RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Tue Apr 21 06:03:02 UTC 2026.
No Mesoscale Discussions are in effect as of Tue Apr 21 06:03:02 UTC 2026.
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1237 AM CDT Tue Apr 21 2026
Valid 211200Z - 221200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms are expected today over much of Texas, from Illinois
into Ohio, and over portions of central California. Severe weather
is not currently forecast.
...Synopsis...
An upper ridge will move into the Plains as an upper trough moves
inland over the West, with a strong cyclonic speed max moving across
CA and into the Great Basin. Meanwhile, northwest flow aloft will
extend from the Great Lakes into the Mid Atlantic. Farther south, a
weakening disturbance will move out of TX and toward the lower MS
Valley.
At the surface, high pressure will remain over much of the eastern
states and across the Gulf Coast. Southerly winds across the Plains
and around this high may support mid to upper 50s F dewpoints as far
north as IA and IL by 00Z, while higher dewpoints remain relegated
to southern TX. Here, scattered showers and thunderstorms will
likely be ongoing early on Tuesday where weak elevated instability
will remain.
...IL/IN/OH...
A surface trough is forecast to develop from Lower MI into southern
WI and northern IL by late afternoon, beneath the northwest flow
regime and with cool midlevel temperatures. Southwest surface winds
and daytime heating should lead to 40s and 50s F dewpoints, with a
relatively dry boundary layer overall. Models suggest at least
isolated late day and evening thunderstorms will develop ahead of
this trough, though instability levels are uncertain. Despite
marginal dewpoints/moisture, the cool temperatures aloft may support
a few cells capable of small hail from IL into IN by late afternoon.
Wind gust potential is more uncertain and dependent on storm
coverage/outflow production, with the dry boundary layer
conditionally helping strong gust potential into the evening and
perhaps overnight.
...Central CA...
Cold temperatures aloft north of the midlevel jet will support weak
instability over parts of the central Valleys. Given early
precipitation and clouds, as well as marginal low-level shear,
severe storms appear unlikely. However, a few strong storms may
occur late in the afternoon if sufficient heating occurs behind the
early day rain. Small hail appears most probable with the strongest
cells.
..Jewell.. 04/21/2026
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1253 AM CDT Tue Apr 21 2026
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE HIGH PLAINS...
...SUMMARY...
Severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening on Wednesday across portions
of the High Plains.
... Synopsis ...
A closed upper low across the western US will devolve into an open
wave as it lifts northeast toward the northern Plains. At the same
time, a surface low will gradually deepen as it moves across
northern Montana east into North Dakota by Thursday morning.
Lee troughing will strengthen during the day with the approach of
the western trough. The surface wind field within this lee trough
will function to sharpen a dryline from the surface low south across
much of the High Plains. To the east of the dryline, strengthening
southerly winds will draw Gulf moisture northward into the
strengthening cyclone. The quality of this moisture return remains a
significant source of uncertainty regarding thunderstorm chances
with northward extent.
... Northern High Plains including areas of eastern Montana...
By late afternoon increasing large-scale ascent, driven by modest
height falls, will overspread northern portions of the dryline.
Despite moisture concerns, isolated to scattered thunderstorms
should develop across portions of the dryline during the afternoon.
Large temperature/dewpoint spreads may support strong wind gusts
with the strongest storms.
The best synoptic scale forcing for ascent will move across portions
of eastern Montana during the late afternoon and evening. Should
boundary layer moisture be richer than currently anticipated (e.g.,
closer to 40F than 25F), a threat for marginally severe wind gusts
may materialize. This area will continued to be assessed in
subsequent outlooks for an upgrade to Level 1/Marginal.
... Southern High Plains ...
Midlevel height falls will not be as great here as compared to areas
farther north. However, richer boundary layer moisture and strong
dryline circulations aided by temperatures approaching 90F to the
west of the dryline should support at least isolated thunderstorm
development. Around 40 knots of cloud-layer shear should support at
least a marginal hail risk with any storm that develops.
..Marsh.. 04/21/2026
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1220 AM CDT Tue Apr 21 2026
Valid 211200Z - 221200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL FLORIDA AND
THE WEST FLORIDA COAST...
...Synopsis...
Broad northwest flow aloft will encompass much of Northeast and Mid
Atlantic in the wake of a departing upper-trough. A dry airmass will
remain in place across the eastern U.S., Southeast and Deep South as
surface high pressure shifts into the Atlantic. Farther west, a
negatively-tilted upper trough will surge into the Western U.S.,
with dry and breezy conditions focused over the Great Basin ahead of
an advancing cold front.
...Florida into Southern Georgia...
East to northeast winds of 10-15 mph on the southern fringe of the
surface high are expected today across portions of southern GA into
FL. Stronger sustained east winds of 15 mph (with higher gusts) will
be located farther south across the FL Peninsula, while drier
conditions including relative humidity as low as 15% amid higher
temperatures in the lower 80s will be displaced to the north over
the FL Panhandle and southern GA. Critical fire weather conditions
are expected across portions of central FL and the West FL Coast
where sustained winds are likely to reach 15 mph and RH falls into
the 25-35% range. Elevated fire weather concerns were extended into
much of the FL Panhandle where offshore trajectories will maintain a
dry boundary layer through much of the afternoon. Fuels remain very
receptive amid worsening drought conditions with ongoing fire
activity.
...Lower Mississippi Valley...
A relative minimum in recent rainfall and existing dry fuels
coupled with dry return flow on the western periphery of the broad
surface high pressure moving off the Mid Atlantic, will bring a fire
weather threat to portions of western TN/MS and eastern AR. South to
southwest winds of 10-15 mph amid relative humidity of 20-25%
supports a continuation of Elevated fire weather highlights across
portions of the lower MS River Valley.
...East-Central Wyoming...
A limited fire weather threat will emerge across east-central WY
with a weak downslope warming and drying regime in place across the
central High Plains. A shallow near-surface temperature inversion
will quickly mix out under mostly sunny skies through the late
morning hours, following possible poor RH recoveries overnight in
eastern WY/CO. RH of 10% or below is likely by the afternoon across
the central High Plains. However, weak boundary layer flow and lack
of substantial surface lee troughing across the region should limit
spatial extent and duration of sustained west winds of up to 15 mph
across east-central WY, precluding introduction of Elevated
Highlights.
..Williams.. 04/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue Apr 21 2026
Valid 221200Z - 231200Z
...CRITICAL FIRE WEATHER AREA FOR NORTHEASTERN NEW MEXICO INTO THE
SOUTHERN INTO NORTH-CENTRAL HIGH PLAINS...
...Synopsis...
A pronounced, eastward progressing upper-level trough, accompanying
55-65 knot mid-level jet and deepening lee surface troughing over
the High Plains will promote a broad fire weather threat across the
central/southern High Plains and portions of the Southwest
Wednesday. A surface trough and associated frontal boundary will
traverse the Southern Great Lakes and Mid Atlantic regions.
Increased southwesterly flow south of the trough will contribute to
fire weather concerns across the Mid Atlantic.
...Southwest into the Southern and North-Central Plains...
A lee surface low will deepen across the northern High Plains as the
robust mid-level trough advances into Intermountain West, with the
associated mid-level jet moving over the Upper CO River Basin. An
expansive fire weather concern will emerge across portions of the
Southwest into the central and southern Plains as southwest winds
accelerate beginning late Wednesday morning. Downslope enhanced
southwest winds of 20-25 mph with higher gusts aligning with
critically low relative humidity below 10% should be most pronounced
across eastern WY/CO and into portions of northeastern NM and
adjacent TX/OK Panhandle areas, where Critical Highlights were
introduced. Locally extremely critical fire weather conditions
including southwest winds of 30-35 mph and single digit RH are
possible in favored terrain gaps along and east of the Sangre De
Cristo Mountains and the CO Front Range where fuels remain receptive
to wildfire spread.
...Piedmont and portions of Mid Atlantic...
Dry and breezy conditions ahead of an approaching trough and
associated cold front will bring a fire weather threat to portions
of the Carolinas and southern VA Wednesday. Persistent northwest
flow aloft and tighter surface pressure gradients will support
increasing winds and downslope drying in the lee of the
Appalachians. West to southwest winds of 10-20 mph along with RH
falling to 20-30% during peak heating will align with a receptive
fuelscape to promote several hours of elevated fire weather
conditions. Elevated Highlights were expanded slightly northward and
eastward based on latest forecast guidance.
..Williams.. 04/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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