Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
240 AM EDT Fri Apr 17 2026

Valid 12Z Mon Apr 20 2026 - 12Z Fri Apr 24 2026

...Overview...

A fairly active weather pattern is expected as a uppper-level low
and trough over Western U.S. will support cyclogenesis bringing
chances for showers and thunderstorms, as well as mountain snow,
over portions of Western U.S. into Northern and Central
Rockies/Plain by mid-week. Chances for active weather pushes
eastward into Ohio Valley/Great Lakes and Mid-Atlantic towards
late
week. Cooler temperatures for much of Eastern U.S. for the start
of
week, until above normal temperatures over Central and parts of
Western U.S. pushes eastward by midweek.


...Guidance/Predictability Assessment...

Models show decent agreement on large scale features of the ridge
over Central U.S., troughing over Eastern U.S., and the closed low
positioned off the West Coast. The uncertainty comes in towards
Tuesday into Wednesday, where models diverge specifically for the
system off the West Coast. The GFS continues to show a slower
progression, while the CMC/ECMWF/UKMET pushes the system closer
inland by late Tuesday into early Wednesday. Run-to-run
variability
increasing with the GFS as well. Therefore, the forecast was based
on a even mult-model blend for the first portion of the period,
then
gradually phasing in the ensemble means and lowering the GFS
weight a bit, to be able to account for some of the timing
differences.


...Weather/Hazards Highlights...

Increasing return flow from the Gulf will support a broad axis of
moisture convergence and instability along the frontal system over
the Gulf. This will favor organized convection and potential heavy
rainfall for parts of the Southern Plains on Monday and gradually
expanding into the Mississippi Valley and Ohio Valley by
Wednesday.
Late Wednesday into Thursday, the low pressure system over the
High
Plains will continue to shift eastward, bringing chances for rain
and thunderstorms well across the Plains into the Ohio Valley, Mid-
Atlantic, and parts the Great Lakes. The possibility for localized
areas of flash flooding continues as the lingering frontal
boundary
near Texas may produce training storms and repeated convection
along
the boundary. Therefore, the Marginal Risk for Day 4 will continue
for parts of south Texas.

Meanwhile, another system will move inland from the eastern
Pacific
by Monday, bringing chances for rain and thunderstorms across much
of the West Coast. Over higher elevations, expect chances for
light
to moderate snow. With the system expected to bring 1-2 inches of
rainfall on Monday and the risk of runoffs and burn-scars, the
Marginal Risk over parts of northern California have been
maintained. Similarly, for Day 5, a Marginal Risk has been placed
as
an additional 1-2 inches is expected for Tuesday into Wednesday
and
soil moisture will likely be saturated from recent rainfall. As
the
cold front moves eastward, chances for accumulating snow is likely
across portions of Central and Northern Rockies from Tuesday and
expands into the Northern Plains by Thursday. While impacts should
be mainly confined to higher elevations, some travel impacts may
be
possible.

Temperatures will trend below average on Monday over much of
Eastern
U.S. and Texas as the cold front continues to depart off the
coast,
and high pressure begins to build. Max temperatures will be in the
60s over Texas and dipping into the low 40s across parts of the
Northeast. Frost/freeze concerns will occur for Monday night for
parts of the Northeast. Over much of Central and Western U.S.
above
normal temperatures will build ahead of the frontal system, with
the
Rockies/Plains seeing 15-20 degrees above average. Towards
mid-week,
warmer temperatures will spread across to the East Coast, while
behind the frontal system, temperatures return to below normal
across parts of Western U.S.


Oudit


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 forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key
Messages 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
https://www.wpc.ncep.noaa.gov/#page=ovw