RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Wed May 27 16:34:02 UTC 2026.
MD 0875 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF THE OHIO VALLEY AND MID ATLANTIC
Mesoscale Discussion 0875
NWS Storm Prediction Center Norman OK
1131 AM CDT Wed May 27 2026
Areas affected...portions of the Ohio valley and Mid Atlantic
Concerning...Severe potential...Watch possible
Valid 271631Z - 271830Z
Probability of Watch Issuance...60 percent
SUMMARY...Scattered to numerous thunderstorms are expected this
afternoon across parts of southern OH and northeastern KY into WV
and the DelMarVA. A mixed storm mode should promote a risk for
damaging gusts, though some hail is also possible. One or more
severe thunderstorm watches will probably be issued in the next
couple of hours.
DISCUSSION...As of 1630 UTC, visible and radar imagery showed
initial thunderstorms gradually intensifying over the OH Valley with
clearing and deepening cumulus farther east. Weak ascent from a
broad upper trough over the northern Great Lakes is overspreading an
east-west frontal zone amidst midday heating. To the south of the
front, a very moist air mass is in place with dewpoints in the low
70s F. As surface temperatures warm near 80 F, destabilization
should continue this afternoon. Despite modest mid-level lapse
rates, 1000-1500 J/kg of MLCAPE and little inhibition will allow for
scattered to widespread thunderstorms.
A belt of enhanced westerly flow associated with the upper trough
will continue to shift eastward near the front supporting modest
deep-layer shear around 20-25 kt. Initial storms over OH and KY are
likely to be multi cellular with brief organization potential and
some clustering. As deep-layer shear increases to 30-35 kt over WV
and the Mid Atlantic states, a few marginal supercell structures and
some linear segments are also possible.
As thunderstorms develop and eventually cluster, damaging gust
potential should increase this afternoon over the OH Valley, with
additional development and the severe threat spreading eastward with
time. The brief stronger updrafts may also pose a risk for some
hail, but mid-level temperatures and lapse rates are not overly
favorable. Hail potential may be maximized with any storms that
remain more discrete.
Confidence in a sustained severe risk is highest farther east where
the best overlap of deep-layer shear and buoyancy are expected
(WV/VA into southern MD/DE). Given the expected increase in severe
potential this afternoon, a WW is possible in the next couple of
hours.
..Lyons/Gleason.. 05/27/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RAH...RNK...PBZ...RLX...JKL...ILN...
LAT...LON 37388207 38458274 38908272 39778148 39838111 39277960
38747775 38487633 38387501 36917591 36317558 36257640
36407905 37388207
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Wed May 27 2026
Valid 271300Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC...
...SUMMARY...
Scattered severe thunderstorms are possible across parts of the
Mid-Atlantic states this afternoon into the early evening. Strong
to severe gusts (50-65 mph) capable of wind damage will be the
primary hazard with the stronger thunderstorms.
...Mid-Atlantic/Ohio Valley...
An upper-level trough over the Great Lakes will move southeast
towards the upper OH Valley/Mid-Atlantic states during the period.
Water-vapor imagery this morning shows a lead disturbance over
southern OH moving east across the central Appalachians. In the low
levels, an analyzed frontal zone has been modulated by ongoing
showers/thunderstorms and it will move southeast today. A moist
airmass ahead of the front, featuring dewpoints in the upper 60s to
lower 70s F, will gradually destabilize through early afternoon.
East-southeastward moving clusters are forecast to evolve by later
this afternoon. Scattered strong to severe gusts (50-65 mph)
capable of wind damage will be the primary risk with the stronger
thunderstorms, although marginally severe hail may accompany the
stronger cores this afternoon.
...Southern ID into eastern OR...
A belt of strong easterly mid-level flow will remain over southwest
ID into southeast OR to the north of a stationary, deep-layer
cyclone over the Sierra Nevada. Heating of an adequately moist
boundary layer will steepen low-level lapse rates by early
afternoon. Widely scattered to scattered thunderstorms are forecast
to develop this afternoon. Forecast hodographs show 20-45 kt
700-500 mb flow (strongest over southeast OR) and mean storm motions
35-45 kt. These flow fields coupled with evaporatively cooled
downdrafts will likely result in a mix of quickly moving cells and
smaller-scale linear clusters. This activity will potentially be
capable of severe gusts (60-75 mph) before diminishing by mid-late
evening.
...Western Great Lakes...
Northwesterly mid-level flow will be in place across the western
Great Lakes today, as a shortwave trough moves southeastward across
the region. At the surface, a pocket of maximized low-level
moisture will be located over Wisconsin, where MLCAPE is expected to
peak in the 1500 to 2500 J/kg range. An isolated risk for large
hail/damaging gusts are possible with the stronger thunderstorms.
...Southern Texas Panhandle/West Texas/Far Western Oklahoma...
Somewhat displaced from an expansive overnight MCS along the TX
coast, an airmass featuring upper 50s to lower 60s F dewpoints will
destabilize beneath a weak mid- to upper-level trough. Widely
scattered to scattered storms are forecast to develop by late
afternoon and aggregate into small clusters this evening. Isolated
large hail/severe gusts are the primary severe hazards.
..Smith/Weinman.. 05/27/2026
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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 AM CDT Wed May 27 2026
Valid 271630Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY INTO THE MID-ATLANTIC...
...SUMMARY...
Scattered severe thunderstorms are possible across parts of the Ohio
Valley and Mid-Atlantic this afternoon and evening. Strong to severe
gusts capable of producing wind damage should be the primary hazard,
but isolated hail may also occur.
...Ohio Valley/Mid-Atlantic...
30-40 kt of mid-level westerly flow will be present today across
parts of the OH Valley and Mid-Atlantic, sandwiched between an upper
trough over Ontario/Quebec and a mid-level anticyclone centered over
the western Atlantic. A west-east oriented front, modulated by
ongoing convection, will serve as a focus and northern limit for
severe potential. Latest surface observations show a rather moist
low-level airmass present along/south of this boundary (also
reference the 12Z observed soundings from IAD/RNK), with surface
dewpoints generally in the mid 60s to low 70s. Lapse rates aloft are
expected to remain poor, and persistent cloud cover will slow
daytime heating.
Still, weak to moderate instability (MLCAPE 500-1500 J/kg) coupled
with 30-40 kt of westerly deep-layer shear will support organized
thunderstorms this afternoon and early evening as a weak mid-level
shortwave trough moves eastward across the OH Valley/Mid-Atlantic. A
mix of multicells and marginal supercell structures is anticipated
along/south of the front, with scattered damaging winds the main
severe risk. Some hail could also occur with the strongest cores.
The Slight Risk for severe/damaging winds has been expanded westward
into parts of WV and vicinity, where a favorable
environment/convective evolution should occur, similar to locations
farther east in VA/MD along/south of ongoing precipitation.
...Pacific Northwest/Northern Rockies...
A closed mid/upper-level low is not expected to move much over CA/NV
today. Enhanced east-southeasterly mid-level flow and modest
large-scale ascent to the north of this cyclone will likely support
isolated to widely scattered thunderstorms this afternoon and
evening across parts of OR/ID and western MT. Cool temperatures
aloft and adequate low-level moisture should support at least weak
instability as filtered daytime heating occurs. As low-level lapse
rates steepen with the well-mixed boundary layer, isolated severe
gusts appear possible with the high-based convection that develops
and spreads west-northwestward through the afternoon/evening. Some
gusts may reach up to 70-75 mph on a localized basis, but confidence
in a more focused corridor of severe winds remains too low to
include greater probabilities at this time. Isolated hail may also
occur.
...Coastal Texas to the ArklaTex...
An expansive MCS has moved offshore from coastal TX into the western
Gulf late this morning. A leading MCS/outflow is also present across
parts of southern/central LA. Current expectations are for limited
redevelopment and severe risk through the period in the wake of this
ongoing activity across coastal TX/southern LA. However, there may
be an opportunity for modest destabilization near an MCV across the
ArkLaTex vicinity this afternoon. Favorable/veering wind profiles
with height through mid levels and related deep-layer shear (see
recent VWPs from KSHV) would conditionally support organized
thunderstorms this afternoon, assuming sufficient instability can
develop amid widespread cloud cover. Have opted to add a focused
Marginal Risk across portions of the ArkLaTex and vicinity for this
potential, with both occasional damaging winds and a tornado or two
possible with the stronger cells that develop.
...Upper Midwest/Western Great Lakes...
Modest north-northwesterly mid-level flow should exist today across
the Upper Midwest and western Great Lakes. With continued daytime
heating, moderate instability should develop along/south of a weak
surface front. Thunderstorms that initiate along/near the front this
afternoon could pose an isolated threat for severe hail and damaging
winds, particularly across parts of WI where the best convective
signal exists in various short-term model guidance. However, overall
convective coverage is uncertain, as large-scale ascent should
remain fairly weak.
...Southern High Plains...
Cool temperatures aloft in association with a weak mid-level trough
over the southern High Plains should aid at least weak
destabilization this afternoon across parts of northwest TX into the
TX Panhandle and far western OK. While low-level moisture will
remain fairly muted and deep-layer shear rather modest, a few
stronger thunderstorms capable of producing isolated hail/gusty
winds and perhaps a landspout may occur.
..Gleason/Lyons.. 05/27/2026
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1120 AM CDT Wed May 27 2026
Valid 271700Z - 281200Z
...Great Basin and portions of the Southwest...
A 50-60 kt mid-level jet on the eastern periphery of an upper-low
centered over the Sierra Nevada will remain anchored over eastern NV
and western UT today into Day 2/Thursday. Recent downslope enhanced
wind gusts of 50-60 mph have been observed across southwestern UT.
Further boundary layer mixing today will yield minimum RH of 10-20%
across portions of the Southwest and eastern Great Basin. Widespread
southerly winds of 15-25 mph (locally higher in downslope favored
areas) developing through peak afternoon heating along with low RH
and drying/cured lower elevation fuels, will result in elevated fire
weather conditions today. A slight northward expansion of Elevated
Highlights was warranted across central UT in the lee of the central
UT mountain chain based current observation trends and latest short
term forecast guidance.
Otherwise, the forecast remains on track for northeastern MT. Please
see previous discussion for more details.
..Williams.. 05/27/2026
.PREV DISCUSSION... /ISSUED 1235 AM CDT Wed May 27 2026/
...Synopsis...
An upper level low will hover over the CA/Great Basin region today
as an upper ridge will continue to reside across the central CONUS.
Strengthening southerly flow aloft and tightening surface pressure
gradients east of a persisting surface low will promote a fire
weather threat for portions of the Southwest and Upper Colorado
River Basin. Farther east, a weak shortwave is expected to eject
across the central and southern Plains, bringing additional chances
of appreciable precipitation to a drought-stressed landscape.
...Great Basin...
Broad southwesterly flow associated with the hovering upper low will
sustain fire weather concerns for portions of the eastern Great
Basin, Upper CO River Basin, and parts of the Southwest. Southerly
surface winds of 15-25 mph and RH reductions of 10-20% will promote
Elevated to locally critical fire weather conditions this afternoon
amid available dry fuels.
...Northeastern Montana...
Prolonged lee surface troughing and increasing mid level flow will
promote strong southeasterly winds of 15-25 mph across the northern
High Plains. Despite some upper level cloud cover, a deep and
well-mixed boundary layer will support RH reductions of 15-20%
across northeastern MT and extreme western ND. Elevated highlights
have been slightly trimmed to exclude where appreciable 12-24h
precipitation has fallen.
...Please see www.spc.noaa.gov/fire for graphic product...
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