Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 271500
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EDT SAT MAY 27 2017

...VALID 15Z SAT MAY 27 2017 - 12Z SUN MAY 28 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SSE CAV 30 WSW MFI 15 SE AIG 10 ESE ATW 10 NNW UNU
20 WNW FEP 30 ESE MLI CMI 10 ENE HNB 35 S LEX 15 S CRW EKN
15 ESE NYG 25 ESE MFV 75 ENE FFA 40 E FFA 15 SSW SFQ 20 SW FVX
20 NW MTV 10 WSW MRN 25 NNW GVL 10 NNW 3A1 25 NNE GWO 10 SE ELD
OSA CRS 10 NNW 05F 10 N SEP 25 NW GLE 10 SW SNL 15 ESE BVO
25 ENE AAO 15 N MHK 10 W AIO 15 SSE CAV.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 W MDH 25 W HOP 30 NW CSV 30 SSE CSV 40 NE MDQ 30 WNW MSL
40 SSW UTA 40 ENE TXK 15 SSE AQR 25 NW MLC 15 SSE GMJ 20 WSW JLN
30 WNW CNU 10 ENE EMP 20 WNW MCI 20 W IRK 15 S CPS 20 W MDH.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW AIZ 45 SW FAM 30 WNW POF 35 NNW ARG 10 S UNO 25 SSE SGF
40 NNE JLN 40 SW SZL 25 NW AIZ.


...SOUTHERN MISSOURI / FAR NORTHERN ARKANSAS...

UPGRADE TO MODERATE RISK FOR PARTS OF SOUTHERN MISSOURI. THE
PRIMARY DETERRENT TO MODERATE RISK GOING INTO TODAY WAS THE RATHER
BROAD WARM SECTOR WITH SEVERAL POCKETS OF STRONG CONVECTION
EXPECTED...ALONG WITH ANTECEDENT HYDROLOGIC CONDITIONS THAT HAD
RECOVERED FROM EARLY MAY FLOODING...PARTICULARLY WHEN VIEWED
THROUGH THE RIVER FORECAST CENTER FLASH FLOOD GUIDANCE. CONFIDENCE
HAS GROWN IN THE NEAR TERM...HOWEVER...WITH THE HRRR LOCKING ON TO
THE CAPE GRADIENT AND MID LEVEL TEMPERATURE GRADIENT AND PRODUCING
HIGHER END PRECIPITATION AMOUNTS OF 2 TO 4 INCHES THIS
AFTERNOON/EVENING IN CONSECUTIVE MODEL RUNS. AFTER DISCUSSING THE
GROWING CONFIDENCE HERE...ALONG WITH THE TENDENCY FOR FLASH
FLOODING IN THE TERRAIN OF THE OZARKS...WPC IS UPGRADING TO
MODERATE RISK.

OTHER POTENTIAL FOCI FOR EXCESSIVE RAINFALL ON SOMETHING LARGER
THAN COUNTY-SCALE...INCLUDE THE HIGH-CAPE ENVIRONMENT AND WELL
TIMED SHORTWAVE OVER SOUTHEAST OKLAHOMA...AND LATER IN THE NIGHT A
GROWING MID LEVEL CONFLUENCE ZONE EXTENDING FROM EASTERN ARKANSAS
EASTWARD INTO TENNESSEE AND PERHAPS ADJACENT PARTS OF KY/MS. FOR
NOW WE WILL MAINTAIN A BROAD SLIGHT RISK FOR THESE AREAS WHILE
MONITORING SHORT TERM TRENDS. LOOK FOR MESOSCALE PRECIPITATION
DISCUSSIONS WHICH MAY BE ISSUED AS EVENTS BEGIN TO UNFOLD.


...MID ATLANTIC...

PORTIONS OF NC/VA WERE ADDED TO MARGINAL RISK GIVEN THE
OPPORTUNITY FOR ISOLATED BOUTS OF TRAINING CONVECTION.


...PREVIOUS DISCUSSION...
...LOWER MISSOURI VALLEY / LOWER-MID MISSISSIPPI VALLEY /
TENNESSEE VALLEY / LOWER OHIO VALLEY...

THE POSITIVELY TILTED TROUGH EXTENDING FROM THE FOUR CORNERS
REGION NORTHEAST TO THE NORTHERN PLAINS SATURDAY MORNING WILL
PIVOT EAST ACROSS THE CENTRAL PLAINS AND UPPER MS VALLEY DURING
THE DAY 1 PERIOD. BY 12Z SUN...THE RESULTANT HEIGHT FALLS WILL
HAVE PUSHED THE ASSOCIATED SURFACE COLD FRONT INTO THE SOUTHERN
PLAINS AND MID MS VALLEY. BROADLY DIFFLUENT UPPER FLOW DOWNSTREAM
OF THIS TROUGH...ALONG WITH MODEST FRONTOGENETIC SUPPORT AS A
SUBTLE UPPER JET STREAK ELONGATES NORTHEAST OF THE TROUGH
BASE...WILL SPARK WIDESPREAD PRE-FRONTAL CONVECTION OVERNIGHT
ACROSS EASTERN KS-OK EASTWARD TO THE LOWER OH VALLEY AND NORTHERN
TN VALLEY. DESPITE THE FAVORABLE MASS FIELD AGREEMENT WITH THE 00Z
GUIDANCE...THE MODEL QPFS CONTINUE TO EXHIBIT SIGNIFICANT N-S
SPREAD WITH THE HEAVIER TOTALS...AND IN SOME INSTANCES (AS WITH
THE NAM AND GFS)...NOTING A BIMODAL DISTRIBUTION WITH THE MAXIMA.
AS WITH THE INHERITED QPF FROM THE PREVIOUS SHIFT...WPC
INCORPORATED MORE ECMWF AND WRF-ARW GUIDANCE FOR 00-12Z
SUN...WHICH CONTINUE TO BE ON THE SOUTHERN PERIPHERY OF THE
GUIDANCE SPREAD. GIVEN THE THERMODYNAMIC SETUP (GREATER DEEP-LAYER
INSTABILITY...PWS 1.5-1.75+ INCHES...AND SW-WSW LOW-LEVEL INFLOW
OF 40-50 KTS INTO WHAT WILL LIKELY BE AN EFFECTIVE W-E DRAPED
FRONTAL BOUNDARY)...BELIEVE THE WRF-ARW/PARALLEL ARW AND ECMWF
CONTINUE TO HAVE THE RIGHT IDEA. MOREOVER...THE MODELS CONTINUE TO
SHOW THE INITIALLY-CAPPED PROFILE ERODING AS THE DEEP-LAYER ASCENT
ENSUES.

THE CONCERN OVERNIGHT WILL CERTAINLY BE WITH TRAINING CELLS FROM
EASTERN OK/MUCH OF AR/SOUTHERN MO EASTWARD THROUGH NORTHERN
MS...WESTERN AND CENTRAL TN...AND SOUTHERN KY. OTHERWISE...THE MCS
ACROSS KS/NE EARLY SAT AND RESULTANT MCV WILL TRACK ENE AHEAD OF
THE APPROACHING TROUGH...THEREBY CARVING OUT A SECONDARY MAX OF
RAINFALL ACROSS NORTHERN KS AND SOUTHERN NE INTO WESTERN IA.

BURKE/HURLEY
$$





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