WW 599 SEVERE TSTM IA NE 191450Z - 192100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 599
NWS Storm Prediction Center Norman OK
950 AM CDT Wed Aug 19 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far Southwest Iowa
Central into Eastern Nebraska
* Effective this Wednesday morning and afternoon from 950 AM
until 400 PM CDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph possible
Scattered large hail events to 1.5 inches in diameter possible
SUMMARY...A small cluster of severe thunderstorms is forecast to
continue to move to the southeast through the Watch during the
morning and into the afternoon. Some upscale growth may occur
through the late morning and into the afternoon. Large hail and
severe gusts 60 to 70 mph will be the primary hazards with these
storms.
The severe thunderstorm watch area is approximately along and 60
statute miles east and west of a line from 45 miles northeast of
Burwell NE to 15 miles south southeast of Lincoln NE. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU9).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
31025.
...Smith
WW 0599 Status Updates
STATUS FOR WATCH 0599 HAS NOT BEEN ISSUED YET
MD 2038 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF CENTRAL AND EASTERN NEBRASKA
Mesoscale Discussion 2038
NWS Storm Prediction Center Norman OK
0901 AM CDT Wed Aug 19 2026
Areas affected...parts of central and eastern Nebraska
Concerning...Severe potential...Watch possible
Valid 191401Z - 191600Z
Probability of Watch Issuance...40 percent
SUMMARY...An isolated supercell structure, perhaps with some upscale
growth into a small organizing cluster, may be maintained at least
into the 11 AM-1 PM CDT time frame, posing a continuing risk for
large hail and locally strong to severe gusts while moving
south-southeastward. It is not yet certain that this will require a
severe weather watch, but trends are being monitored for this
possibility.
DISCUSSION...Downstream of a low amplitude short wave trough,
digging within broader cyclonic northwesterly mid-level flow, at
least a localized area of stronger forcing for ascent (largely
associated with warm advection centered near/below the 700 mb level)
is maintaining isolated vigorous convection now propagating slowly
southeastward to the west and southwest of O'Neill. Strong shear
within the convective layer is contributing to a sustained supercell
structure, which still appears rooted above a relatively cool/stable
near surface layer.
Based on forecast soundings, convection appears based around 850 mb,
where a narrow corridor of higher moisture content may be supporting
updraft inflow of air characterized by most unstable CAPE on the
order of 1500-2000 J/kg. It appears that this could be maintained
at least into the 17-18Z time frame, as the stronger forcing for
ascent develops south-southeastward toward the Columbus and Grand
Island vicinities.
..Kerr/Smith.. 08/19/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OAX...GID...LBF...
LAT...LON 42249883 42399849 41939743 41489698 40939724 41179803
41779905 42059923 42249883
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0754 AM CDT Wed Aug 19 2026
Valid 191300Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OZARKS
INTO THE MID MS VALLEY AND SOUTHERN AZ....
...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
afternoon across the mid Mississippi Valley. Isolated severe gusts
and hail will also be possible from the lower to mid Missouri Valley
westward into the Great Plains. A few severe gusts could also occur
in southern Arizona and in the Southeast.
...Mid MO Valley...
Early-morning satellite imagery depicts a low-amplitude shortwave
trough moving through western SD/NE. Showers and thunderstorms are
ongoing downstream of this wave across central/eastern SD and
north-central/northeast NE. Recent surface analysis place a corridor
of moderate low-level moisture (i.e. upper 60s dewpoints) from
eastern NE northwestward to a weak surface low over central SD.
Instability will likely build within this corridor as the shortwave
continues eastward, potential resulting increasing thunderstorm
coverage and intensity later this morning into the afternoon across
eastern NE. Vertical shear will be strong enough for organized storm
structures and the potential for a few supercells. This potential
will be largely dictated by how much the airmass can destabilize
amid the cloud cover and limited heating. Large hail is possible
within the initially more cellular activity, but a transition to a
more linear mode results in damaging gusts becoming the primary
hazard with eastward/southeastward extent.
...Ozarks into the Mid MS Valley...
Regional radar imagery shows a large cluster of showers and
thunderstorms progressing across the region. A few stronger updrafts
are possible within this cluster, but limited buoyancy downstream
and a weakening low-level jet are forecast to result in gradually
diminishing storm strength over the next few hours. The airmass is
forecast to gradually recover in the wake of this cluster, with
strong buoyancy (i.e. MLCAPE over 2000 J/kg) in place by the late
afternoon. The shortwave trough mentioned in the preceding paragraph
is forecast to continue southeastward, and ascent attendant to this
wave coupled with weak low-level convergence along the cold front
will support thunderstorm development within this destabilized
airmass this evening. Strengthening mid-level flow will result in
moderate to strong deep-layer vertical shear supportive of
supercells. Large hail and damaging gusts are the primary hazards,
but a strengthening low-level jet will result in enough low-level
shear to support the potential for a few tornadoes as well. Storms
will tend to cluster with eastward extent, with the threat for
damaging gusts persisting within these bowing line segments.
...Ohio Valley...
A somewhat secondary area of late afternoon/early evening
thunderstorm development is anticipated from central IL into central
IN and central OH. Moderate buoyancy and strong westerly flow aloft
support the potential for isolated supercells capable of large hail
and isolated damaging gusts.
...Central/Southern High Plains...
Surface analysis places 60s dewpoints into the Colorado Foothills
this morning, increasing into the upper 60s farther east/southeast
into southwest KS. Strong heating/mixing of this airmass is
anticipated this afternoon, promoting the development of moderate
buoyancy. Thunderstorm development is expected across the high
terrain before then progressing eastward into the lower elevations.
Moderate northwesterly flow aloft will be support organized storms
structures, and large hail is possible along the Foothill.
Thereafter, a trend towards an outflow-dominant storm mode will
result in strong to severe gusts across portions of the
central/southern High Plains. Higher probabilities may be needed in
later outlooks if guidance continues to indicate increased coverage.
...AZ...
The presence of monsoon moisture will support moderate buoyancy
across the lower elevations of south-central AZ during the late
afternoon. This should allow for storms that develop over the high
terrain to maintain intensity as they process southwestward into the
lower elevations this afternoon/evening. Steep low to mid-level
lapse rates and large temperature-dewpoint spreads will support the
potential for severe gusts.
...Southeast into northern FL...
A very moist airmass (i.e. dewpoints in the 70s) will be in place
today from MS into FL. Strong heating is anticipated, with high
temperatures in the upper 90s across much of the region. As surface
temperatures warm, moderate instability will develop, with scattered
thunderstorms expected amid modest low-level convergence from MS
into western/southern AL and across the FL Panhandle into northern
FL. The deep low-level moisture combined with steep low-level lapse
rates will support an isolated wind-damage threat during the mid to
late afternoon.
..Mosier/Bunting.. 08/19/2026
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1000 AM CDT Wed Aug 19 2026
Valid 191700Z - 201200Z
...NO CRITICAL AREAS...
No changes to the existing no areas outlook. Hot and dry conditions
remain in place, continuing to desiccate fuels across much of the
western CONUS, with diurnal winds across most locations as was
previously mentioned.
..Stearns.. 08/19/2026
.PREV DISCUSSION... /ISSUED 1238 AM CDT Wed Aug 19 2026/
...Synopsis...
Upper ridging will expand farther into the Intermountain West today,
supporting hot and dry conditions amid generally lighter winds.
Deeper monsoonal moisture will remain embedded within the Desert
Southwest, but residual mid-level moisture in the Great Basin could
support a few isolated showers in the higher terrain. In the
southern Plains, a weak frontal boundary will sag into the Texas
Panhandle and Oklahoma throughout the day. Models vary on the timing
of the front, and progression will largely depend upon thunderstorm
outflow across Kansas in the early morning hours. Nevertheless, a
deeply mixed profile will lead to another day of high temperatures
in the 100s F and RH values of 15-20% ahead of the front, promoting
locally elevated fire weather concerns amid a drought stressed
fuelscape.
...Please see www.spc.noaa.gov/fire for graphic product...
|
