Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 19 2025

Valid 12Z Tue Apr 22 2025 - 12Z Sat Apr 26 2025


...Heavy rain threat for the South-Central U.S. next week...


...Guidance/Predictability Assessment...

Tonight's WPC medium range 500mb and surface progs were mainly
derived from a composite of best clustered mass field and QPF
guidance of the 12 UTC ECMWF/UKMET/Canadian models valid Tuesday
into Wednesday. Switched to best compatible 12 UTC ECMWF/NAEFS
ensemble means and the 12 UTC ECMWF model for better details for
the remainder of next week amid growing forecast spread, but still
with seemingly near normal predictability beyond local convective
foci. In addition to smaller scale embedded system differences,
this solution in particular offers stronger than concensus upper
trough amplification and wavy surface system support from the
eastern Pacific through the West Coast heading Friday into next
weekend. This is strongly supported by machine learning guidance.

...Weather/Hazards Highlights...

A protracted series of generally progressive upper features and
associated surface based systems are set to work over the lower 48
next week in multiple stream flows to locally focus April weather,
but there is a growing signal to amplify the flow from the eastern
Pacific into the West heading into and through next weekend.

A WPC Excessive Rainfall Marginal Risk area for portions of the
Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been
introduced given the potential for repeat/training of cells during
the day and with overnight activity with emerging moist and
unstable return flow into and over several frontal boundaries.
Portions of this area are also forecast to have enhanced rainfall
this weekend that would lead to wet soil conditions. Heavy rain and
runoff threats along with strong convective potential in this
region and into the Mississippi Valley will also be monitored for
mid-later next week given lingering support and multi-day
potential, albeit with greater uncertainty on the details.

An expectation for upper trough amplification, wavy surface system
genesis and slow translation from the eastern Pacific to the West
Coast Friday into next weekend has the potential to offer increased
moderate rain chances with unsettled/cooling weather conditions.

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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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