PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
407 AM EST MON FEB 06 2012
 
VALID 12Z MON FEB 06 2012 - 12Z THU FEB 09 2012
 
...DAY 1 (12Z MON TO 12Z TUE)...

...COLORADO/FAR NRN NEW MEXICO ROCKIES...

A RARE QUIET STRETCH WINTER WEATHER WISE ACROSS THE CONUS. THE
HIGHLY-AMPLIFIED UPPER PATTERN OVER THE WRN CONUS WILL PERSIST
TODAY INTO TUE...HOWEVER THE SRN PERIPHERY OF THE NEXT NRN STREAM
SHORTWAVE TROUGH (CURRENTLY DROPPING THROUGH ALBERTA/SASKATCHEWAN
EARLY THIS AM) WILL FINALLY PICK UP THE STUBBORN CLOSED LOW
CURRENTLY OVER THE EAST-CENTRAL GREAT BASIN. THE MID LEVEL TROUGH
OPENS AS IT GETS PUSHED INTO THE CENTRAL PLAINS BY EARLY
TUE...HOWEVER LINGERING WEAK QS FORCING (DPVA/UPPER AGEOS
DIVERGENCE) AND ASSCD MOIST...UPSLOPE SOUTHERLY FLOW WILL BRING A
SWATH OF LIGHT SNOWFALL OVER PORTIONS OF THE CENTRAL
ROCKIES...ESPECIALLY IN CEN/SW COLORADO. THE THE PROBABILITY OF
SIGNIFICANT SNOWFALL (8 OR MORE INCHES) WILL BE LESS THAN 10
PERCENT ON DAY ONE. HOWEVER...THERE WILL BE A MODERATE RISK FOR AT
LEAST 4 INCHES ACROSS THE SAN JUAN
RANGE IN SW CO. 

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...DAY 2 (12Z TUE TO 12Z WED)...

...SIERRA NEVADA...

A HIGHLY-AMPLIFIED...NARROW MID/UPPER LEVEL TROUGH APPROACHES THE
WEST COAST ON TUE...EVENTUALLY LEADING TO A CLOSED MID LEVEL LOW
OFF THE SOCAL COAST TUE NIGHT/WED MORNING. WHILE THE MODELS
CONTINUE TO DIFFER WITH THE DETAILS IN TERMS OF THE LOCATION AND
TIMING OF THE DEVELOPING MID LEVEL CIRCULATION...THE RAMIFICATIONS
ARE RATHER INSIGNIFICANT IN TERMS OF THE SNOWFALL POTENTIAL OVER
THE HIGH SIERRAS. INCREASING DPVA/UPPER AGEOS DIVERGENCE AND
DIFFLUENCE ENHANCED FROM THE LEFT EXIT REGION OF AN APPROACHING
UPPER JET STREAK (~120 KTS AT 300 MB) WOULD FAVOR A WIDESPREAD
AREA OF MOD TO HEAVY RAINFALL ACROSS THE CA CSTL RANGES (SEE
QPFPFD FOR FURTHER DETAILS). GIVEN THE ORIENTATION OF THE
TROUGH...THE INCREASING E/SE OR OFFSHORE COMPONENT AT LOWER LEVELS
WILL LEAD TO A SIGNIFICANT DROP OFF IN THE QPF OVER THE
SIERRAS...WHILE ALSO FAVORING THE ERN SLOPES THIS GO AROUND GIVEN
THE UPSLOPE COMPONENT. SNOW LEVELS WILL BE ON THE RISE GIVEN THE
PRE-FRONTAL WAA (ABOVE 5-5.5 KFT)...AND AS SUCH PROBABILITIES FOR
8 OR MORE INCHES WILL BE LESS THAN 10 PERCENT. HOWEVER...AT LEAST
MODERATE PROBS ARE ANTICIPATED ABOVE 7500 FT.

...DAY 3 (12Z WED TO 12Z THU)...

THE PROBABILITY OF HEAVY SNOWFALL AND/OR SIGNIFICANT ICING ACROSS
THE CONUS WILL BE
LESS THAN 10 PERCENT ACROSS THE CONUS.

HURLEY
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