Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Sun Nov 07 2021
Valid 12Z Wed Nov 10 2021 - 12Z Sun Nov 14 2021
...Deep Midwest/Great Lakes Low mid-later week...
...Moisture Plume to focus into Pacific Northwest later week...
...Pattern Overview...
Positive height anomalies over northern Canada and off the
Southwest and Southeast U.S. will favor increased troughing over
the central-eastern U.S. in an amplifying pattern. This favors a
deepening central states cyclone that will lift northeastward
through the Midwest/Great Lakes into Canada. Milder air over much
of the Lower 48 will trend cooler with time as the trailing cold
front sweeps eastward bringing a widespread swath of enhanced but
overall progressive rains across the broad region along with some
wrap-back snows across the Dakotas/Upper Midwest/Great Lakes and
Northern Appalachians.
Upstream, there is a growing guidance signal bringing a long fetch
plume of Pacific moisture into the Pacific Northwest, especially
later this week. Favorable flow should focus heavy rains and
elevation snows over the Olympics and Cascades.
...Guidance/Predictability Assessment...
Guidance continues to illustrate a reasonably similar larger scale
pattern evolution, but with continued uncertainty in timing,
track, and strength of the embedded systems including run to run
continuity issues. Accordingly, the WPC medium range product suite
was primarily derived from a composite blend of the latest
GEFS/ECMWF ensemble means and the National Blend of Models that
seem reasonably compatible.
...Weather/Hazards Highlights...
Amplified upper troughing carving out over the central U.S. is
slated to be sandwiched between upper ridges over the West Coast
and East Coast amid the pattern transition. Cyclogenesis and
frontogenesis will act to favor an emerging lead organized
rainfall/convective pattern over the east-central U.S. Thursday as
theta-e advection increases. Surface wave development could act to
enhance rainfall along the front from the southern Appalachians
northward. Backside cold air flow by next Friday also suggests
potential for some snow over the Dakotas/Upper Midwest/Great
Lakes/northern Appalachians as moisture feeds back around the
developing/exiting main low. Temperatures will be near to above
normal early in the week, with possible record highs ahead of the
front, trending cooler by week's end especially into the
Southeast. Please see WPC links below for all the details in
graphical format.
Upstream, there is a growing guidance signal bringing a long fetch
plume of Pacific moisture into the Pacific Northwest, especially
later this week. Favorable flow should focus heavy rains and
elevation snows over the Olympics and Cascades.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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