Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 200838
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
337 AM EST SAT JAN 20 2018

VALID 12Z SAT JAN 20 2018 - 12Z TUE JAN 23 2018


...FOUR CORNERS REGION/CENTRAL ROCKIES THROUGH CENTRAL
PLAINS/UPPER MS VALLEY INTO UPPER GREAT LAKES/NORTHERN NEW
ENGLAND...

A MULTI-DAY WINTER STORM WILL IMPACT A GOOD PORTION OF THE COUNTRY
OVER THE WEEKEND IN EARLY NEXT WEEK WITH HEAVY SNOWFALL AND
POSSIBLE TRANSITION ZONE OF FREEZING RAIN/SLEET.

A SWEEPING LARGE SCALE UPPER TROUGH ACROSS THE WEST WILL SEE
SOUTHERN STREAM UPPER DYNAMICS TAKE OVER ACROSS THE FOUR CORNERS
REGION ON SAT. THE AMPLIFICATION OF THE SOUTHERN STREAM AND
CLOSING OFF OF A 500MB LOW SHOULD ALLOW BETTER UPPER JET DYNAMICS
TO DEVELOP AND HEAVY SNOW TO FLOURISH ACROSS THE CENTRAL ROCKIES
AND POSSIBLY SPREAD OUT INTO THE CENTRAL HIGH PLAINS. HEAVY SNOW
IS ANTICIPATED ACROSS MUCH OF THE FOUR CORNERS REGION AND
ESPECIALLY THE TERRAIN, WITH THE HEAVIEST ACCUMULATIONS OCCURRING
ACROSS UT (WASATCH/UINTAS) INTO CO (SAN JUANS/ROCKIES) AND
SPREADING NORTH
INTO SOUTHERN/CENTRAL AND EASTERN WY. ITS THE LATTER WHERE SNOW
LEVELS WILL DROP TREMENDOUSLY DUE TO INTENSE UPSLOPE COMPONENT AND
SPREAD DOWN THE FOOTHILLS/FRONT RANGE OF THE WIND RIVER/BIG
HORNS/LARAMIE RANGES INTO THE HIGH PLAINS OF NWRN NE/SWRN SD.

THIS INTENSE STORM SYSTEM WILL EJECT AND DEEPEN OVER THE PLAINS/MS
VALLEY ON SUN. A LARGE CLOSED 500MB LOW WILL PROGRESS FROM
CO/NORTHERN NM INTO THE CENTRAL PLAINS, WHILE A DEVELOPING WAVE OF
SURFACE LOW PRESSURE WILL FORM NEAR SERN CO AND TRACK
NORTHEASTWARD TOWARD NERN KS/SERN NE/SWRN IA/NWRN MO. THIS SURFACE
LOW WILL GRADUALLY BEGIN CYCLOGENESIS AND CAPITALIZE ON INCREASING
MOISTURE CONTENT FROM THE GULF OF MEXICO TO ALLOW A FULL-FLEDGED
WINTER CYCLONE TO TAKE FORM. THE OVERNIGHT GUIDANCE SHOWS VERY
MINIMAL SPREAD WITH MASS FIELDS AND GOOD RUN TO RUN CONTINUITY, TO
PROVIDE CONFIDENCE IN WPC USING A ENSEMBLE APPROACH FOR CRITICAL
THERMALS/PTYPE. THE NWRN SECTION OF THE STORM SYSTEM WILL LIKELY
SEE A FLOURISHING DEFORMATION ZONE AND COMMA HEAD OF HEAVY SNOW
FROM NERN CO/NWRN KS AND WRN NE, ESPECIALLY THROUGH ALL OF CENTRAL
NE INTO SERN SD AND SPREADING INTO SOUTHERN MN. MEANWHILE, A
RATHER LARGE AND PROMINENT TRANSITION ZONE OF SLEET/FREEZING RAIN
APPEARS POSSIBLE FROM SOUTHERN WI INTO SERN MN, NORTHERN/WESTERN
IA AND SERN NE.

FINALLY ON MON... THE IMPRESSIVE WINTER STORM WILL CONTINUE TO
PRESS OFF TO THE NORTH AND EAST AND REACH LOWER MI BY TUES
MORNING. ONCE AGAIN WIDESPREAD HEAVY SNOWFALL AND EXTENSIVE ICING
WILL BE POSSIBLE. THE INCREASING CONFIDENCE IN WPC QPF AND A
MULTI-MODEL ENSEMBLE APPROACH WITH THERMALS SUGGESTS A VERY HEAVY
SNOWFALL AXIS FROM SERN MN THROUGH NORTH CENTRAL WI INTO THE UP OF
MI, WHICH MAY INCLUDE THE MSP/STP METRO AREA IN A HIGH END EVENT.
THE ICING COULD BE A CONSIDERABLE PROBLEM FROM NORTHERN LOWER MI
INTO SERN ONTARIO AND PARTS OF INTERIOR NEW ENGLAND, AS SHALLOW
COLD AIR MASS HAS DIFFICULTY ERODING.


...NORTHWEST INTO NORTHERN ROCKIES...

ON THE HEELS OF THIS INTENSIFYING SYSTEM OVER THE GREAT BASIN, A
CLOSED LOW BECOMING AN OPEN WAVE UPPER TROUGH WITH A RATHER
EXTENDED FETCH OF PAC MOISTURE WILL SWEEP INTO THE NWRN QUAD OF
THE
COUNTRY ON SUN. A POSSIBLE RIVER OF PAC MOISTURE TRANSPORT WILL
TRANSITION DOWN THE COAST FROM WA TO NORTHERN CA. AS A RESULT,
EXPECT HEAVY SNOWFALL TO OCCUR FROM THE WA CASCADES/OLYMPICS AND
OR CASCADES INTO THE NORTHERN CA MTNS AND NORTHERN SIERRA, WHILE
ACCUMULATIONS SHOULD ALSO STACK UP ACROSS THE OR BLUE MTNS AND ID
BITTERROOTS. THE ONSHORE FETCH INTO THE PAC NW SHOULD GRADUALLY
RELAX SOME ON MON BUT EXPECT SOME ADDITIONAL ACCUMULATIONS IN THE
FAVORED TERRAIN.

MUSHER


$$




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