Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Sat Jan 30 2021
Valid 12Z Tue Feb 02 2021 - 12Z Sat Feb 06 2021
...Winter Storm for the Mid-Atlantic/Northeast early next week and
from the West to the Midwest/Northeast mid-later next week...
...Weather/Threats Highlights and Guidance/Predictability
Assessment...
For the major coastal storm persisting early next week, a signal
for heavy snowfall remains from the interior Mid-Atlantic to
southern New England, bolstering mid-larger scale forecast
confidence. Some areas along or offshore the coast should also see
a period of brisk to strong winds. This deepened low will also
remain a significant maritime threat.
Guidance meanwhile agrees to dig a strong upper trough into CA
Tue-Wed to support a period of enhanced moisture/rains and heavy
Sierra snows, with more modest enhanced amounts focusing on
favored terrain and with deformation for the cooled south-central
Great Basin/Rockies. Variance with the extent of digging leads to
subsequent ejection differences. Differences grow downstream along
with uncertain stream phasing/central U.S. storm genesis mid-later
next week. It is expected that as the energy comes out of the West
and Rockies, a deepening low to the lee of the Rockies will to
lift toward the Upper Midwest. Strong warm air advection and
moisture return on the backside of the departing high will allow
for copious amounts of moisture to work with the better dynamics
and forcing. Over the central then eastern U.S., this offers a
threat for heavy wrap-back snows to the north as per the WPC
winter weather outlook, QPF and weather type grids along with an
expanding area of enhanced warm sector/frontal heavy
rains/convection farther south. Recent GFS and Canadian runs offer
less than stellar run to run continuity. Recent ECMWF runs have
tended to be on the slower/wrapped side of solution envelope, but
have been more run to run consistent and a bit better clustered
with ensembles. Given initial deep system amplitude over the West,
the ECMWF and ECMWF/GEFS ensemble means were heavily incorporated
into the WPC forecast product blend.
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