Severe Thunderstorm Warning 8, NWS Des Moines, IA

IAZ057-070>071-081>086-092>097-030300-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
335 PM CDT FRI MAY 2 1997

HAZARD--ISOLATED THUNDERSTORMS PRODUCING SMALL HAIL AND BRIEF HEAVY
RAINS...ALONG WITH THE POSSIBILITY OF COLD AIR FUNNELS.

AREA OF CONCERN--THE SOUTHERN QUARTER OF IOWA...ALONG AND SOUTH OF A
AUDUBON TO OTTUMWA LINE.

TIMING DETAILS--THUNDERSTORMS ARE POSSIBLE IN THE OUTLOOK AREA BETWEEN
4 AND 8 PM.

METEOROLOGICAL COMMENTS...AN AREA OF LOW PRESSURE ALOFT IS FORECAST TO
SLOWLY PUSH ACROSS THE STATE THIS EVENING AND TONIGHT. ASSOCIATED WITH
THIS UPPER LEVEL STORM SYSTEM ARE SOME FAIRLY COLD TEMPERATURES FROM
10,000 TO 20,000 FEET IN THE ATMOSPHERE. THE COMBINATION OF THE COLD
TEMPERATURES ALOFT AND SOME LOW LEVEL WARMING THAT OCCURRED OVER PARTS
OF SOUTHWEST AND EXTREME SOUTHERN IOWA THIS AFTERNOON WILL ENHANCE THE
THREAT FOR ISOLATED THUNDERSTORMS...ALONG WITH THE POSSIBILITY OF ONE
OR TWO OF THESE STORMS PRODUCING A COLD AIR FUNNEL. IN ADDITION...WITH
THE TEMPERATURES COOLING OFF IN THE UPPER ATMOSPHERE LATE THIS
AFTERNOON...FREEZING LEVELS AND WET BULB ZERO HEIGHTS WILL BE LOWERING
WHICH WILL INCREASE THE LIKELIHOOD OF HAIL WITH THE THUNDERSTORMS.

PRECAUTIONS...PEOPLE PLANNING OUTDOOR ACTIVITIES FOR LATE THIS
AFTERNOON INTO THIS EVENING SHOULD BE PREPARED FOR SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS TO DISRUPT THEIR EVENTS FOR A BRIEF PERIOD.
ALTHOUGH THE THREAT IS THERE FOR A FEW COLD AIR FUNNELS WITH THE
SHOWERS AND THUNDERSTORMS...STUDIES OF COLD AIR FUNNELS SHOW THAT THEY
RARELY TOUCH THE GROUND. THEY ARE USUALLY QUITE SMALL AND ARE NOT AS
VIOLENT AS THOSE ASSOCIATED WITH SEVERE THUNDERSTORMS. COLD AIR
FUNNELS NORMALLY PROTRUDE A FEW HUNDRED FEET DOWNWARD FROM THE PARENT
CLOUD...ROTATE OR SPIN LIKE A TOP...AND LAST FOR A FEW MINUTES BEFORE
DISSIPATING.

AT THIS TIME IT APPEARS THAT SPOTTER ACTIVATION WILL NOT BE REQUIRED
LATE THIS AFTERNOON OR EVENING.

SMITH

IAZ057-070>071-081>086-092>097-030300-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
335 PM CDT FRI MAY 2 1997

HAZARD--ISOLATED THUNDERSTORMS PRODUCING SMALL HAIL AND BRIEF HEAVY
RAINS...ALONG WITH THE POSSIBILITY OF COLD AIR FUNNELS.

AREA OF CONCERN--THE SOUTHERN QUARTER OF IOWA...ALONG AND SOUTH OF A
AUDUBON TO OTTUMWA LINE.

TIMING DETAILS--THUNDERSTORMS ARE POSSIBLE IN THE OUTLOOK AREA BETWEEN
4 AND 8 PM.

METEOROLOGICAL COMMENTS...AN AREA OF LOW PRESSURE ALOFT IS FORECAST TO
SLOWLY PUSH ACROSS THE STATE THIS EVENING AND TONIGHT. ASSOCIATED WITH
THIS UPPER LEVEL STORM SYSTEM ARE SOME FAIRLY COLD TEMPERATURES FROM
10,000 TO 20,000 FEET IN THE ATMOSPHERE. THE COMBINATION OF THE COLD
TEMPERATURES ALOFT AND SOME LOW LEVEL WARMING THAT OCCURRED OVER PARTS
OF SOUTHWEST AND EXTREME SOUTHERN IOWA THIS AFTERNOON WILL ENHANCE THE
THREAT FOR ISOLATED THUNDERSTORMS...ALONG WITH THE POSSIBILITY OF ONE
OR TWO OF THESE STORMS PRODUCING A COLD AIR FUNNEL. IN ADDITION...WITH
THE TEMPERATURES COOLING OFF IN THE UPPER ATMOSPHERE LATE THIS
AFTERNOON...FREEZING LEVELS AND WET BULB ZERO HEIGHTS WILL BE LOWERING
WHICH WILL INCREASE THE LIKELIHOOD OF HAIL WITH THE THUNDERSTORMS.

PRECAUTIONS...PEOPLE PLANNING OUTDOOR ACTIVITIES FOR LATE THIS
AFTERNOON INTO THIS EVENING SHOULD BE PREPARED FOR SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS TO DISRUPT THEIR EVENTS FOR A BRIEF PERIOD.
ALTHOUGH THE THREAT IS THERE FOR A FEW COLD AIR FUNNELS WITH THE
SHOWERS AND THUNDERSTORMS...STUDIES OF COLD AIR FUNNELS SHOW THAT THEY
RARELY TOUCH THE GROUND. THEY ARE USUALLY QUITE SMALL AND ARE NOT AS
VIOLENT AS THOSE ASSOCIATED WITH SEVERE THUNDERSTORMS. COLD AIR
FUNNELS NORMALLY PROTRUDE A FEW HUNDRED FEET DOWNWARD FROM THE PARENT
CLOUD...ROTATE OR SPIN LIKE A TOP...AND LAST FOR A FEW MINUTES BEFORE
DISSIPATING.

AT THIS TIME IT APPEARS THAT SPOTTER ACTIVATION WILL NOT BE REQUIRED
LATE THIS AFTERNOON OR EVENING.

SMITH