Quantitative Precipitation Forecast
Issued by NWS

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910
FOUS30 KWBC 261404
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1004 AM EDT FRI AUG 26 2016

...VALID 15Z FRI AUG 26 2016 - 12Z SAT AUG 27 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NW KMIU 35 W VCT GTU 10 N FWS AQR 15 ESE MKO 15 S GMJ
15 ESE CFV 25 WNW BVO 10 NNE WDG GAG DUX TCC 30 NNW ROW
30 NW GDP 35 E ELP 25 W HMN 20 SW 4MY 10 S E33 20 WSW AFF
30 ENE COS 20 ENE LIC 25 SSE AKO 10 NNW OGA 55 WNW TIF
20 SSE CUT 50 ENE HEI 35 ESE DVL 15 NW FSE ILL 20 ENE FRM
35 E VOK RAC UGN 30 NNE DNV 20 NNE HUF 20 N BNA 25 W MSL
50 NNE GWO 35 NNE GLH 10 NW BQP AEX 30 SE ACP 10 SSE 7R3
10 S 9F2 20 SSW KMYT.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 ENE 40G 15 ESE FLG 20 NE PRC 45 WNW PRC 25 SE IGM 20 ENE LSV
25 WNW SGU 40 N BCE 25 NE BCE 45 W PGA 25 ENE 40G.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 WSW HLC SDA 20 SSE DBQ C09 10 ENE DEC 30 SW PPQ 15 SSE GBD
50 N EHA LAA 30 SSW ITR 45 WSW HLC.


15Z UPDATE...
EXPANDED MARGINAL RISK AREA WWD INTO THE MTNS OF SRN CO INTO NM
WITH APCH OF 4 CORNERS S/WV THIS AFTN WHICH SHOULD PROVIDE AN
INCREASE IN AFTN/EVE CONVECTION..LEADING TO POTNL ISOLD HEAVY RAIN
CORES OVER THE MOUNTAINOUS TERRAIN..AS DEPICTED BY HI RES CAM
ALLOWING GUIDANCE.  ALSO A SLIGHT EXPANSION EWD TO THE MARGINAL
RISK AREA WAS MADE ACRS PARTS OF THE LOWER MS/TN VALLEY GIVEN
SIGNAL FROM SEVERAL HI RES RUNS FOR ISOLD HEAVY/EXCESSIVE RAIN
THREAT PRIMARILY FROM AFTN/EVEN TSTMS WITHIN AXIS OF GREATER THAN
2" PWS THAT COULD LEAD TO SOME INTENSE SHORT TERM RAINFALL RATES.
OTHERWISE...NO SIGNIFICANT CHANGES MADE TO PREVIOUS EXCESSIVE RAIN
OUTLOOK AND REASONING.  SULLIVAN


SOUTHWEST
~~~~~~~~~
A SLOWLY PROGRESSIVE UPPER TROF WITH EMBEDDED SHORTWAVES WILL
ACROSS OUT OF THE INTERMOUNTAIN WEST/ROCKIES.  THIS WILL LEAD TO
UNSETTLED CONDS ACROSS MUCH OF THE ROCKIES INTO THE 4 CORNERS
REGION WITH SCATTERED SHOWERS AND THUNDERSTORMS DURING THE NORMAL
DIURNAL CYCLE.  LOCAL AMOUNTS OF 2-3" COULD CAUSE ISSUES IN
NORTHWEST AZ, FAR SOUTHERN NV, AND SOUTHWEST UT, SO INCLUDED A
MARGINAL RISK IN THIS AREA.


NORTHERN & CENTRAL PLAINS/MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PORTIONS OF KS/MO/IA/IL COULD BE THE FOCUS FOR HEAVY RAINS AS
DEEPER MOISTURE/INSTABILITY ATTEMPTS TO INTERSECT A FRONTAL TRYING
TO RETURN NORTHWARD INTO THE UPPER MISSISSIPPI VALLEY.  LOW-LEVEL
INFLOW INTERACTING WITH THE AVAILABLE INSTABILITY COULD ALLOW FOR
ORGANIZED CONVECTION.  MODEL QPF SHOWS SIGNIFICANT SPREAD, AS SOME
PIECES OF GUIDANCE ALLOW AN OUTFLOW BOUNDARY SOUTH OF THE WARM
FRONT TO REMAIN ACTIVE ACROSS PORTIONS OF MO AND IL DURING THE
AFTERNOON AND EVENING HOURS, WHICH WOULD ERODE INSTABILITY WHICH
WOULD OTHERWISE BE AVAILABLE FARTHER NORTHWARD ACROSS WI WHERE THE
WARM FRONT`S 850 HPA SLICE WOULD BE RETURNING NORTH.  THIS LED TO
A BROAD MARGINAL RISK AREA DUE TO UNCERTAINTY.  THE MESOSCALE
GUIDANCE SHOWS POCKETS OF 3-5" SCATTERED ACROSS NE, KS, MO, AND IL
WHICH WOULD EXCEED THREE HOURLY FLASH FLOOD GUIDANCE VALUES,
THOUGH THERE IS NOT MUCH AGREEMENT AS TO WHERE EXACTLY THIS WOULD
OCCUR.  MAINTAINED THE SLIGHT RISK AREAS SEEN ON DAY 2 YESTERDAY,
THOUGH REARRANGED IT SLIGHTLY BASED ON THE 06Z QPF CYCLE.

ROTH
$$





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