Quantitative Precipitation Forecast
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FOUS30 KWBC 162309
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
708 PM EDT TUE MAY 16 2017

...VALID 2308Z TUE MAY 16 2017 - 12Z WED MAY 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
SWO 20 SE MWL 30 WSW 6R9 15 SSW E29 60 WNW E29 20 SSW SNK CDS
15 SW HHF 20 S LBL 15 SW GCK 55 SW HLC 45 ESE GLD 20 SSE ITR
35 WSW ITR 30 NW AKO 30 ENE SNY LBF 35 SSW YKN 20 N JMR
25 SE GNA 35 S P59 35 WNW MNM 15 SSW CMY IIB 35 ESE LWD 35 E UKL
SWO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NE JYG ROS 15 SW ASX 20 WNW LNL 30 NNE AIG 30 W MFI
25 SE MCW 10 NW LWD 15 NNW TOP 15 ENE HUT 40 SSE DDC 25 ESE LBL
15 E LBL 35 SSE GCK 30 NNE DDC 15 WNW HYS 10 ESE HLC 15 WNW HLC
50 E GLD 25 ENE GLD 30 SW MCK 25 E MCK 10 SE HSI 25 E SUX
15 WNW FRM 15 NE JYG.


...SOUTHWEST AND CENTRAL KANSAS...

PREDOMINANT SEVERE WEATHER MODE MAY TRANSITION TO A FLASH FLOOD
MODE AT LEAST ON SMALL SCALES...AND THIS TRANSITION MAY HAVE
ALREADY OCCURRED ALONG AN AXIS FROM BEAVER COUNTY OKLAHOMA INTO
SOUTHWEST KANSAS AS OF 2230Z. SUPERCELL STORMS THERE HAD ALIGNED
WITH THE DEEP LAYER FLOW...AND WERE SHARING A COMMON ANVIL...THUS
BOOSTING RAINFALL EFFICIENCY AND THE OPPORTUNITY FOR MULTIPLE
SUPERCELL UPDRAFTS TO TRACK CLOSE TO OR OVER A GIVEN LOCATION.
RECENT HRRR RUNS HAD DONE A DECENT JOB OF SIGNALING THIS
POTENTIAL...INDICATING SOME TRAINING AND A NARROW SWATH OF 2 TO 3
INCHES OF RAIN. PLEASE REFER TO MESOSCALE PRECIPITATION DISCUSSION
NUMBER 220 FOR OTHER DETAILS. IN THE EXCESSIVE RAINFALL OUTLOOK WE
HAVE EXPANDED THE MARGINAL AND SLIGHT RISK AREAS TO COVER THIS
DEVELOPMENT.


...NORTHEAST KANSAS THROUGH ADJACENT NE/MO INTO IOWA...

ON THE LARGER SCALE THERE IS A STRONG MODEL SIGNAL FOR UPSCALE
GROWTH TO OCCUR...WITH AN MCS TRACKING NORTHEASTWARD OUT OF
SOUTHERN AND CENTRAL KANSAS LATE IN THE EVENING. THIS SHOULD LAY
DOWN AN OUTFLOW BOUNDARY THAT WOULD THEN BECOME THE FOCUS FOR A
RENEWED FLASH FLOOD THREAT OVERNIGHT SOMEWHERE IN CENTRAL AND
EASTERN KANSAS...POSSIBLY INTO ADJACENT NORTHWEST MISSOURI AND FAR
SOUTHEAST NEBRASKA. MODEL QPF SIGNAL IS NOT ESPECIALLY
HIGH...ALTHOUGH MOST HI-RES MODELS DO PREDICT SWATHS OF 2 TO 4
INCHES. GIVEN THE BROAD LOW LEVEL JET THAT IS ANTICIPATED AHEAD OF
THE UPPER SHORTWAVE EJECTING FROM THE ROCKIES...IT WILL BE
POSSIBLE FOR SOME HIGHER-END RAINFALL TOTALS...ABOVE 4 INCHES...TO
OCCUR...PARTICULARLY IF A LARGER SCALE COLD POOL BECOMES
ESTABLISHED MORE QUICKLY THAN THE MODELS ARE PROJECTING. THE MOST
LIKELY REGION FOR A MORE EXTREME EVENT TO OCCUR WOULD BE FROM
CENTRAL/EASTERN KS INTO ADJACENT SOUTHEAST NE AND NORTHWEST
MO...BUT GIVEN THE LACK OF MODEL SUPPORT WE WILL MAINTAIN THE
SLIGHT RISK CATEGORY FOR NOW.

WITH NORTHWARD EXTENT INTO THE OMAHA AREA AND OVER INTO IOWA...THE
MAIN CONCERN MAY BE THE VERY HEAVY RAIN RATES THAT WILL ACCOMPANY
THE MCS EXPECTED TO DEVELOP OUT OF KANSAS...WITH STEERING FLOW IN
THE MID LEVELS TAKING THE SYSTEM RAPIDLY NORTHEASTWARD. ANY LONGER
DURATION...PERSISTENT HEAVY RAINFALL...SHOULD OCCUR ALONG THE
SOUTHERN FLANK OF THE OUTFLOW...LIKELY FARTHER TO THE SOUTH...BUT
SYNOPTIC FORCING WILL INCREASE THROUGHOUT THE NIGHT...WHICH MAY
BOOST EVENT TOTAL RAINFALL THROUGH REDEVELOPMENT OF ELEVATED
CONVECTION.


...MINNESOTA AND WISCONSIN TO THE U.P. OF MICHIGAN...

SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS WESTERN WISCONSIN AND
SOUTHEAST MINNESOTA AT 23Z SHOULD TRACK EAST TO NORTHEAST AS
CLUSTERS OF STORMS THROUGH LATE EVENING. VISIBLE SATELLITE SHOWED
SOME STABLE WAVE CLOUDS INTO THE LATE AFTERNOON OVER
WISCONSIN...AND THE DEEP LAYER ASCENT PER THE RAP IS NOT
ESPECIALLY STRONG. WATER VAPOR SATELLITE IMAGERY ALSO INDICATED
SOME OVERALL DRYING OF THE COLUMN WITH THE ARRIVAL OF THE WEAK TO
MODERATE FORCING THAT WAS OCCURRING. ALL OF THESE FACTORS MAY
HINDER THE PRODUCTIVITY OF THE EVENING THUNDERSTORMS IN TERMS OF
RAINFALL...ALTHOUGH BRIEF EPISODES OF TRAINING COULD LEAD TO RAPID
ACCUMULATION OF 1 TO 2 INCHES OF RAIN IN THE MORE ROBUST STORMS.
PERHAPS OF GREATER CONCERN IS THE STRONG MODEL CONSENSUS FOR
RENEWED FORCING LATER TONIGHT. AFTER 03Z OUTFLOWS FROM NE/IA MAY
WORK THEIR WAY UP ALONG THE SURFACE FRONTAL BOUNDARY...IGNITING
NEW DEEP CONVECTION OVER MN/WI WITHIN THE POOL OF RESIDUAL CAPE
MEASURING STILL ABOVE 1000 J/KG IN THE OVERNIGHT HOURS.
THEREAFTER...SYNOPTIC DEEP LAYER LIFT WILL INCREASE WITHIN THE
ENTRANCE REGION OF STRENGTHENING JET STREAK...WHICH MAY RESULT IN
ADDITIONAL STRATIFORM RAINFALL AND EMBEDDED CONVECTION THROUGH
MORNING. ON AVERAGE ANOTHER 0.75 TO 1.00 INCHES IS PREDICTED
OVERNIGHT IN SE MN / WRN WI...CUTTING ACROSS THE SAME AREAS THAT
RECEIVED UP TO 4 INCHES OF RAIN ON MONDAY. LOCALLY HIGHER
AMOUNTS...PERHAPS GREATER THAN 2 INCHES...ARE POSSIBLE
TONIGHT...AND WOULD CERTAINLY POSE A FLASH FLOOD RISK...ESPECIALLY
FOR THE AREAS COMPROMISED BY RECENT SATURATION.


...NORTHWEST KANSAS AND ADJACENT CO/NE...

MARGINAL RISK WAS EXPANDED TO COVER MORE OF THE AXIS THAT SAW 1 TO
2 INCHES OF RAIN MONDAY NIGHT IN THE TRI-STATE AREA. SLIGHT RISK
WAS ALSO EXPANDED AS FAR WEST AS THOMAS AND RAWLINS COUNTIES IN
KANSAS AND SOUTHEASTERN HITCHCOCK COUNTY IN NEBRASKA. GENERALLY A
STEADIER RAIN WITH EMBEDDED CONVECTION WILL DOMINATE THIS EVENT
LATER IN THE NIGHT...BUT THERE IS WINDOW OF TIME THIS
EVENING...DURING THE EARLY DEVELOPMENT OF A CLOSED LOW
ALOFT...WHEN MOISTURE AND INSTABILITY WRAPPING NORTH AND
WESTWARD...AND OVERRUNNING A SURFACE FRONTAL BOUNDARY...WILL
CONTRIBUTE TO SOME HEAVIER RAIN RATES. DEEP LAYER WIND FIELDS ARE
STRONG ENOUGH THAT PREDICTED CELL MOTIONS REMAIN GREATER THAN 20
KNOTS BY MOST MEASURES THROUGHOUT THE NIGHT...BUT RADAR TRENDS AT
23Z SUGGESTED SLOWER MOTION AS CELLS ATTEMPT TO REMAIN ROOTED NEAR
THE STALLED SURFACE BOUNDARY IN NORTHWEST KANSAS. SOME LOCAL
2-INCH IN THREE HOUR RAINFALL MAY OCCUR...WHICH WOULD EXCEED THE
1.5 INCH IN 3-HOUR FLASH FLOOD GUIDANCE HERE.

BURKE
$$





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