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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0907Z Feb 23, 2018)
 
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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
407 AM EST FRI FEB 23 2018

VALID 12Z FRI FEB 23 2018 - 12Z MON FEB 26 2018


...CENTRAL PLAINS TO UPPER MS VALLEY...

A POTENTIAL MAJOR WINTER STORM APPEARS MORE AND MORE LIKELY ACROSS
PARTS OF THE MIDWEST LATE FRI THROUGH EARLY SUN. A POWERFUL AND
DYNAMIC SHORT WAVE TROUGH IS TRACKING THROUGH CENTRAL/SOUTHERN CA
INTO SOUTHERN NV EARLY THIS MORNING. THIS IMPOSING FEATURE WILL
SLIDE THROUGH THE FOUR CORNERS REGION TO THE CENTRAL ROCKIES/FRONT
RANGE ON FRI. BROAD SWRLY UPPER DI-FLUENT FLOW AHEAD OF THE MAIN
SHORT WAVE TROUGH SHOULD YIELD HEAVY SNOW ACROSS PARTS OF THE FOUR
CORNERS TERRAIN BEFORE BEGINNING TO SPREAD OUT INTO THE CENTRAL
HIGH PLAINS. THIS IS WHEN THE SHORT WAVE EJECTS OUT INTO THE
PLAINS ON SAT TO INDUCE A LOW NEAR THE OK PANHANDLE AND TRACKS
TOWARD NORTHERN MO OR EAST OF THE KC METRO AREA BY SAT EVENING
WITH THE LOW DEEPENING BY AOA 8MB. THE LOW THEN SHIFTS UP INTO THE
UP OF MI, WHILE DEEPENING BY ANOTHER 15 MB AND COMPLETE THE
CYCLOGENESIS. THE RESULTANT WILL BE A PLUME OF MOISTURE
FLOURISHING WITHIN THE PRIME SPOT FOR A HEALTHY DEFORMATION ZONE
AND COMMA HEAD. NOW THE GFS AND ECMWF HAVE VERY SIMILAR MASS
FIELDS BUT DIFFER ON QPF AND THE CONVECTIVE ACTIVITY NEAR THE MID
MS VALLEY AND UP THE OH RIVER COULD PROHIBIT AN ANOMALOUS SURGE OF
MOISTURE REACHING THE COLD SECTOR AND INTENSIFYING LOW. THE GFS
HAS DEFINITELY BACKED OFF QPF AMOUNTS OVER THE PAST 24 HRS. WPC
FOLLOWED WPC QPF WITH A 4 WAY BLEND OF THE 00Z GFS, 12Z/22 ECMWF,
12Z/22 ECMWF MEAN AND 00Z NAM PTYPES FOR AN AXIS OF DYNAMIC
COOLING SNOWS OF 4 TO 8 INCHES FROM NERN NE THROUGH NWRN IA AND
THROUGH SOUTH/EASTERN MN INTO NWRN WI, WITH LOCALLY HIGHER AMOUNTS
FROM SOUTH/SERN MN (INCLUDING THE MSP METRO AREA) THROUGH NWRN WI.

...INTERIOR NEW ENGLAND/NORTHEAST...

A THREE DAY WINDOW OF POTENTIAL ICING APPEARS POSSIBLE ACROSS
INTERIOR NEW ENGLAND AND NORTHEAST THROUGH THE UPCOMING WEEKEND. A
1040MB RIDGE OVER THE NERN PORTION OF THE COUNTRY WILL GIVE WAY TO
A DEVELOPING AREA OF LOW PRESSURE PROGRESSING FROM THE UPPER MS
VALLEY TO EASTERN CANADA. INCREASING MOISTURE CONTENT FROM THE OH
RIVER VALLEY WILL OVERRUN INTO THE ESTABLISHED COLD SECTOR FOR
POSSIBLE FREEZING RAIN ON FRI. AFTER THIS LOW CLEARS-OUT, ANOTHER
SURFACE RIDGE WILL BUILD OVERHEAD WITH ANOTHER SURGE OF MOISTURE
REACHING INTERIOR NEW ENGLAND FOR MORE FREEZING RAIN. FINALLY ON
SUN, THIS RIDGE ATTEMPTS TO HOLD ON, AS A POWERFUL SHORT WAVE BACK
NEAR THE UPPER MS VALLEY ALLOWS ANOTHER SURGE OF MOISTURE TO
OVERRUN INTO THE INTERIOR NORTHEAST. SOME SPOTS OVER THE THREE
DAYS MAY SEE ICE ACCUMULATIONS ADD UP TO A .25 INCH OR GREATER.

...WEST...

A SERIES OF POTENT SHORT WAVE TROUGHS WILL DIG SOUTH AND EAST
TOWARD THE PAC NW OVER THE NEXT THREE DAYS. THESE VERY COLD
SYSTEMS ALOFT MAY YIELD SNOW TO LOWER ELEVATIONS WEST OF THE
CASCADES. THE FIRST SYSTEM ARRIVES LATE FRI INTO EARLY SAT,
FOLLOWED BY ANOTHER ACTIVE UPPER JET LATE SAT INTO SUN AND FINALLY
SUN, ADDITIONAL HEIGHT FALLS ARE ANTICIPATED TO DROP DOWN THE
WESTERN SEABOARD. OVERALL THE GUIDANCE HIGHLIGHTS THE CASCADES OF
WA/OR GETTING CRUSHED OVER THE THREE DAYS, WITH SNOW AS MENTIONED
EARLIER POSSIBLE WEST OF THE CASCADES INTO THE LOWER LYING AREAS
AND COASTAL RANGES ALONG ACROSS THE NORTHERN INTER-MOUNTAIN WEST.

MUSHER