Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue Mar 22 2022
Valid 12Z Fri Mar 25 2022 - 12Z Tue Mar 29 2022
...Overview...
An amplified upper level pattern is expected during the medium
range period, beginning Friday with troughing across the East and
ridging in the West. Additional impulses coming into the trough
will reinforce it at least for the northeastern U.S. through early
next week, with cool temperatures and periodic light
precipitation. Meanwhile the ridge should be gradually pushed
toward the central U.S., spreading warmer temperatures there after
potentially record-setting warmth in the West, as troughing
approaches from the East Pacific. There is uncertainty in the
trough's timing and amplitude, but it should cause increased
precipitation chances and cooler temperatures in the West when it
comes in, with potential for a surface low pressure system to
strengthen in the Plains but the end of the period next Tuesday.
...Guidance Evaluation/Predictability Assessment...
Model guidance from the 12/18Z yesterday cycle begins with
generally good agreement for the large scale pattern, with typical
differences with shortwaves embedded within the trough over the
eastern third of the country. An initial coastal low just off New
England early Friday clusters well among guidance. Models show
stronger energy with the possibility of a small closed upper low
early Saturday likely over the Great Lakes/Ohio Valley, but with
some latitudinal variations in how far south the trough/low
reaches--ECMWF runs have generally been among the farthest south.
But the bigger outlier with this feature was likely the 12Z UKMET,
which separated streams by Sunday to create a southern stream low
in the Southeast, so leaned away from that solution. There is
generally good agreement in principle that troughing will lift
gradually early in the workweek for the Southeast, but with some
semblance remaining in the Northeast.
However, farther west, more significant differences in the pattern
arise. While early agreement for ridging shifting eastward is
reasonably good, there are notable timing issues with individual
models as well as ensemble means with the incoming troughing, as
well as differences in potential stream separation and its timing.
The 12Z and newer 00Z ECMWF show a much slower closed low compared
to most of the recent guidance and its ensemble mean, after its
previous runs were among the faster solutions. In contrast, GFS
runs are now faster with an inland track and more phased, after
runs about a day ago showed an upper low hovering in the Pacific
longer. This flip-flop as well as individual ensemble member
spread becoming very broad late in the period leads to fairly low
confidence in the trough's timing. The CMC and its mean are faster
and more clustered with the GFS/GEFS, but did think the 12Z CMC
ensemble mean may be slightly fast with the trough axis by next
Tuesday.
Thus the WPC medium range forecast favored an operational model
blend at the beginning of the period. Lessened the proportion
especially of the ECMWF by the end of the period as better
clustering seemed to be with the ECMWF mean, GFS runs, GEFS means,
and CMC. Given the uncertainty, shifts in the forecast are
possible if not likely particularly with the timing of the trough
and the associated fronts ahead of it.
...Weather Highlights/Threats...
Snow may linger in Maine on Friday as a coastal low forms. Then
shortwave energy and weak low pressure/frontal systems could lead
to light precipitation spreading across the northeastern quadrant
of the country through early next week, from the Great Lakes
region to the central/northern Appalachians and Northeast late
week into the weekend. Some of this precipitation will be in the
form of snow in higher elevations and northern latitudes, and
gusty winds are also possible. Precipitation ahead of the
approaching eastern Pacific upper trough is likely to reach the
Pacific Northwest around Friday and then spread across more of the
West thereafter. Most of this activity should be in the light to
moderate range but some locally heavier totals could be possible
depending on exact system details. Coverage and intensity of this
precipitation becomes increasingly uncertain by late weekend into
early next week.
Unseasonably warm temperatures will build and expand underneath
upper ridging from the western U.S. into the Plains. Highs that
are 10-20F above normal will be common over California and the
Great Basin/Southwest Friday, with some plus 20-25F anomalies
appearing in the Great Basin Saturday and moving to the
northern/central High Plains early next week as the upper ridge
axis shifts. Daily record temperatures could be tied or set across
California and eastward. Temperatures in the West are likely to
cool closer to normal by around Monday but the exact timing will
depend on the trough's movement inland. Meanwhile the East should
see near to slightly below average temperatures given mean upper
troughing, with coolest temperatures of 10-15F below normal in the
central Appalachians for the weekend and in the Great Lakes 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