Monday, January 28, 2013

MESO: Mesoscale Discussion 0059

ACUS11 KWNS 282009
SWOMCD
SPC MCD 282009
MNZ000-SDZ000-NDZ000-290215-

MESOSCALE DISCUSSION 0059
NWS STORM PREDICTION CENTER NORMAN OK
0209 PM CST MON JAN 28 2013

AREAS AFFECTED...CNTRL/N-CNTRL/NERN SD...SERN ND...W-CNTRL/N-CNTRL
MN

CONCERNING...HEAVY SNOW

VALID 282009Z - 290215Z

SUMMARY...A BAND OF PRECIPITATION WILL DEVELOP NEWD THROUGH LATE
THIS AFTERNOON INTO THE EVENING. SNOW...WITH 1-IN/HR RATES...ALONG
WITH AREAS OF SLEET AND FREEZING RAIN...WILL BE POSSIBLE.

DISCUSSION...PRECIPITATION WILL INTENSIFY ALONG A NE/SW-ORIENTED
DEFORMATION ZONE THAT WILL BECOME BETTER DEFINED THROUGH LATE THIS
AFTERNOON INTO THIS EVENING. STRENGTHENING CONFLUENCE WITHIN THIS
ZONE WILL FORCE THE DEVELOPMENT OF FRONTOGENETIC CIRCULATIONS THAT
WILL AUGMENT ASCENT TO CREATE A NE/SW-ORIENTED BAND OF HEAVY SNOW.
REGIONAL MOSAIC RADAR IMAGERY SUGGESTS THAT INCIPIENT DEVELOPMENT IS
UNDERWAY ACROSS CNTRL/N-CNTRL/NERN SD. THE SNOW BAND IS FORECAST TO
EXPAND NEWD THROUGH THE EVENING...REACHING THE INTERNATIONAL BORDER
BY 04Z. THE HEAVIEST SNOW -- WITH RATES OF AROUND 1 IN/HR -- WILL
LIKELY COVER A 60-90-MILE-WIDE CORRIDOR CENTERED FROM NEAR PIR TO 40
ESE INL. THIS IS AFFIRMED BY CONSENSUS AMONGST RECENT
HIGH-RESOLUTION WRF GUIDANCE.

IMMEDIATELY TO THE SE OF THE AFOREMENTIONED CORRIDOR...MULTIPLE
WINTER PRECIPITATION TYPES MAY OCCUR. AN ELEVATED WARM LAYER SHOULD
SUPPORT PARTIAL/COMPLETE HYDROMETEOR MELTING TO YIELD SLEET/FREEZING
RAIN AS PRECIPITATION INITIALLY FALLS. AMDAR FOR DESCENDING ROUTES
INTO MSP FROM THE W SAMPLED 850-MB TEMPERATURES AROUND 6-7 C IN
CONJUNCTION WITH THE WARM LAYER. WHILE THESE TEMPERATURES ARE LIKELY
SOMEWHAT LOWER ACROSS THE MCD AREA...AT LEAST A BRIEF PERIOD OF
SLEET/FREEZING RAIN WILL BE OF CONCERN. FREEZING RAIN RATES COULD
REACH 0.05-0.07 INCH PER 3 HOURS. THE INFLUX OF DEEPER COLD AIR
SHOULD ALLOW FOR A TRANSITION TO SNOW FROM SW TO NE WITH SNOW RATES
LOCALLY REACHING 1 IN/HR THROUGH THE EVENING.

..COHEN.. 01/28/2013

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

ATTN...WFO...DLH...MPX...FGF...FSD...ABR...BIS...UNR...

LAT...LON 48519291 48099179 47059216 45749525 44789717 43789922
43470078 44290127 46249877 47369675 48389426 48519291

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