LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Thu Aug 27 2026
Valid 272000Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC/NORTHEAST...CENTRAL PLAINS...AND CENTRAL MONTANA...
...SUMMARY...
Scattered strong to severe thunderstorms remain possible across
parts of the Northeast and Mid-Atlantic today. Damaging winds,
severe hail, and a tornado or two may accompany these thunderstorms.
Large to very large hail and severe gusts are also possible across
parts of northern High Plains and central Plains.
...20z Update...
The forecast remains on track with only minor changes made to the
existing outlook. See the discussion below as well as MCDs 2148,
2149, and 2150 for additional details.
..Chalmers/Thornton.. 08/27/2026
.PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Aug 27 2026/
...Mid-Atlantic/Northeast...
Recent surface analysis places a low over western Quebec, with a
cold front arcing from this low southwestward through the middle OH
Valley, western TN Valley and then westward across central AR and
central OK. Satellite imagery reveals a shortwave trough extending
from northeastern Ontario through western PA, just west of the
analyzed surface low. There also appears to be a more subtle
shortwave trough farther south moving through WV towards VA.
Expectation is for the primary shortwave trough and cold front to
continue eastward, interacting with the very moist airmass across
the Northeast to support thunderstorm development this afternoon.
12Z ILN and PIT soundings sampled the moderate westerly flow aloft,
supporting the potential for strong multicells along both the cold
front and pre-frontal troughing. A few supercells are possible if
warm sector development can mature without too much interaction with
other convection. Primary risk will be damaging gusts, although the
modestly cool temperatures aloft (i.e. -10 to -12 deg C at 500-mb)
suggest some hail is possible as well.
A somewhat displaced area of earlier thunderstorm development is
manifesting across the northern Mid-Atlantic. As mentioned in MCD
#2145, a broken band of thunderstorms is ongoing as of mid-morning
from the New York City vicinity southwest toward Baltimore, with
that activity potentially being aided by forcing for ascent
associated with the subtle shortwave trough moving into VA. Airmass
across this region is very moist, and instability is steadily
building under modest diurnal heating. Most guidance suggests this
activity gradually increases in coverage and intensity over the next
few hours. The presence of a vertically veering wind profile
with around 30 to 35 kt of effective bulk shear would support a
conditional risk for embedded supercell structures capable of
locally damaging winds, marginally severe hail, and perhaps a brief
tornado.
...Northern Rockies/High Plains...
Recent satellite imagery depicts a shortwave trough progressing
across eastern OR towards ID and western MT. Moderate mid-level
moisture and forcing for ascent associated with this wave are
forecast to initiate thunderstorms across the northern Rockies this
afternoon. This activity is then forecast to progress northeastward
off the higher terrain into central MT, where a deeply mixed airmass
is forecast to be in place. Despite this deep mixing and somewhat
limited low-level moisture, the mid-level moisture associated with
the shortwave will allow for at least modest buoyancy (i.e. MLCAPE
over 500 J/kg). This should support storm maintenance off the
terrain, with a trend towards outflow-dominant bowing segments with
time. Primary severe risk is damaging gusts, including the potential
for gusts from 65 to 75 mph.
...Central Plains...
Moist southerly flow will help maintain moderate low-level moisture
through the NE Panhandle and into southwest SD amid the strong
heating and boundary-layer mixing expected this afternoon.
Additionally, this modest, but persistent, warm-air advection is
likely to force convective initiation this afternoon over the
western NE/SD border vicinity. Low-level southerly flow veering to
moderate northwesterlies aloft will support deep-layer shear of 40
to 50 kt, more than adequate for supercell development with any
mature convective. Any sustained supercells will be capable of
producing large hail (some 2+ inches) as they track
south-southeastward through the late afternoon into the evening.
Upscale growth into one or more bowing segments appears likely this
evening, with strong to severe gusts (65 to 75 mph) possible.
An isolated threat for severe hail/gusts may also exist
farther west/south across the CO Front Range to Raton Mesa vicinity.
Weaker buoyancy and deep-layer shear should keep any more organized
updrafts confined to the higher terrain and Foothills.
-- No other changes needed to the outlook with the text for the
additional areas appended from the 13Z Outlook below --
...Great Basin...
High-based thunderstorms should also develop this afternoon across
portions of northeast NV into northwest UT and southeast ID. While
low/mid-level winds and related thunderstorm organization will
likely be somewhat weaker/limited compared to areas farther north,
steep lapse rates and large DCAPE will support potential for strong
to severe outflow gusts as this convection spreads northeastward
into the early evening.
...South-Central/Coastal Texas into Southern Louisiana...
Ongoing thunderstorms across southern LA may pose a threat for gusty
winds this morning before they move offshore. Additional
thunderstorms may develop this afternoon from parts of south-central
TX towards the upper TX Coast, with isolated severe/damaging
downburst winds possible given ample moisture/instability forecast.
Weak deep-layer shear should limit the overall severe threat.
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