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
   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.
 
Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0700Z Dec 09, 2019)
 
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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Mon Dec 09 2019

Valid 12Z Thu Dec 12 2019 - 12Z Mon Dec 16 2019

...Heavy Southeast Rains to lift northward over a Wintry/Cold Air
Dammed East...
...Wet flow from the Pacific Northwest to the Snowy North-Central
Great Basin/Rockies...

...Pattern Overview and Guidance/Predictability Assessment...

The cold Hudson Bay mean upper vortex will linger this week. Flow
underneath over the lower 48 will become less amplified, but
remain quite active and unsettled/stormy this week as a long
series of northern and southern stream systems traverse overall
mean cyclonic flow.

The WPC medium range product suite was mainly derived from a blend
of reasonably compatable GEFS/ECMWF ensemble means. This is amid
rapidly growing forecast spread that includes significant system
and stream phasing uncertainties despite a similar larger scale
pattern evolution. This maintains good WPC continuity vs more
run-run inconsistent model solutions.


...Weather Highlights/Threats...

Models still offer varied low scenarios from the Gulf of Mexico to
the Southeast then up the Eastern Seaboard into next weekend.
Forecast spread has been considerable, especially with recent
outlier GFS runs, but seems to trending a bit better with the 00
UTC guidance with respect to the timing/stream phasing,
cyclogensis potential and eventual system tracks. This pattern
seems likley to focus moisture and lift to produce a risk of heavy
rainfall across the Southeast. Subsequent system lift up through
the East Coast and interaction with a slow to recede lower
atmospheric cold air damming offers an interior snow/ice threat to
monitor. As is often the case, the degree of phasing/interaction
between the two initially separate streams and baroclinic
zone/coastal setup will be determining factors of eventual
evolution and any potential for any deeper coastal storm
developments and threats.

Out West, the pattern will become wet across the Pacific Northwest
into later this week as Pacific shortwave energies/height falls
punch onshore. Moderate to heavier snows will develop with system
progressions inland, especially for favored terrain of the
north-central Great Basin/Rockies later week through the weekend.

Schichtel


Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml