Quantitative Precipitation Forecast
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FOUS30 KWBC 180828
QPFERD

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

...VALID 12Z 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
20 NNE IRK 15 WNW STJ 10 SSW TQE 20 NE YKN 10 S OTG 15 WSW ALO
20 SE MUT 20 NNE IRK.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NE BWG 15 W EVV 15 N BMG 25 WNW WMO 15 S LCK 25 S JKL
15 NE BWG.


...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".

CHENARD

$$





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