Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0730 AM CDT Mon Jul 13 2026

Valid 131300Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST AND MONTANA...

...SUMMARY...
Thunderstorms with isolated strong to severe winds may occur this
afternoon and evening across parts of the Southeast and Montana.

...Southeast...
A very weak mid-level trough will persist over the Deep South and
Carolinas today, with modest westerly flow. Although rich low-level
moisture remains present across these areas, multiple days of
convective overturning has resulted in rather poor lapse rates
aloft. This, along with persistent cloudiness, should limit to some
degree how much instability will develop this afternoon with
filtered daytime heating. Deep-layer shear will also remain weak,
and thunderstorms should generally be disorganized. Some loose
clustering may eventually occur with convection spreading eastward
from the central Gulf Coast towards the FL Peninsula, where
low-level lapse rates should become steepened by peak afternoon
heating. Isolated damaging winds appear possible with the strongest
cores from parts of FL into eastern GA and SC ahead of the weak
mid-level trough.

...Montana...
Mid/upper-level ridging will extend from the southern/central
Rockies to the northern Plains/Upper Midwest through the period,
with a belt of enhanced southwesterly mid-level flow over
western/central MT. High-based thunderstorms may develop this
afternoon across parts of southwest into central MT amid a deeply
mixed boundary layer. While low-level moisture and related
instability are both expected to remain limited, some risk for
occasional strong to severe gusts may accompany this convection as
it spreads northward through the early evening before weakening.

...Arizona...
Showers and isolated thunderstorms are still ongoing this morning
across parts of southern AZ. While mid-level east-southeasterly flow
will persist today across much of AZ on the southern periphery of
prominent upper ridging, it remains unclear how much destabilization
will occur in the wake of this morning's convection. Whether
convection will be able to spread westward off the higher terrain of
southeast AZ and the Mogollon Rim is also uncertain. Have therefore
not included low severe wind probabilities with this update.

..Gleason/Thornton.. 07/13/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0405 AM CDT Mon Jul 13 2026

Valid 161200Z - 211200Z

...DISCUSSION...
All ensemble guidance suites are in broad agreement that the central
US ridge will once again build westward in response to the
development of a eastern North America long-wave trough during the
forecast period. However, significant differences exist within and
between ensembles regarding the timing and exact nature of this
transition. 

At the start of the forecast period, a frontal boundary will be
pushing south and west in the wake of a strong short-wave trough
that moved across New England in the prior days. The trend over the
past 48 hours is for this front to push farther south and west,
bringing a continental dry airmass into New England and portions of
the Mid-Atlantic. For example, several days ago ensemble guidance
was in good agreement that the front would be draped across the
Mid-Atlantic on Friday. Many, but not all, of the recent runs now
push the front south into southern Virginia and northern North
Carolina. This results in significant uncertainty regarding the
potential severe weather environment on Friday (Day 5) across the
Mid-Atlantic. For example, the GEFS mean temperature for Washington
D.C. is 93F on Friday afternoon, while the EPS mean temperature is
102F. However, both ensembles have dewpoint temperatures in the
50Fs.

Given the increasing uncertainty as to the location of the surface
boundary on Friday and the overall quality of the severe weather
environment, unconditional 15% severe probabilities for Friday are
removed with this forecast. It is possible that severe probabilities
may be reintroduced in later outlooks should it become apparent that
the surface boundary washes out earlier than expected and quality
low-level moisture is able to return sooner.

That said, the front should begin to dissipate by Saturday in
response to a mid-level trough digging southeast across the Great
Lakes. This will allow rich boundary-layer moisture to advect
northeastward into the Mid-Atlantic and southern New England. This
increase in boundary-layer moisture and strong diurnal heating will
allow for afternoon MUCAPE values between 1000-2000 J/kg, perhaps
locally higher on Saturday and into Sunday. 

This unstable and vertically sheared environment will be ripe for
thunderstorm/severe thunderstorm development ahead of any digging
mid-level trough. However, as alluded to previously, the timing,
magnitude, and number of these troughs is highly variable within the
ensemble guidance, leading to too little confidence to pinpoint
where and when unconditional severe probabilities should be added.
As confidence in the timing, track, and strength of these embedded
troughs becomes clear, severe probabilities will likely be needed
somewhere across the region stretching from the Upper Midwest
southeast into the Mid-Atlantic for one or more days.