Damaging Wind in Michigan, December 5, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
359 PM EST WED DEC 5 2001

THE CURRENT APX 88D SHOWS SCATTERED SHOWERS MOVING INTO EAST UPPER
MICHIGAN...WITH REGIONAL RADAR DATA SHOWING AN AREA OF SHOWERS AND
THUNDERSTORMS MOVING NORTHEAST OVER WISCONSIN. THE LATEST SURFACE
CHART SHOWS A WARM FRONT STRETCHING OVER THE STRAITS INTO NORTHERN
LAKE HURON...FROM A LOW PRESSURE CENTER IN MINNESOTA. ALSO A COLD
FRONT WAS LOCATED OVER WESTERN WISCONSIN. SURFACE CONDITIONS ALONG
AND IN ADVANCE OF THE COLD FRONT...CONSIST OF TEMPERATURES IN THE
MID 60S WITH DEW POINTS IN THE UPPER 50S. THE LATEST MODEL DATA WAS
IN GOOD AGREEMENT WITH THIS SYSTEM...MOVING INTO THE STATE THIS
EVENING AND EXITING INTO THE EASTERN LAKES OVERNIGHT. THE MAIN
FORECAST CONCERNS WILL BE CENTERED ON THE CHANCE OF PRECIPITATION
AND THUNDERSTORMS TONIGHT...ALONG WITH CLOUDS AND SNOW INTO THE
WEEKEND.

TONIGHT...THE COLD FRONT CURRENTLY OVER WESTERN WISCONSIN...WILL
BECOME LOCATED OVER EASTERN WISCONSIN THIS EVENING AND MOVE EAST OF
THE LAKES BY 12Z THURSDAY. THE WIDESPREAD CONVECTION THAT IS
CURRENTLY IN ADVANCE OF THIS FRONTAL BOUNDARY...HAS FORMED IN A THTE
RIDGE WITH 850 MB DEW POINTS BETWEEN 8C AND 9C. ALSO...THE 700/500MB
LAPSE RATES WERE BETWEEN 6C/KM AND 7C/KM. THIS AIRMASS IS PROGGED TO
MOVE INTO THE WESTERN LAKES THIS EVENING AND EASTERN LAKES BY
MIDNIGHT. THEREFORE WILL FORECAST SHOWERS WITH A CHANCE OF
THUNDERSTORMS ALL ZONES TONIGHT. MODEL SOUNDINGS AND MOISTURE
PROGS...SHOW EXTREMELY DRY AIR TO MOVE OVER THE LAKES REGION
TONIGHT BEHIND THE COLD FRONT...850/500 MB MOISTURE WILL DROP FROM
90 PERCENT IN ADVANCE OF THE SYSTEM...TO UNDER 30 PERCENT BEHIND THE
FRONT. THEREFORE WILL ALSO MENTION SKIES BECOMING PARTLY CLOUDY
OVERNIGHT NORTHWEST LOWER AND EAST UPPER MICHIGAN. MODEL SOUNDINGS
SHOW STRONG 925 MB WINDS OF 45 KNOTS...OVER NORTHERN LOWER AND EAST
UPPER THIS EVENING...HOWEVER MODEL SOUNDINGS SHOW WINDS OF ONLY 20
TO 30 KNOTS MIXING TO THE SURFACE.

THURSDAY...IT WILL BE WINDY AGAIN WITH 925 MB WINDS 25 TO 30 KNOTS
...WITH MODELS SOUNDINGS SHOWING THESE MIXING DOWN TO THE SURFACE.
SO WILL CONTINUE WITH THE WINDY WORDING MOST ZONES INTO THE EVENING.
MODEL DATA SHOWS THE COLD FRONT WILL BE WELL EAST OF THE FORECAST
AREA BY 12Z THURSDAY...WITH SOME LINGERING CYCLONIC FLOW OVER EAST
UPPER MICHIGAN. MODEL SOUNDINGS AND MOISTURE PROGS SHOW A DRY AIR
MASS OVER NORTHERN LOWER AND EAST UPPER MICHIGAN...WITH 900/700 MB
MOISTURE AROUND 40 PERCENT OVER EAST UPPER AND 30 PERCENT OVER LOWER
MICHIGAN. THIS WILL BE GENERALLY 8K FEET OF MID LEVEL DRY AIR OVER
THE FORECAST AREA INTO THE EVENING. 850 MB TEMPERATURES FALL TO
AROUND -4C OVER LOWER MICHIGAN AND -8C OVER EAST UPPER IN THE
AFTERNOON. THE LAKE EFFECT SNOW WILL BE LIMITED DUE TO DRY MID
LEVELS...AND LOW LEVEL MOISTURE NOT EXTENDING INTO TEMPERATURES
COLDER THAN -10C. WILL HOWEVER MENTION LAKE EFFECT FLURRIES OVER
EAST UPPER THURSDAY AFTERNOON...WHERE OVER LAKE INSTABILITY WILL BE
THE GREATEST. WILL MENTION PARTLY TO MOSTLY SUNNY SKIES ACROSS THE
REST OF THE FORECAST AREA.

THURSDAY NIGHT/FRIDAY...SURFACE RIDGING CONTINUES TO BUILD ACROSS
THE UPPER MIDWEST AND INTO THE GREAT LAKES REGION IN THE EVENING...
AND BECOMES CENTERED OVER THE STATE OVERNIGHT. MODEL SOUNDINGS
CONTINUE TO SHOW DRY MID AND UPPER LEVELS LINGERING OVER THE ENTIRE
FORECAST AREA THROUGH THE EVENING...WITH LOW LEVELS REMAINING FAIRLY
MOIST AROUND 60 PERCENT AT THE SURFACE. THE INFLUENCES OF LAKE
EFFECT BECOMES MORE EVIDENT AS 850 MB TEMPERATURES DROP TO AROUND
-12C OVER EAST UPPER AND -10C OVER NORTHERN LOWER...THURSDAY NIGHT
AND LINGERING INTO FRIDAY. 900/700 MB MOISTURE WILL BE BETWEEN 60
AND 70 PERCENT AND EXTENDS TO TEMPERATURES AROUND -10C. WINDS WILL
BE FROM THE NORTHWEST THURSDAY NIGHT AND FRIDAY AT SPEEDS AROUND 20
KNOTS. THEREFORE WILL MENTION LAKE EFFECT SNOW SHOWERS/FLURRIES...
IN THE LAKE SUPERIOR AND LAKE MICHIGAN SNOW BELTS.

EXTENDED DISCUSSION...EXTENDED MODELS SWEEP AN UPPER TROUGH OVER THE
GREAT LAKES SATURDAY AND SUNDAY...WITH WEAK UPPER RIDGING/ZONAL
FLOW DEVELOPING OVER THE STATE MONDAY. ALSO ON SUNDAY...A DEEPENING
UPPER TROUGH WILL BE DEVELOPING OVER THE PACIFIC NORTHWEST...WHICH
IS FORECAST TO MOVE OVER THE NORTHERN PLAINS TUESDAY...AND INTO THE
WESTERN LAKES WEDNESDAY. THE MODELS DID DIFFER WITH RESPECT TO 850
MB TEMPERATURES THROUGH MUCH OF THE EXTENDED PERIOD...WITH THE MOST
NOTABLE BEING TUESDAY WHEN THE MRF PROGGED -4C OVER EAST UPPER WHILE
THE ECMWF PROGGED -12C. OTHERWISE THE DIFFERENCES WERE AROUND 4C OR
LESS. WITH THE LARGE AREA OF UPPER TROUGHING PROGGED OVER CANADA AND
THE NORTHERN US EARLY NEXT WEEK...COLDER 850 TEMPERATURES ARE
POSSIBLE OVER THE STATE TUESDAY INTO WEDNESDAY. THEREFORE WILL LEAN
TOWARD THE ECMWF 850 MB TEMPERATURES...BUT WILL NOT GO AS COLD.

.APX...NONE.

SWR