Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 PM EDT Wed May 13 2026

Valid 12Z Sat May 16 2026 - 12Z Wed May 20 2026


...Central U.S. Heavy Rainfall/Runoff and Severe Weather Threat...


...Guidance/Predictability Assessment...

The latest guidance captures the evolution from a zonal flow
pattern at the beginning of the period, this weekend, to a more
amplified one next week. There's uncertainty as to the timing and
amplitude of certain embedded shortwaves within the broader digging
trough in the West next week. There's consensus on a broad
diffluent pattern setting up over the Central U.S., which will
support severe storms and heavy rain potential. There's also a
strong signal for an strong upper ridge to set up over the East.

A general model blend consisting of the available deterministic
guidance was used on day 3, followed by some inclusion of an
ensemble mean on day 4 due to some of that uncertainty out West.
Means are gradually increased in the blend through the end of the
period due to some notable differences in another potential split
flow pattern illustrated by the deterministic models.


...Weather/Hazards Highlights...

Energetic upper trough/deepened surface low ejection over south-
central then eastern Canada will lay down a trailing front with
from the north-central U.S to the Northeast. Impulses, right
entrance region upper jet lift and moisture/instability focus into
the Upper Midwest portion of this front may support emerging
convective development and potential for local training has
prompted the expansion of a WPC Excessive Rainfall Outlook
Marginal Risk area valid for Day 5/Sunday.

Farther upstream system energies subsequently work into the West
and downstream up across the central U.S. with less certainty this
weekend into next week in amplifying flow. Passage may yield
enhanced weekend winds and wildfire threat potential across the
southern Rockies/high plains. There is also then an increasing
signal that Plains cyclogenesis/frontogenesis, upper jet support
and growing lead Gulf return flow may further set the stage to
fuel an expanding central U.S. convective rainfall/runoff and
severe weather threat pattern to monitor as indicated by SPC.

Meanwhile, an eastward spreading upper ridge will spread well
above normal pre-frontal temperatures across the Central to Eastern
U.S. downstream this period that may support some local high
temperature values. To the south, low level onshore flow will bring
shower into Florida in proximity to upper low development
near/east of the Bahamas.

Kebede/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, 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