ACUS48 KWNS 190901
SWOD48
SPC AC 190900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Tue May 19 2026

Valid 221200Z - 271200Z

...DISCUSSION...
...D4/Friday...
Moist southerly return flow will begin across the southern/central
Plains into the weekend. Modest westerly flow aloft across the
dryline on D4/Friday may support potential for severe storms.
Guidance shows disagreement in the location of the dryline, with
some guidance depicting the dryline back in the OK/TX Panhandle and
others with a further east dryline into western Oklahoma. Forecast
soundings show limited inhibition by the afternoon, with strong
daytime heating and temperatures warming into the mid to upper 80s.
Steep low to mid-level lapse rates are also noted, with moderate to
strong instability ahead of the dryline. Given weak inhibition and
modest mid-level flow, convective initiation is possible by the
afternoon. Shear profiles are marginally sufficient to support
organized storms, with a mix of multi-cell and supercell modes. A
15% area was added with this outlook where confidence is greater in
convection occurring.

...D5/Saturday-D8/Tuesday...
Through the end of the extended period, height rises are expected
across the central US as a high amplitude ridge settles in from the
west. While moisture will continue to move northward into the
central/northern Plains, generally weak flow and subsidence will
keep severe potential low.

..Thornton.. 05/19/2026

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ACUS48 KWNS 200858
SWOD48
SPC AC 200856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Wed May 20 2026

Valid 231200Z - 281200Z

...DISCUSSION...
Severe potential will remain low through the extended period. Weak
troughing will continue across the central Plains through the
weekend before height rises begin across the central US with a high
amplitude ridge settling in from the west. This pattern will remain
in place through early to middle of next week. Slow moisture return
will be ongoing across much of the Plains into the Midwest with
occasional rounds of widespread rainfall and thunderstorms, but
generally weak flow and subsidence will keep organized storm
potential low through D8/Wednesday.

..Thornton.. 05/20/2026

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ACUS48 KWNS 210849
SWOD48
SPC AC 210847

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CDT Thu May 21 2026

Valid 241200Z - 291200Z

...DISCUSSION...
Severe potential will remain low through the beginning of the
extended period. Weak troughing will continue across the central
Plains D4/Sunday before height rises begin across the central US
with a high amplitude ridge settling in from the west D5/Monday.
This pattern will remain in place through early next week. Slow
moisture return will be ongoing across much of the Plains into the
Midwest with occasional rounds of widespread rainfall and
thunderstorms, but generally weak flow and subsidence will keep
organized storm potential low.

By the midweek, a trough is progged to begin deepening across the
Pacific Northwest. As the upper low slowly shifts eastward, stronger
flow will overspread the Intermountain West into the Northern
Rockies, resulting in strengthening lee troughing across the
central/northern Plains D6/Tuesday and D7/Wednesday. Moisture
advection will spread northward amid strengthening southerly flow
across the central/northern Plains. While there are some differences
in the placement of upper-level and surface features, it is possible
that severe chances will return across portions of northern High
Plains. For now, confidence in exact corridors remains low given
model guidance differences.

..Thornton.. 05/21/2026

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ACUS48 KWNS 220903
SWOD48
SPC AC 220901

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0401 AM CDT Fri May 22 2026

Valid 251200Z - 301200Z

...DISCUSSION...
Severe potential will remain low D4/Monday. Height rises begin
across the central US with a high amplitude ridge settling in from
the west. Slow moisture return will be ongoing across much of the
Plains into the Midwest with widely scattered areas of rainfall and thunderstorms. A few strong to marginally severe storms will be
possible, but generally weak flow and subsidence will keep organized
storm potential low.

A trough is progged to begin deepening across the Pacific Northwest
D5/Tuesday into D6/Wednesday. As the upper low slowly shifts
eastward, stronger flow will overspread the Intermountain West into
the Northern Rockies, resulting in strengthening lee troughing
across the central/northern Plains. Moisture advection will spread
northward amid strengthening southerly flow across the
central/northern Plains. There remains uncertainty in the northward
and westward extent of moisture return and in progression of the
western trough. Severe storms may occur each day across some portion
of the northern and northern/central High Plains. For now,
confidence in exact corridors remains low.

By D7/Thursday-D8/Friday, guidance suggests the western low becomes
cut off and slowly wobbles towards the Great Basin before becoming
absorbed back into the northern stream. This is likely due to
continued high amplitude ridging across the central US. Some severe
potential may extend into the eastern US as a cold front shifts
southward as flow enhances in the trough across Quebec in the D7-D8
period.

..Thornton.. 05/22/2026

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ACUS48 KWNS 230855
SWOD48
SPC AC 230853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Sat May 23 2026

Valid 261200Z - 311200Z

...DISCUSSION...
A trough will deepen and shift eastward across the Pacific Northwest D4/Tuesday-D5/Wednesday. As the upper low slowly shifts eastward,
stronger flow will overspread the Intermountain West into the
Northern Rockies which will result in strengthening lee troughing
across the central/northern Plains. Moisture advection will spread
northward with the strengthening southerly flow across the
central/northern Plains. Severe storms may occur each day across
some portion of the northern and northern/central High Plains. In
addition, strengthening southern stream flow may bring stronger
storms across the Sierra Madre which may bring severe potential into
portions of far southern Texas. For now, confidence in exact
corridors of greater severe potential remains low.

By D6/Thursday-D8/Saturday, guidance suggests the western low
becomes cut off and slowly wobbles towards the Great Basin before
becoming absorbed back into the northern stream, likely due to the
high amplitude ridging across the central. Some severe potential may
extend into the eastern US as a cold front shifts southward as flow
enhances in the trough across Quebec in the D6-D7 period.

..Thornton.. 05/23/2026

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ACUS48 KWNS 240902
SWOD48
SPC AC 240900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sun May 24 2026

Valid 271200Z - 011200Z

...DISCUSSION...
The western US trough will shift southward into the Great Basin on
D4/Wednesday with strengthening westerly flow overspreading the
southwestern US. The axis of the central US ridge will shift
eastward, with heights continuing to rise across portions of the central/northern Plains. A few stronger storms may be possible
across portions of central/eastern Montana. Overall, confidence is
low in any areas of organized severe potential. Widely scattered
thunderstorm activity will be possible from the Southern/Central
Plains to the southeastern US. Generally weak flow should keep
organized severe potential low. The exception may be across far
western Texas where modest mid-level flow will continue, though
large scale forcing for ascent will decrease from D3/Tuesday.

For the D5/Thursday through D6/Friday period, ensemble guidance
suggests the western low will shift northward again and phase with
the northern jet stream. There is low confidence in chances for
strong to severe storms, pending details on moisture, across the
northern Rockies into the central/northern high Plains as lee
troughing strengthens. Some severe potential may also extend into
the eastern and southeastern US as a cold front shifts southward as
flow enhances in the trough across Quebec from D6/Friday to
D7/Saturday.

..Thornton.. 05/24/2026

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ACUS48 KWNS 250845
SWOD48
SPC AC 250843

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CDT Mon May 25 2026

Valid 281200Z - 021200Z

...DISCUSSION...
...D4/Thursday through D5/Friday...
The western low is expected to shift northward again and phase with
the northern jet stream D4/Thursday - D5/Friday. There is low
confidence in chances for strong to severe storms, pending details
on moisture, across the Intermountain West and northern Rockies.

Guidance suggests that as the western trough shifts northward and
weak disturbances rotate across the Rockies, lee troughing across
the Plains may strengthen D5/Friday, bringing a potential for low
end severe risk into the central/northern High Plains. For now
confidence in any corridors of organized severe risk remain too low.

A cold front will sag southward across the east coast D4/Thursday
through D5/Friday as enhanced flow digs an upper level trough across
Quebec southward into the eastern Great Lakes. Some low end severe
potential may accompany this frontal passage each day, but
uncertainty remains high in overlap of deep layer shear with better moisture/instability.

...D6/Saturday through D8/Monday...
Toward the end of next weekend D7/Sunday through D8/Monday, ensemble
guidance is increasing in confidence for a large scale ridge to
build in across the central/western US with rising heights and
warming temperatures. Building surface high pressure across the
Midwest/Great Lakes may shunt moisture southward to the Gulf states.
Should this pattern continue to hold, severe potential will remain
low through much of the CONUS.

..Thornton.. 05/25/2026

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ACUS48 KWNS 260840
SWOD48
SPC AC 260838

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Tue May 26 2026

Valid 291200Z - 031200Z

...DISCUSSION...
An upper low is forecast to be located over the Great Basin on
Friday/D4, moving into the northern Rockies/High Plains through
Saturday/D5, and weakening all the while. Models indicate 500 mb
winds by Saturday will only be in the 20-25 kt range with this
feature. Therefore, despite low 60s F dewpoints, the severe risk is
expected to be somewhat disorganized. However, at least low
probabilities may be required in later outlook updates.

Meanwhile, a low-latitude shortwave trough is forecast to move
across the southern Plains and into the lower MS Valley, from
Saturday/D5 into Sunday/D6. Given the expected very moist air mass
in place with 70s F dewpoints, and lack of capping, scattered areas
of thunderstorms are likely throughout the period. Much of the
activity will occur over TX and OK, where moderate instability is
forecast. However, shear will be generally weak. Given the daily
cycle of thunderstorms and resulting outflow boundaries across the
entire region, predictability is too low to denote any concentrated
severe areas. However, sporadic severe winds, perhaps isolated hail,
cannot be ruled out from the southern Plains into the lower MS
Valley from Saturday/D5 into Monday/D7.

..Jewell.. 05/26/2026

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ACUS48 KWNS 270747
SWOD48
SPC AC 270746

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 AM CDT Wed May 27 2026

Valid 301200Z - 041200Z

...DISCUSSION...
On Saturday/D4, an upper low will weaken as it moves from UT into
WY, with midlevel wind speeds at or below 25 kt across the northern Rockies/Plains. This feature will persist into Sunday/D5 and
Monday/D6 as it moves toward MT and eventually into Canada. Given
the weak winds aloft, severe potential should be relatively low, but
isolated strong storms may occur over parts of the northern Plains.

Farther south, stronger instability is forecast over the southern
and central Plains, where 60s to lower 70s F dewpoints will exist.
Although unstable, shear will be quite weak. Saturday/D4 may hold
slightly greater severe potential compared to other days, as the
southern lobe of the western trough lifts north out of the
southern/central Plains. However, shear will still be marginal, and
the likelihood antecedent precip/outflows lessens predictability in
the weak forcing pattern. The stronger instability air mass appear
most prominent through about Monday/D6. Thereafter, an upper trough
may amplify over the eastern CONUS, driving high pressure south
across the eastern CONUS/MS Valley.

..Jewell.. 05/27/2026

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ACUS48 KWNS 280839
SWOD48
SPC AC 280837

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CDT Thu May 28 2026

Valid 311200Z - 051200Z

...DISCUSSION...
For much of the D4-D8 period, an upper trough is forecast to reside
over the Northeast, with high pressure over the Great Lakes and much
of the Midwest to Mid Atlantic. West of this surface high, southerly
winds across the Plains will maintain a moist air mass with 60s and
70s F dewpoints prevalent.

In the upper levels, a weak negatively tilted trough will shift
slowly northward across the northern Plains & Rockies on Sunday/D4
and Monday/D5, providing cooler temperatures aloft and slightly
stronger wind speeds. Farther south into the central and southern
Plains, winds aloft will be even weaker, however, the midlevels will
remain relatively cool, supporting areas of strong instability due
to steep lapse rates aloft.

In general, areas of strong thunderstorms appear likely on a daily
basis across much of the Plains during the peak heating hours. Areas
of severe storms will be possible as well due to the widespread
2000+ J/kg MUCAPE, with localized hail & wind potential where
clusters develop. The NE/KS/OK/MO area in particular will be within
the heart of the instability axis, with 3000-4000 J/kg possible.

Predictability is low in this pattern due to lack of large-scale
forcing, and the fact that clusters of storms may persist overnight
as various outflow boundaries affect storm potential each subsequent
day. However, smaller/more focused areas of potential may become
evident in subsequent outlook cycles.

..Jewell.. 05/28/2026

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ACUS48 KWNS 290828
SWOD48
SPC AC 290826

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0326 AM CDT Fri May 29 2026

Valid 011200Z - 061200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
At mid-levels, a ridge is forecast to move from the north-central
U.S. on Monday into the Great Lakes by Wednesday, as a shortwave
trough moves slowly eastward from the northern Rockies into the
northern Plains. In the vicinity of the ridge on Monday, an axis of
moderate to strong instability is forecast to develop. In spite of
limited forcing, isolated severe storms may form on Monday afternoon
over parts of the north-central U.S., mainly in areas where
low-level convergence becomes maximized. On Tuesday, isolated severe
storms will be possible ahead of the approaching trough along a
north-to-south corridor of instability in the Dakotas and Nebraska.
Storms will again be possible ahead of the trough in the upper
Mississippi and mid Missouri Valleys on Wednesday. The primary
threats would be isolated severe gusts and hail.

...Thursday/Day 7 and Friday/Day 8...
The mid-level trough is forecast to move into the Great Lakes on
Thursday and into the Northeast on Friday, as another trough moves
into the central U.S. Ahead of this second trough, isolated severe
storms will be possible on Thursday and Friday in parts of the
central and northern Plains. A few of the stronger storms could be
associated with severe wind gusts and hail.

..Broyles.. 05/29/2026

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