Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Text Only | 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
000
FOUS11 KWBC 230756
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EST SUN NOV 23 2014

VALID 12Z SUN NOV 23 2014 - 12Z WED NOV 26 2014


PACIFIC NORTHWEST/GREAT BASIN/NORTHERN AND CENTRAL ROCKIES...

PASSAGE OF THE SHORTWAVE TROUGH PRESENTLY OVER THE PACIFIC
NORTHWEST AND GRADUAL DEVELOPMENT OF A DEEP BAROCLINIC ZONE ALONG
THE U.S./CANADA BORDER BY LATE TUESDAY AND TUESDAY NIGHT THAT THE
ATMOSPHERE ULTIMATELY RESPONDS TO WILL PROMOTE CONTINUED
OROGRAPHIC-FOCUSED SNOWS FROM THE WINDWARD SLOPES OF THE
WASHINGTON CASCADES INTO THE BITTERROOTS...TETONS...AND MOST OF
THE REMAINDER OF THE NORTHERN AND THE CENTRAL ROCKIES THROUGH
EARLY WEDNESDAY.  THE MOST LIKELY AREAS FOR HEAVY SNOW SHOULD
SHIFT SLOWLY EASTWARD THROUGH THE PERIOD AS THE LONGWAVE RIDGE
ALONG THE WEST COAST SLOWLY AMPLIFIES...WITH WESTERN MONTANA THE
MOST LIKELY AREA FOR HEAVY SNOW BY TUESDAY AND TUESDAY NIGHT.  THE
PROBABILITIES OF HEAVY SNOW ARE CENTERED AROUND THE 12Z ECMWF
ENSEMBLE MEAN AS WELL AS PORTIONS OF THE 12Z OPERATIONAL ECMWF AND
12Z UKMET.

NORTHERN PLAINS AND UPPER MIDWEST...

MODELS CONTINUE TO SHOW ENOUGH VARIABILITY IN THE PRECISE
PATH...INTENSITY...AND VERTICAL STRUCTURE OF THE LOW REACHING LAKE
MICHIGAN BY EARLY MONDAY TO WARRANT A EMPHASIS ON CONTINUITY AND
THE ENSEMBLE MEANS.  THE 12Z ECMWF ENSEMBLE MEAN HAS BEEN VERY
CONSISTENT WITH MANY DETERMINISTIC SOLUTIONS SLOWLY TRENDING
TOWARD IT...SO THIS FORECAST EMPHASIZES ITS SOLUTION MOST...WITH
SOME SUPPORT PROVIDED BY THE 12Z UKMET.  THE 00Z NAM AND 00Z GFS
WERE MORE WESTWARD AND FASTER THAN THE MEANS
RESPECTIVELY...ALTHOUGH THE GFS IS CLOSER THAN IN PREVIOUS RUNS
AND SO IS SOMEWHAT USABLE.  EXPECT AREAS FROM NORTHWEST WISCONSIN
INTO THE UPPER PENINSULA OF MICHIGAN TO RECEIVE THE MAJORITY OF
SNOW ON THE WESTERN PERIPHERY OF THE LOW....WITH THE PROBABILITIES
CORRESPONDINGLY THE HIGHEST IN THESE AREAS FOR TODAY THROUGH
MONDAY AND MONDAY NIGHT.  LAKE ENHANCEMENT AND LAKE EFFECT ARE
ALSO EXPECTED TO BOOST SNOWFALL TOTALS DOWNWIND OF LAKES SUPERIOR
AND MICHIGAN...ALTHOUGH NOT AS MUCH AS WITH RECENT EVENTS DUE TO
LESS FAVORABLE CONDITIONS.  A SECONDARY AXIS OF LIGHT SNOW WITH
SLIGHT PROBABILITIES OF 4 INCHES EXTENDS ACROSS NORTHEASTERN NORTH
DAKOTA FOR LATE TUESDAY AS THE NEXT LOW CROSSES THE REGION...WITH
THE 12Z ECMWF ENSEMBLE MEAN AND 21Z SREF MEAN GIVEN THE GREATEST
WEIGHTING...WITH MINOR CONTRIBUTIONS FROM THE 12Z ECMWF AND 12Z
UKMET.

EASTERN GREAT LAKES...

LOW AND MODERATE PROBABILITIES OF 4 INCHES OF SNOW ARE DEPICTED
DOWNWIND OF LAKES ERIE AND ONTARIO FOR TUESDAY INTO TUESDAY NIGHT
AS SLIGHTLY FAVORABLE CONDITIONS FOR LAKE EFFECT DEVELOP.  USED A
COMBINATION OF THE 00Z NAM AND 21Z SREF MEAN TO DERIVE THE
DETERMINISTIC SNOWFALL AMOUNTS WHICH ALSO FORMED THE BASIS FOR THE
SNOW PROBABILITIES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT DAYS
1-3.

JAMES




$$





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