Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
000
FOUS30 KWBC 170830
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
430 AM EDT SUN JUL 17 2016

...VALID 12Z SUN JUL 17 2016 - 12Z MON JUL 18 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNW MIW 20 NNE DBQ 15 ESE UGN SBN 15 S AID 20 E HNB HSB ALN
35 W UIN 10 N LWD 20 N OMA 25 NNW MIW.


...MID AND UPPER MS VALLEY/GREAT LAKES/OHIO VALLEY...

AS OF 08Z A WELL ORGANIZED CONVECTIVE SYSTEM CONTINUES TO TRACK
SOUTHEASTWARD ACROSS IA. OVERALL A SLIGHTLY SOUTH SHIFTED PARALLEL
HRRR AND THE 0Z HIGH RES ARW APPEAR TO BE HANDLING THE EVOLUTION
OF THIS FEATURE THE BEST. THESE SOLUTIONS SUGGEST A GENERAL
WEAKENING TREND OF CONVECTION AFTER 12Z. GIVEN THE WEAKENING
MOISTURE TRANSPORT INTO THE SYSTEM AND A DECREASING SYNOPTIC
SUPPORT AS THE FORCING LIFTS NORTH...THIS WEAKENING MAKES SENSE.
THUS IN GENERAL EXPECT THE FLASH FLOOD THREAT FROM THIS COMPLEX TO
RAPIDLY DECREASE BY 12Z AS THE CONVECTION WEAKENS AND BECOMES MORE
PROGRESSIVE.

STILL SOME UNCERTAINTY WITH REGARDS TO CONVECTIVE REDEVELOPMENT
THIS AFTERNOON. GROWING CONSENSUS AMONG THE HIGH RES GUIDANCE FOR
REDEVELOPMENT ACROSS NORTHERN IL THIS AFTERNOON ON THE REMNANT
BOUNDARY LEFTOVER FROM THE CONVECTION THIS MORNING. THE FORWARD
SPEED OF THE FRONT SUGGESTS THIS CONVECTION SHOULD INITIALLY BE
FAIRLY PROGRESSIVE AS IT MOVES SOUTHEASTWARD ACROSS IL/IN.
ALTHOUGH HIGH RAINFALL RATES COULD STILL POSE AT LEAST AN ISOLATED
FLASH FLOOD THREAT.

AS WE HEAD INTO TONIGHT SHOULD SEE AN INCREASE IN LOW LEVEL
CONVERGENCE AS THE FRONT TIGHTENS UP AND SLOWS DOWN ACROSS
IN/IL/IA...BECOMING MORE ORIENTED WEST TO EAST. THIS COMBINED WITH
INCREASING UPPER LEVEL DIVERGENCE IN THE RIGHT ENTRANCE REGION OF
A DEVELOPING JET...SHOULD PROVIDE A FAVORABLE SYNOPTIC ENVIRONMENT
FOR CONVECTION. AS LOW LEVEL MOISTURE TRANSPORT INCREASES INTO THE
BOUNDARY...SEEMS PROBABLE THAT WE SEE ELEVATED CONVECTION BREAK
OUT FROM EASTERN NE INTO IA AND IL/IN. STORM MOTIONS ARE EXPECTED
TO EXHIBIT A LARGE COMPONENT PARALLEL TO THE
BOUNDARY...INTRODUCING THE POTENTIAL OF TRAINING AS NEW STORMS
FORM AND PROPAGATE EAST SOUTHEASTWARD. COMBINE THIS WITH
PRECIPITABLE WATER VALUES POTENTIALLY APPROACHING 2"...AND A FLASH
FLOOD THREAT COULD DEVELOP. SOME DIFFERENCES IN THE AXIS OF
HEAVIEST PRECIPITATION...DUE IN PART TO OUTFLOW FROM CONVECTION
TODAY AND EXACTLY WHERE CONVECTION INITIATES THIS AFTERNOON. IN
GENERAL ALL THE HIGH RES GUIDANCE ARE FURTHER SOUTH THAN THE
GLOBAL GUIDANCE...WITH THE 0Z ARW BEING THE FURTHEST SOUTH. THE 0Z
ESRL HRRR (WHICH RUNS OUT 36 HOURS) IS ACTUALLY THE FURTHEST NORTH
WITH THE AXIS. FOR NOW OPTED TO CUT THE DIFFERENCE...AND GO WITH A
SOLUTION GENERALLY IN BETWEEN THE ARW AND ESRL HRRR...WHICH ENDS
UP BEING PRETTY CLOSE TO THE NMMB. THIS ENDS UP SOUTH OF THE
GLOBAL GUIDANCE...BUT GIVEN THE EXPECTED EVOLUTION OF CONVECTION
THIS MORNING...GOING SOUTH OF THE GLOBAL GUIDANCE SEEMS TO MAKE
SENSE.

THE HIGH RES CONSENSUS IS FOR LESS QPF FURTHER NORTH ACROSS MI.
STILL EXPECTING SCATTERED CONVECTION WITH THE COLD FRONTAL
PASSAGE...BUT THE FRONT SHOULD BE PRETTY PROGRESSIVE...AND THE
CONVECTION TO THE SOUTH VERY WELL COULD INTERRUPT MOISTURE INFLOW
FURTHER NORTH. THUS WPC QPF UNDERCUTS MOST OF THE GLOBAL
GUIDANCE...AND RESEMBLES SOMETHING CLOSER TO A HIGH RES CONSENSUS.

THUS SHIFTED THE DAY 1 EXCESSIVE RAINFALL AREA A BIT SOUTH ACROSS
IA/IL/IN TO ACCOUNT FOR THE AFTERNOON CONVECTION ACROSS
IL/IN...AND THE POTENTIAL FOR TRAINING STORMS OVERNIGHT FROM IA
SOUTHEAST INTO IL/IN. ALSO CUT BACK THE AREA OVER MI FOR THE
REASONS MENTIONED ABOVE.


CHENARD
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.