SPC AC 190105
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0805 PM CDT Mon May 18 2026
Valid 190100Z - 191200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR NORTHERN OKLAHOMA...SOUTHERN AND EASTERN KANSAS INTO NORTHWEST
MISSOURI...FAR SOUTHEAST NEBRASKA AND SOUTH-CENTRAL IOWA...
...SUMMARY...
Numerous severe thunderstorms are expected this evening from the
southern and central Plains into the mid Missouri Valley. Supercells
and bowing line segments capable of producing severe wind gusts,
tornadoes and large hail remain likely from eastern and southern
Kansas into far southeast Nebraska, Iowa and northwest Missouri.
...Southern and Central Plains/Mid Missouri Valley...
At the synoptic level, multiple shortwave troughs are ejecting
northeastward across the central U.S. early this evening. A 50 to 70
knot mid-level jet is translating northeastward across the central
Plains, with a 40 to 50 knot low-level jet in place from northern
Oklahoma into eastern Kansas and western Missouri. A squall-line is
ongoing along the western edge of the low-level jet, and this line
will move east-southeastward across the remainder of eastern Kansas
into western Missouri this evening into tonight. Ahead of the line,
strong instability is analyzed by the RAP with MLCAPE in the 3000 to
4000 J/kg range. This, combined with strong large-scale ascent to
the southeast of the mid-level jet, and moderate deep-layer shear
evident on regional WSR-88D VWPs, will continue to support a severe
threat with this line for the remainder of the evening. Severe wind
gusts with be likely along the leading edge of the line. Large hail
and tornadoes will also be possible with rotating elements embedded
in the line.
Further north-northeast into northeast Kansas, northwest Missouri
and south-central Iowa, several semi-discrete supercells are
ongoing. The Kansas City WSR-88D has 0-3 km storm-relative helicity
near 475 ms/s2, which appears representative of the environment
ahead of these storms. For this reason, a potential will continue
for strong tornadoes over the next few hours. These supercells will
also be capable of producing large hail and severe wind gusts.
The squall-line will gradually move east-southeastward into the
lower Missouri Valley and Ozarks from late this evening into the
overnight period. The severe threat will become less widespread as
relatively weaker instability is encountered later tonight.
...Southern Plains...
At the surface, a 997 mb low is located over far northwestern
Oklahoma, with a dryline extending southward across far western
Oklahoma into west Texas. To the east of the dryline, the RAP has
MLCAPE in the 3000 to 4000 J/kg range. Near the axis of the
strongest instability, a few storms are ongoing across southwest
Oklahoma, but weakening has recently occurred. Redevelopment will be
possible later this evening. The strong instability combined with
moderate deep-layer shear and steep low to mid-level lapse rates
would support a threat for large hail and severe wind gusts, if
cells can re-intensify. An isolated tornado threat will also be
possible if a supercell could develop. Thunderstorms are expected to
increase in coverage over much of Oklahoma during the overnight
period, as a cold front moves southward. However, the severe threat
should become more isolated tonight as instability gradually
decreases across the region.
..Broyles.. 05/19/2026
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 181720
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1220 PM CDT Mon May 18 2026
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE GREAT
LAKES INTO SOUTHERN PLAINS...
...SUMMARY...
Widely scattered severe thunderstorms will be possible along a cold
front extending from the Great Lakes into the Ohio Valley and the
southern Plains on Tuesday. Damaging winds and large hail will be
the primary threats.
...Synopsis...
A short-wave trough over the northern Plains into upper MS Valley
Tuesday morning will translate northeast into Ontario with an
associated belt of strong mid-level flow overspreading the Great
Lakes. The stronger mid-level winds will extend southwest into the
central High Plains, downstream from a positively tilted trough
moving through the Great Basin and lower CO Valley.
At the surface, low pressure associated with northern Plains
disturbance will develop from the upper Great Lakes through
southeast Ontario into Quebec. Meanwhile, a trailing cold front will
move through the Great Lakes and OH Valley, with the trailing
extension of the boundary advancing through the mid MS Valley and
southern Plains. The cold front and any preceding outflow boundaries
associated with early-day convection will serve as the main foci for
diurnally enhanced strong to severe storm development.
...Ohio Valley into the Great Lakes and New England...
A southwesterly low-level jet will sustain a moist boundary layer
across the pre-frontal warm sector with dewpoints in the 60s to
perhaps low 70s in the OH Valley. The moisture will combine with
daytime heating to support MLCAPE ranging from 1000-1500 J/kg across
the mid/lower Great Lakes into New England, with as high as
2000-3000 J/kg forecast in the OH Valley. A broad zone of low-level
warm advection coupled with the glancing influence of the Ontario
short-wave trough are expected to support a gradual increase in
thunderstorm coverage and intensity through the afternoon along and
ahead of the synoptic cold front.
The strongest low/mid-level flow and resultant deep-layer shear is
forecast to reside across the Great Lakes and northern New England,
where transient bowing and/or supercell structures appear possible.
Weaker shear with southward extent into the OH Valley will be
supportive of multicell clusters. Damaging wind gusts appear to be
the primary hazard in both regimes, though isolated occurrences of
marginally severe hail are also possible.
...Mid Mississippi Valley into the Southern Plains...
Thunderstorms are expected to be ongoing Tuesday morning along or
ahead of the cold front from the Ozarks into OK. Daytime heating of
the downstream air mass coupled with boundary-layer dewpoints in the
60s to low 70s and steepening mid-level lapse rates with
southwestward extent will support moderate to strong afternoon
instability with MLCAPE of 2000-3000+ J/kg. The 12z models suggest
that a subset of the early-day storms will intensify by afternoon
across the Ozark Plateau with additional thunderstorm development
anticipated along the synoptic cold front and preceding convective
outflow boundaries from the mid MS Valley into the southern Plains.
There is some model signal that one or multiple, weak disturbances
will translate from the southern Plains into Ozark Plateau during
the day, which will aid in the diurnally enhanced storm development.
As alluded to in the synopsis, the strongest mid-level flow and
associated vertical shear is expected remain confined to the
post-frontal air mass. The exception will be across parts of the TX
Permian Basin into the Big Bend and Edwards Plateau, where easterly
low-level winds ahead of front will augment modest mid-level flow to
support 30-40 kt of effective bulk shear. As such, predominant
convective modes will be multicell clusters and line segments
capable of damaging winds and marginally severe hail. Large hail
potential (some hailstones in excess of 2") increases with
southwestward extent into TX owing to steeper mid-level lapse rates
and the potential for supercell storm modes, given the stronger
vertical shear.
..Mead.. 05/18/2026
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 181913
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0213 PM CDT Mon May 18 2026
Valid 201200Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
NEW ENGLAND INTO THE MID-ATLANTIC AND OVER THE SOUTHERN HIGH PLAINS
INTO SOUTHWEST TEXAS...
...SUMMARY...
Scattered thunderstorm activity across the Mid-Atlantic region
Wednesday may pose a risk for sporadic occurrences of damaging
wind. Large hail is expected to be the predominant hazard with
isolated to widely scattered thunderstorms developing over the
southern High Plains into southwest Texas.
...Synopsis...
A short-wave trough and attending mid/upper-level jet streaks will
progress from the Great Lakes through the St. Lawrence Valley, with
a modest enhancement to the westerly, mid-level flow as far south as
southern New England and the Mid-Atlantic region. Elsewhere, a
short-wave trough initially near the Four Corners region will weaken
while moving into confluent, mid-level flow over the central and
southern High Plains. At the surface, a cold front will advance
southeast through New England and the Mid-Atlantic Wednesday, with
an upslope regime becoming established over the southern High
Plains.
...Southern New England into the Mid-Atlantic...
A moist and moderately unstable air mass is expected to develop
ahead of the front Wednesday afternoon, along the immediate southern
fringe of the stronger mid-level flow and resultant deep-layer
shear. The generally weak warm-sector shear and poor mid-level lapse
rates are expected to limit the potential for a more robust
severe-weather threat. However, the presence of steep low-level
lapse rates will support locally strong up/downdrafts capable of
isolated occurrences of damaging winds during the afternoon and
early-evening hours.
...Southern High Plains into southwest Texas...
Surface ridging initially over the southern High Plains Wednesday
morning is forecast to weaken through the day with a narrow wedge of
50s to low 60s boundary-layer dewpoints from the Edwards Plateau
into southeast NM, to the south of a weakening surface front. The
moisture will combine with steep low/mid-level lapse rates to
support a corridor of moderate, surface-based instability by
afternoon. A broader envelope of moderate, elevated instability is
expected to develop over the southern High Plains Wednesday
afternoon into night, to the north of the front.
Low-level upslope flow into the high terrain of NM and southwest TX
will be augmented by the glancing influence of the short-wave trough
to support isolated to widely scattered thunderstorms during the
afternoon amidst a kinematic environment featuring 30-40 kt of
deep-layer shear. The primary hazard will be sporadic large-hail
occurrences. Additional, elevated thunderstorms are expected to
develop Wednesday afternoon into evening across the TX South Plains
into west-central TX, within a strengthening warm-advection regime.
While deep-layer shear is expected to be weaker than locations to
west/southwest, the presence of steep mid-level lapse rates will
support vigorous updrafts capable of isolated, large hail
occurrences.
..Mead.. 05/18/2026
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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