Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center

 
 

 

Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
   Satellite Images
   National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Accomplishments
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
 
Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0914Z Nov 18, 2017)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
414 AM EST SAT NOV 18 2017

VALID 12Z SAT NOV 18 2017 - 12Z TUE NOV 21 2017


DAYS 1-3...

...GREAT LAKES/NORTHEAST...

LOW PRESSURE OVER THE MID MS VALLEY SAT MORNING WILL CONTINUE TO
DEEPEN AND TRACK TO THE NORTHEAST ACROSS THE OH VALLEY LATER IN
THE DAY AS A WELL-DEFINED SHORTWAVE EMERGING FROM THE ROCKIES
MOVES ACROSS THE CENTRAL U.S.  THIS SHORTWAVE IS EXPECTED TO MOVE
ACROSS THE MIDWEST...ASSUMING A NEGATIVE TILT AS IT LIFTS INTO THE
NORTHEAST SUN MORNING WITH A STRONG SURFACE CYCLONE TRACKING ALONG
THE ST LAWRENCE VALLEY. WARM LOW LEVEL TEMPS WILL SUPPORT MOSTLY
RAIN...HOWEVER THERE MAY BE ENOUGH SHALLOW LOW LEVEL COLD AIR TO
SUPPORT SOME FREEZING RAIN AND MINOR ICE ACCUMULATIONS AT THE
ONSET OF PRECIPITATION ACROSS NORTHERN MAINE SUN MORNING BEFORE
CHANGING OVER TO RAIN.  COLD AIR ADVECTION ON THE BACKSIDE OF THE
SYSTEM MAY SUPPORT A CHANGE FROM RAIN TO SNOW ACROSS PORTIONS OF
NORTHERN NY AND NEW ENGLAND AS THE LOW TRACKS FURTHER NORTHEAST
INTO SOUTHERN CANADA SUN AFTERNOON-EVENING.  STRONG
WEST-NORTHWESTERLY FLOW IN THE WAKE OF THE SYSTEM...WITH EMBEDDED
SHORTWAVE ENERGY ALOFT...IS EXPECTED TO SUPPORT LAKE-EFFECT SNOW
SHOWERS...WITH SOME OF THE OVERNIGHT GUIDANCE SHOWING THE
POTENTIAL FOR SOME LOCALLY HEAVY ACCUMULATIONS SUN INTO EARLY MON.

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

HEAVY SNOWS ARE EXPECTED TO RETURN TO PORTIONS OF PACIFIC
NORTHWEST LATE SUN INTO EARLY MON AS A POSITIVELY-TILTED SHORTWAVE
TROUGH DROPS INTO THE REGION.  STRONG SOUTHWESTERLY INFLOW ALONG
THE ASSOCIATED FRONTAL BAND ALONG WITH FAVORABLE FORCING ALOFT IS
EXPECTED TO CONTRIBUTE TO HEAVY ACCUMULATIONS ALONG THE NORTHERN
CASCADES...WHERE WPC DAY 2 PROBABILITIES (ENDING 12 UTC MON) SHOW
A HIGH RISK FOR ACCUMULATIONS OF A FOOT OR MORE ACROSS THE
OROGRAPHICALLY FAVORED HIGHER PEAKS.  THIS SHORTWAVE IS EXPECTED
TO MOVE SOUTHEAST OVER THE TOP OF WHAT IS FORECAST TO BE A RAPIDLY
BUILDING RIDGE OVER THE WESTERN U.S.  THIS WILL SUPPORT SNOW
SHOWERS FURTHER SOUTH AND EAST ACROSS THE NORTHERN ROCKIES ON MON
INTO TUE.  HOWEVER...WITH SNOW LEVELS RISING...ANY HEAVY
ACCUMULATIONS WILL LIKELY BE CONFINED TO THE HIGHER
TERRAIN...MAINLY ABOVE 6000 FT IN THE CENTRAL IDAHO TO THE WESTERN
WYOMING RANGES.

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

PEREIRA