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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1900Z Sep 28, 2014)
 
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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
300 PM EDT SUN SEP 28 2014

VALID 00Z MON SEP 29 2014 - 00Z THU OCT 02 2014


DAYS 1 THROUGH 3...


...ROCKIES...

A CLOSED MID LEVEL LOW OVER THE GREAT BASIN ON DAY 1 OPENS UP INTO
A LONG WAVE TROUGH ACROSS THE ROCKIES ON DAY 2...WHICH TAKES ON A
NEGATIVE TILT OVER THE NORTHERN PLAINS AND SOUTHERN CENTRAL CANADA
BY DAY 3. DYNAMIC COOLING ASSOCIATED WITH THE MID LEVEL FEATURE
ALLOWS SNOW LEVELS TO DROP TO BETWEEN 8500 AND 9500 FEET ACROSS
THE ROCKIES DURING THE PERIOD.

MOISTURE DRAWN NORTH AHEAD OF THE CLOSED MID LEVEL LOW ON DAY 1
WILL PROVIDE ENOUGH QPF ACROSS THE ROCKIES IN CO AND THE UINTA
RANGE IN NORTHEAST UT FOR 1 OR 2 INCHES OF SNOWFALL ABOUT 8500
FEET. FURTHER NORTH...THE MOISTURE WRAPS TO THE WEST IN A WEAK
TROWAL...PROVIDING MOISTURE FOR AN INCH OR TWO OF SNOW ACROSS THE
GRAND TETONS ON WY. AS THE MID LEVEL SYSTEM CROSSES THE ROCKIES ON
DAY 2...MOISTURE AND LIFT BECOMES A BIT MORE DIFFUSE. SNOW LEVELS
REMAIN BETWEEN 8500 AND 9500 FEET...SO AN INCH OR TWO OF SNOW IS
EXPECTED ACROSS THE ROCKIES IN NORTH CENTRAL CO AND THE GRAND
TETONS ON WY.

WEAK UPSLOPE AND COLD AIR ADVECTION BEHIND THE MID LEVEL SYSTEM
ACROSS THE NORTHERN AND CENTRAL ROCKIES SHOULD MAKE THE MOST OF
THE AVAILABLE MOISTURE TO PRODUCE SNOWFALL. THE BEST COMBINATION
OF LIFT AND UPSLOPE FLOW SHOULD OCCUR ACROSS THE GRAND TETONS OF
WY...WHERE ENOUGH QPF IS EXPECTED TO PRODUCE AN AREA OF 2 TO 4
INCHES OF SNOWFALL...MAINLY ABOVE 8500 FEET. THE LATEST ECMWF
ENSEMBLE MEAN OUTPUT SHOWS A FEW MEMBERS WITH AS MUCH AS 8 INCHES
OF SNOWFALL IN THIS AREA. GIVEN THE LACK OF MOISTURE...SNOWFALL
AMOUNTS THIS HIGH SEEMS LIKE A LOW PROBABILITY EVENT AT BEST.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

HAYES