Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
150 AM EST Tue Feb 16 2021
Valid 12Z Fri Feb 19 2021 - 12Z Tue Feb 23 2021
...Much below normal temperatures continuing through Saturday from
the Plains to the East...
...Active weather expected across the Pacific Northwest and
northern Rockies through the period...
...Overview and Guidance Evaluation...
Following a very active short range period, the medium range
should finally begin transitioning towards a less amplified/less
active weather regime into early next week. The exception to this
will be in the Pacific Northwest where multiple shortwaves will
keep the weather active with several opportunities for heavy
mountain snow and lower elevation rain.
Synoptically, the latest guidance continues to show very good
agreement through the period, with mainly typical timing and
detail differences needing to still be resolved. In the East, the
CMC/UKMET are faster with the surface low exiting the Northeast on
Friday, while the GFS/ECMWF show better agreement with the
ensemble means for low position. The next system ejecting out of
the Rockies on Sunday also has some minor timing differences, but
a blend of the CMC/ECMWF seems to agree best with the ensemble
means. Given this assessment, the WPC blend relied heavily on the
ECMWF/GFS for days 3-4, replacing the GFS with the CMC thereafter
while also increasing contributions from the ensemble means. This
maintains good continuity with the previous forecast.
...Weather/Threats Highlights...
Lingering heavy snow across interior and northern New England will
continue through Friday associated with the storm system exiting
the East Coast. The heaviest rainfall will have pushed off the
coast by the start of the period, although some lingering showers
are possible across the Outer Banks and Florida along the trailing
cold front. The West should stay active through the entire period
as multiple fronts pass through the region. These will each bring
the potential for additional focused rainfall along coastal
portions of Washington/Oregon with heavy mountain snow in the
Cascades, Northern Rockies, and Northern California. Precipitation
should begin to break out across the Plains this weekend as a
frontal system moves through, with wintry precipitation possible
on the northern side of the system across the Upper Great Lakes
region.
Temperatures will remain much below normal Friday into Saturday
from much of the Southern Plains to the East, with departures from
normal as much as 20-30F for some areas. By Sunday, temperatures
should finally begin to moderate back close to normal into early
next week. Meanwhile, expect a warming trend across especially the
Southwest and Northern Plains, with above normal temperatures
maybe creeping into parts of the southern/central Plains as well
by next Tuesday.
Santorelli
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