Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 180828
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 AM EDT THU MAY 18 2017

...VALID 12Z THU MAY 18 2017 - 12Z FRI MAY 19 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE DEQ 25 NW COT 10 E DLF 25 SSW E29 10 N SJT 25 NNW DYS
40 WSW F05 25 W F05 35 WNW CSM HHF 10 ENE PYX 30 E LBL
20 WSW DDC 25 ENE GCK 45 NE GCK 45 SW HLC 15 WSW HLC 25 NW HLC
20 SSE MCK 25 E IML 20 WSW IML 40 SW IML 15 WNW ITR 40 NNE LHX
15 SSE MNH MNH 10 S GXY 20 NE CYS 20 NE BRX 30 N TOR 20 E CDR
20 SSW VTN ONL 35 ESE ONL 15 WNW DNS 15 ESE ADU 25 WNW IRK JEF
25 SW HRO 15 ENE DEQ.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NNE RSL 25 WSW CNK 30 SSW BIE 25 SSW FNB 25 WSW CDJ 20 S CDJ
30 NNE DMO 10 WSW DMO 60 NNE JLN 40 E CNU 15 ESE CFV 10 ESE BVO
25 WSW BVO 10 WSW PNC 30 NNW WDG 20 SSE P28 35 W P28 30 SE DDC
15 E DDC 15 SE HYS 15 NNE RSL.


SOUTHERN TO CENTRAL PLAINS INTO THE LOWER MO VALLEY

WIDESPREAD HEAVY PRECIP LIKELY TO THE EAST AND NORTHEAST OF THE
SLOW MOVING STRONG CLOSED LOW PUSHING FROM THE GREAT BASIN INTO
THE CENTRAL ROCKIES.  TWO MAX REGIONS OF HEAVY PRECIP LIKELY THIS
PERIOD AHEAD OF THIS CLOSED LOW.  ONE OVER THE CENTRAL HIGH PLAINS
INTO THE CENTRAL ROCKIES IN A REGION OF STRONG UPPER DIFFLUENCE
AND STRENGTHENING EAST NORTHEASTERLY UPSLOPE FLOW.  THE SECOND
WILL BE OVER PORTIONS OF THE SOUTHERN TO CENTRAL PLAINS INTO THE
LOWER MO VALLEY IN THE VICINITY OF THE NEARLY STATIONARY FRONTAL
BOUNDARY EXPECTED TO LIE ACROSS THESE AREAS.

A MARGINAL RISK AREA WAS MAINTAINED FOR THE RAIN COMPONENT OVER
THE CENTRAL HIGH PLAINS WHERE THE SLOW MOVEMENT OF THE CLOSED LOW
WILL LIKELY FOCUS AN AREA OF MODERATE TO OCCASIONALLY HEAVY PRECIP
FROM FAR NORTHEAST COLORADO INTO NEBRASKA.  HI RES GUIDANCE IS
SHOWING HOURLY RATES MOSTLY IN THE .10-.25" RANGE--WITH ANY RUNOFF
RISK LIKELY TO BE MORE OF A DURATION EVENT.

A GREATER RISK OF EXCESSIVE RAINFALL AMOUNTS LIKELY IN THE
VICINITY OF THE NEARLY STATIONARY FRONTAL BOUNDARY STRETCHING FROM
PORTIONS OF THE SOUTHERN PLAINS---NORTHEASTWARD INTO EASTERN
PORTIONS OF THE CENTRAL PLAINS---LOWER MO VALLEY INTO THE MID MS
VALLEY TO THE EAST NORTHEAST OF THE SLOW MOVING UPSTREAM CLOSED
LOW.  CONVECTION SHOULD BECOME INCREASINGLY ACTIVE LATE THURSDAY
AFTERNOON INTO THURSDAY NIGHT/EARLY FRIDAY AS THE LOW LEVEL SOUTH
SOUTHWESTERLY FLOW STRENGTHENS INTO THIS BOUNDARY IN A REGION OF
WELL DEFINED UPPER DIFFLUENCE TO THE EAST OF THE GREAT
BASIN/CENTRAL ROCKIES CLOSED LOW.  THE 0000 UTC RUN OF THE ARW AND
NSSL WRF ARE SHOWING A FARTHER SOUTHEASTWARD AXIS OF HEAVY PRECIP
INTO SOUTH CENTRAL TO SOUTHEAST OK AND NORTHWEST AR THAN MOST OF
THE OTHER GUIDANCE---AS THEY DEVELOP MORE OF A COLD POOL WITH THIS
ORGANIZING CONVECTION AND PUSH IT MORE RAPIDLY SOUTHEASTWARD.
WHILE THIS TYPE OF SOLUTION IS POSSIBLE---THE WPC QPF AT THE
MOMENT LEANED AWAY FROM THIS SOLUTION WHICH WERE SIGNIFICANT
CONTINUITY CHANGES FROM THEIR RESPECTIVE PREVIOUS RUNS---FOCUSING
PRECIP CLOSER TO THE NEARLY STATIONARY WEST SOUTHWEST TO EAST
NORTHEASTERLY ORIENTED FRONTAL BOUNDARY.  THERE MAY BE A PERIOD OF
TRAINING OF CELLS PARALLEL TO THE FRONT IN THE 0000-1200 UTC TIME
FRAME.  IN AREAS OF TRAINING---RAINFALL TOTALS OF 1-2"+ IN AN HOUR
POSSIBLE.


ORAVEC
$$





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