Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EDT Fri May 3 2024


As a main/closed upper low tracks out of the West with additional
energies reaching the West Coast, widespread precipitation will
include some enhanced snow potential given cooled temperatures. The
higher elevations of the Great Basin into the Intermountain
West/Rockies will see May snow as the medium-range period begins
Monday morning. Vigorous troughing aloft in conjunction with a
potent cold front will lead to windy conditions and a threat of
high winds from much of the Rockies to High Plains as the
cyclogenesis should be well under way across the northern High
Plains into Tuesday. Precipitation is forecast to be ahead of the
system as it spreads across the northern Plains to Midwest Monday
and Tuesday with some timing differences among models (faster with
the ECMWF). Rainfall on the west side of the strong surface low
could be heavy across eastern Montana into the Dakotas given strong
upper- level support for lift with a gradual slowdown of the storm
track. However, this region is not particularly sensitive to
flooding concerns, and instability should be limited wrapping
around the low. A WPC Excessive Rainfall Outlook (ERO) Marginal
Risk area remains in place in the Day 4/Monday and into Day
5/Tuesday for this area given the potential for protracted heavy
rain, but likely without widespread significant flooding impacts.
The Marginal Risk extends southeast into the Upper/Mid- Mississippi
Valley, where more instability will be in place for higher rain
rates, but storms will likely be faster-moving. The Storm
Prediction Center also has portions of the Plains delineated with
potential for severe weather on Monday. Convective rainfall is
forecast to shift east into the Great Lakes and Ohio Valley Tuesday
into Wednesday with system progression and intercepting return
flow. The Marginal Risk ERO was maintained farther east into the
Great Lakes, Ohio Valley and down toward the mid-Mississippi Valley
for Day 5 as the fronts push farther toward the east and
northeast.

Upstream, aforementioned Pacific upper trough energy will work
inland over an unsettled West and over the south-central U.S. into
later next week, riding under the base of the lingering main upper
low/trough. These will interact with wavy and stalling fronts and
combine with pooling moisture and instability to fuel a favorable
pattern for rain and thunderstorms across the south-central
states/Mid-South and onward to the East where downstream energy
track may support moderate late next week coastal low development.

Much cooler than average maximum temperatures will slowly moderate
while spreading next week from the West to the northern Plains
as the closed upper low ejects eastward. But farther southeast,
mean upper ridging will meanwhile spread quite warm pre-frontal
temperatures from the South through the Appalachians/Mid-Atlantic
to threaten record seasonal values. 90s are forecast to become more
widespread across the southern tier, with temperatures over 100F
(and even higher heat indices) into south Texas and the possibility
for the first excessive heat days of the year.

Kong/Schichtel