LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1234 AM CDT Mon Sep 25 2023
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF
SOUTHERN TEXAS AND CENTRAL FLORIDA...
...SUMMARY...
Isolated strong to severe thunderstorms will be possible across
parts of Texas and Florida today.
...Synopsis...
Strong to severe thunderstorm potential is expected to remain
confined to southern portions of Texas and the Florida Peninsula for
today. An occluding low over the upper MS River Valley will continue
to weaken as an attendant mid-level impulse shifts east through the
day. In its wake, upper-level ridging will become established across
the Intermountain West. This synoptic regime will favor a gradually
building surface high over the Plains (as evidenced by steady
pressure rises over the past 12 hours). As a result, the diffuse
cold front draped across the southern Plains will continue to
migrate south through the day, and will be a focus for thunderstorm
development later this afternoon and evening.
...Texas...
Latest forecast guidance shows reasonably good agreement in the
southward progression of the cold front across southern TX today.
This boundary may be convectively reinforced by ongoing thunderstorm
clusters across eastern TX at the start of the period. This
early-morning convection may re-intensify and pose a severe wind
threat for the TX coastal plain during the afternoon hours amid
diurnal warming of a moist air mass downstream. To the west, closer
to the Edwards Plateau and the Big Bend region, thunderstorm develop
along the cold front is expected by mid/late afternoon. MLCAPE
values are forecast to reach near 2000 J/kg as temperatures warm
into the low to mid 90s. Although mid-level winds will be somewhat
modest (20-30 knots), southeasterly low-level flow will support
elongated hodographs with effective bulk shear values near 30-40
knots. Such wind profiles and weak ascent along the front may
support initially discrete modes, including the potential for a
supercell or two with an attendant large-hail threat. However,
deep-layer shear and storm-motion vectors largely along the frontal
boundary may favor a tendency for storm clustering through the late
afternoon/evening. Thunderstorm development off the higher terrain
of the Davis and Serranias del Burro mountains may also support
discrete supercells, but confidence in storm coverage via orographic
ascent is limited.
...Florida...
A weak tropical low north of the Yucatan Peninsula is establishing a
plume of rich moisture into FL (as sampled by 00z soundings).
Moderate heating of this air mass through the day should support a
modestly buoyant, but uncapped environment (MLCAPE upwards of 1000
J/kg) by mid afternoon over central FL. Glancing ascent from the
passing mid-level trough to the north will support scattered to
widespread thunderstorms, and may sufficiently strengthen mid-level
flow to support effective bulk shear values between 20-25 knots.
Although the kinematic environment will be meager, a few instances
of hail approaching severe criteria are possible. Additionally,
steepening low-level lapse rates and PWAT values approaching 2
inches will be conducive for wet downbursts capable of strong to
severe winds.
..Moore/Leitman.. 09/25/2023
Read more CHECK UPDATE ZOOM GRAPHIC
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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.
CONVECTIVE | TORNADO | WIND | HAIL
Monday, September 25, 2023
SPC Sep 25, 2023 0600 UTC Day 1 Convective Outlook
Saturday, September 23, 2023
SPC Sep 23, 2023 0600 UTC Day 1 Convective Outlook
LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Sat Sep 23 2023
Valid 231200Z - 241200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
MISSOURI VALLEY INTO NORTHEAST OKLAHOMA...
...SUMMARY...
Thunderstorms, associated with large to very large hail, wind
damage, and tornadoes, will be possible today across eastern parts
of the Great Plains, and Mississippi Valley. A couple of tornadoes
are also possible in parts of the Mid-Atlantic.
...Eastern Great Plains/Mississippi Valley...
Early-morning water-vapor imagery depicts a well-defined upper low
over northern WY, advancing east toward the Black Hills, in line
with latest model guidance. 60kt 500mb speed max is forecast to
translate across NE to near FSD by 18z, then into northern MN during
the overnight hours. This evolution will encourage a surface low to
lift into northeast NE by 18z, with some deepening expected during
the latter half of the period as the low occludes over southeastern
ND by 24/12z.
A north-south cluster of strong convection has evolved ahead of the
upper trough over the High Plains from western NE into southwestern
SD. This activity may continue through sunrise as it propagates
east, aided by large-scale ascent ahead of the trough. Additionally,
latest model guidance suggests LLJ will strengthen ahead of this
activity into western IA by mid day such that renewed development is
likely. NAM aggressively strengthens the LLJ in excess of 60kt over
south-central MN by late afternoon. Wind profiles and low-level
shear will strengthen ahead of the deepening surface low. This
supports the potential for supercells across the upper MS Valley,
especially near/south of the northward-advancing warm front.
Forecast soundings exhibit strong shear with substantial sfc-3km
SRH, though lapse rates will remain weak. Aside from the threat for
damaging winds with this pre-frontal activity, it appears
environmental conditions also support a tornado risk. In addition to
supercell threat, large-scale forcing may encourage some clustering
and potential line segments. Severe risk will spread into central MN
by late evening as the low occludes over the upper Red River (of the
North) Valley.
Farther south, high-level difluent flow will be noted across the
lower MO Valley into eastern OK. 500mb flow is expected to
strengthen south of I-70 to near the TX/OK Red River as weak height
falls will be noted at these lower latitudes. Surface front will
advance into eastern KS, arcing across central OK into northwest TX
by late afternoon. Strong boundary-layer heating will be noted ahead
of this wind shift, with surface temperatures forecast to rise into
the mid 90s to near 100F from portions of western OK into northwest
TX. As a result, convective temperatures will be breached as CINH is
reduced. Scattered thunderstorms should readily develop along the
wind shift, initially over eastern KS, then southwest along the
boundary at least into central OK. Forecast soundings exhibit
seasonally steep lapse rates with high PW values (approaching 2
inches). Wind profiles strongly favor organized convection and
initial activity should be supercellular in nature. With time, one
or more MCSs may ultimately evolve over the ENH Risk area, with
southward propagation expected across eastern OK/western AR late in
the period. Hail should be common with the initial activity, some of
it likely exceeding 2 inches in diameter. While a few tornadoes may
be noted with the supercells, storm mode may ultimately lead to a
complex that could produce damaging winds as convection spreads
southeast during the overnight hours.
...TS Ophelia...
Ophelia will soon move onshore along the NC Coast, then advance
inland before arcing northeast toward the Delmarva late in the
period. Strong low-level shear will develop across the southern
Middle Atlantic east of the low track. Convection that develops
across this region will be sufficiently sheared for supercells and
possibly a few tornadoes, in addition to gusty winds.
..Darrow/Moore.. 09/23/2023
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SwVVcp
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Friday, September 22, 2023
SPC Sep 22, 2023 0600 UTC Day 1 Convective Outlook
LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1246 AM CDT Fri Sep 22 2023
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN AND CENTRAL HIGH PLAINS...AND OVER THE SOUTHERN COASTAL
MIDDLE ATLANTIC...
...SUMMARY...
Severe thunderstorms are possible across parts of the central and
northern High Plains, mainly this afternoon and this evening. A few
tornadoes are also possible along the Mid-Atlantic Coast early
Saturday morning in association with the approaching potential
tropical system.
...Northern/Central High Plains...
Strong upper low that has settled into the northern Great Basin will
advance into western WY by late afternoon as a 70kt 500mb speed max
rotates through the base of the trough to near WY/UT/CO border by
23/00z. Seasonally cold mid-level temperatures (-20C at 500mb
beneath the upper low) will spread east in association with this
feature, and the exit region of aforementioned jet will overspread
the High Plains of eastern WY by early afternoon.
Latest model guidance suggests boundary-layer flow will remain
decidedly easterly across NE and the Dakotas into eastern WY. As a
result, strongest boundary-layer heating will be noted across the
higher plateau region of WY immediately ahead of the approaching
trough. Forecast soundings suggest convective temperatures will be
breached by 19z, and thunderstorms should develop shortly
thereafter. Soundings across eastern WY exhibit substantial SBCAPE
with steep lapse rates through 8km. NAM 21z forecast sounding for
LUS strongly favors supercells with 60kt surface-6km bulk shear.
Very large hail may accompany some of this activity as it spreads
toward the southern Black Hills region/northwestern NE.
Additionally, relatively moist boundary-layer conditions and low
LFCs suggest some tornado threat. It's not clear how far this
activity will spread east before weakening, as the updrafts will
likely decouple from the boundary layer due to much cooler surface
temperatures and weaker low-level lapse rates. For this reason have
focused higher severe probabilities across the High Plains where
stronger surface heating is expected.
...Potential Tropical Cyclone Sixteen...
PTC 16, currently located well southeast of the Carolina Coast, is
forecast to move north-northwest over the next 24hr, likely
intensifying as it approaches the NC Coast early Saturday. As this
system intensifies, low-level shear will increase markedly across
the southern Middle Atlantic Coast. Probabilities for supercells
will increase late, especially after 06Z, along with some risk for
tornadoes, primarily east of the low track.
Reference
https://www.nhc.noaa.gov for more information on this developing system. ..Darrow/Moore.. 09/22/2023 Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SwSDxk
https://www.nhc.noaa.gov for more information on this developing system. ..Darrow/Moore.. 09/22/2023 Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SwSDxk
Tuesday, September 19, 2023
SPC Sep 19, 2023 1300 UTC Day 1 Convective Outlook
LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0744 AM CDT Tue Sep 19 2023
Valid 191300Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE SOUTHERN PLAINS...
...SUMMARY...
Severe thunderstorm gusts and large hail are possible today and
tonight across portions of the southern Plains.
...Synopsis...
In mid/upper levels, amplification of the pattern is forecast over
parts of the northwestern and north-central CONUS later today into
day-2, related substantially to a strong shortwave trough and
embedded 500-mb cyclone now over the AK Panhandle and adjacent
coastal waters. This trough should dig southeastward to
southwestern AB, southern BC and WA by 12Z tomorrow, while a
downstream ridge builds across parts of the upper Mississippi Valley
into ON. As this occurs, initially zonal but increasingly difluent,
westerly to northwesterly flow will prevail downstream to the
trough's southeast, over the central/southern parts of the Rockies
and Plains.
Within the increasing difluence, a shortwave trough now over parts
of western KS to the TX Panhandle will shift eastward to eastern
portions of KS/OK by 00Z. This feature may decelerate in the
difluent regime tonight over the Ozarks to Arklatex. Following
that, just upstream, a smaller perturbation is evident in moisture-
channel imagery over southeastern CO and northeastern NM. This
trough should track eastward to parts of western/central KS and
northern/central OK through 00Z, then weaken eastward in favor of
convectively driven vorticity processes, and perhaps merge with the
lead wave late in the period.
At the surface, 11Z analysis showed a cold front over south-central
FL, becoming quasistationary over the north-central Gulf, and a warm
front northwestward across southeast to north-central TX. This
boundary is expected to move slowly northward/northeastward over the
east TX/eastern OK region today, while a dryline develops across
western KS, western OK, northwest TX, to the Big Bend area. A
pseudo-warm-frontal zone of relatively backed near-surface flow may
develop over parts of OK, in the western/modifying part of outflow
air and behind morning convection, encouraged by isallobaric forcing
related to weak cyclogenesis along the dryline. There is
uncertainty on this process -- depending on mesobeta-scale
thermodynamic recovery and kinematic response behind morning
convection.
...Southern Plains...
Widely scattered to scattered showers and thunderstorms are ongoing
across portions of northwest Texas, northward and northeastward over
parts of OK, in a zone of large-scale ascent (warm advection and
DCVA preceding the leading mid/upper perturbation. This activity
should remain largely nonsevere as it shifts eastward through the
remainder of the morning, though an isolated, marginally severe
instance of hail cannot be ruled out.
Convective and severe potential should ramp up this afternoon as the
boundary layer diurnally/diabatically destabilizes south of the
morning clouds/convection (across parts of southern OK and north
TX), southwest of it atop a strongly heated/mixed boundary layer
near the dryline, and perhaps behind it over western/central OK late
this afternoon. The latter potential is more uncertain and
conditional, given time needed for both direct heating/
destabilization and warm advection in the recovering low-level air
mass immediately preceding the second mid/upper-level perturbation.
Where convection can develop over northwest TX and OK, especially
near any dryline/outflow intersection, supercells are possible amid
strong veering of winds with height in low/middle levels, yielding
well-curved and favorably enlarged hodographs. Development appears
best focused near the dryline over the southwestern OK/northwest TX
area, with sustained heating and MLCINH erosion likely, but less
low-level shear. Conversely, coverage is more uncertain in and
north of the backed-flow regime, though hodographs will be more
favorable. As such, too much mesoscale uncertainty lingers to
assign a more-specific, focused area of higher unconditional
probabilities at this time.
Forecast soundings near the trailing dryline depict small 0-1-km SRH
and shear due to uniformity of winds in that layer, however, 200-400
J/kg effective SRH and 40-45-kt effective-shear magnitudes should be
common (with larger values northward). A corridor of mid 50s to
lower 60s F surface dewpoints -- even after diurnal mixing -- should
combine with steep low/middle-level lapse rates to yield 1500-2500
J/kg MLCAPE, in a northward-narrowing moist-sector corridor. In
addition to severe downdrafts encouraged by the deep mixed layer,
isolated significant (2+ inch) hail appears possible given the
supercell-favoring shear, the shape/depth of the buoyant profile,
sounding analogs, and peak size given by 2D hail models applied to
progged soundings. Some evening/nocturnal clustering of convection
also is possible, locally boosting wind potential for a couple
hours. However, given aforementioned mesoscale uncertainties, great
spread understandably appears among convection-allowing guidance on
where and how intensely any such wind threat will organize.
..Edwards.. 09/19/2023
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SwKdrw
http://dlvr.it/SwKdrw
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