIVE RAIN RATES WILL LIKELY LEAD TO RUNOFF AND FLASH
FLOOD CONCERNS. PLEASE REFER TO LATEST ADVISORIES FROM VEF AND FGZ
WFOS. MEANWHILE PRETTY MUCH KEPT CONTINUITY FROM THE EARLIER 09Z
AND SPECIAL 12Z UPDATE WITH A FEW MINOR TWEAKS HERE AND THERE.

...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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