Quantitative Precipitation Forecast
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489
FOUS30 KWBC 280343
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1142 PM EDT SAT MAY 27 2017

...VALID 12Z SUN MAY 28 2017 - 12Z MON MAY 29 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NW 3A1 20 N GWO 30 ENE ELD 15 SSE PRX TKI 15 NNW LUD
25 NE DUC 20 NNW BVO 30 SSE LXT 40 SSW IRK 30 S OTM 15 E PEA
20 WSW DSM BNW 25 SSE MCW 15 SSE ONA 15 E CWA CLI 20 W OSH
15 SW MSN 20 WNW FEP 20 ESE MLI 15 NW DEC 30 S BMG 15 NE LEX
35 WSW HTS 20 ESE 3I2 20 WNW W22 20 N EKN 15 SE W99 10 SW CJR
20 SSW NHK 10 ESE MFV 75 ENE FFA 40 E FFA 15 SSW SFQ 20 SW FVX
20 NW MTV 10 WSW MRN 25 NNW GVL 15 NW 3A1.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SSE M89 25 NNW PRX 10 SSW GYI 20 WNW 1F0 20 ENE CQB
15 SSE CFV 35 NNE SGF FAM 15 ENE M30 15 NNE HOP 40 WNW SME
10 S JKL 15 NNW GEV 20 WSW TNB 25 NNW AVL 30 NE DNN 35 N 4A9
30 NNE TUP 45 SSW UTA 20 SSE M89.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NE GCM 15 SE JLN 35 SW TBN 45 SW FAM 15 W POF 25 ENE ARG
20 WSW JBR 15 SSE FLP 10 SSW FYV 15 SW TQH 10 NE GCM.


...0338 UTC UPDATE...

ADJUSTED THE PREVIOUSLY ISSUED MODERATE AND SLIGHT RISK AREAS TO
ACCOUNT FOR LATEST RADAR/STLT/OBS/HRRR TRENDS AND TO BETTER MATCH
RECENTLY ISSUED WPC MESOSCALE DISCUSSIONS.

FOR FURTHER DETAILS REGARDING ANY ACTIVE MESOSCALE PRECIPITATION
DISCUSSIONS (MPD) WITHIN THE EXCESSIVE RAINFALL OUTLOOK
AREA...PLEASE REFER TO THE LINK ON THE WPC HOME PAGE UNDER "WPC
TOP STORIES"...OR GO DIRECTLY TO THE MPD PAGE:
WWW.WPC.NCEP.NOAA.GOV/METWATCH/METWATCH_MPD.PHP.

SCHICHTEL/HURLEY


...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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