SPC MESOSCALE DISCUSSION 0177 FOR PORTIONS OF FAR NRN
NEB/SRN SD
AND ERN WY
CONCERNING...HEAVY SNOW...

MODERATE TO HEAVY SNOW SHOULD DEVELOP OVER PORTIONS OF FAR
SWRN AND
SCENTRAL SD...NWRN AND NCENTRAL NEB BY 13/19Z. ACCUMULATION
RATES
APPROACHING 1 IN/HR WILL BE POSSIBLE. HEAVY SNOW WILL BE
LIKELY
LATER THIS AFTERNOON OVER PORTIONS OF ERN WY.

LATEST IR/WV IMAGERY AND AREA PROFILERS INDICATE THE
PRESENCE OF
TWO UPPER LEVEL JET MAXIMA. ONE JET MAX WAS CENTERED OVER
FAR WRN
WY...WITH THE OTHER OVER MN. STRONG VERTICAL MOTION DUE TO
AGEOSTROPIC CIRCULATIONS IN THE ENTRANCE/EXIT REGIONS OF
THESE TWO
JET MAX/S ALONG WITH INCREASING MID LEVEL FRONTOGENETIC
FORCING HAS
AIDED IN A RAPID DEVELOPMENT OF AN ELEVATED BAND OF HEAVY
SNOW OVER
NRN NEB/FAR SRN SD OVER THE LAST FEW HOURS. 12Z NORTH PLATTE
SOUNDING INDICATES SUBSTANTIAL DRY AIR IN THE 850-700 MB
LAYER...LIMITING RAPID SURFACE SNOW DEVELOPMENT OVER THE
AREA.
HOWEVER...RECENT SFC OBS INDICATE CEILINGS CONTINUE TO
FALL...WITH
LIGHT SNOW DEVELOPING OVER NWRN NEB/SWRN SD. AS LOW LEVELS
CONTINUE
TO SATURATE AND STRONG FRONTOGENETIC FORCING IN A FAVORABLE
DENDRITIC SNOW GROWTH LAYER /600-700 MB/ REMAINS OVER THE
AREA...EXPECT INCREASING SNOWFALL RATES THROUGH 13/19Z.
ALTHOUGH
MODERATE SNOWFALL OVER ERN WY AIDED BY WRN WY UPPER JET AND
LOW
LEVEL UPSLOPE FLOW WILL CONTINUE THROUGH THE EARLY
AFTERNOON...HEAVY SNOW WILL BECOME MORE LIKELY OVER THIS
AREA
DURING THE MID TO LATE AFTERNOON AS MID LEVEL
FRONTOGENETICAL
FORCING FARTHER EAST SHIFTS NWWD IN RESPONSE TO DEEPENING
TROUGH
OVER THE GREAT BASIN.
 
 
 

..CROSBIE.. 03/13/02

...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT...
NNNN
ZCZC SPCSWOMCD ALL
ACUS11 KWNS 140255
SPC MCD 140255
SDZ000-NEZ000-WYZ000-140800-

SPC MESOSCALE DISCUSSION 0179 FOR SERN WY...WRN AND NRN
NEB...AND
EXTREME SRN SD
CONCERNING...HEAVY SNOW...

A MESOSCALE BAND OF MODERATE TO HEAVY SNOW IS EXPECTED TO
PERSIST
THROUGH MUCH OF THE OVERNIGHT PERIOD FROM SERN WY ENEWD
ALONG THE
NEB/SD BORDER. LOCALIZED SNOWFALL RATES AROUND 1 IN/HR ARE
LIKELY
WITHIN THE BAND.

RADAR IMAGERY AT 0245Z SHOWS AN INCREASE IN MESOSCALE
ORGANIZATION
OF BANDED PRECIPITATION ALONG THE NEB/SD BORDER. THIS REGION
IS
COINCIDENT WITH STRONG MID-LEVEL BAROCLINICITY WITH AN 11C
TEMPERATURE DIFFERENCE AT 700MB BETWEEN LBF AND RAP THIS
EVENING.
MODEL GUIDANCE SUGGESTS THAT BAROCLINIC ZONE WILL CONTINUE
TO
SHARPEN IN THIS REGION WITH THE BROAD SWLY FLOW AND WARM
ADVECTION
SOUTH OF THE FRONTAL ZONE. ADDITIONALLY...MID-LEVEL JET
STREAK NEAR
THE FOUR CORNERS AREA LATE THIS EVENING WILL LIKELY ENHANCE
MID TO
UPPER-LEVEL DIVERGENCE/UVV OVER THE DISCUSSION AREA LATE
TONIGHT...
RESULTING IN AN INCREASE IN PRECIPITATION INTENSITY.
FRONTOGENESIS FORCING IN THE PRESENCE OF MID-LEVEL RH VALUES
AT OR
ABOVE 90 PERCENT AND FAVORABLE TEMPERATURE PROFILES WILL
PRODUCE A
NARROW BAND OF HEAVY SNOWFALL THROUGH THE OVERNIGHT HOURS.
LOW-
LEVEL ELY FLOW WILL LIKELY RESULT IN SOME OROGRAPHIC
ENHANCEMENT OF
SNOWFALL ACROSS SERN WY/I-80 VICINITY THROUGH 14/08Z. THERE
MAY BE
A TENDENCY FOR A SLIGHT SWD SHIFT OF THE HEAVY PRECIPITATION
AXIS
INTO THE NEB PANHANDLE AND THE SANDHILLS REGION OF N-CENTRAL
NEB
AFTER 14/06Z AS THE FRONTAL ZONE PROPAGATES SEWD WITH TIME.

..BANACOS.. 03/14/02

...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT...
NNNN
ZCZC SPCSWOMCD ALL
ACUS11 KWNS 141136
SPC MCD 141136
NEZ000-SDZ000-MNZ000-141600-

SPC MESOSCALE DISCUSSION 0180 FOR WRN SD...NRN NEB...S CNTRL
THROUGH E CNTRL SD AND SWRN MN
CONCERNING...PRECIPITATION TRENDS AND HEAVY SNOW...

SNOW SHOULD GRADUALLY INCREASE IN INTENSITY ALONG A BAND
FROM N
CNTRL NEB NEWD THROUGH E CNTRL SD THIS MORNING WITH HEAVIER
SNOWFALL SPREADING AS FAR E AS SWRN MN BY LATE MORNING.
SNOWFALL
RATES FROM .5 TO 1 INCH PER HOUR ARE ANTICIPATED.

STRONG DOWNSLOPE COMPONENT ASSOCIATED WITH SWLY MID LEVEL
JET
LIFTING NEWD THROUGH CO HAS RESULTED IN A DECREASE IN
SNOWFALL
RATES ACROSS WRN NEB. HOWEVER...SNOW SHOULD REORGANIZE AND
INTENSIFY FARTHER E ALONG BAROCLINIC ZONE FROM NRN NEB NEWD
THROUGH
E CNTRL SD AND SWRN MN. LATEST SURFACE ANALYSIS SHOWS
SURFACE LOW
REDEVELOPING OVER S CNTRL KS WHERE STRONG PRESSURE FALLS
CURRENTLY
EXIST. THIS FEATURE SHOULD CONTINUE TO DEEPEN AND LIFT NEWD
TOWARD
IA AS UPPER DIVERGENCE IN EXIT REGION OF CYCLONICALLY CURVED
JET
SPREADS NEWD WITH TIME. LIFT ASSOCIATED WITH FRONTOGENETIC
FORCING/WARM ADVECTION SHOULD INCREASE N AND E OF SURFACE
LOW
ACROSS PORTIONS OF NEB AND SD AS UPPER JET AND ASSOCIATED
SHORTWAVE
TROUGH EJECTS NEWD. MOREOVER...STEEPER MID LEVEL LAPSE RATES
SHOULD
ACCOMPANY UPPER TROUGH AS IT EJECTS INTO THE NRN PLAINS AND
THIS
MAY SUPPORT SOME CONVECTIVE ENHANCEMENT TO THE SNOW BY LATE
MORNING. RATES ARE GENERALLY EXPECTED TO INCREASE TO BETWEEN
.5 AND
1 INCH PER HOUR.

SPC MCD 141804
NEZ000-SDZ000-MNZ000-142100-

SPC MESOSCALE DISCUSSION 0181 FOR NERN NEB/SE SD/SW MN
CONCERNING...HEAVY SNOW...

SNOW RATES WILL INCREASE THIS AFTERNOON ACROSS SOUTHEAST
SOUTH
DAKOTA AND SOUTHWEST MINNESOTA...WHERE 3 TO 4 HOUR PERIOD OF
SNOW
RATES IN EXCESS OF 1 INCH PER HOUR APPEAR LIKELY.

TIGHTENING MID-LEVEL THERMAL GRADIENT CONTINUES TO PROVIDE
FOCUS
FOR QUASI-STATIONARY BAND OF MOSTLY MODERATE SNOW...FROM
NORTH
CENTRAL NEBRASKA THROUGH EAST CENTRAL SOUTH DAKOTA/CENTRAL
MINNESOTA/AND NORTHERN WISCONSIN. MOISTURE CONTENT OF AIR
MASS
ALONG BAROCLINIC ZONE IS RELATIVELY LOW...AND THIS HAS
TENDED TO
MINIMIZE OVERALL AREAL COVERAGE AND INTENSITY OF SNOWFALL.
HOWEVER...STRONG FORCING FOR UPWARD VERTICAL MOTION IN LEFT
EXIT
REGION OF JET NOSING INTO SOUTH CENTRAL NEBRASKA IS
ENHANCING SNOW
RATES IN AREA JUST AHEAD OF ASSOCIATED CYCLONIC VORTICITY
CENTER...WHICH IS REDEVELOPING NORTHEASTWARD AROUND 20 KT.
UPWARD
VERTICAL MOTION FIELD AND AREA OF STEEPENING MID-LEVEL LAPSE
RATES...SUPPORTING SOME CONVECTIVELY ENHANCED SNOWFALL
RATES...WILL
PROGRESS INTO/ACROSS SOUTHEAST SOUTH DAKOTA AND SOUTHWEST
MINNESOTA
BETWEEN 14/20Z AND 15/00Z. AXIS OF HEAVIEST SNOW APPEARS
LIKELY
NEAR/JUST SOUTH OF MITCHELL SD INTO THE REDWOOD FALLS AREA.

..KERR.. 03/14/02

...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT...
NNNN
ZCZC SPCSWOMCD ALL
ACUS11 KWNS 142235
SPC MCD 142235
MNZ000-WIZ000-MIZ000-150400-

SPC MESOSCALE DISCUSSION 0182 FOR CENTRAL AND E-CENTRAL
MN...NWRN
AND EXTREME N-CENTRAL WI...AND WRN UPPER MI
CONCERNING...HEAVY SNOW...

BAND OF HEAVY SNOW EXTENDING FROM 45 NW RWF TO 25 NE STC TO
40 S OF
DLH WILL GRADUALLY PROPAGATE NEWD...SPREADING 1-2 IN/HR
SNOWS INTO
THE NWRN COUNTIES OF WI DURING THE EARLY EVENING HOURS...AND
INTO
WRN UPPER MI BETWEEN 15/03-06Z.

AXIS OF HEAVY PRECIPITATION IS DISPLACED WELL NORTH OF 994MB
SURFACE LOW CENTERED OVER S-CENTRAL IA AT 2230Z AND IS
JUXTAPOSED
WITH STRONG 700-600MB BAROCLINIC ZONE EXTENDING ACROSS
CENTRAL/SRN
MN AND CENTRAL WI AT THE PRESENT TIME. MINNEAPOLIS VAD
INDICATES A
WELL-DEVELOPED 60KT ELY JET AROUND 5KM AGL...IN ASSOCIATION
WITH
COLD CONVEYOR BELT AND STRONG GEOSTROPHIC FLOW NORTH OF LOW
CENTER.
FRONTOGENESIS FORCING BASED ON 14/12Z ETA IS EXTREMELY
STRONG
ACROSS NWRN AND N-CENTRAL WI BETWEEN 00-06Z. ASSOCIATED
STRONG
VERTICAL CIRCULATION AND SATURATED MODEL SOUNDINGS FROM THE
SURFACE
THROUGH 500MB WILL RESULT IN A MESOSCALE BAND OF HEAVY
SNOWFALL
PROPAGATING INTO NWRN WI THIS EVENING AND ULTIMATELY INTO
THE UPPER
PENINSULA OF MI LATE TONIGHT. THE AXIS OF HEAVIEST SNOWFALL
RATES...LOCALLY UP TO 2 IN/HR AT TIMES...IS EXPECTED TO
SET-UP FROM
40 S DLH TO 20 S IWD TO 50 NW IMT.
 

..BANACOS.. 03/14/02

...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT...
NNNN
ZCZC SPCSWOMCD ALL
ACUS11 KWNS 150136
SPC MCD 150136
MIZ000-150730-

SPC MESOSCALE DISCUSSION 0183 FOR UPPER MI
CONCERNING...HEAVY SNOW...

A NARROW E-W ORIENTED BAND OF HEAVY SNOW /RATES OF 1-2
IN/HR/ WILL
DEVELOP EWD ACROSS CENTRAL/ERN UPPER MI...INCLUDING THE
KEWEENAW
PENINSULA...LATE THIS EVENING AND PERSIST THROUGH THE
OVERNIGHT
HOURS.

MOSAIC RADAR IMAGERY AT 0115Z SUGGESTS THE STRONGEST
LARGE-SCALE
LIFT OWING TO WARM ADVECTION IS OCCURRING ALONG THE MN/WI
BORDER
EAST OF MSP. THIS LIFT IS ENHANCING THE 700MB BAROCLINIC
ZONE AND
STRENGTHENING THE FRONTOGENETIC CIRCULATION IN A 40-50NM
WIDE BAND
JUST SOUTH OF DLH. FRONTOGENESIS FORCING EXTENDS EWD WITH
BANDED
CHARACTER OF REFLECTIVITY ACROSS UPPER MI AT THE PRESENT
TIME...AND
SNOWFALL RATES WITHIN THIS BAND WILL GRADUALLY INCREASE
THROUGH
15/04Z AS SYNOPTIC-SCALE SUPPORT FOR HEAVY PRECIPITATION
MOVES INTO
THE DISCUSSION AREA. PRESENT INDICATIONS ARE THAT THE
MESOSCALE
BAND WILL BECOME ESTABLISHED VERY NEAR THE LAKE SHORE FROM
BARAGA
COUNTY EWD TO CHIPPEWA COUNTY. SOME OROGRAPHIC ENHANCEMENT
IS ALSO
POSSIBLE OVER THE HIGHER TERRAIN AREAS OWING TO 20KT NELY
FLOW
EVIDENT ON MQT VAD WIND PROFILE AT 2KM AGL. FAVORABLE
THERMODYNAMIC
PROFILES IN ADDITION TO STRONG AND FOCUSED UVV WILL PROVIDE
AN
ENVIRONMENT FAVORABLE FOR PERIODIC 1-2 IN/HR SNOW RATES
THROUGH THE
OVERNIGHT HOURS.
 

..BANACOS.. 03/15/02