Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
308 AM EDT Fri Mar 31 2023

Valid 12Z Mon Apr 03 2023 - 12Z Fri Apr 07 2023

...Strong Plains through Upper Midwest storm early-mid next week
to bring strong winds and Rockies to northern Plains/Upper Midwest
snow along with heavy rainfall and severe thunderstorms from the
South into the Ohio Valley...
...Winter cold for the West and North-central U.S. to starkly
contrast summer heat from the South to the East/Southeast,
including record values...

...Synoptic Overview...

The main weather story next week will begin with the continued
digging of a series of cooling/wintry Pacific systems into an
unsettled West. The downstream ejection of potent upper trough
energy will support genesis of another strong low pressure system
set to consolidate and deepen as it tracks from the central High
Plains Tuesday northeastward to the Midwest/Great Lakes Wednesday.
This storm should bring a broad area of significant/hazardous
weather to areas from the Rockies eastward and drive a large area
of well below normal temperatures in its wake from the West
through the northern Plains. Expect a large swath of heavy
wrapback snows across the northern Plains and Upper Midwest/Great
Lakes along with possible blizzard conditions in stark contrast to
widespread convective warm sector showers/thunderstorms to develop
and spread across the eastern half of the country that includes a
threat for severe weather with a Mid-South focus Tuesday as per
the Storm Prediction Center (SPC). Upper ridging over the Gulf
Coast should build northward over the eastern U.S. and support
anomalous warmth ahead of the storm's associated cold front. This
pattern may lead to the stalling of the trailing front into later
next week across the U.S. southern tier. Frontal wave enhancements
with the ejection of southern stream upper energies may focus
convergence/convection and potential training/runoff issues,
perhaps especially from Texas into the lower Mississippi Valley.


...Model Guidance/Predictability Assessment...

The models paint a reasonably similar picture for early-mid next
week in an overall pattern with good ensemble support and
seemingly above normal forecast predictability, bolstering
confidence in the main systems and threats. Forecast clustering is
best Monday-Wednesday when preference is for a composite of the 18
UTC GFS and 12 UTC ECMWF/UKMET/Canadian models for max details.
However, the blending process tends to mitigate the least
predictable smaller scale variances that may otherwise errantly
direct local focus. Forecast spread slowly increases into later
next week, lending transition to a preference for the more run to
run consistent 18 UTC GEFS and 12 UTC ECMWF ensemble means along
with the 01 UTC National Blend of Models (NBM) and WPC continuity.
Latest 00 UTC guidance generally remains in line for much of this
forecast period.

...Weather/Hazards Highlights...

It generally remains the case that the reloading of upper level
troughing over the northwestern U.S. by the weekend and continuing
into early next week will support multiple days of rain/mountain
snow with terrain enhancement from the Pacific Northwest and
northern California/Sierra Nevada into the northern and central
Rockies, with the moisture shield pushing gradually farther
southeast with time.  Heavy snow is likely for the Cascades and
the Olympic Mountains and significant snow may reach central and
northern portions of the Sierra Nevada by early next week.  Also
expect a period of heavy snow to extend across favored terrain
from the Great Basin eastward into the Rockies into Monday. 
Activity may reload with less certainty back into the
West/Southwest/Rockies into mid-later next week with renewed
Pacific system energy feed back into the region.

The big headline will be the deepening Plains low that develops
along a strong frontal boundary early next week.  Numerous showers
and thunderstorms are likely from the Gulf Coast to the Ohio
Valley Tuesday and especially into Wednesday as this storm system
gets better organized across the central Plains and advects
copious Gulf moisture and instability northward.  Also the threat
of strong to severe storms is increasing in the expansive warm
sector, with the Storm Prediction Center already monitoring that
possibility on Tuesday.  At the same time recent model runs
maintain/add confidence for the idea of a significant cold sector
snow event northwest of the low track, with probabilities for
heavy snow steadily increasing out from the Rockies along a main
axis from eastern Wyoming across much of South Dakota/portions of
North Dakota and then northern Minnesota Monday night into
Wednesday.  Heavy snow will be possible within portions and in
vicinity of this band.  This storm will also produce strong winds,
with best potential for the highest wind speeds extending from the
Southwest through southern High Plains and northward through the
northern Plains where blizzard conditions are again possible. 
Other areas farther east may see brisk to strong winds even if to
a less extreme degree.

A pronounced temperature contrast will develop across the nation
early-mid week with well below average readings spreading across
much of the western U.S. and central/northern Plains, and well
above average temperatures expanding from the southern Plains/Gulf
Coast through much of the eastern U.S.  Tuesday-Wednesday look to
be the coldest days versus normal over the West/Plains with some
areas seeing highs as much as 20-30F below normal.  The reverse
will hold true over the southern Plains early in the week and
farther eastward thereafter, with highs generally 10-20F above
normal and lows 15-25F above normal.  Daily records mainly for
cold highs will be possible over the West during the first half of
the week.  Farther east in the warm sector, Tuesday-Thursday will
offer the best potential for some daily records, with warm lows
tending to be more numerous than record highs.

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, experimental excessive rainfall
outlook, 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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml