THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


PROBABILISTIC HEAVY SNOW AND ICE DISCUSSION




PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
506 PM EDT WED APR 16 2014

VALID 00Z THU APR 17 2014 - 00Z SUN APR 20 2014


DAYS 1 - 3...

...UPPER MISSISSIPPI VALLEY/GREAT LAKES...

AN INTENSE HEAVY SNOW DEFORMATION AXIS IS EXPECTED TO LINGER FOR
THE NEXT 12 TO 18 HRS FROM EAST CENTRAL MN THROUGH NRN WI INTO THE
UP OF MI... BEFORE THE INTENSE SHORT WAVE TROUGH LIFTS INTO
ONTARIO. THE COMBINATION OF A COUPLED UPPER JET STREAK ZONE AND
STRONG 850-650MB FRONTOGENETIC FORCING SHOULD BE IDEAL FOR A
THRIVING COMMA HEAD DESPITE THE INTENSE SURFACE WAVE GRADUALLY
WEAKENING. THE 12Z GUIDANCE IS IN SOLID SYNOPTIC SHAPE ON THE
SYSTEM AND APPEAR TO HAVE INCREASED THE QPF AMOUNTS OVER THE NEXT
24 HRS. THUS WPC STUCK WITH HEAVY SNOW PROBS OF 4 TO 12 INCHES
WITH THE HEAVIEST AMOUNTS OCCURRING ACROSS NRN WI INTO THE WRN UP
OF MI.

ON THE HEELS OF THIS LATE SPRING STORM SYSTEM... ANOTHER
MARITIME/POLAR SHORT WAVE TROUGH WILL TRACK ALONG THE US/CANADIAN
AND ARRIVE INTO THE UPPER MIDWEST/MS VALLEY LATE FRI INTO SAT.
THIS SYSTEM ACCORDING TO THE GLOBAL MODELS WILL TRACK MUCH FARTHER
NORTH... THUS THE SIGNIFICANT LACK OF COLD AIR PRESENT AND LIKELY
JUST WARM ADVECTION/ISENTROPIC PRECIP OUT IN ADVANCE OF THE SYSTEM
STARTING OFF AS WINTRY MIX FOR VERY LOW PROBS.


...CENTRAL/SOUTHERN ROCKIES...

A SEPARATE SHORT WAVE CROSSING THE SOUTHERN ROCKIES... SOMEWHAT
ASSOCIATED WITH THE SHORT WAVE UP OVER THE UPPER MS VALLEY... WILL
PROVIDE THE ASCENT FOR SNOWFALL ACROSS THE CENTRAL/SOUTHERN
ROCKIES LATE WED INTO THURS. THE MODEL CONSENSUS FOR THE HEAVIEST
SNOW OCCURRING ACROSS THE EASTERN SLOPES OF THE CENTRAL/SOUTHERN
COLORADO ROCKIES TO THE SANGRE DE CRISTO RANGE.


...NORTHERN ROCKIES...

ANOTHER PAC SHORT WAVE TROUGH WILL ARRIVE INTO THE PAC NW LATE
THURS BEFORE MOVING INTO THE NRN ROCKIES FOR FRI. DECENT PAC
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM WITH LOWERING OF UPPER
HEIGHTS SHOULD RESULT IN LOCALLY HEAVY OROGRAPHIC SNOWFALL ACROSS
THE NRN ROCKIES/BITTERROOTS. WPC FOLLOWED A BLEND OF THE GFS/ECMWF
FOR 4 INCH HEAVY SNOW PROBS.


THE PROBABILITY FOR SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

MUSHER






Last Updated: 506 PM EDT WED APR 16 2014