Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EDT Mon Mar 29 2021
Valid 12Z Thu Apr 01 2021 - 12Z Mon Apr 05 2021
...Overall Weather Pattern...
A deep upper trough and a cold surface high pressure system will
settle across the eastern U.S. late week into weekend behind a
deepening cyclone exiting New England. On the other hand, an
upper ridge edging into the Plains will bring persistent warmth
into the northern Plains. Meanwhile, models continue to show
uncertainty across the Pacific Northwest where the next upper
trough/low should bring an increasing chance of light to possibly
moderate precipitation moving into the Northwest and northern half
of California by next Sunday into Monday.
...Model Guidance and Predictability...
The model guidance suite the morning continues to show excellent
agreement on predicting the amplitude and timing of the deep upper
trough settling across the eastern U.S. late this week into the
weekend. The excellent model agreement also extends westward
through much of the Plains and into the southern Rockies as the
cold high in the East gradually modifies and persistent southerly
flow expands the warm air mass across the northern Plains. The
greatest uncertainty is across the Pacific Northwest where models
continue to show some difficulties in handling an upper trough
digging down from the Gulf of Alaska and its interaction with a
southern stream wave lifting across the eastern Pacific. The
ECMWF has continued to be the slowest guidance with a closed off
upper low off the West Coast early next week. The GFS is not as
slow. The ECMWF and GEFS means agree quite well however. The CMC
offers the fastest solution regarding this system. The WPC
guidance was based on a general compromise of the 00Z ECMWF/00Z EC
mean and the 06Z GFS/06Z GEFS together with some contributions
from the 00Z CMC and CMC mean. This yielded a solution quite
similar to the previous WPC forecast package.
...Sensible Weather and Potential Hazards...
A cold air mass will be ushered into the eastern U.S. in the wake
of an intensifying low pressure system exiting New England on
Thursday. Rain initially over Maine should change over to a
period of snow before ending across northern New England. Windy
conditions are also likely for the East Coast on Thursday with a
strong pressure gradient in place. Temperatures will then dip
well below freezing by Friday morning over much of the interior
eastern U.S. before warm air gradually filters in from the west as
the cold high pressure system modifies and settles into the
Southeast. Meanwhile, a extended period of very warm and dry
weather ins forecast to settle across the northern Plains under a
slow-moving upper ridge and persistent southerly surface flow.
This could enhance the fire danger across the region by this
weekend and early next week.
Temperatures will be more reminiscent of late February for much of
the eastern half of the nation to close out the work week with
blustery conditions behind the cold front, and subfreezing low
temperatures likely reaching as far south as northern Georgia and
South Carolina by Friday morning. The cold weather will abate
going into the weekend as the airmass modifies and the upper level
trough lifts out across eastern Canada. Much warmer weather is
forecast to return to much of the central and western U.S. in time
for the weekend, as an upper level ridge builds in along with
southerly flow ahead of the next frontal boundary, and results in
readings of 15 to potentially 25 degrees above normal. Highs
could reach the low 80s across portions of Nebraska and South
Dakota, and the low-mid 90s for the lower elevations of the Desert
Southwest.
Kong/Hamrick
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