Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
310 PM EST Mon Jan 04 2021
Valid 12Z Thu Jan 07 2021 - 12Z Mon Jan 11 2021
...Weather Pattern Overview...
Progressive flow of shorter waves is expected next week across the
CONUS. Relatively mild Pacific air will dominate, generally
keeping colder air contained to Canada at least into the late
parts of next week, resulting in near to above normal temperatures
for most of the CONUS. The Pacific Northwest will remain in a
stormy pattern as successive systems persist. The wave of greatest
note arrives at the Pacific Northwest coast Monday and meanders
east through the CONUS all week, perhaps amplifying enough to be
of winter storm concern in the east-central CONUS by Friday.
...Guidance/Predictability Assessment...
Given the shorter wavelength of activity progressive across the
CONUS next week, there are notable differences in deterministic
guidance even by Day 3. The 00Z ECMWF compared most favorably to
their ensembles and was preferred along with an increasing blend
of ensembles through the week (with a preference for the 00Z ECENS
over the 06Z GEFS). Consensus by later next week generally kept an
eastward motion of the system out of the Plains Wednesday toward
the VA/NC coast by Friday.
...Weather/Threats Highlights...
An area of low pressure lingering near/off New England Monday
night through Tuesday night will bring at least modest
precipitation to eastern New England depending on its proximity to
the coast and structure. A slow exodus could prolong oceanic
affects at the least, but perhaps remain a coastal threat as well.
The Pacific Northwest will see the brunt of the precipitation next
week with a string of systems, about one every other day, coming
ashore. Multi-day precipitation totals could exceed several inches
in many areas (even lower elevations west of the Cascades) with
considerable snowfall in the Cascades. Expect windy conditions and
variable snow levels (though not too low) as the systems move
through. By later in the week, that Pacific system reaching the
coast on Monday will move out of the Plains with an expanding area
of at rain and at least some snow on the north side of the system
as Canadian air fills in behind the system.
Temperatures will be well above normal along the Canadian border
by about 10-20 degrees, especially for overnight lows, through
next week. Modestly above normal temperatures can be expected for
most of the rest of the CONUS east of the Rockies and north of the
Southeast. The exception area could be the east-central CONUS
depending on the low track and intensity of the main wave of
concern crossing the CONUS next week. The interior West should see
near normal temperatures in the active pattern.
Jackson
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
Hazards:
- Heavy snow across portions of the Southeast, the Mid-Atlantic,
and the Southern Appalachians,
Thu-Fri, Jan 7-Jan 8.
- Heavy rain across portions of the Pacific Northwest and
California, Thu-Fri, Jan 7-Jan 8.
- Flooding occurring or imminent across portions of the Southeast,
the Southern Plains, the
Mid-Atlantic, and the Pacific Northwest.
- Flooding likely across portions of the Mid-Atlantic.
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