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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2041Z Mar 23, 2015)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
441 PM EDT MON MAR 23 2015

VALID 00Z TUE MAR 24 2015 - 00Z FRI MAR 27 2015


...EASTERN OH VALLEY INTO CENTRAL APPALACHIANS...
A SMALL SCALE DE-AMPLIFYING MID-LEVEL CIRCULATION IS DROPPING
SOUTH AND EAST THROUGH THE OH VALLEY THIS AFTN. THIS FEATURE IS
CREATING A BURST IN HEAVY SNOW FROM A NARROW BUT INTENSE AXIS OF
FRONTOGENESIS... EARLIER IN CHICAGO TO FWA... AND SHOULD REACH
PARTS OF OH INTO SWRN PA/CENTRAL APPALACHIANS LATER THIS EVENING
INTO THE OVERNIGHT HRS. THE MAX 6 HR WINDOW WILL LIKELY PRODUCE A
DUSTING TO AN INCH OR TWO FROM SWRN PA INTO THE HILLS OF THE
CENTRAL APPALACHIANS/LAUREL HIGHLANDS WITH A SLIGHT DUSTING EAST
OF THE TERRAIN NEAR THE MASON DIXON LINE OF PA/MD.

...WEST INTO UPPER MIDWEST...
AN ASSORTMENT OF PAC SHORT WAVE DYNAMICS WILL NOT ONLY PROGRESS
THROUGH THE WRN PORTION OF THE COUNTRY OVER THE NEXT DAY BUT
EMERGE OUT INTO THE CENTRAL PORTION OF THE COUNTRY TO INDUCE TWO
SURFACE LOWS. THE RESULTANT WILL BE THE THREAT FOR HEAVY MTN SNOW
FOR THE WEST ON TUES AND PERHAPS EARLY WED BUT THE THREAT FOR
WINTER WX FROM THE NRN HIGH PLAINS INTO THE UPPER MS VALLEY AND
GREAT LAKES BOTH DAYS.

A STREAM OF UPPER DYNAMICS AND SLIGHTLY ABOVE AVG PAC MOISTURE
TRANSPORT SHOULD YIELD WELCOME HEAVY SNOWFALL ACROSS A LARGE
PORTION OF THE WRN TERRAIN. THE GUIDANCE PINPOINTS HEAVY SNOWFALL
LIKELY FROM THE WA/OR CASCADES THROUGH THE
BLUE/SAWTOOTH/BITTERROOT RANGES INTO THE NRN ROCKIES/TETONS AND
POSSIBLE SPREAD INTO THE BIG HORN/WIND RIVER MTNS AND NRN CO
ROCKIES. THE MAJORITY OF THE ACTION WILL TAKE PLACE ON TUES BUT
LINGER INTO WED NEAR THE EAST FACING SLOPES OF THE FAVORED TERRAIN
IN WY/CO... AS THE SURFACE COLD FRONT MOVES SOUTH AND EAST TO
PRODUCE A SMALL WINDOW OF UPSLOPE SNOW.

MEANWHILE DOWNSTREAM... LOWERING HEIGHTS WILL INDUCE A SURFACE
WAVE OVER ERN MT LATE MON. THIS LOW WILL INTENSIFY AS IT TRACKS
ACROSS THE DAKOTAS TOWARD NRN MN AND ITS 500MB TROUGH AXIS TAKES A
SLIGHT NEG TILT. THIS SHOULD SPAWN A DECENT DYNAMIC COOLING ZONE
OF HEAVY SNOWFALL FROM NERN MT THROUGH NRN ND ON TUES AND SPREAD
DOWNSTREAM THROUGH NRN MN ON WED BUT LOSE A BIT OF ITS LUSTER.

FINALLY... THE SRN TIER OF UPPER DYNAMICS WILL INDUCE A SURFACE
LOW OVER THE CENTRAL/SRN PLAINS MON EVENING INTO TUES MORNING.
THIS LOW AND SHORT WAVE WILL LIFT NORTH AND EAST INTO THE MID MS
VALLEY ON TUES AND PROCEED INTO THE GREAT LAKES ON WED... AS A
LARGE SURFACE RIDGE SLOWLY RETREATS TO THE EAST. THE INITIAL SURGE
OF WARM ADVECTION INTO PARTS OF THE MID MS VALLEY COULD RESULT IN
LIGHT ICING FROM IA BACK INTO IL/NRN MO ON DAY 1. BUT AS THE
SURFACE LOW GRADUALLY ORGANIZES AND DEEPENS ON WED... MUCH MORE
MOISTURE WILL FLOURISH AND EXPAND ACROSS THE UPPER MS VALLEY INTO
THE GREAT LAKES. ITS ON THE NWRN FRINGE OF THE WAVE WHERE
GFS/ECMWF THERMAL PROFILES SUGGEST THE THREAT FOR HEAVY SNOW AND
POSSIBLE ICING CORE FROM SERN MN NORTH AND EAST THROUGH WI INTO
MI. THIS IS THE GENERAL BLEND OF GUIDANCE WPC USED FOR THE HEAVY
SNOW PROBS OVER THE NEXT COUPLE OF DAYS. BY THURS... THE ENTIRE
SYSTEM WILL THEN LIFT UP INTO ERN CANADA.  


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

MUSHER