Quantitative Precipitation Forecast
Issued by NWS

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842
FOUS11 KWBC 262045
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
345 PM EST SUN FEB 26 2017

VALID 00Z MON FEB 27 2017 - 00Z THU MAR 02 2017

DAYS 1 THROUGH 3...

...WEST...

A RATHER UNSETTLED FORECAST PERIOD FOR THE WESTERN PORTION OF THE
COUNTRY... AS WIDESPREAD HEAVY SNOWFALL IS ANTICIPATED. MULTIPLE
SHORT WAVES EMBEDDED WITHIN WRLY FLOW ALOFT AND A LARGE SCALE
UPPER TROUGH WILL SWEEP THROUGH THE WEST.

ON MON...A STRONG SHORT WAVE ARRIVING OVER THE NW WILL PROCEED
DOWNSTREAM BUT SHEAR OUT INTO THE NRN ROCKIES/INTER-MOUNTAIN WEST.
THE KEY HERE THOUGH IS THE STEADY LOWERING OF UPPER HEIGHTS.
MEANWHILE THE ASSOCIATED THERMAL ZONE SLICING THROUGH THE
INTER-MOUNTAIN WEST AND DOWN THE WEST COAST WILL BEGIN TO TAP INTO
A FEED OF SUBTROPICAL MOISTURE TRANSPORT. EXPECT WIDESPREAD SNOW
OVER MUCH OF THE WEST WITH THE HEAVIEST SNOWFALL TOTALS ACROSS THE
NRN WASATCH/UINTAS OF UT.

THEN ON TUES... THE ENTIRE AMPLIFIED UPPER TROUGH BEGINS TO SHIFT
DOWNSTREAM AND A SLIGHT NEG TILT NEAR THE BASE OR OVER THE FOUR
CORNERS REGION SHOULD YIELD ENHANCED UPPER DIFLUENT FLOW AND
FAVORABLE OROGRAPHICS FOR IMPRESSIVE ACCUMULATIONS FROM THE SRN
WASATCH/ENTIRE MOGOLLON RIM INTO THE CO ROCKIES. ALSO... STEADY
ONSHORE FLOW INTO THE PAC NW/NRN ROCKIES SHOULD CONTINUE TO
PRODUCE SNOW FROM THE COASTAL RANGES/OLYMPICS INTO THE CASCADES
AND DOWNSTREAM INTO THE NRN ROCKIES/BITTERROOTS/BLUE
MTNS/SAWTOOTH.

FINALLY ON WED... UPPER HEIGHT SHOULD STEADILY INCREASE ACROSS THE
WEST BUT ENOUGH ONSHORE FLOW INTO THE PAC NW SHOULD CONTINUE TO
PRODUCE HEAVY SNOWFALL FROM TH CASCADES INTO THE NRN ROCKIES.

OVERALL THE GUIDANCE IS IN REALLY GOOD AGREEMENT WITH MASS FIELDS
AND QPF EACH DAY THAT WPC REALLY FAVORED A GLOBAL BLEND OF THE
GFS/ECMWF.


...UPPER MS VALLEY/UPPER GREAT LAKES...

THE DYNAMIC UPPER TROUGH ARRIVING INTO THE PAC NW TODAY WILL
SHEAR-OUT THROUGH THE INTER-MOUNTAIN WEST ON MON AND EVENTUALLY
SOME VORTICITY WILL POTENTIALLY STREAK ACROSS THE UPPER MIDWEST ON
TUES. THE GFS AND ECMWF BOTH INDICATE THIS SMALL SCALE SYSTEM WITH
DEEPENING SURFACE LOW BUT DIFFER ON THE AMOUNT OF LOW LEVEL
MOISTURE CONTENT REACHING THE COLD SECTOR. THE GFS IS BOLDER THAN
THE ECMWF WITH THE NAM CONEST BEGIN IN BETWEEN AND WPC FOLLOWED A
COMPROMISE OF THE DATA FOR A STREAK OF LOCALLY HEAVY SNOWFALL FROM
WRN/NWRN SD TO CENTRAL/NERN MN AND EXTREME NRN/WESTERN UP OF MI.

THEN ON WED... THE MAIN WESTERN TROUGH AXIS EMERGES OUT INTO THE
PLAINS AND PARTIALLY CATCHES UP TO TUES SYSTEM. THIS WILL ALLOW A
SECONDARY WAVE OR LOW TO FORM NEAR LAKE MI AND PERHAPS ANOTHER
STRETCH OF HEAVY SNOW. THIS TIME AROUND... THE ECMWF IS MUCH MORE
AGGRESSIVE TO PRODUCE HEAVY SNOW FROM NRN IL INTO LOWER MI...
WHILE THE GFS FOCUSES FARTHER NORTH FROM NRN WI INTO THE UP OF MI.
OBVIOUSLY SOME SPREAD AND WPC COMPROMISED BY CARRYING BOTH AREAS
OF SNOWFALL BUT WENT EXTREMELY CONSERVATIVE.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


MUSHER



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