SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0246 PM CDT Mon Apr 20 2026

Valid 202000Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected today.

...20Z Update...
The TSTM area over the coast of southern New England and the
Mid-Atlantic was removed, as large-scale forcing for ascent and
related thunderstorm activity has shifted offshore. Elsewhere, the
previous forecast remains on track.

..Weinman.. 04/20/2026

.PREV DISCUSSION... /ISSUED 1052 AM CDT Mon Apr 20 2026/

...Synopsis...
An upper impulse will continue to pose a risk of scattered
thunderstorms over parts of NM and south/west TX through the
afternoon, with activity spreading into north-central TX late
tonight.  

Other thunderstorms are possible this afternoon and evening over
south FL in a moist and marginally unstable air mass, along the
coast of southern New England, and over portions of OR/WA.  In all
areas, weak instability will preclude the risk of organized severe
storms.

SPC 1930Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0230 PM CDT Mon Apr 20 2026

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
HIGH PLAINS...

...SUMMARY...
Severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening across portions of the High
Plains.

...Synopsis...
A broad trough will begin to move into the Rockies and adjacent High
Plains. A shortwave trough will eject into the northern Plains in
association with the broader trough. At the surface, a deep surface
low will develop in eastern Montana with a lee trough/dryline
extending into the southern High Plains.

...High Plains...
As the upper-trough approaches the Rockies, the lee trough and
dryline are expected to sharpen. Forcing for ascent will be
strongest in the Nebraska Panhandle/western South Dakota vicinity.
This area is also has the largest variability in terms of moisture
return (the NAM being much more bullish than the ECMWF). Farther
south, moisture will generally be greater. Guidance is in agreement
that 60s F dewpoints are probable in the Texas South Plains and
perhaps parts of the Panhandle. The issue farther south will be the
lack of synoptic ascent. Temperatures behind the dryline will be in
the upper 80s F to perhaps low 90s F. The depth of the circulation
may be enough to initiate an isolated storm or two, but confidence
is still not overly high. Environmentally, deep-layer shear will be
oriented roughly perpendicular to the dryline, especially from
western Kansas southward. Supercells would be favored if storms
develop. MLCAPE of 1000 J/kg in South Dakota to 1500-2500 J/kg
farther south is expected by the afternoon. Large hail and severe
wind gusts would be possible.

...Central/Easter Montana...
With the surface low deepening through the day, at least modest
moisture return northwestward is anticipated into central/eastern
Montana. However, moisture will still be quite scant across the
region. Dewpoints may not reach the 40s F. Given the forcing for
ascent, high-based convection is possible. The very dry sub-cloud
layers could lead to gusty outflow winds. At present, confidence in
severe gusts is too low to warrant wind probabilities.

..Wendt.. 04/20/2026

SPC Day 2 Fire Weather Outlook

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1253 PM CDT Mon Apr 20 2026

Valid 211200Z - 221200Z

...Portions of the Mid-South...
As an upper trough exits the Eastern Seaboard and the pattern
transitions to upper-level ridging, 20-30 kt south-southwesterly
flow aloft and tightening surface pressure gradients will promote
dry and breezy conditions for portions of the Mid-Mississippi valley
on Tuesday. Southwesterly winds of 10-15 mph (gusts up to 20 mph)
and low RH values of 20-30 percent amid drying fuels are supportive
of a fire weather threat, thus Elevated highlights have been
introduced. 

The rest of the forecast remains on track, see the previous
discussion for more information.

..Elizalde-Garcia.. 04/20/2026

.PREV DISCUSSION... /ISSUED 0129 AM CDT Mon Apr 20 2026/

...Synopsis...
Upper-level ridging will gradually slide east over the Great Plains
on D2/Tuesday as a closed upper-level low moves onshore across the
West Coast. At the surface, high pressure will build into the
Southeast while a frontal system advances across the northern Great
Plains and Upper Midwest.

...Portions of Florida into southern Georgia...
Sustained easterly winds of 10-15 mph along the southeastern
periphery of high pressure building into the Southeast will overlap
reduced RH of 20-30% across much of the Florida Peninsula and into
southern Georgia Tuesday afternoon. Continued dry conditions amid
extreme to exceptional drought continues to promote receptive fuels
across this region, with ERCs currently at or above the 95th
percentile. This combination is expected to support elevated fire
weather concerns for at least a few hours. While winds are currently
forecast to remain below critical criteria, locally critical
conditions may be possible given the dryness/receptiveness of fuels
and potential for occasional wind gusts to 20 mph.

...Please see www.spc.noaa.gov/fire for graphic product...

SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 PM CDT Mon Apr 20 2026

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will be possible across the West, portions of the
southern Plains, and the southern Great Lakes on Tuesday. Potential
for severe weather appears low.

...Synopsis...
Upper-level ridging is expected to build into the Plains on Tuesday.
Moderate northwesterly flow aloft will remain across the Upper
Midwest/Great Lakes. In the West, an upper trough will move into
California and the western Great Basin. At the surface, a high
pressure system will persist in the Southeast. Initial moisture
return around the western flank of this anticyclone will occur
through the day. This moisture will interact with a weak boundary
within the Midwest/Lower Great Lakes.

...Midwest/Lower Great Lakes...
Ahead of the weak surface boundary, some increase in low-level
moisture can be expected. Moisture should generally be greater along
the Iowa/Missouri border with diminishing dewpoints towards the
Lower Great Lakes/Ohio Valley. Within moderate northwesterly flow
aloft, a subtle shortwave trough is expected to move towards
southern Lake Michigan during the afternoon. Temperatures at 500 mb
of around -18C should promote some convection along the boundary by
late afternoon. Farther west, forcing for ascent will be weaker and
capping will be stronger. The main question in this scenario
continues to be the quantity of moisture return ahead of the
boundary. Guidance does suggest low 50s F are possible, but given
how dry the current airmass across the region is and how late this
initial moisture return will be, confidence in that forecast is low.
The current expectation is that isolated to widely scattered storms
are possible by late afternoon/early evening, particularly near
southern Lake Michigan. These storms may briefly strengthen and be
capable of gusty winds/small hail. Thereafter, nocturnal cooling
should lead to a weakening trend. Development near the Iowa/Missouri
is far more conditional.

...Trans-Pecos/Big Bend into Central Texas...
Convection will be ongoing Tuesday morning in central Texas.
Isolated small hail and gusty winds are possible, but deep-layer
shear will be weakening as the ridge builds into the Plains through
the day. Farther west, a weak dryline is possible into the Big Bend
region. An isolated storm or two could develop. Weak vertical shear
and marginal buoyancy should limit severe potential.

...California Central Valley...
After an initial period of precipitation in the morning, pockets of
surface heating in the afternoon may lead to MLCAPE of 250-500 J/kg.
While a stronger storm or two is possible, the severe threat will be
limited by weak deep-layer shear.

..Wendt.. 04/20/2026