Skip Navigation Links 
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
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
WPC Overview
   About the WPC
   WPC History
   Other Sites
Meteorological Calculators
Contact Us
   About Our Site 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 1836Z Sep 18, 2020)
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
236 PM EDT Fri Sep 18 2020

Valid 12Z Mon Sep 21 2020 - 12Z Fri Sep 25 2020

...Heavy rainfall threat for the Western and Northwest Gulf Coast
next week from TD Twenty-Two...

...Hurricane Teddy may pose a threat to the Canadian
Maritimes/parts of New England...


Upper ridging will build into the Rockies and toward the Plains
next week as troughing eases into the Pacific Northwest and
eventually the East. Confidence is increasing on twin tropical
systems having an affect on the Gulf (TD Twenty-Two) and perhaps
Maine (Hurricane Teddy) directly or indirectly. At the very least,
Teddy will churn up waves in the Atlantic into the medium range
period before it races into Eastern Canada as an extra Tropical

...Guidance/Predictability Assessment...

The latest 00z/06z deterministic guidance offered a reasonable
cluster to start the forecast period, and so a general model blend
was used for days 3-4. After this, the trend continues towards a
more amplified/deeper solution offshore New England which should
eventually encapsulate/absorb Hurricane Teddy around day 5 over
the Canadian Maritimes/Nova Scotia. To the south, what is
currently TD Twenty-Two is forecast to meander near/off the Texas
coast (as a TS or Hurricane) and then perhaps drift slowly
northward/northeastward by the end of the week. Especially after
mid-week, there remains significant spread with respect to timing
of this evolution (both with deterministic and ensembles), which
is tied to strength/path of ridging to the north initially holding
it in place before troughing from the northwest pulls it
northward. The ECMWF is the fastest of the deterministic solutions
with this scenario, while the CMC keeps the system out over the
Gulf waters. The latest forecast from the NHC appears to prefer a
consensus of the GFS/ECMWF deterministic solutions along with
ensemble means.

...Weather/Hazard Highlights...

Teddy will bring heavy rain and strong winds to at least Atlantic
Canada but perhaps back to Maine depending on its
track/interaction with the upper trough. High pressure initially
over New England on Monday will bring in much cooler temperatures
to the East with a slow moderation the rest of the week. Over the
Gulf, models show good agreement that TD Twenty-Two should bring
heavy rain and coastal flood concerns to at least parts of the
western to northwestern Gulf coast, regardless of the current
spread in eventual track. Over the Pacific Northwest, a cold front
will bring in rainfall to western WA/OR later in the week.
Elsewhere, temperatures will remain above to much above normal
throughout the period across the north-central U.S. and back into
the interior West. Highest anomalies will lie over the
Dakotas/Upper Midwest where 70s/80s will be common.


Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:

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