Heavy Snow in Michigan, March 22, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
321 AM EST FRI MAR 22 2002

HUDSON BAY VORTEX REMAINS DOMINANT FEATURE ON THE WEATHER MAP THIS
FORECAST. A DIGGING SHORTWAVE WAS RACING SOUTHEAST THRU THE LAKE
WINNIPEG REGION...EVIDENT ON IR IMAGERY WITH COOLER CLOUD TOPS JUST
UPSTREAM OF LAKE SUPERIOR. AT THE SURFACE...HIGH PRESSURE OVER THE
NORTHERN PLAINS...AND LOW PRESSURE OVER HUDSON BAY. RESULT...A
CONTINUED COLD WNW FLOW AT LOW LEVELS ACROSS THE GREAT LAKES.
VIGOROUS LAKE EFFECT SNOW (LES) IS ONGOING DOWNWIND OF LAKE
SUPERIOR. NORTHERN LOWER LES IS SPARSER AND MUCH LESS INTENSE. RADAR
LOOPS SHOW A 290/300 FETCH AT THE PRESENT. LAKE EFFECT/ENHANCED SNOW
IS THE OBVIOUS PROBLEM ON THIS LOVELY SPRING DAY.

MAIN MODEL DIFFERENCE SHOWS ITSELF SAT NIGHT...IN BEHAVIOR OF
REORGANIZING HUDSON BAY LOW. ETA/AVN BOTH REORGANIZE THE LOW OVER
LABRADOR/NE QUEBEC...BUT THE ETA HAS A STRONGER REMNANT OF THE
ORIGINAL LOW ROTATING SSE PAST JAMES BAY. THIS RESULTS IN A SOMEWHAT
MORE EMPHATIC REINFORCING SURGE OF POLAR AIR SAT NIGHT. COLDER
SOLUTIONS HAVE BEEN WORKING PRETTY WELL RECENTLY...WILL LEAN TOWARD
THE ETA. ETA ALSO PREFERRED IN LES PATTERN...FOR THE USUAL
RESOLUTION REASONS. INITIALIZATION APPEARS DECENT.

TODAY...THE SHORTWAVE BLASTS THRU AROUND MIDDAY. SURFACE HIGH
CONTINUES SE INTO THE LOWER MS VALLEY. MODELS PROG 1000-850MB WINDS
TO SWITCH TO A 280 FETCH BETWEEN 09Z AND 12Z. INSTABILITY PROGS
REMAIN FAVORABLE THRU EARLY AFTERNOON (DELTA T/S 18-19 WITH
INVERSIONS AT 9K FEET FOR EASTERN UPPER...6-7K NW LOWER). LESS
FAVORABLE CONDITIONS LATE AS POST-SHORTWAVE SUBSIDENCE LOWERS
INVERSIONS AND WARMS 850-700MB TEMPS. FOR EASTERN UPPER...THE FETCH
IS THE MAIN STICKING POINT...WITH AN EXPECTED SWITCH TO 280 LEAVING
ONLY WHITEFISH/PARADISE AS A HIGH-THREAT AREA. HOWEVER...RADARS SHOW
LITTLE SIGN OF THE SWITCH HAPPENING SOON. IN FACT...CURRENT WSW
SURFACE WINDS NOTED IN CENTRAL UPPER MI OBS WILL CONTINUE TO ENHANCE
CONVERGENCE AND BANDING ACTIVITY. EXPECT 3-6 FOR CHIPPEWA. WITH
REPORTS OF UP TO 9 INCHES OF SNOW (SUGAR ISLAND) DURING THE NIGHT SO
FAR...WILL HOIST LES WARNING...EMPHASIZING HIGHEST SNOWFALL AMOUNTS
NEAR WHITEFISH. MACK WILL SEE MUCH LESS...EVEN A FAVORABLE W FETCH
FOR THE ST IGNACE AREA IS TEMPERED BY THE AMOUNT OF LAKE ICE
UPSTREAM.

NORTHERN LOWER...INVERSION HEIGHTS PROGGED TO REMAIN (JUST) BELOW 7K
FEET ALL DAY. WITH NO LAKE SUPERIOR CONTRIBUTION THANKS TO THE 280
FETCH...HEAVY LES APPEARS UNLIKELY. DO EXPECT A SIGNIFICANT UPTICK
IN LES DURING THE MORNING AS SHORTWAVE APPROACHES...AND AS UPSTREAM
AIR MOISTENS (NOTE...SUB-ZERO DEW POINT AIR CROSSING LAKE MI NOW...
BUT SINGLE-DIGIT DEW POINTS ARE UPSTREAM IN NW WI). WILL ISSUE
ADVISORY FOR THE MOST THREATENED AREAS WITH A W FETCH...ELK RAPIDS
TO GAYLORD AND NORTH TO THE BRIDGE...FOR 3-5. OTHER AREAS WILL SEE
LESS...THOUGH SHSN SHOULD BE WIDESPREAD AGAIN WITH STRONG DIURNAL
HEATING ACTING ON THE UNSTABLE AIRMASS. EXPECT BANDS TO BECOME
POORLY DEFINED AGAIN THIS AFTERNOON FOR THIS SAME REASON.

A DUE WEST FETCH CONTINUES TONIGHT. ANOTHER STRONG SHORTWAVE ROTATES
IN FROM THE NW LATE...COOLING TEMPS ALOFT AND PUSHING INVERSIONS
ABOVE 10K FEET FOR EASTERN UPPER. BUT 850MB TEMPS REMAIN VERY
MARGINAL (LOWER TEENS)...AND THE FETCH AGAIN SUGGESTS WHITEFISH PT
IS THE MAIN PROBLEM SPOT IF ANY. DIURNAL SHSN WILL DIMINSH IN THE
EVENING...LEAVING SPOTTY LES ACTIVITY DOWNWIND OF LAKE MI (ST IGANCE
AND SOUTH). A STRONGER W-E LES BAND WILL OCCUR OVER LAKE SUPERIOR...
POSSIBLY AFFECTING WHITEFISH...MORE LIKELY STAYING JUST OFFSHORE.
WILL CONTINUE CURRENT LES DIMINISHING WORDING IN THE ZFP...THOUGH
WILL ADD IN SOMETHING A BIT STRONGER FOR WHITEFISH.

FOR SAT...DELTA T/S REMAIN IN THE LOWER TEENS IN NW LOWER...INCREASE
TO THE MID TEENS FOR EASTERN UPPER. NORTHERN LOWER REMAINS LOCKED TO
AN EAST FETCH...KEEPING LAKE SUPERIOR OUT OF THE PICTURE AND
MOISTURE LEVELS UNIMPRESSIVE. THUS...EVEN AS INVERSION HEIGHTS CLIMB
TOWARD 7K FEET BY EARLY AFTERNOON...LES SHOULD NOT GET OUT HAND.
DIURNAL AFFECT WILL AGAIN MAKE SHSN FAIRLY WIDESPREAD...BUT WILL
ALSO DISRUPT BANDS. SO ANOTHER 1-2 POSSIBLE IN FAVORED AREAS.
EASTERN UPPER IS MORE INTERESTING...AS FETCH TURNS TOWARD 300 DURING
THE MORNING IN THE WAKE OF THE SURFACE REFLECTION OF THE SHORTWAVE
GOING BY. THOUGH DELTA T/S ARE NOT IMPRESSIVE (SEE ABOVE)...
INVERSIONS REMAIN ABOVE 10K FOR MOST OF THE DAY...AND MOISTURE
LEVELS REMAIN HIGH AS CHANNELED VORTICITY GOES THRU ALOFT. A LOCALLY
DERIVED LAKE SNOW INDEX SUPPORTS HEAVY LES...BUT THE DURATION OF
FAVORABLE FETCH AND HIGH INVERSIONS IS NOT LENGTHY. FOR NOW...WILL
ADVERTISE ADVISORY CRITERIA SNOW FOR CHIPPEWA (3-5)...BUT LATER
SHIFTS WILL NEED TO WATCH THIS CLOSELY.

POLAR AIR RETURNS SAT NIGHT AS HUDSON BAY LOW REMNANT MOVES NE OF
THE LAKES. THOUGH 850MB PLUNGE 6-8C DURING THE NIGHT...INVERSION
HEIGHTS DO THE SAME AS THE COLD AIR APPEARS SHALLOW. THOUGH
MEASURABLE LES IS AGAIN LIKELY...AMOUNTS SHOULD REMAIN UNDER
CONTROL. WILL KEEP NW FLOW FAVORED COUNTIES IN LIKELY POPS...CHANCE
ELSEWHERE.

NO CHANGES TO LATER PERIODS.

.APX...LAKE EFFECT SNOW WARNING...TODAY...MIZ008.
       WINTER WEATHER ADVISORY...TODAY...MIZ016-017-019-021-022.

ZOLTOWSKI