Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Mon May 01 2023

Valid 12Z Mon May 01 2023 - 12Z Wed May 03 2023

...Heavy rain to continue across northern Maine through Monday, as areas
further south begin to clear out...

...Heavy snow will persist across Upper Peninsula of Michigan through
early work week; Well-below-average temperatures across Great Lakes and
Ohio Valley through Tuesday, spreading into Northeast and Mid-Atlantic on
Wednesday...

...Cool and unsettled weather spreads into the West Coast, while well
above average temperatures continue across the Intermountain West,
northern/central Rockies, and northern High Plains...

After widespread heavy rainfall across the Mid-Atlantic and Northeast this
weekend, with localized areas receiving as much as 3-5" of rain over the
past 48 hours, conditions are expected to slowly improve from south to
north as the heaviest axis of precipitation progresses northward into
northern New England during the Monday morning hours. Additional rainfall
amounts of 1"+ will be confined to northern Maine, with some localized
higher elevations forecast to see upwards of 2" over the next 24 hours.
Although much of the precipitation will have ended by late Monday,
conditions will remain cool and damp, with scattered showers possible
through Wednesday.

Meanwhile, a highly anomalous upper-low, which has been partly responsible
for heavy rainfall in the Northeast, remains nearly stationary over the
Great Lakes and will continue to lead to much below-average temperatures
and localized heavy snowfall across northern Wisconsin and the Upper
Peninsula (U.P.) of Michigan through Tuesday. Shortwave energy traveling
around the base of the upper low will lead to a continued rapid deepening
of a surface low over Lake Superior and the Ontario Province late through
Monday, with several locations potentially approaching May monthly
low-pressure records.

The ongoing snowfall in the northern Great Lakes region will persist
through Tuesday as gusty, northwesterly winds on the backside of the
strengthening surface low, in conjunction with cold air advecting
southward and orographic lifting, will lead to localized additional totals
of 1-2 feet across higher elevations of the interior U.P. of Michigan.
Given the late-season event, surface temperatures hovering around freezing
will lead to a very heavy, wet snow, which may result in downed trees and
powerlines. The snow will diminish on Tuesday as the system weakens and
slowly pushes eastward as high pressure builds in. Portions of the West
Virginia Appalachians may also experience accumulating snow through
Wednesday, with localized Winter Storm Warnings in effect. Furthermore, a
broader area of much-below-average temperatures (10-20 degrees F below
average), encompassing much of the Midwest, Great Lakes region, and Ohio
Valley, will be possible through Tuesday, as daytime highs remain in the
low 40s and numerous locations approach or break daily record low maximum
temperatures. As the upper low begins to push northeastward, the
below-average temperatures will spill into the Mid-Atlantic and Northeast,
with nighttime lows dipping into the low 40s across nearly the entirety of
the I-95 urban corridor.

For the Western U.S., a cool and unsettled weather pattern is currently
spreading into the West Coast as an upper-level low is forecast to slide
into the region early this week. This will lead to showers and
high-elevation snow chances, along with below-average temperatures.
Further inland, gusty southerly winds and well above average temperatures
are anticipated for much of the Intermountain West, with warm weather also
spreading into the northern and central Rockies and northern High Plains.
Regions experiencing river flooding due to snow melt across the Great
Basin can expect more significant snowmelt this week. Additionally,
scattered shower and thunderstorm chances will overspread much of the
Rockies by Tuesday as well.


Russell/Snell


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php