Flash Flood Warning 12, NWS Topeka, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
250 AM CDT SUN OCT 4 1998

...MAIN FORECAST PROBLEM IS SEVERE WEATHER THREAT TODAY...

06Z SURFACE MAP PUT DEVELOPING SURFACE LOW OVER EAST CENTRAL
COLORADO WITH 1 TO 2 MB PRESSURE FALLS OVER WESTERN KANSAS.  LAPS
DATA SHOWS ELEVATED INSTABILITY DEVELOPING OVER SOUTH CENTRAL KANSAS
WITH SHOWALTER INDICES AROUND -6.  PROFILERS HAVE A 45 KNOT
SOUTHERLY LOW LEVEL JET OVER WESTERN AND CENTRAL KANSAS.  EXPECT
CONVECTION TO BREAK OUT OVER CENTRAL KANSAS WITHIN THE NEXT 1 TO 2
HOURS AS FIRST SHORT WAVE EJECTS NORTHEAST INTO THE PLAINS.  COULD
SEE SOME ELEVATED SEVERE STORMS THIS MORNING.

FOR LATER PERIODS OF THE FORECAST...GENERALLY FOLLOWED THE ETA
MODEL.  THE NGM SURFACE LOW PLACEMENT IS TOO FAR NORTH INITIAL AND
AVN SEEMS TO PUT TOO MUCH ENERGY INTO THE SOUTHERN STREAM.

ETA SUGGESTS THE WARM FRONT SHOULD PUSH NORTH TO THE NEBRASKA BORDER
BY THIS AFTERNOON AS A THE SURFACE LOW DEEPENS OVER NORTHWEST KANSAS
IN RESPONSE TO A SECOND STRONGER WAVE EJECTING OUT OF THE MEAN TROUGH.
THIS WOULD PUT MOST OF NORTH CENTRAL AND NORTHEAST KANSAS INTO THE
WARM SECTOR BY LATE AFTERNOON.  AFTER MORNING CONVECTION CLEARS OUT
...ATMOSPHERE SHOULD BEGIN TO DESTABILIZE IN THE WARM SECTOR.
FORECAST SOUNDINGS FROM THE ETA MODEL SHOW IMPRESSIVE INSTABILITY IN
THE WARM SECTOR WITH CAPES AROUND 2000 J/KG.  VERY STRONG WIND
FIELDS ARE ALSO FORECAST WITH HELICITY VALUES OF 350 TO 400
J/KG...AND RATHER STRONG STORM RELATIVE MID LEVEL FLOW.  700-300 MB
DIVERGENCE OF Q-VECTORS SUGGEST THE STRONGEST UPWARD MOTION SHOULD
SWEEP ACROSS NORTH CENTRAL AND NORTHEAST KANSAS LATE THIS AFTERNOON.
THIS WOULD POINT TO THE HIGH POTENTIAL FOR SUPERCELLS ALONG THE DRY
LINE OVER CENTRAL KANSAS THIS AFTERNOON.  WILL MENTION SEVERE STORMS
IN THE ZONES FOR TODAY AND TONIGHT.

ETA HAS DRY SLOT PUNCHING RAPIDLY NORTHEAST ACROSS THE AREA
TONIGHT.  THIS SHOULD END PRECIPITATION OVER NORTH CENTRAL KANSAS
THIS EVENING...AND OVER EAST AROUND MIDNIGHT.

DRY SLOT AND STRONG SUBSIDENCE AROUND DEEP SURFACE LOW OVER EASTERN
SOUTH DAKOTA SHOULD PRECLUDE ANY CHANCES FOR PRECIPITATION OVER
NORTH CENTRAL AND NORTHEAST ON MONDAY.  SURFACE GRADIENT SUGGESTS
NORTH CENTRAL KANSAS COULD BE QUITE BREEZY...WITH LIGHTER WINDS IN
THE NORTHEAST.

GENERALLY TRENDED TOWARD COOLER AVN/FAN GUIDANCE OVER WARMER NGM/FWC.

.TOP...NONE.

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