Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Wed Mar 23 2022
Valid 12Z Sat Mar 26 2022 - 12Z Wed Mar 30 2022
...Overview...
Over the weekend, troughing will be present across the eastern
U.S. while periodic shortwaves and fronts cause light
precipitation and cool temperatures from the Great Lakes to
Northeast. Meanwhile a ridge causing potentially record warmth
will shift from the Intermountain West slowly eastward into the
High Plains ahead of another trough/upper low entering the West
from the eastern Pacific. While there remain some timing
differences with the trough/low, when it enters the country it
should cool down the West and increase precipitation chances. By
Tuesday/Wednesday, there is decent agreement for a surface low
pressure system to develop in the central Plains, leading to
wetter conditions across the central U.S. and potentially some
springtime snow for the Midwest/Great Lakes.
...Guidance Evaluation/Predictability Assessment...
Recent model guidance shows fairly good agreement for the early
part of the medium range period over the weekend with the initial
western ridge/eastern trough pattern. Shortwave energy embedded
within the trough shows minor variations among models, but with
the general idea that the shortwave/clipper will track from the
Great Lakes Saturday to the east Sunday and possibly induce modest
cyclogenesis just off the New England Coast. Though deterministic
models vary with the exact positioning of the low, ensemble
members and means indicate this potential, and the differences are
within typical spread for a medium range forecast.
Greater model differences arise with the eastern Pacific upper
trough. Recent model guidance has at least converged on indicating
a closed low on the southern end of the trough just west of
California early next week, whereas models were more mixed on a
closed/open solution over the past couple of days. This has led to
a slower trend with the incoming trough/low overall, though the
past 3 or 4 ECMWF deterministic runs have been the exceptionally
slow solutions compared to other guidance. By late Monday into
Tuesday, guidance varies with the handling of the upper low
potentially phasing back with the northern stream as additional
shortwave energy in the northern stream may interact with it. In
the 12/18Z yesterday model cycle, the ECMWF showed no phasing
between the features as the southern stream low was farther west
and the shortwave farther east, missing each other. The 12Z GFS
was phased by Tuesday with the 18Z GFS phased by Wednesday, while
the CMC showed some separation. Thus there are ample timing
differences with the feature and ensemble members show
considerable variability as well. Regardless of these differences,
most models/ensembles show a developing surface low in the Plains
by Tuesday/Wednesday.
Thus the WPC medium range forecast utilized a multi-model
deterministic blend for the early part of the period, but with
increasing proportions of the somewhat better clustered GEFS and
EC ensemble means by the latter part of the period given the
operational model differences. Overall the track of the western
low/trough was a bit slower than continuity but not nearly as slow
as the deterministic ECMWF runs.
...Weather Highlights/Threats...
Shortwave energy and weak low pressure/frontal systems are
expected to produce light precipitation as they move across the
Great Lakes region to the central/northern Appalachians and
Northeast over the weekend. Some of the precipitation will be in
the form of snow in higher elevations (West Virginia in
particular) and near the Canadian border, followed by strong and
gusty winds with falling temperatures. Precipitation ahead of the
approaching eastern Pacific upper trough could affect the Pacific
Northwest Saturday with light amounts, but spread farther south to
California and east into the Rockies and Intermountain West early
next week. Most of this activity should be in the light to
moderate range but some locally heavier totals are possible,
particularly in higher elevations where upslope flow could enhance
amounts. Rain chances could increase in the south-central U.S. by
Tuesday ahead of low pressure forming. Meanwhile farther north,
precipitation including some snow/wintry weather could affect the
Midwest and Great Lakes region, but with considerable uncertainty
in the details.
Unseasonably warm temperatures will build and expand underneath
upper ridging from the western U.S. into the Plains. Highs that
are 10-25F above normal will be common over the weekend from the
West Coast across the Great Basin and Southwest to the Plains, and
several daily record high temperatures could be set or tied. As
the ridge axis shifts eastward, warm anomalies of 15-25F are
likely for the High Plains Monday while the West Coast moderates
closer to normal. Warmer than normal temperatures remain forecast
in the south-central U.S. on Tuesday but may moderate Wednesday
while pushing into the Southeast. Meanwhile the East should see
near to below average temperatures given mean upper troughing,
with coolest temperatures of 10-20F below normal in the Great
Lakes and central Appalachians for the weekend and spreading into
the Northeast early next week.
Tate
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
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