Quantitative Precipitation Forecast
Issued by NWS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
000
FOUS11 KWBC 012134
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
433 PM EST MON FEB 01 2016

VALID 00Z TUE FEB 02 2016 - 00Z FRI FEB 05 2016


DAYS 1 THROUGH 3...

...GREAT BASIN/ROCKIES/CENTRAL PLAINS/UPPER MS VALLEY/UPPER GREAT
LAKES...

A MAJOR SNOWSTORM WAS TAKING SHAPE OVER THE ROCKIES AND IT IS
EXPECTED TO PROGRESS OUT OF THE ROCKIES ONTO THE CENTRAL PLAINS
AND GREAT LAKES THRU TUE.

AS OF EARLY THIS AFTERNOON...SATELLITE IMAGERY SHOWED A COMPLEX
AREA OF LOW PRESSURE WITH MULTIPLE SWIRLS MAKING ITS WAY ACROSS
PARTS OF UT/AZ ALONG WITH COOLING CLOUD TOPS IN A HIGHLY DIFLUENT
REGION OVER PARTS OF CO/NM.

AS THIS AREA MOVES EAST TONIGHT....IT WILL BECOME CONSOLIDATED
WITH CYCLOGENESIS TAKING PLACE OVER SOUTHERN/SOUTHEAST COLORADO.
THIS SHOULD BRING HEAVY UPSLOPE SNOW TO THE COLORADO FRONT
RANGE...WITH SNOW EXTENDING NORTH INTO THE FOOTHILLS AND FRONT
RANGE OF SOUTHEAST WY WITH SLIGHTLY LOWER AMOUNTS.  IN
ADDITION...STRONG STRONG LIFT WITHIN THE LEFT EXIT REGION OF AN
UPPER JET...COMBINED WITH ANOMALOUS MOISTURE AND STEEPENING LAPSE
RATES SHOULD LEAD TO HEAVY ACCUMULATIONS OVER THE WINDWARD SIDE OF
THE TERRAIN ACROSS THE REGION.

ON THE PLAINS...LOW-MID LEVEL FRONTOGENESIS AND 850-700 MB
WARM/MOIST ADVECTION RESULT IN HEAVY SNOWS TO THE NORTH AND WEST
OF THE SURFACE-850 MB LOW WHILE IT LIFTS NORTHEASTWARD THROUGH THE
CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY...AND THEN INTO THE
UPPER GREAT LAKES REGION TUE.  ALONG THE 850 MB LOW TRACK THE
MODELS FCST TEMPERATURES TO RISE ABOVE FREEZING...WHICH PRESENTS
AN ADDED CHALLANGE FOR SNOWFALL AMOUNTS.  AS MENTIONED
EARLIER...ANY ADDITIONAL NUDGES IN THE 850 MB LOW TRACK WILL BE
CRITICAL TO DISCERNING WHERE ACCUMULATIONS TAPER GOING SOUTHEAST
OF THE SNOW BAND.

THE MULTI-MODEL AGREEMENT ON AN INCH TO INCH AND A HALF LIQUID
EQUIVALENT QPF IN THE COLD SECTOR SUPPORTS POTENTIAL FOR 12 TO
PERHAPS AS MUCH AS 18 INCHES OF SNOW IN THE AREA OF HEAVIEST SNOW
IN THE CENTRAL PLAINS...CENTERED ON EASTERN NEBRASKA.  AMOUNTS
TAPER A BIT IN THE UPPER MS VALLEY TO UPPER LAKES AS THE LOW
STARTS MOVING FASTER AS IT EJECTS ACROSS THESE AREAS.

THE 12Z MODEL PRODUCTION CYCLE TENDED TO BRING THE SYSTEM A BIT
NORTH OF ITS PREVIOUS TRACK.  THE GFS HAD THAT IDEA BUT IT SLOWED
DOWN THE FORWARD SPEED OF THE SYSTEM AS A RESULT OF IT PUTTING
MORE EMPASIS ON A SFC LOW WHICH OCCLUDES OVER NE/MO WHILE OTHER
MODELS MOVED THE SYSTEM ALONG MORE STEADILY.  AS A RESULT...WE
GAVE THE GFS LESS CREDENCE.  THE GEFS AND ECMWF ENSEMBLE MEANS
CLUSTER WELL WITH THE NON GFS LOW TRACKS...SO THESE SOLUTIONS WERE
GIVEN MORE WEIGHTING FOR QPF AND TEMPERATURE PROFILES.


...PACIFIC NORTHWEST/NORTHERN ROCKIES...

LIGHT SNOW SHOWERS SHOULD CONTINUE OVER THE HIGHER ELEVATIONS OF
THE PACIFIC NORTHWEST AND NORTHERN ROCKIES THE NEXT FEW
DAYS...WITH AN UPTICK IN COVERAGE ON DAY 3 AS THE NEXT UPPER
TROUGH APPROACHES THE REGION.  THE MODELS STILL DIFFER ON THE
AMPLITUDE OF THE TROUGH MORE THAN USUAL WITH THE LOWER AMPLITUDE
FORECASTS THEN MOVING THE WAVE INLAND FASTER AND PRODUCING LIGHTER
ACCUMULATIONS.  WPC FORECAST WAS FOR A FEW INCHES OF SNOW IN THE
CASCADES ON DAY 2 FOLLOWED BY ANOTHER 6 INCHES ON DAY 3...WITH
LOCALLY HIGHER AMOUNTS POSSIBLE IN FAVORED TERRAIN AND LESSER
AMOUNTS IN REGIONS OF SHADOWING BY THE MOUNTAINS.  SNOWFALL IS
THEN EXPECTED TO MAKE IT INTO THE NORTHERN ROCKIES AND AS FAR
SOUTH AS NORTHEAST NV.


...NORTHERN MAINE...

THE MODELS SHOW LOW PRESSURE MOVING WEST OF MAINE ACROSS
QUEBEC...PRODUCING A WARM ADVECTION PATTERN ACROSS THE STATE.
INITIALS SOUNDINGS ARE WELL BELOW FREEZING SO A PERIOD OF SNOW IS
LIKELY.  THE SURGE OF WARM AIR DOES RAISE TEMPERATURES ALOFT ABOVE
FREEZING SO A TRANSITION TO RAIN IS POSSIBLE...OR THE PRECIP COULD
END AND MOVE NORTH ACROSS THE BORDER AS THE WARM FRONT PROGRESSES
FURTHER NORTH OUT OF THE STATE.

...LOWER MICHIGAN...
STILL THINK THAT SOME LIGHT ICING IS POSSIBLE ACROSS PARTS OF
NORTH CENTRAL TO NORTHERN LOWER MICHIGAN...ALTHOUGH THE
PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT DAYS 1
AND 3. LIGHT ICING IS EXPECTED IN PARTS OF NORTH CENTRAL TO
NORTHERN LOWER MI ON DAY 2 WITHIN THE MID LEVEL WARM ADVECTION
PATTERN AS TEMPERATURES ALOFT WARM ABV FREEZING ALOFT BEFORE THEY
DO AT THE SFC...RESULTING IN A TRANSITION TO SLEET AND SOME LIGHT
FREEZING RAIN BEFORE ASCENT DEPARTS OUT OF THE AREA.  THE THREAT
IS LOW DUE TO LIMITED DURATION FOLLOWING MULTIPLE PRECIP TYPES IN
THE AREA.

BANN


$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.