MESOSCALE PRECIPITATION DISCUSSION 0822
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
738 PM EDT SUN SEP 24 2017

AREAS AFFECTED...WRN KS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 242337Z - 250535Z

SUMMARY...TRAINING CONVECTION OVER PORTIONS OF WRN KS MAY LEAD TO
FLASH FLOODING BEGINNING NEAR 03Z. RAINFALL RATES OF 1-2 IN/HR
WITH LOCALIZED TOTALS OVER 4 INCHES ARE EXPECTED THROUGH 06Z.

DISCUSSION...SURFACE OBSERVATIONS AT 23Z PLACED A SLOW MOVING COLD
FRONT INTO N-CNTRL KS...WITH THE BOUNDARY EXTENDING SWWD INTO SERN
CO AS A STATIONARY FRONT. BASE REFLECTIVITY DATA FROM KDDC AND
KGLD SHOWED SCATTERED SHOWERS AND THUNDERSTORMS ALONG AND NORTH OF
THE FRONT OVER WRN KS AT 2315Z WITH INDIVIDUAL CELLS FOLLOWING THE
850-300 MB MEAN WIND TOWARD THE NNE AT ABOUT 20-30 KT. RAP
ANALYSIS SOUNDINGS SUGGEST THIS ACTIVITY IS ROOTED BETWEEN 850-700
MB AND KDDC VAD WIND DATA SUPPORTED WINDS OF 20-25 KT IN THE
850-700 MB LAYER OVER THE PAST 1-2 HOURS OF SIMILAR DIRECTION TO
THE MEAN CELL MOVEMENT. A LACK OF BETTER ORGANIZATION HAS KEPT THE
MAJORITY OF RADAR DERIVED RAINFALL RATES BELOW 1 IN/HR SO FAR.

WHILE WATER VAPOR IMAGERY SHOWED A FAIR AMOUNT OF DRY AIR ALOFT
OVER THE WRN HALF OF KS...LOW LEVEL MOISTURE APPEARS SUFFICIENTLY
HIGH TO SUPPORT LOCALLY HEAVY RAIN IF CELLS ARE ABLE TO TRAIN
GIVEN PRECIPITABLE WATER VALUES RANGING BETWEEN 1.3 AND 1.6 INCHES
PER RECENT GPS DATA.

THE 20Z AND 21Z HRRR RUNS WERE THE FIRST TO PICK UP ON THE FLASH
FLOOD POTENTIAL OVER WRN KS WITH 3-6+ INCH TOTALS THROUGH 05Z
BETWEEN GCK AND HLC...CONTINGENT UPON CONVECTION DEVELOPING OVER
THE SRN CO/KS BORDER AND MOVING INTO WRN KS AROUND 00Z.

WHILE CONVECTION ALONG THE SRN CO/KS BORDER HAS YET TO MATERIALIZE
THE WAY FORECAST BY THE 20Z/21Z HRRR...LARGE SCALE UPPER LEVEL
FLOW SHOULD BECOME MORE DIFFLUENT THROUGH 06Z OVER THE WRN HALF OF
KS WHICH SHOULD HELP AID IN UPWARD MOTION AND AN EXPANSION OF CELL
COVERAGE. IN ADDITION...1000-1500 J/KG CAPE PRESENT OVER THE OK/TX
PANHANDLES VIA RECENT SPC MESOANALYSES SHOULD PROVIDE THE FUEL FOR
MORE ROBUST CONVECTION WITH NEARLY UNIDIRECTIONAL FLOW SUPPORTING
TRAINING...SOME OF WHICH MAY OVERLAP WITH 1-2 INCHES OF RAINFALL
WHICH FELL OVER THE PAST 24 HOURS. SIX HOUR RAINFALL TOTALS IN
EXCESS OF 4 INCHES ARE EXPECTED IN ONE OR TWO AREAS WHICH MAY
CAUSE FLASH FLOODING.

OTTO

ATTN...WFO...DDC...GID...GLD...ICT...

ATTN...RFC...ABRFC...MBRFC...

LAT...LON   39829903 38839885 37960038 37640148 38060188
            39160126 39810045