Heavy Snow in Michigan, February 24 to 25, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
430 AM EST SUN FEB 24 2002

MAIN CONCERN WITH THIS FCST PACKAGE IS THE SNOW POTENTIAL TDA AND
TNGT AND MON.

WV IMAGERY INDCT LOW CENTER EMBEDDED IN A BROAD LONGWAVE TROF OVR
THE PLAINS OF S CAN...FOLLOWED BY A NARROW RDG OVR E PAC. A SHRTWV
TROF IS OVR THE CNTRL RCKY. SFC ANLYS DEPICTING A LOW OVR E ONT WITH
A CDFNT STRETCHING W TO A LOW OVR KS. A SFC RDG RUNS ALONG THE APLCN
AND THE ATLC SEABOARD.

MDLS IN GOOD AGREEMENT THRU 30 HRS...AND START TO SEE VARIATION AT
36HRS (12Z MON). AVN SHOWING A LTL STRONGER SHRTWV THAN ETA/NGM OVR
UPR MS VALLEY BY 12Z MON. ALSO THE ETA IS LTL FASTER ON THE MOVEMENT
OF THE SFC LOW INTO N LOWER MI BY 12Z MON THAN AVN. AVN IS ABOUT
6HRS SLOWER THAN ETA/NGM. RUN TO RUN TREND HAS BEEN FOR MDLS TO SLOW
DN A BIT AND TRENDING MORE TO THE AVN SOLN. GEM/UKMET FAVOR AVN
ALSO. THUS WILL FAVOR THE SLOWER AVN AS WELL ATTM.

A SHRTWV WILL MOV THRU CWA TDA...AS THE MIDLVL LOW OVR SASK DEEPENS
A BIT. 850-500MB Q-VEC CNVRGNC WILL INCR THRU THE AFTN OVR FCST
AREA. SFC LOW WILL REACH TO N MO BY 00Z MON...STEERING A WRMFNT
INTO LWR MI AND S WI. 290K ISENTROPIC ANLYS DEPICTING SIG ASCENT OVR
U.P. BY LATE AFTN. MEAN SFC-500MB RH OF >90 PERCENT WILL STRETCH
ACRS UPR GRTLKS THIS AFTN AND TNGT WITH PWS RANGING FM .5 TO .7
INCHES ACRS THE FCST AREA. MIXING RATIO AT 290K OVR CWA THIS AFTN
WILL AVERAGE 3G/KG SUG SOME 4 TO 6 INCHES OF SNOW THIS TDA FOR MUCH
OF CWA. 850MB TEMPS WILL BE RUNNING ARND -6C AND BLYR WND WILL BE
LGT...SO TDA DO NOT XPC LES TO BE A FACTOR.

THE 528M MID LVL LOW OVR S CAN WILL TREK INTO S MAN AND W ONT BY 12Z
MON. AVN DEPICTING A VERY WEAK SHRTWV REACHING W U.P. AT THAT TIME.
GEM/AVN PLACES THE 1004MB SFC LOW OVR CNTRL LK MICHIGAN. A WRMFNT
LOOKS AS IF IT WILL BE OVR THE STRAITS AREA AND ACRS E ONT.
ISENTROPIC ASCENT WILL BCM MARGINAL. HOWEVER...MIXING RATIO WILL
REMAIN ARND 3G/KG OVR S AND E SECTIONS OF FCST AREA. PWS WILL BE ON
THE ORDER OF .5 TO .8 IN ACRS MUCH OF CWA. THIS AGAIN SUG 4 TO 6
INCHES OF ADDITIONAL SN OVRNGT. LIMITING FACTOR WILL BE THE LIFT
WHICH WILL BE PROVIDED THE SHRTWV. BY SR...WNDS WILL BE BACK TO THE
N AND NW OVR W PART OF CWA. LK-850MB DELTA-TS WILL INCR
10C-12C...MARGINAL FOR LES. WITH AVAILABLE MSTR PRESENT...STILL
LOOKING FOR SOME LES ENHANCEMENT...AS WEAK SHRTWV PASSES OVR W LK
SUPERIOR.

MOSTLY NVA ENERGY WILL SLIDE OVR CWA ON MON AS THE SHRTWV DEPARTS.
DELTA-TS WILL INCR TO 15C TO 16C ACRS W U.P. AS CAA AND WND SHIFT
OUT OF THE NW BHND THE SFC LOW. STILL SHOWING DECENT Q-VEC
CONVERGENCE. AVN STAYS NR SATURATION OVR UPR GRTLKS THRU MON. 290K
MIXING RATIO WILL FALL OFF TO 1-2G/KG OVR CWA. SYS SN WILL
TRANSISTION TO LES AS LES MECHANISMS TAKE OVR AS THE MAJOR SOURCE OF
SNOWFALL ACRS AREA ON MON. AVN SHOWING FAIR AMNT OF LOW LVL WND
CNVRGNC ACRS LK SUPERIOR. OMEGA STRENGTH OF 2 UBAR/S IS LIKELY OVR E
LK SUPERIOR THRU MON AFTN. TOGETHER...COND FAVOR LES 1 TO 3 INCHES
OF LES AGAIN ON MON...SPCLY OVR N CWA.

ANOTHER SHRTWV WILL SLIDE ACRS CWA MON NGT AS WELL AS THE MID LVL
LOW ON TUE. SFC LOW WILL TREK INTO SW QUE BY TUE AM TAKING THE
CDFRNT WITH IT. CYC FLOW WILL BRING CAA TO CWA. DELTA-TS WILL INCR
TO 20C OVR THE W LK SUPERIOR AND 14-16C OVR E LK SUPERIOR. CYC FLOW
WILL ALSO KEEP WND OUT OF THE N ACRS THE LK MON NGT AND TUE. ETA
SHOWING THE INVRN AT 900MB MON EVE...AND THEN INCR TO 850MB (4.7K)
BY SR. THE LWR RESOLUTION AVN FCST SOUNING KEEPING THE INVRN ARND
850MB THRU THE PERIOD. STRONG LIFT IS INDCT FOR E LK SUPERIOR INTO
TUE...IN ASSOC WITH THE SHRTWV/MID LVL LOW MOV ACRS U.P. ALSO INDCT
IS SOME STRONG LOW LVL CNVRGN. AVN STILL SHOWING NR SATURATION AT
THE LOW LVL MON NGT AND TUE. THUS COND FAVOR INTENSE LES OVR E U.P.
MON NGT AND TUE...WITH 6 TO 8 INCHES POSSIBLE. ETA FAVORS DRIER COND
AND SHOWING LESS ACCUM.

COORDINATED WITH DLH...APX...GRB.

.MQT...SN ADV THIS AFTN INTO MON MIZ001
       WINTER STORM WARNING THIS AFTN INTO MON MIZ002>005-009>011.
       WINTER STORM WARNING TNGT AND MON MIZ006>007-012>014.

DLG