Quantitative Precipitation Forecast
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FOUS30 KWBC 170049
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
849 PM EDT FRI JUN 16 2017

...VALID 01Z SAT JUN 17 2017 - 12Z SAT JUN 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNE DPL 45J 20 S EQY 15 SW UZA CEU 30 SSW 1A5 10 WSW 1A5
30 NNW AVL 10 N TNB 20 NNE 6V3 20 N I16 30 W 48I 30 ESE PKB
15 NNW CKB 15 W 2G4 20 NE CBE 40 SSE UNV 25 WNW CXY MDT
15 SW LNS 10 NW APG 10 NNE W29 10 SSW SFQ PGV 10 NNE DPL.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNE IJX 30 WSW FAM 15 SSW UNO 15 SSW SGF 10 SSE FOE
10 NNE LNK 20 NE SLB 15 WSW LSE 15 WNW ETB MDW 10 NNE IJX.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NNE HDC 20 E HEZ 25 SE BQP 25 N BQP 10 NW LLQ 20 SE PBF
25 E LLQ 15 SSE GLH 35 NNE HKS 55 SE GWO 35 SW GTR 25 S GTR
35 WSW TCL 45 E NMM 40 WNW GZH 35 SW GZH 30 NW PNS 15 W JKA
35 S PQL 20 S GPT ASD 15 NNE HDC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 NNE JLN 20 SW FNB AFK 10 NNE ICL 30 NNE CDJ 10 SE COU
20 S TBN 25 ESE SGF 55 NNE JLN.


0100 UTC UPDATE


CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO ADD A MARGINAL RISK AREA OVER CENTRAL TO SOUTHERN MS INTO FAR
SOUTHWEST ALABAMA FOR ORGANIZED CONVECTION PRESSING SOUTHWARD
AHEAD OF THE SOUTHWARD MOVING VORT OVER NORTHERN MS.  AT THE
MOMENT---THE ARW---NMMB---NAM CONEST AND NSSL WRF DO NOT HAVE A
GOOD HANDLE ON THE CURRENT CONVECTION.  THE LATEST HRRR DOES SHOW
A FAIRLY GOOD DEPICTION OF THE CURRENT ACTIVITY---SHOWING
CONTINUED ORGANIZED ACTIVITY--HEAVY RAINS FOR THE NEXT 4 TO 5
HOURS AS IT PRESSES SOUTHWARD INTO SOUTHERN MS AND SOUTHWEST AL.
RAINFALL TOTALS OF 1-1.5"+ POSSIBLE WITH THIS CONVECTION.

OVER THE CENTRAL APPALACHIANS INTO THE MID ATLANTIC---THE SLIGHT
RISK AREA WAS REMOVED OVER NORTHWEST VA/SOUTHEAST WV GIVEN
DIMINISHING CONVECTION.  THERE WERE SOME MINOR CHANGES TO THE
MARGINAL RISK AREA ACROSS THESE REGIONS TO ACCOUNT FOR CURRENT
RADAR TRENDS.

NO CHANGES MADE TO THE MARGINAL AND SLIGHT RISK AREAS OVER THE
LOWER MO VALLEY/MID MS VALLEY REGION.

ORAVEC


1900 UTC UPDATE

UPDATED THE MARGINAL RISK AREA OVER THE LOWER MO VALLEY INTO THE
MIDWEST...WHILE INTRODUCING A SLIGHT RISK AREA ACROSS FAR
SOUTHEAST NE-NORTHEAST KS INTO WESTERN AND CENTRAL MO...BASED ON
THE CURRENT MESOANALYSIS AND TRENDS ALONG WITH THE GROWING
CONSENSUS OF RECENT HIGH-RES CAM GUIDANCE WITH RESPECT TO A LIKELY
MCS/RESULTANT MCV OVERNIGHT ACROSS THE CENTRAL U.S... SPECIFICALLY
THE LOWER MO VALLEY. THE ACTIVITY EARLY ON WILL BE AIDED BY
STEEPENING MID-LEVEL LAPSE RATES (~7.5 C/KM) ALONG WITH ROBUST
DEEP-LAYER INSTABILITY OVER SOUTHEAST NE-NORTHWEST MO (3500-4000+
J/KG). GIVEN THE SOUTHWESTERLY LLJ INCREASING TO 40-50 KTS ALONG
WITH THE CONTINUED DIRECTIONAL SHEAR OVERNIGHT...EXPECT FAIRLY
PROGRESSIVE SOUTHWARD PROPAGATION PER THE MODEL FORECAST CORFIDI
VECTORS. THIS IDEA (PROGRESSIVE NATURE) WOULD FAVOR A LIMITED
AREAL FLASH FLOOD THREAT...HOWEVER DESPITE THE LIMITED POTENTIAL
FOR CELL TRAINING...GIVEN THE HIGHLY-FAVORABLE
THERMODYNAMICS...SOME OF THE HIGH-RES CAMS (NSSL-WRF AND PARALLEL
ARW IN PARTICULAR) DEPICT LOCALIZED AMOUNTS OF 3-5+ INCHES FALLING
WITHIN A 3 HOUR PERIOD (WHICH WOULD COME CLOSE TO IF NOT EXCEED
THE FFG). WPCQPF INCORPORATED THESE HIGH-RES RUNS IN TERMS OF THE
GENESIS AND TIMING OF THE MCS OVERNIGHT...GIVEN WHAT WOULD APPEAR
TO BE A BETTER HANDLE ON THE SOUTHWARD PROGRESSION CONSIDERING THE
THERMODYNAMIC AND KINEMATIC ENVIRONMENT. ELSEWHERE...WPC UTILIZED
A MULTI-MODEL BLEND WITH IN GENERATING THE QPF...PARTICULARLY
WEIGHTED TOWARD THE ENSEMBLE MEANS (INCLUDING HIGH-RES).


1200 UTC UPDATE

UPDATED THE DAY 1 ERO TO BROADEN THE MARGINAL RISK AREA A BIT
FARTHER TO THE WEST ACROSS WV...WHILE ALSO INCORPORATING A NARROW
SLIGHT RISK AREA ALONG THE VA-WV BORDER CORRESPONDING TO THE LOWER
FFG/HIGHER ANTECEDENT SOIL MOISTURE. WITHIN THE SLIGHT RISK
AREA...THE LATEST (06Z-BASED) SSEO 40KM NEIGHBORHOOD GUIDANCE
INDICATES 3 HOURLY QPF>FFG EXCEEDANCE PROBABILITIES OVER 50%
DURING THE AFTERNOON WHEN MIXED LAYER CAPES ARE EXPECTED TO
AVERAGE BETWEEN 1000-1500 J/KG...WHILE THE AREA REMAINS ON THE
WESTERN PERIPHERY OF THE MOISTURE PLUME/WARM CONVEYOR BELT FOR
MUCH OF THE DAY AHEAD OF THE SLOWLY ADVANCING UPPER SHORTWAVE.

HURLEY


PREVIOUS DISCUSSION BELOW...


...MID ATLC REGION...

ACRS THE EAST COAST...STABLE HIGH PRES WILL CONTINUE TO SHIFT OFF
THE EAST COAST ALLOWING DEEPER MSTR AND INCREASING INSTABILITIES
TO DVLP ACRS THE REGION ON FRI/FRI NIGHT.  POTNLY HEAVY
SHWRS/TSTMS ARE LIKELY ACRS PORTIONS OF THE MID ATLC REGION FRI
AFTN AND NIGHT AS WEAK NEARLY UNIDIRECTIONAL FLOW DVLPS IN ADVANCE
OF UPSTREAM BROAD UPPER TROF..POSSIBLY SUPPORTING SOME SLOW MOVING
BANDS OF CONVECTION THAT COULD LEAD TO ISOLD HEAVIER RAIN TOTALS
THERE. THERE IS MULTI HI RES MODEL SUPPORT FOR ISOLD RAINFALL
TOTALS IN EXCESS OF 3 INCHES IN A COUPLE HOURS PARTICULARLY ACRS
PORTIONS OF CNTL VA NWD INTO CNTL MD.  TIME LAGGED ENSEMBLE RUNS
OF THE HRRR SHOW PROBABILITIES OF 3 INCH OR GREATER RAINFALL
AMOUNTS IN 3 HOURS EXCEEDING 50 PCT WHICH WOULD SUPPORT AT LEAST A
MARGINAL RISK OF EXCESSIVE RAINS AT THIS TIME.

...MID MISSISSIPPI VALLEY...
MODELS SUGGEST AN INCREASING THREAT OF CONVECTION FRI AFTN/NIGHT
INITIALLY ALONG AND NORTH OF OF STATIONARY FRONT AND WEAK SFC LOW
DVLPG AHEAD OF JET STREAK PUSHING ACRS THE NORTHERN PLAINS.  WITH
MODELS SHOWING STGLY DIFFLUENT THICKNESSES..HIGH INSTABILITY..AND
MODEST SWLY WAA DIRECTED INTO THE STALLED FRONT...INGREDIENTS
APPEAR FAVORABLE FOR RAPID CELL GROWTH WITH POTNL FOR MULTIPLE
CELL CLUSTERS OR PERHAPS MCS DVLPMENT.  MODELS HOWEVER SHOW QUITE
A BIT OF VARIABILITY WITH QPF AMOUNTS AND PLACEMENT ACRS THIS
REGION LEADING TO RATHER LOW CONFIDENCE IN QPF DETAILS.   AT THIS
TIME IT WOULD APPEAR THE GREATER THREAT OF HEAVIER RAINS WOULD
TEND TO FOCUS FROM PARTS OF IOWA SWD INTO NRN MO AND PERHAPS ERN
KS WITH LATEST HIGH RES GUIDANCE INDICATING THE POTNL FOR ISOLD
RAINFALL AMOUNTS IN EXCESS OF 3 INCHES.  GIVEN THE
UNCERTAINTY..HAVE ONLY INDICATED A MARGINAL RISK FOR EXCESSIVE
RAINS...BUT WILL CONTINUE TO MONITOR WITH PERHAPS THE 12Z GUIDANCE
PROVIDING BETTER CLARITY.

SULLIVAN


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