Severe Thunderstorm Warning 25, NWS Milwaukee, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
230 PM CDT FRI MAY 25 2001

FCST CHALLENGE IS WHETHER SHOWERS AND STORMS ASSOCIATED WITH THE
UPPER LOW WILL BE OVER ON MEMORIAL DAY. SECOND CHALLENGE IS
TEMPERATURES DUE TO WIDE VARIATIONS IN CLOUD COVER. THIRD CHALLENGE
IS NIGHT TIME AND EARLY MORNING FOG.

LARGE UPPER LOW CONTINUES TO SPIN ACROSS THE WESTERN GREAT LAKES.
APPEARS THAT TIMING OF AREAS OF VERTICAL MOTION CONTINUES TO BE
PROBLEMATIC DUE TO THE NATURE OF THESE TYPES OF SYSTEMS. MODELS
TYPICALLY DO NOT HANDLE THE TIMING OF PRECIPITATION VERY WELL AND
THIS COMPLICATES ANY TIMING OF PRECIPITATION...AS WELL AS MAX
TEMPERATURES DURING THE DAY...AS SEEN TODAY WITH SOME AREAS IN THE
40S WITH THUNDERSTORMS AND OTHERS THAT ARE IN THE SUN AND AROUND 60
DEGREES.

AND WITH THIS VARIED CLOUD COVER TYPICAL OF THIS PATTERN COMES
CLEAR SKIES IN MANY LOCALES AT NIGHT...AND WITH LIGHT WINDS AND
MOISTURE AT LOW LEVELS FROM DAYTIME SHOWERS...FOG FORMATION WILL BE
COMMON OVER THE NEXT THREE NIGHTS.

IN ANY CASE...IT IS APPARENT THAT THE LOW WILL CONTINUE TO INFLUENCE
THE WEATHER ACROSS SOUTHERN WISCONSIN THROUGH SUNDAY AND EVEN INTO
MEMORIAL DAY. AVN POINTS TOWARDS LIGHT PRECIP AMOUNTS ON MEMORIAL
DAY AND AS AREA REMAINS UNDER CYCLONIC FLOW AND HIGH PRESSURE
PUSHING DRY AIR IN BEHIND TROF/COLD FRONT...MAY BE ENOUGH LIFT AND
INSTABILITY LEFT OVER AND COMBINED WITH DAYTIME HEATING FOR A FEW
BRIEF SHOWERS ON MEMORIAL DAY.

WILL KEEP COOLER TEMPS PER AVN MOS.

.MKX...NONE.

EISE

WIZ046-047-051-052-056>060-062>072-252330-

COLD AIR FUNNELS
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
220 PM CDT FRI MAY 25 2001

...COLD AIR FUNNELS POSSIBLE ACROSS SOUTHERN WISCONSIN...

REPORTS OF COLD AIR FUNNEL SIGHTINGS HAVE BEEN RECEIVED AT THE
MILWAUKEE SULLIVAN FORECAST OFFICE FROM THE PUBLIC SINCE 2 PM...FROM
NORTH OF IXONIA TO THE WATERTOWN AREA.

GENERALLY FUNNEL CLOUDS DEVELOP AND OCCUR IN CONJUNCTION WITH WELL
DEVELOPED AND INTENSE THUNDERSTORMS WHICH HAVE FORMED IN A WARM
MOIST AIR MASS.  THUNDERSTORMS OF THIS VARIETY AND INTENSITY NEARLY
ALWAYS FORM ALONG AND SOME DISTANCE AHEAD OF A STRONG COLD FRONT.
WHEN FUNNEL CLOUDS ARE IN ASSOCIATION WITH THIS TYPE OF THUNDERSTORM
THEY FREQUENTLY DIP TO THE GROUND AND HAVE SUFFICIENT FORCE TO
DESTROY EVERYTHING ALONG THEIR PATH.  A FUNNEL CLOUD THAT TOUCHES
THE GROUND IS CALLED A TORNADO.

AN ENTIRELY DIFFERENT CONDITION PREVAILS OVER WISCONSIN TODAY. THERE
ARE NO STRONG COLD FRONTS IMPINGING ON A HOT AND HUMID AIRMASS.
INSTEAD WE HAVE A COOL AIRMASS WITH VERY COLD TEMPERATURES ALOFT.
THIS IS GENERALLY NOT A SITUATION THAT PRODUCES SEVERE WEATHER.

RESEARCH STUDIES OF FUNNEL CLOUD OCCURRENCES DURING THE PAST
SEVERAL YEARS INDICATE THAT A SOMEWHAT DIFFERENT SPECIES OF FUNNEL
CLOUD FORMS WHEN WEATHER CONDITIONS ARE SIMILAR TO THOSE OF TODAY.
THESE ARE CALLED COLD AIR FUNNELS AND ARE NOT AS VIOLENT AS THOSE
ASSOCIATED WITH WARM AND HUMID CONDITIONS.

THESE STUDIES OF COLD AIR FUNNELS SHOW THEY RARELY DO ANY DAMAGE.
THESE FUNNEL CLOUDS NORMALLY PROTRUDE A FEW HUNDRED FEET DOWNWARD
FROM THE PARENT CLOUD...ROTATE OR SPIN LIKE A TOP...AND LAST A FEW
MINUTES BEFORE DISSIPATING.

REPORTS OF SMALL FUNNEL CLOUDS MAY BE EXPECTED OVER SOUTHEAST
WISCONSIN THIS AFTERNOON. WARNINGS MAY BE ISSUED IF ANY OF THEM
TOUCH THE GROUND.

COLLAR