Quantitative Precipitation Forecast
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FOUS30 KWBC 281431
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1030 AM EDT FRI APR 28 2017

...VALID 15Z FRI APR 28 2017 - 12Z SAT APR 29 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSW AOH 15 ENE AGC 20 NNW W99 20 SE 48I 10 NNE BKW
15 WNW I16 10 ESE LOZ 30 NNW BNA 30 S JBR 25 NNE PRX 15 NNE GLE
25 W RPH 10 NW SWW 10 SW SNK 30 NNE SNK 25 E CDS 20 ESE WWR
10 SSW IAB 20 SSE DMO 10 SSW AOH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNW OLY FFO 20 ENE ZZV 20 W MGW 30 NW 48I 10 NNW LEX
30 N HOP 35 ENE RUE 20 E AQR 15 SSE PVJ 25 N FSI 15 NW JWG
15 WNW BVO 35 WSW TBN 10 NNW OLY.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 N UNO 10 SSE FAM 20 NW CGI 25 SW CGI 15 N ARG 30 ENE FSM
25 W MLC 10 SE TIK 15 SE SWO 25 W GMJ 30 SE SGF 25 N UNO.


1500 UTC UPDATE

THE ONLY CHANGE MADE TO THE PREVIOUS DAY 1 EXCESSIVE RAINFALL
POTENTIAL OUTLOOK WAS TO PUSH THE MARGINAL RISK AREA SLIGHTLY TO
THE SOUTH OVER CENTRAL TO EASTERN KY.  THIS WAS TO COVER SOME OF
THE LATEST HRRR RUNS THAT WERE SHOWING A FARTHER SOUTHWARD HEAVY
AXIS LATER THIS AFTERNOON INTO THIS EVENING.  HOWEVER---OVER THE
LAST SEVERAL RUNS OF THE HRRR---THIS AXIS HAS BEEN SHIFTING
FARTHER AND FARTHER TO THE NORTH.

ORAVEC


...SOUTHERN PLAINS / OZARKS...

THE CONVECTIVE FORECAST HERE COMES WITH THE USUAL SMALL SCALE
UNCERTAINTIES...BUT ON THE LARGE SCALE AN IMPRESSIVE INFLUX OF
MOIST AND UNSTABLE AIR WILL LEAD TO A BROAD ZONE OF HEAVY
CONVECTIVE RAINFALL AND EMBEDDED SWATHS OF VERY INTENSE RAINFALL.
FLOODING AND FLASH FLOODING IMPACTS ARE LIKELY...BEGINNING FRIDAY
NIGHT FROM OKLAHOMA TO SOUTHERN ILLINOIS.

THERE ARE QUESTIONS REGARDING THE TIMING AND PLACEMENT OF THE
INITIAL CONVECTIVE DEVELOPMENT THIS AFTERNOON. THE DEEP RETURNING
MOISTURE MAY BE CAPPED AND SOMEWHAT REMOVED FROM THE MORE
FAVORABLE UPPER LEVEL ASCENT LOCATED IN CENTRAL OKLAHOMA
NORTHWARD. BY LATE AFTERNOON AND EVENING...HOWEVER...DEEP MOISTURE
MAY ENCOUNTER AN ENVIRONMENT JUST FAVORABLE ENOUGH FOR SCATTERED
INITIATION WHEN IT REACHES SOUTHERN OK AND PARTS OF NORTH TX. IF
WARM SECTOR CONVECTION BECOMES ESTABLISHED IN ANY SIGNIFICANT
WAY...IT WILL LIKELY PRODUCE A FEW PERSISTENT OUTFLOWS TO YIELD
FURTHER INITIATION THROUGHOUT THE NIGHT AS LOW LEVEL FLOW
STRENGTHENS. SYNOPTICALLY FORCED PRECIPITATION WILL ALSO BREAK OUT
TO THE NORTH AND WEST AS THE FRONTAL ZONE TIGHTENS AND A CLOSED
LOW BEGINS TO APPROACH OVERNIGHT FROM THE WEST. BETWEEN THE
VARIOUS FORCING MECHANISMS THERE MAY BE SEVERAL CLUSTERS OF STRONG
THUNDERSTORMS PRODUCING HEAVY RAINFALL ACROSS THE SOUTHERN PLAINS
AND THE OZARKS. COVERAGE AND INTENSITY SHOULD GENERALLY INCREASE
TOWARD THE END OF THE DAY 1 PERIOD FRIDAY NIGHT...WITH THE FLASH
FLOOD RISK BECOMING PARTICULARLY PRONOUNCED FROM EASTERN OKLAHOMA
THROUGH NORTHERN ARKANSAS AND SOUTHERN MISSOURI...IN AN AREA THAT
RECEIVED VERY HEAVY RAINFALL ONLY A FEW DAYS AGO.

THE FLASH FLOOD RISK IS FORECAST TO INCREASE EVEN FURTHER ON DAY 2
IN PARTS OF THIS REGION. PLEASE REFER TO THE DAY 2 EXCESSIVE
RAINFALL GRAPHIC AND WPC QPF DISCUSSION FOR DETAILS ON A DAY 2
HIGH RISK.


...SOUTHERN OHIO VALLEY TOWARD THE CENTRAL APPALACHIANS...

TODAY WILL SEE AN IMPRESSIVE EXPANSION OF WARM...MOIST AIR INTO
THE SOUTHERN AND EASTERN UNITED STATES...WITH DEW POINTS RISING TO
THE 60S / LOW 70S PER THE NAM...AS FAR NORTH AS THE OHIO RIVER.
SURFACE BASED INSTABILITY MAY BE UNCAPPED WITH NORTHWARD /
EASTWARD EXTENT...AND UPGLIDE NORTH OF A WARM FRONT WILL FURTHER
CONTRIBUTE TO ASCENT AND CONVECTIVE INITIATION. ONCE THUNDERSTORM
CLUSTERS ARE ESTABLISHED...OUTFLOWS MAY HELP TO FOCUS
BACK-BUILDING / TRAINING AS LOWER LEVEL MOISTURE AND WIND PROFILES
CONTINUE TO IMPROVE AHEAD OF A DEEPENING LARGE SCALE SYSTEM. THE
CONSENSUS OF MODEL QPFS PAINTS A SWATH OF MODERATE TO HEAVY RAIN
STRADDLING THE OHIO RIVER FROM SOUTHERN ILLINOIS TO NORTHERN WEST
VIRGINIA...OCCURRING FROM THIS AFTERNOON THROUGH TONIGHT. HI-RES
MODELS INDICATE HEAVY HOURLY ACCUMULATIONS APPROACHING 2
INCHES...AND LOCAL BOUTS OF TRAINING CONVECTION COULD BRING
24-HOUR TOTALS TO 3 TO 4 INCHES IN PLACES. THIS WILL LIKELY
OVERLAP WITH SOME AREAS THAT RECEIVED HEAVY RAIN EARLIER IN THE
WEEK AND MAY ALREADY HAVE SATURATED GROUND / SWOLLEN STREAMS.

BURKE
$$





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