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
  GOES-East Satellite
  GOES-West Satellite
  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 2039Z Apr 28, 2018)
 
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
439 PM EDT SAT APR 28 2018

VALID 00Z SUN APR 29 2018 - 00Z WED MAY 02 2018

RANGES OF PACIFIC NORTHWEST TO THE NORTHERN ROCKIES

HEAVY SNOW IS EXPECTED TO DEVELOP OVER THE RANGES NEAR THE
SOUTHWEST MT/ID BORDER AND ACROSS THE WIND RIVER/ABSAROKA/BIGHORN
MOUNTAINS OF WY. THERE IS POTENTIAL FOR 1-2 FEET IN THE MOUNTAINS
OF WESTERN AND NORTHERN WY.

THE CLOSED UPPER LEVEL LOW OVER THE PACIFIC NORTHWEST PROGRESSES
SLOWLY EASTWARD.  PRECIP AMOUNTS ARE ON THE ORDER OF A QUARTER TO
LOCALLY HALF AN INCH IN THE RANGES OF WESTERN OR TO NORTHERN CA
AND SOUTHERN ID...SO NY HEAVY SOW WILL BE ISOLATED.

AMOUNTS PICK UP SUNDAY NIGHT AS AN UPPER TROUGH ROTATING
UNDERNEATH THE CLOSED LOW CROSSES FROM NV THROUGH NORTHERN UT AND
INTO ADJACENT ID AND WESTERN WY.  ENHANCED UPPER DIVERGENCE IN
ADVANCE OF THE APPROACHING WAVE FOCUSES HEAVY SNOW AT HIGHER
ELEVATIONS OF THE UT UINTAS INTO THE MOUNTAINS OF WESTERN WY. THE
WIND RIVER MOUNTAINS ARE A FOCUS AS A FEW MODELS INDICATE A LARGE
300 MB DIVERGENCE/700 MB CONVERGENCE MAXIMA SUN ON MONDAY.

THE NAM/GFS SHOW THE 700 MB WAVE AND POTENTIAL FOR A CLOSED LOW TO
DEVELOP OVER WY AS THE FOCUS FOR MODERATE TO HEAVY SNOW CONTINUING
INTO SUNDAY NIGHT BEFORE THE WAVE DEPARTS AND COLD FRONT MOVES
ACROSS THE REGION...LEADING TO A DECREASE IN SNOW COVERAGE AND
INTENSITY ON TUE. SLIGHT TIMING DIFFERENCES REMAIN WITH THE WAVE
AS THE NAM PRODUCES MORE SNOW THAN THE GFS/GEFS/ECMWF/UKMET
FORECASTS. HIGHER AMOUNTS IN THE BIGHORNS ARE EXPECTED WITH A
LONGER DURATION SNOW. 

THE MODELS WERE IN GOOD AGREEMENT ON THE MASS FIELDS WITH THE GFS
INDICATING HIGHER QPF MAXIMA THAT WERE TEMPERED WITH THE MORE
CONSISTENT GEFS MEMBERS...ALONG WITH THE NAM/UKMET/ECMWF QPF AND
TEMPERATURE PROFILES.


NORTHEAST U.S.

A CLOSED LOW IS FORECAST TO DEVELOP ALOFT TONIGHT OVER NORTHERN
NEW YORK AND MOVE SLOWLY EAST
INTO VT AND NH SUNDAY.  AS THE LOW MOVES EAST, FALLING HEIGHTS AND
LOWERING FREEZING LEVELS WILL ALLOW PRECIPITATION TO CHANGE OVER
TO SNOW FOR THE NEW YORK ADIRONDACK MOUNTAINS, AND PROBABLY FOR
THE CATSKILL MOUNTAINS AS WELL SUNDAY NIGHT.  A FEW INCHES OF
ACCUMULATION ARE LIKELY SUNDAY INTO MONDAY IN THE ADIRONDACKS AS
POST-FRONTAL NORTHWEST WINDS PROVIDE UPSLOPE FLOW OVER WINDWARD
FACING TERRAIN.  DECENT AGREEMENT ON THE TIMING OF THE MID-LEVEL
LOW JUSTIFIED A BLEND OF THE ECMWF/GFS/NAM FOR THE THERMAL
PROFILES AND QPF.  THE LOW REFORMS OFF THE COAST LATER MON...WITH
WANING PRECIPITATION LOWERING THE SNOW THREAT. 

THE PROBABILITY OF ICING GREATER THAN 0.25 INCHES IS LESS THAN 10
PERCENT FOR DAY 1 THROUGH 3.

PETERSEN