Quantitative Precipitation Forecast
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FOUS30 KWBC 181446
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1046 AM EDT MON JUL 18 2016

...VALID 15Z MON JUL 18 2016 - 12Z TUE JUL 19 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SW C75 10 E IND 20 W UNI 10 N 2G4 25 WNW OKV 25 NW HSP
25 NE 1A6 10 W BWG 10 ENE SET 15 SSE CDJ 20 ESE BIE AUH
15 SE FET 10 SE AWG 10 SW C75.



15Z UPDATE...

WPC WENT AHEAD AND COMBINED THE TWO SLIGHT RISK AREAS FOR
EXCESSIVE RAINFALL INTO ONE TO INCLUDE LATEST AVAILABLE MODEL
GUIDANCE AND CURRENT RADAR TRENDS. ALSO... WPC ADDED A SEE TEXT
ACROSS PARTS OF THE INTERIOR NORTHEAST WITH ANTICIPATED CONVECTION
THIS AFT/EVENING AND LOCALIZED LOW FFG VALUES.

A FRONTAL ZONE APPROACHING THE OH VALLEY WILL SINK SOUTH AND EAST
THROUGH THE REGION AND STALL BACK UPSTREAM NEAR THE NRN/NERN
PERIPHERY OF THE ANOMALOUS UPPER RIDGE OVER THE SRN PLAINS. AHEAD
OF THIS ZONE IS A PLUME OF DEEP POOLING LOW LEVEL MOISTURE AOA 2
INCHES... 1.98 NEAR ILN AND 1.96 NEAR SPI AND 1.87 NEAR OMA. THIS
FRONT ALONG WILL INTERACT WITH THIS MOISTURE CONTENT AND
INCREASING INSTABILITY FOR MULTIPLE ZONES OF CONVECTION HEAVY
RAINS. AS A RESULT... WPC WENT AHEAD AND COMBINED THE TWO SLIGHT
RISKS AND EXPANDED A BIT MORE WITH ONE AREA EXTENDING FROM WV TO
SERN NE. THE ONE AREA THE GUIDANCE INCLUDING GLOBAL AND HI-RES HAS
A DECENT HANDLING ON IS A SMALL SCALE VORT TRACKING THROUGH
CENTRAL IL SLIDING SOUTH AND EAST OVER TIME WHICH COULD PRODUCE
LOCALLY 1-2 INCH AREAL AVG AMOUNTS AND PRODUCE LOCALIZED ISSUES.
SPEAKING OF LOCALIZED ISSUES... THE POSSIBLE SLOW MOVING
CONVECTION INTO WV AND ERN KY COULD SPELL A FEW ISSUES WHEN ADDING
IN HILLS/TERRAIN... WHILE UPSTREAM OVER SERN NE INTO SWRN IA
RE-DEVELOPING NARROW LINE OF CONVECTION IS NOT HANDLED WELL BY THE
GUIDANCE AND WITH DECENT INFLOW INTO THIS REGION WPC IS WORRIED
THIS COULD PERSIST AND  PRODUCE LOCALIZED ISSUES.

A SEE TEXT WAS INTRODUCED ACROSS THE ERN PORTION OF NY STATE AND
PA INTO NEW ENGLAND FOR THIS AFTN AND EVENING FOR POCKETS OF
CONVECTIVE CLUSTERS PRODUCING LOCALIZED RUNOFF ISSUES ACROSS THE
REGION. RELATIVELY LOW 1 HR FFG VALUES ACROSS NRN NJ...PARTS OF NY
FROM BGM TO ALB AND ACROSS MUCH OF VT AND CURRENT CONVECTIVE
CLUSTER OF HEAVY RAIN JUST UPSTREAM ANTICIPATED TO ARRIVE
MIDDAY/EARLY AFTN COULD PRODUCE SOME LOCALIZED 1-2 INCH AMOUNTS
COULD RESULT IN LOCALIZED AND URBAN ISSUES.

PREVIOUS DISCUSSION BELOW...


...INDIANA/OHIO/KENTUCKY...

THE AREA OF CONVECTION OVER OVER IL/IN THIS MORNING FORMED IN A
REGION OF ENHANCED LOW LEVEL CONVERGENCE NEAR THE SURFACE
FRONT...AND INCREASED UPPER LEVEL DIVERGENCE IN THE RIGHT ENTRANCE
REGION OF AN UPPER JET. THE CONSENSUS AMONG THE HIGH RES GUIDANCE
IS FOR THIS CONVECTION TO CONTINUE TO ORGANIZE EARLY THIS
MORNING...EVENTUALLY TURING MORE SOUTHEASTWARD AS SUGGESTED BY
CORFIDI VECTORS ACROSS THE REGION. THIS SHOULD BRING THE HIGHER
AMOUNTS AFTER 12Z SOUTHEAST TOWARDS THE IN/OH/KY BORDERS. OVERALL
FAVORED A SOLUTION CLOSE TO THE PARALLEL HRRR AND THE 0Z NSSL
WRF...BOTH OF WHICH APPEARED TO HAVE A DECENT HANDLE ON CURRENT
ACTIVITY AND SHOWED PLAUSIBLE EVOLUTIONS INTO THE MORNING HOURS.
IN GENERAL EXPECT THE CONVECTION TO BE MORE PROGRESSIVE BY
12Z...WHICH SHOULD GENERALLY LIMIT THE FLOOD THREAT. EXPECT A
GRADUAL WEAKENING OF CONVECTION AS IT CONTINUES TO SHIFT SOUTH
THROUGH KY/WV/SOUTHWEST VA AFTER 12Z AS IT OUTRUNS THE BETTER
SUPPORT. THERE IS SOME POTENTIAL FOR REDEVELOPMENT THIS AFTERNOON
ACROSS PORTIONS OF SOUTHERN IN/OH AND NORTHERN KY. THE APPROACH OF
A LOW LEVEL BOUNDARY ALONG WITH A SHORTWAVE RIDING ON THE NORTHERN
PERIPHERY OF THE SOUTHERN US RIDGE COULD BE ENOUGH TO GET THIS
ACTIVITY GOING. ALTHOUGH DEFINITELY UNCERTAINTY ON WHETHER THE
ATMOSPHERE WILL BE ABLE TO RECOVER ENOUGH AFTER THE MORNING
ACTIVITY TO SUPPORT ADDITIONAL CONVECTION. ONLY THE 0Z NSSL WRF
REALLY INDICATES THIS ADDITIONAL DEVELOPMENT...SO CONFIDENCE IS
LOW. HOWEVER THE COMBINATION OF THE CONVECTION THIS MORNING MOVING
THROUGH...AND THE POTENTIAL OF AFTERNOON REDEVELOPMENT WARRANTS A
SLIGHT RISK OF EXCESSIVE RAINFALL. AGAIN THINK THE THREAT THIS
MORNING IS PROBABLY MARGINAL GIVEN THE EXPECTED FORWARD MOVEMENT
OF CONVECTION...WITH THE RISK POTENTIALLY INCREASING THIS
AFTERNOON IF STORMS ARE ABLE TO REDEVELOP OVER AREAS THAT RECEIVED
RAIN THIS MORNING. STORM MOTIONS WOULD BE SLOW WITH ANY AFTERNOON
ACTIVITY...WITH PRECIPITABLE WATER ABOVE 1.75" SUPPORTING A HEAVY
RAINFALL THREAT SHOULD STORMS DEVELOP.

...IOWA...

AN AREA OF CONVECTION THIS MORNING ACROSS SOUTHWEST IA AND
VICINITY HAS FORMED ON THE NOSE OF INCREASING LOW LEVEL JET
POINTED INTO THE REGION...MAXIMIZING MOISTURE FLUX CONVERGENCE
INTO A STALLED OUT BOUNDARY. ALSO AN UPPER JET PASSING TO THE
NORTH PUTS THE REGION IN THE FAVORED RIGHT ENTRANCE REGION. THIS
COMBINATION OF LOW LEVEL CONVERGENCE AND UPPER LEVEL DIVERGENCE
HAS ALLOWED FOR BLOSSOMING CONVECTION OVER THE AREA...WITH STORM
MOTIONS FAVORING TRAINING. IN GENERAL EXPECT THIS CONVECTION TO BE
IN A WEAKENING STATE BY 12Z...WITH THE FLASH FLOOD THREAT RAPIDLY
DECREASING.

ATTENTION THEN TURNS TO TONIGHT...WHEN A SIMILAR SETUP APPEARS TO
UNFOLD. MOISTURE TRANSPORT WILL INCREASE INTO THE STALLED OUT
BOUNDARY...WITH ANOTHER UPPER JET PLACING PORTIONS OF SD/NE/IA/MN
IN THE FAVORED RIGHT ENTRANCE REGION. THUS WOULD EXPECT A
REGENERATION OF ELEVATED CONVECTION BY OR SHORTLY AFTER 06Z. ONCE
AGAIN STORM MOTIONS SHOULD EXHIBIT A LARGE COMPONENT PARALLEL TO
THE BOUNDARY OFF TO THE SOUTHEAST...THUS TRAINING APPEARS LIKELY.
WITH PRECIPITABLE WATER VALUES REMAINING ABOVE 1.75"...ANOTHER
FLASH FLOOD THREAT MAY DEVELOP. THE FRONT IS FORECAST TO LIFT
NORTH THROUGH THE DAY TODAY...BUT UNCERTAINTY ON HOW FAR NORTH IT
GETS. NOTICED VERY GOOD AGREEMENT BETWEEN THE 0Z NSSL WRF AND THE
12Z ECMWF WITH REGARDS TO THE AXIS OF CONVECTION...AND GIVEN ONE
OF THESE IS TYPICALLY THE BEST GLOBAL GUIDANCE AND THE OTHER THE
BEST HIGH RES GUIDANCE...GENERALLY FOLLOWED CLOSE TO A CONSENSUS
OF THOSE SOLUTIONS. THIS KEEPS THE AXIS SOUTH OF THE LATEST GFS.
CURRENTLY EXPECT THE FOCUS TO BE FROM NEAR THE NE/SD BORDER INTO
WESTERN IA. DID NOTICE THAT THE LOW LEVEL MOISTURE TRANSPORT IS
FORECAST TO BE A BIT LESS TONIGHT INTO THE BOUNDARY COMPARED TO
THIS MORNING...AND THE CONVERGENCE AXIS MAY BE A BIT MORE
PROGRESSIVE THAN THIS MORNING. THESE ARE BOTH SIGNS THAT TONIGHTS
CONVECTION MAY NOT BE QUITE AS INTENSE AS WHAT WE ARE SEEING THIS
MORNING ACROSS SOUTHWEST IA. ALTHOUGH STILL THINK THE SETUP
WARRANTS A SLIGHT RISK OF EXCESSIVE RAINFALL GIVEN THE TRAINING
POTENTIAL AND PRECIPITABLE WATER VALUES APPROACHING 2".

MUSHER/CHENARD

$$





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