[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 020021
SWOMCD
SPC MCD 020021 
MIZ000-WIZ000-ILZ000-IAZ000-MNZ000-020615-

MESOSCALE DISCUSSION 0006
NWS STORM PREDICTION CENTER NORMAN OK
0621 PM CST SAT JAN 01 2005

AREAS AFFECTED...SERN MN...NCNTRL/NERN IA...MUCH OF WI...FAR NRN IL
AND MUCH OF LOWER MI/SRN UPPER MI

CONCERNING...FREEZING RAIN AND SLEET 

VALID 020021Z - 020615Z

SIGNIFICANT ICE/SLEET EVENT WILL CONTINUE TO DEVELOP WHILE
PROGRESSING ENEWD FROM THE UPPER MS VALLEY ACROSS THE WRN/NRN GREAT
LAKES REGION THROUGH 06Z. TWO CORRIDORS OF HEAVIEST ACCUMULATIONS
ARE ANTICIPATED TO OCCUR DURING THIS TIME. ONE AXIS IS ANTICIPATED
TO EXTEND FROM NCNTRL/NERN IA NEWD ACROSS SERN MN...CENTRAL/NERN WI
AND THE WRN U.P. OF MI. THE OTHER AXIS ACROSS PORTIONS OF WCENTRAL
WI EWD INTO CENTRAL LOWER MI. IN BOTH OF THESE AREAS...ISOLATED 0.15
TO 0.25 IN/HR LIQUID EQUIVALENT PRECIPITATION RATES ARE POSSIBLE
THROUGH 06Z.

RECENT WV IMAGERY SHOWS A WELL DEFINED UPPER LVL JET MAX ROTATING
OUT OF THE CENTRAL ROCKIES INTO THE CENTRAL HIGH PLAINS OF WRN
KS/NEB. UPPER DIVERGENCE IN THE LEFT EXIT REGION OF THIS JET HAS
ALREADY ENHANCED CLOUD TOP COOLING ON IR IMAGERY OVER WRN IA/SWRN MN
AND INCREASING CONVECTIVE PRECIPITATION IN THESE AREAS. AS THE UPPER
JET MAX CONTINUES TO MOVE NEWD...IT WILL CONTINUE TO SUPPORT NEWD
ENHANCEMENT OF ALREADY MODERATE TO STRONG LIFT IN RIGHT ENTRANCE
REGION OF NRN JET MAX OVER THE U.S/CANADIAN BORDER AND LOW LEVEL
ISENTROPIC ASCENT ALONG AND NORTH OF SFC WARM FRONT BOUNDARY. THUS A
DEEP LAYER OF VERTICAL MOTION WILL EXTEND ALONG AND NORTH OF THE SFC
LOW/WARM FRONTAL TRACK FROM NCENTRAL IA NEWD INTO NCENTRAL WI
THROUGH 06Z. THE TRANSITION ZONE FOR FREEZING RAIN/SLEET IN THIS
REGION HAS BEEN SOMEWHAT MUDDLED BY THE CONVECTIVE NATURE OF THE
PRECIPITATION. THUS A MIX OF FREEZING RAIN/SLEET IS ANTICIPATED TO
OCCUR THROUGH THE PERIOD WITH A CONTINUATION OF THE CONVECTIVE
NATURE OF PRECIPITATION GIVEN THE DEGREE OF FORCING...STEEP MID
LEVEL LAPSE RATES AND 100-200 J/KG OF MUCAPE.  STRONGEST VERTICAL
MOTION DUE TO COUPLED JET STRUCTURE WILL EXIST FROM NCENTRAL IA NEWD
INTO NCENTRAL WI/WRN U.P OF MI THROUGH 06Z.

ELSEWHERE...AS THE SFC LOW LIFTS NEWD INTO SERN MN THROUGH 06Z...THE
SFC FREEZING LINE IS ANTICIPATED TO LIFT NWD TO A ALO TO MSN TO MKE
LINE BY 06Z. THUS FREEZING RAIN OVER ERN IA/FAR NRN IL AND FAR SRN
WI WILL GRADUALLY CHANGE TO RAIN FROM SOUTH/NORTH THROUGH THIS
PERIOD. FARTHER ENE...A DRY BOUNDARY LAYER WILL CONTINUE TO AID IN A
SLOW DEVELOPMENT OF SIGNIFICANT FREEZING RAIN AND/OR SLEET OVER MUCH
OF ECENTRAL WI THROUGH 02Z AND WRN/CENTRAL LOWER MI THROUGH 03Z.
WELL REMOVED FROM THE SFC LOW DRY ELY FLOW WILL LIMIT THE NWD
MOVEMENT OF THE SFC FREEZING ISOTHERM BEFORE AND AFTER ONSET OF
PRECIPITATION OVER CENTRAL/SRN LOWER MI. INITIAL PRECIPITATION OVER
ECENTRAL WI EWD INTO WRN/CENTRAL LOWER MI WILL LIKELY FORM IN THE
FORM OF SLEET DUE TO THE DRY BOUNDARY LAYER. HOWEVER...INCREASING
MOISTURE ADVECTION ON THE HEELS OF A 40-50 KT LOW LEVEL JET/SUBTLE
MID LEVEL SHORTWAVE CURRENTLY AIDING IN MODERATE PRECIPITATION OVER
ERN IA/WRN IL WILL AID IN QUICK SATURATION IN THE LOW LEVELS FROM
SW-NE FROM 02-06Z. COMBINED WITH MODERATE INSTABILITY...MUCAPES FROM
100-300 J/KG...MODERATE TO HVY FREEZING RAIN IS ANTICIPATED TO OCCUR
ACROSS THIS REGION BETWEEN 02-06Z. THE LEADING EDGE OF THE HEAVIEST
PRECIPITATION GIVEN CURRENT EXTRAPOLATION WILL REACH A JXN TO HTL
LINE BY 06Z.

..CROSBIE.. 01/02/2005

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
USED FROM DECEMBER 1 THROUGH FEBRUARY 28.

ATTN...WFO...DTX...APX...IWX...GRR...MQT...GRB...LOT...MKX...DVN...DLH...ARX...MPX...DMX...

46119001 46188721 45658586 44888475 44258404 43428350
42588355 42338420 42208600 41888777 41859080 42389303
42889359 43719385 45219321 45699205 

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