107
FXUS02 KWBC 281710
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
110 PM EDT Tue Apr 28 2026

Valid 12Z Fri May 01 2026 - 12Z Tue May 05 2026


...Heavy rain and flooding threat increasing from Central Texas to
the Lower Mississippi Valley later this week...


...Overview...

A persistent upper level low spinning over southeast Canada will
keep conditions cool and unsettled through the weekend into early
next week. Meanwhile, a potent storm system with plenty of moisture
to work with will set the stage for heavy rain and potential
flooding concerns from the southern Plains to the Southeast late
week into the weekend. Looking ahead to next week, another Pacific
low may bring showers to parts of the Great Basin and Intermountain
West.


...Guidance/Predictability Assessment...

Latest model runs continues to show good agreement on the upper-
level pattern with the low/trough over northeast U.S. and a rex
block pattern developing over the West. Although the models seem
to show some slight differences in timing and amplitude of the
trough/low moving inland over the West and some shortwave trough
differences over the Northeast, models continue to show less
uncertainties among the smaller scale features. The ECMWF continues
to show a slower solution compared to the other model guidances
with the trough moving into the Southwest. Therefore, the WPC
forecast was composed of an even blend of the deterministic models
and EC- AIFS for the start of the period. Later in the period, the
ensemble means were gradually incorporated to smooth out some
differences after Day 5. This solution maintained continuity with
the National Blend of Models.


...Weather/Hazards Highlights...

An occluding coastal low pressure system pivoting from northern
New England into southeast Canada will continue to foster cool,
breezy, and showery conditions across parts of the Northeast Friday
into the weekend. Chances for some light snow across the higher
elevations of northern New England or the Interior Northeast will
be possible on Friday, as colder air wraps in on the backside of
the low, but the risk is lower than previous days. Temperatures
from the north- central U.S. to much of the eastern U.S. will run
several degrees below seasonal norms over the course of the
weekend, setting up the potential for nighttime frost and freeze
concerns over parts of the region.

Meanwhile, a potent southern stream Pacific low scooting along the
U.S./Mexico border will eject into the southern Plains on Friday
As this disturbance progresses eastward, it will begin to interact
with a lingering frontal boundary. Anomalous Pacific and Gulf
moisture overrunning this frontal zone combined with impressive
dynamics and forcing from a strong upper jet will lead to the
increasing potential for significant rainfall and scattered
flooding concerns from Central Texas to the Lower Mississippi
Valley and parts of the Southeast Friday into Saturday. Given an
environment favorable for heavy rainfall, models continue to
produce a growing signal for widespread rainfall totals of 2-4"
with locally higher amounts possible. The existing Slight Risk on
Day 4/Friday ERO remains with slight adjustment eastward across
eastern Texas to southern Arkansas, Mississippi, Louisiana and
Alabama. Machine learning ERO guidance hinted at the potential for
a future eastward expansion of the Slight Risk which will be
monitored.

The risk for heavy rainfall shifts eastward into the Southeast on
Saturday as a frontal wave fueled by still impressive moisture and
forcing tracks towards the Mid-Atlantic coast. Despite this region
currently being affected by significant drought, clusters of
thunderstorms could contain rainfall rates that are heavy enough to
produce runoff, especially when considering grounds and soils that
may have a difficult time absorbing heavy downpours. Thus, a Day
5/Saturday Marginal Risk ERO from the Florida Panhandle
northeastward to southern North Carolina was maintained.

Then looking ahead to Sunday through early next week, the cold
front that follows in the wake of the developing coastal frontal
wave is looking like it may stall across Florida. Should this
occur, the stalled frontal boundary would then become a focus for
additional heavy rain and flooding threats which will need to be
monitored as we get closer.


Oudit/Miller


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








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