PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT WED APR 18 2018

VALID 00Z THU APR 19 2018 - 00Z SUN APR 22 2018


DAYS 1-3...

...GREAT BASIN/FOUR CORNERS AND CENTRAL TO SOUTHERN ROCKIES...

SNOW WILL RETURN TO PARTS OF THE WESTERN TERRAIN THURS THROUGH
SAT, AS A POTENT SHORT WAVE TROUGH ARRIVES FROM THE PAC. THE
GLOBAL MODELS AND ENSEMBLES CAPTURE THIS FEATURE ARRIVING 
INTO CENTRAL CA TOWARD THE DESERT SOUTHWEST ON THURS, THEN SLOWLY
PROGRESSING THROUGH THE FOUR CORNERS REGION INTO THE
CENTRAL/SOUTHERN PLAINS ON FRI/SAT. EXPECT A FEW INCHES OF
ELEVATED SNOWFALL ACROSS OR INTO NV AND THE SOUTHERN CA SIERRA ON
THURS, AS SNOW LEVELS GRADUALLY FALL WITH LOWER UPPER HEIGHTS. ON
FRI, A LARGE CLOSED 500 MB CIRCULATION WILL SPREAD DOWNSTREAM INTO
THE FOUR CORNERS REGION AND SHOULD YIELD SOME DYNAMICALLY DRIVEN
AND UPSLOPE SNOWFALL FROM THE SOUTHERN WASATCH INTO THE CO
ROCKIES, ESPECIALLY FOR THE SAN JUANS OF CO. THE CLOSED UPPER LOW
WILL EMERGE OUT OVER THE CENTRAL/SOUTHERN PLAINS ON SAT, WHILE
ENHANCED VERTICAL LIFT FROM THE PASSING MID-LEVEL LOW AND STEADY
UPSLOPE FLOW SHOULD CONTINUE TO PRODUCE HEAVY SNOW ACROSS CO
TERRAIN. PTYPE ISSUES BEGIN TO EMERGE ON SAT, AS A NUMBER OF
SOLUTIONS ALLOW SNOW TO SPREAD DOWN THE FOOTHILLS AND LEE SIDE OF
THE CENTRAL ROCKIES. WPC STAYED CLOSER TO THE SLOWER AND WARMER
ECMWF, WITH MASS FIELDS AND THERMALS. 


...GREAT LAKES AND NEW YORK/NEW ENGLAND...

A DYNAMIC SHORT WAVE TROUGH PRODUCING HEAVY SNOW OVER IA/MN AND WI
THIS AFTERNOON WILL TRANSITION DOWNSTREAM TO THE GREAT LAKES INTO
NEW ENGLAND. A CLOSED MID TO UPPER LOW ACCOMPANYING THIS COMPACT
SYSTEM WILL BEGIN TO INTERACT WITH A DIGGING NORTHERN STREAM JET.
THE PARENT LOW STREAKING INTO THE NORTHERN MID-ATL STATES WILL
WEAKEN, WHILE A TRIPLE POINT 
JUST OFFSHORE OF SOUTHERN NEW ENGLAND DEEPENS AND LIFTS INTO THE
CANADIAN MARITIMES. THIS SHOULD YIELD OVERALL A LIGHT STREAK OF
SNOW FROM NORTHERN IL/SOUTHERN WI THROUGH SOUTHERN LOWER
MI/NORTHERN IN/OH INTO NORTHERN PA/NY STATE AND NEW ENGLAND ON
THURS AND FRI. THE GUIDANCE SUGGESTS THE HEAVIEST SNOW POTENTIAL
ACROSS NORTHERN PA/SOUTHERN NY, NEAR THE STATE LINE ON THURS.   
 
THE PROBABILITY OF FREEZING RAIN GREATER THAN 0.25 INCHES IS LESS
THAN 10 PERCENT DAYS 1-3.

MUSHER