Heavy Snow in Michigan, February 19 to 21, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
500 PM EST TUE FEB 19 2002

...FORECAST PROBLEM IS ONGOING STORM...

UPPER PATTERN CONSISTS OF AN UPPER LEVEL TROUGH IN PACIFIC NW AND A
TROUGH ACROSS THE PLAINS AND AN UPPER LEVEL RIDGE IN EASTERN U.S.
TROUGH ACROSS THE PLAINS HAS TWO BRANCHES WITH NORTHERN BRANCH
SHORTWAVE SHOWN BY DARKENING ON WATER VAPOR OVER EASTERN MT AND
WYOMING. CYCLONIC CIRCULATION IN SOUTHERN BRANCH WITH SOME EMBEDDED
LIGHTNING IS SHOWN ON WATER VAPOR OVER NORTHEAST NM AND LOOKING AT 6
HOUR FORECAST FROM ETA...ETA DOES NOT SHOW ANY UPPER LOW OR VORT MAX
IN THAT AREA. THIS MIGHT NOT BE THAT BIG OF A DEAL AS ETA HAD UPPER
LOW WEAKENING FROM 12Z TO 18Z...BUT LOOKS LIKE THE UPPER LOW IS A
BIT STRONGER THAN ETA THINKS IT IS. CONCERN IS THAT IF LOW STICKS
AROUND A LITTLE LONGER...THIS COULD SLOW UP SOUTHERN BRANCH
SHORTWAVE AND WHOLE TROUGH COULD BECOME MORE NEGATIVELY TILTED THAN
WHAT ETA HAS. THIS WOULD SLOW THE SYSTEM DOWN AND ETA SEEMS TO KEEP
THE UPPER TROUGH POSITIVELY TILTED. LIKE THE NEGATIVE TILT THAT AVN
HAS ON TROUGH AND ALSO THE FURTHER SOUTH POSITION WITH 500 LOW ON
THU MORNING WITH LOW OVER CENTRAL IOWA VERSUS ETA HAVING IT NEAR
KSTC. WOULD MAKE SENSE TO HAVE LOW FURTHER SOUTH CLOSER TO MORE
POWERFUL SOUTHERN STREAM. NUMEROUS SHORTWAVES EMBEDDED IN THE UPPER
TROUGH AND UPPER LOW DOES NOT FORM IN NORTHERN BRANCH UNTIL 12Z WED.
ETA THEN SHOWS UPPER LOW SITTING OVER LOWER MICHIGAN WEDNESDAY NIGHT
INTO THURSDAY MORNING BEFORE MOVING SLOWLY INTO SOUTHEAST ONTARIO
THURSDAY AFTERNOON. WILL USE A BLEND OF AVN/ETA FOR THIS FORECAST.

FOR TONIGHT AND WEDNESDAY...ETA HAS WEAK TO MODERATE 850-500
Q-VECTOR CONVERGENCE THAT REMAINS THROUGH 00Z THU. AVN SIMILAR...BUT
FURTHER SOUTH WITH STRONGEST Q-VECTOR CONVERGENCE TONIGHT. AVN
SIMILAR WITH 850-500 Q-VECTOR CONVERGENCE FOR THURSDAY. WEAK
ISENTROPIC LIFT OCCURS ON ETA I280-I295 SURFACES BELOW 600 MB WITH
PLENTY OF RH WITH STRONGEST LIFT REMAINING SOUTH OF CWA TONIGHT AND
LIFT IS NON-EXISTENT WEDNESDAY MORNING EXCEPT IN EAST. AVN SIMILAR
WITH I280-I310 SURFACES TO ETA. FOR PCPN TYPE...LOOKED AT 1000-850
THICKNESS. USED ETA FOR THIS AS APPEARS THAT AVN IS TOO COLD WITH
ITS THICKNESSES AS IT IS SHOWING 1305 LINE AT 18Z FROM KIMT OVER TO
ISQ AND KRHI AND KEGV BOTH ARE NORTH OF THAT LINE AND THEY HAVE BEEN
REPORTING RAIN. ETA APPEARS TO HAVE BETTER HANDLE ON THIS AND IT HAS
1305 THICKNESS LINE AT 00Z FROM ABOUT KIWD TO KCMX TO KANJ AND THIS
LINE MOVES SOUTHWARD AT 06Z FROM NEAR KIMT TO KERY AND THEN AT 12Z
FROM KESC TO KISQ. WILL USE THIS TO FORECAST PCPN TYPE TONIGHT AND
LOOKS LIKE WITH MIX OF PCPN...SNOW AMOUNTS WILL NOT BE AS HIGH
EXCEPT OVER HIGHER TERRAIN IN MARQUETTE COUNTY. WILL HIT MARQUETTE
COUNTY THE HIGHEST FOR SNOWFALLS TONIGHT AND GO WITH A WARNING AS
UPSLOPE FLOW AND ENHANCEMENT OFF LAKE SUPERIOR FROM EAST AND
NORTHEAST WILL AFFECT OFFICE. SPLIT OUT BARAGA AS MESOETA SHOWS FLOW
WILL STAY EAST UNTIL AROUND 09Z WHEN IT BECOMES NORTHEAST FOR SOME
LAKE ENHANCEMENT. FELT THAT WARNING CRITERIA WILL NOT BE REACHED IN
BARAGA COUNTY TONIGHT OR IN ALGER BECAUSE OF WIND FLOW AND WENT WITH
A WATCH FOR BOTH AREAS FOR WEDNESDAY AND WEDNESDAY NIGHT. FEEL REST
OF AREAS MIGHT NEED ADVISORIES FOR WEDNESDAY. FOR SNOW
AMOUNTS...COULD NOT USE ANY LAKE EFFECT SNOW CHARTS AS 850 TEMPS AND
DELTA T SIMPLY TOO WARM...SO RELIED MOSTLY ON MODEL QPF FOR SNOW
AMOUNTS EVERYWHERE. WILL HAVE TO WATCH SOUTHERN CWA ALONG LAKE
MICHIGAN TOMORROW AS THIS AREA WILL BE ON NORTHERN EDGE OF PCPN
SHIELD FROM THE STORM AND COULD GET UP CLOSE TO WARNING CRITERIA.
HOWEVER...IF SYSTEM MOVES FURTHER SOUTH...MOISTURE WILL BE LESS AND
DID NOT WANT TO ISSUE A WATCH AT THIS TIME AS NOT REAL CONFIDENT.
CHANGEOVER OF PCPN IS ALSO KEY HERE AND SNOW RATIOS MIGHT BE LOW
ENOUGH NOT TO GET WARNING CRITERIA. SNOW WILL ALSO BE WET AND HEAVY
AND WITH THE STRONG WINDS...SHOULD NOT DRIFT TO BAD OR BLOW AROUND
MUCH.

DRIER AIR COMES INTO AREA WEDNESDAY NIGHT AND WILL DIMINISH THE SNOW
ACROSS THE AREA. MIGHT STILL NEED ADVISORIES ALONG LAKE SUPERIOR
EARLY WEDNESDAY NIGHT AT THIS POINT SINCE DRY AIR DOES NOT COME IN
UNTIL AFTER MIDNIGHT BASED OFF OF MESOETA 1000-850 RH PROGS.

FOR TEMPS...STUCK CLOSE TO GUIDANCE.

IN THE EXTENDED...AVN/MRF/ECMWF/UKMET ALL SIMILAR WITH 500 MB
TROUGHING OVER EASTERN U.S. ON FRIDAY WITH ANOTHER TROUGH IN PACIFIC
NW AND A RIDGE OVER DESERT SW. ECMWF THE SLOWEST THOUGH WITH 500 LOW
AND TROUGH POSITION STILL OVER WESTERN GREAT LAKES WITH OTHER MODELS
HAVING TROUGH AXIS OVER EASTERN GREAT LAKES AND SHORTWAVE RIDGING
OVER WESTERN GREAT LAKES. ECMWF THEN COMES AROUND TO MRF/AVN
SOLUTION FOR SATURDAY OF TAKING TROUGH IN PACIFIC NW EAST INTO
WESTERN GREAT LAKES WITH 500 LOW NORTH OF THE BORDER WHILE UKMET
BECOMES ODD MODEL OUT WITH DROPPING ENERGY WELL SOUTH FROM NORTHERN
CANADA AND FORMING A STRONG CLOSED OFF 500 LOW OVER DAKOTAS. THIS
SOLUTION AT THIS TIME SEEMS STRANGE AS 00Z/SUN UKMET THEN COMES BACK
TO MRF/AVN SOLUTION. ECMWF/UKMET DIFFER FROM MRF ON SUNDAY WITH BOTH
EUROPEAN MODELS KEEPING A 500 LOW BACK OVER WESTERN GREAT LAKES WITH
MRF MUCH MORE PROGRESSIVE WITH 500 LOW OVER SW QUEBEC. BROAD 500
TROUGH DOES REMAIN OVER NORTHERN U.S. THOUGH FROM SUNDAY THROUGH
TUESDAY. CANADIAN ENSEMBLES ON THURSDAY SEEM TO BE HALF AND HALF
WITH SOME MORE PROGRESSIVE WITH TROUGH AND 500 LOW POSITION AND
OTHERS KEEP THE LOW FURTHER WEST IN SUPPORT OF ECMWF SOLUTION.
CANADIAN STILL SEEMS TO SUPPORT ECMWF SOLUTION FOR FRIDAY AND
SUPPORTS A SLOWER SOLUTION WITH TROUGH HANGING BACK IN AREA.
CANADIAN ENSEMBLES THEN KEEP A 500 TROUGH OVER CWA FOR SATURDAY
THROUGH TUESDAY. CANADIAN ENSEMBLES THOUGH ARE ALL OVER THE PLACE
FROM 72-192 HOURS AND DO NOT GIVE ME MUCH CONFIDENCE DUE TO VARYING
SOLUTIONS. MRF/AVN ENSEMBLES ARE SIMILAR...BUT ARE NOISY AT 120
HOURS ONWARD. CONFIDENCE IN EXTENDED ON ANY OF THE MODEL SOLUTIONS
IS VERY LOW...SO BEST COURSE OF ACTION IS TO GO WITH PERSISTENCE IN
FORECAST AND NOT MAKE TOO MANY BIG CHANGES. WILL GO WET THE WHOLE
PERIOD WITH UPPER TROUGHING AROUND. WILL ALSO HAVE A COOLING TREND
IN TEMPS WITH TEMPS AT OR BELOW NORMAL. COORDINATED WITH KAPX AND
KGRB.

.MQT...WINTER STORM WARNING LATE TONIGHT THROUGH WEDNESDAY MIZ005.
    ...WINTER STORM WATCH WEDNESDAY AND WEDNESDAY NIGHT MIZ004-006.
    ...GALE WARNING LAKE SUPERIOR.

MICHELS