Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 PM EST Fri Feb 18 2022
Valid 12Z Mon Feb 21 2022 - 12Z Fri Feb 25 2022
...Heavy to excessive rain threat from the Lower
Mississippi/Tennessee Valley to the Mid-Atlantic Monday-Friday...
...Heavy snow/ice threats across from northern Plains to northern
Maine Monday-Tuesday and southern Plains to Northeast
Wednesday-Friday...
...Pattern Overview...
A very active weather pattern is expected to develop by early next
week as an upper level trough digs across the Western U.S. with
ejecting energies and induced frontal waves progressing
downstream. The upper trough should shift eastward into the
Central Plains and Midwest by later next week as amplified ridging
builds over the East Pacific and West Coast. This very amplified
pattern results in a renewed heavy rain and flooding threat from
roughly the lower Mississippi/Tennessee Valley to the Mid-Atlantic
through most of next week, with a double dose of winter storm
potential -- first across the northern tier to far northern Maine
Monday and Tuesday, and again from the southern Plains to the
Northeast the second half of the week.
...Guidance Evaluation/Predictability Assessment...
Models and ensembles continue to show very good agreement on the
overall large scale pattern described above through most of the
period. The amplifying trough during the early part of next week
over the West is showing better agreement in terms of timing
compared to previous days, though timing becomes a little more
uncertain later in the week as the shortwave energy slides into
the central Plains and the Midwest next Thursday-Friday. Despite
above average large scale agreement, the latest guidance continues
to offer plenty of uncertainty in the details, which will have
more significant impacts to heavy snow/rainfall potential across
much of the eastern half of the nation. Nothing notable stands out
at this time, as most of these differences are the typical
extended range model run to run variations anyways. By later next
week, there's indications an amplified ridge should be located
over the eastern Pacific, and possibly into parts of the West, but
quite a bit of disagreement on individual systems rounding the
top/eastern part of the ridge into western Canada and the
Northwest U.S..
WPCs blend for today used a majority deterministic model blend for
days 3-5. After this, increased the ensemble means to help
mitigate the smaller scale, harder to resolve, detail differences.
This approach maintains good continuity with the overnight WPC
package as well.
...Weather Highlights/Threats...
Moderate to heavy mountain snows are likely to focus early to mid
next week across the cooling West/Rockies as potent trough
energies dig into an amplified western U.S. upper trough position.
A wavy front on the leading edge of a cold surge set to dig into
the central U.S. early-mid next week will have upper support to
favor a swath of heavy snow from the northern plains/Upper Midwest
to northern Maine next Monday-Tuesday with some ice accumulations
possible along the southern edge. Meanwhile, ample upper energies
working downstream from the West next week will also act to induce
waves along a lead front and tap deepening moisture from the Gulf
of Mexico. This is expected to fuel a heavy rain and flood threat
from the Lower Mississippi/Tennessee Valleys to the Mid-Atlantic
starting early next week along with potential for re-development
along the wavy/slowed trailing front later next week. This second
wave may also support a heavy snow/ice threat from parts of the
southern plains and Mid-Mississippi/Ohio Valleys to a cold air
dammed Northeast Wednesday-Friday. Given detail uncertainties in
the guidance, confidence on exact snow/ice amounts and locations
remains very low at these longer lead times, but the potential is
there and the pattern certaintly supports a threat somewhere.
Arctic high pressure surging southward into the Central U.S.
during the first half of next week will support much below
temperatures from the Northwest into much of the Central U.S. as
far south as Texas. Especially from the northern High Plains to
the northern/central Plains, daytime highs and overnight lows
could be 30-40 below normal, which could approach to exceed record
low mins and max values. Daytime highs across the northern part of
this region could struggle to get above 0F Monday and Tuesday.
This cold should moderate somewhat by later next week and spread
eastward into the Mississippi Valley and parts of the Midwest.
Meanwhile, much above normal temperatures are expected across the
South and East early in the period (with some records possible,
especially overnight mins) as upper level ridging builds over the
region. Temperatures should moderate back to normal for the
Northeast next Thursday-Friday, but remain above normal for the
Southeast.
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