RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Wed Mar 18 22:18:02 UTC 2026.
No Mesoscale Discussions are in effect as of Wed Mar 18 22:18:02 UTC 2026.
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0247 PM CDT Wed Mar 18 2026
Valid 182000Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms will be possible today across far south
Florida.
...Synopsis...
The previous forecast remains on track with no adjustments required.
Latest GOES imagery shows shallow convection developing immediately
north of the current thunder line and south of Lake Okeechobee.
While a lightning flash or two is possible with this activity, the
lack of vertical development/limited cloud phase change (per Day
Cloud Phase imagery) limits confidence in lightning potential.
Latest guidance continues to suggest the greatest lightning threat
will remain along the southeast FL coast through evening.
..Moore.. 03/18/2026
.PREV DISCUSSION... /ISSUED 1044 AM CDT Wed Mar 18 2026/
...Synopsis...
A substantial upper high and attendant ridge is apparent in morning
water vapor imagery over the western U.S. Further east, a stalled
front is noted across the Bahamas and Florida Straits. Surface high
pressure in the wake of the frontal boundary across the Southeast
will maintain offshore trajectories and a dearth of boundary layer
moisture. This will preclude thunderstorm activity across most of
the CONUS.
Some lingering low-level moisture and weak elevated instability may
support a couple of thunderstorms over far south FL and portions of
the Keys today, though most activity will remain offshore.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0155 PM CDT Wed Mar 18 2026
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A low chance of a few thunderstorms may develop on Friday near the
Upper Ohio Valley and vicinity, and also near the southeast Florida
coast.
...Synopsis...
An expansive upper ridge will remain in place over most of the
western CONUS on Friday. A downstream large-scale upper trough will
persist over the East. Within the large-scale trough, one shortwave
will move offshore of Florida early in the period, while an upstream
shortwave moves across the Great Lakes. A surface low will accompany
the Great Lakes shortwave trough as it moves southeastward, as a
trailing cold front moves through the Ohio Valley.
A low probability (around 10 percent) thunderstorm threat may
continue from late D2/Thursday into early D3/Friday near the
southeast FL coast. Farther north, modest low-level moistening (with
dewpoints increasing to near/above 50 F) may support isolated
thunderstorm development during the afternoon and evening near the
Upper Ohio Valley, in the vicinity of the advancing cold front. Weak
instability is currently expected to limit organized
severe-thunderstorm potential.
..Dean.. 03/18/2026
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SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0231 PM CDT Wed Mar 18 2026
Valid 191200Z - 201200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL AND EASTERN
WYOMING...
...Oregon...
An Elevated area was introduced over portions of central and eastern
Oregon on Day 2/Thursday. Just west of the large ridge axis,
forecast guidance is indicating sustained southwest surface winds of
10-20 mph with RHs falling to 10-20% during peak heating.
Additionally, temperatures are expected to rise 15-25 degrees above
normal, approaching daily records. While fire concerns are not
normally a concern for this time of year across this area, this hot,
dry, and windy combination warrants highlighting ahead of green up.
...Central/Northern High Plains...
The Elevated area over much of Wyoming was expanded to include
extreme southeastern Montana, portions of southwest South Dakota,
and more of western Nebraska. While forecast certainty in the areal
expansion of elevated wind/RH conditions has increased with the
latest model guidance, fuels guidance has also indicated very dry
vegetation in place over the region adjacent to the earlier Elevated
area. The existing Critical area remains on track as previously
described.
..Stearns/Williams.. 03/18/2026
.PREV DISCUSSION... /ISSUED 0204 AM CDT Wed Mar 18 2026/
...Synopsis...
Upper-level ridging will remain in place across the Southwest for
D2/Thursday, with strong northwesterly upper-level flow persisting
across the northern Rockies and central CONUS. This will support a
continued downslope regime across the central High Plains and
western Wyoming Basin, with elevated to critical fire weather
conditions expected amid strong west-northwest surface winds and
very low RH values.
...Portions of the central High Plains into the western Wyoming
Basin...
The synoptic-scale pattern will remain relatively consistent from
today into D2/Thursday, with anomalously strong upper-level ridging
persisting across the Southwest and strong northwesterly flow in
place across the central Rockies. At the surface, high pressure
across the Intermountain West will couple with surface low pressure
shifting southeastward across southern Canada to support reduced RH
values of 10-15% and west-northwesterly downslope winds of 20-25
mph. With persistent dry/windy conditions continuing to aid in the
maintenance of receptive fuels, this is expected to yield critical
fire weather conditions across much of southeastern Wyoming. Current
guidance indicates mid-level flow will weaken slightly from D1 into
D2, but deep boundary layer mixing may also support wind gusts of
30-35 mph across much of this area.
Elevated fire weather concerns are also expected across adjacent
regions, including much of southwestern Wyoming, portions of extreme
northern Colorado, the western Nebraska Panhandle, extreme
southwestern South Dakota, and extreme northeastern Utah, where
sustained westerly surface winds of 15-20 mph are forecast to
overlap reduced RH of 10-15%. Marginal fuel receptiveness and lower
confidence in higher sustained winds are expected to limit the
northern extent of widespread elevated fire weather concerns at this
time; however, this area will be monitored for potential expansion
as fuels continue to dry given the persistent pattern and resultant
anomalous temperatures expected over much of the region.
...Please see www.spc.noaa.gov/fire for graphic product...
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SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0447 PM CDT Wed Mar 18 2026
Valid 201200Z - 261200Z
A persistent upper-level ridge centered over the California/Arizona
border will dominate the weather across the western US through Day
3/Friday. A shortwave trough will crest the ridge, moving through
the Pacific Northwest on Day 4/Saturday before crossing the northern
Plains and Great Lakes region Day 5/Sunday into Day 6/Monday. The
latest forecast guidance continues to break down the upper-level
ridge, at least temporarily, shifting the corridor of stronger
mid-level flow further south late in the period. This will also
coincide with a cold front pushing south through the Plains on Day
5/Sunday. A ridge begins to build over the western US again starting
on Day 7/Tuesday.
On Day 3/Friday through Day 4/Saturday, moderate northwest flow
aloft will remain in place over much of the central High Plains.
Record warm temperatures are likely as the ridge builds across the
western US, leading to deep boundary-layer mixing and resultant dry
and windy conditions across much of Wyoming, far northern Colorado,
southern Montana, portions of western South Dakota, and Nebraska. A
70% area was introduced for Day 3/Friday, reflecting high confidence
in sustained westerly winds of 20-30 mph overlapping with RH values
of 12-20% during peak heating across portions of eastern Wyoming.
On Day 4/Saturday and Day 5/Sunday, current guidance suggests the
potential for critical conditions over portions of the central and
southern High Plains and a good portion of the Southwest as the
aforementioned cold front passes through. As such, there was a
significant increase in coverage for the 40% area versus the last
issuance. The factor precluding additional expansion into the Great
Basin is currently sub-critical fuel conditions over that region.
The 40% area was also slightly expanded for Day 5/Sunday to account
for strengthening southwesterly flow across portions of Texas and
southwest Oklahoma. Some areas across the southern Plains may see
the burn period extended through much of the Day 4/Saturday night
period due to a well-mixed nocturnal environment.
As the ridge begins to build back over the western US on Day
7/Tuesday, fire weather conditions appear to remain subdued. By Day
8/Wednesday, the latest forecast guidance is hinting at yet another
period of hot, dry, and windy conditions focused over much of
Wyoming and surrounding areas yet again. No areas were included with
this issuance, but they may be needed over this area if forecast
certainty continues to increase during this time period.
Record temperatures and dry conditions will continue to desiccate
fuels over several consecutive days across the southern two-thirds
of the western US through the outlook period. Independent of wind
speeds, high vapor pressure deficits and low RH values suggest
extended burn periods across these areas where fuels become
increasingly receptive to ignition.
..Stearns/Williams.. 03/18/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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