LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Fri Mar 24 2023
Valid 241200Z - 251200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID-MISSISSIPPI VALLEY...
...SUMMARY...
An outbreak of severe weather is expected from the Lower Mississippi
Valley toward the lower Ohio Valley Friday afternoon and evening.
Tornadoes, strong to potentially intense, as well as damaging winds
and hail are expected.
***Tornado Outbreak Possible Across Portions of the Mid Mississippi
Valley Friday Evening***
...Synopsis...
A mid-level trough can be seen on water vapor east of the northern
Baja Peninsula this morning. This trough will move quickly across
the southern Plains through the day and into the Mid
Mississippi/Lower Ohio Valley by Saturday morning. A very strong
mid-level jet (90-100 knots) will develop as this wave impinges on a
strong upper-level High across the Southeast.
Broad warm air advection is expected across the Mid-Mississippi
Valley during the day Friday with a strengthening low-level jet
through the day. Significant mass response is expected across this
area by early evening as the mid-level trough approaches the area.
As a result, the surface low will deepen rapidly between 00Z to 06Z
to around 992-994mb in the southern Illinois/Indiana vicinity.
During this period of rapid deepening, a warm front which is
forecast to be mostly stationary from northeast Arkansas to central
Tennessee during most of the day, will start to move quickly north
during the late afternoon with the northern extent of the warm
sector depicted by the approximate path of the surface low.
...Mid Mississippi Valley...
Thunderstorms will be ongoing at the beginning of the period across
eastern Oklahoma and western Arkansas. Some embedded supercells are
possible with the threat for a few weak tornadoes. Most guidance is
consistent with the convectively enhanced cold front drifting south
into north-central/northeast Arkansas in the morning. Therefore,
this early activity will likely wane as it interacts with this
southward moving front by late morning.
A pocket of drier air can be seen on water vapor moving north in the
west-central Gulf early this morning. This is associated with a
relative minimum in PWAT which will overspread eastern Louisiana and
much of Mississippi during the late morning and through the
afternoon. This seems to be responsible for the significant mixing
and surface dewpoint reductions seen my much of the guidance across
Mississippi in the afternoon where temperatures warm into low 80s.
However, despite this drier air further east, deep moisture will
remain across the western Gulf and will advect northward into
Louisiana during the afternoon as low-level mass response increases.
By mid to late afternoon, upper 60s to potentially low 70s dewpoints
are expected across northern Louisiana and eastern Arkansas,
spreading into northern Mississippi by the evening. This will lead
to an uncapped warm sector featuring MLCAPE of 500-1000 J/kg up the
Mississippi River to near Memphis and 1500-2000 J/kg farther south
across northern Louisiana and west-central Mississippi.
Expect storms to strengthen during the afternoon as the better
moisture advects northward and destabilizes the airmass ahead of
ongoing activity. CAM guidance is in agreement for a strong QLCS to
develop from central to northern Arkansas during the afternoon. This
line of storms will pose a threat for damaging wind and QLCS
tornadoes given the long, curved low-level hodographs with the best
overlap of favorable shear and instability in the vicinity of the
Mississippi River. This line of storms will eventually outrun the
better instability as it moves toward Middle Tennessee/southern
Kentucky, but the strong low-level jet (~70 kts), and strong forcing
with the deepening surface cyclone will help to maintain some severe
threat well into the overnight despite progressively more meager
instability.
Across southeast Arkansas, northern Louisiana, and northwest
Mississippi, a more volatile environment will develop Friday
evening/early overnight. More discrete convection is anticipated on
the southern periphery of the aforementioned QLCS. The more discrete
mode, combined with greater instability and strong shear should
allow for multiple supercells to develop across northern Louisiana
and southern Arkansas and move northeastward. Low-level hodographs
are very favorable in this region with 0-500m SRH around 200 m2/s2
and 0-1km SRH 300+ m2/s2. Therefore, any sustained supercells will
be capable of producing strong to intense (EF3+) tornadoes, with
long-track tornadoes possible with any longer-lived, undisturbed
supercells.
00Z HREF members showed a variety of solutions which cast some
uncertainty on the forecast. WRF members are notably less bullish
with warm sector supercell development from northeast Louisiana into
northern Mississippi while the HRRR was most aggressive with
convective coverage and environment. After further investigation it
appears the more aggressive HRRR solution can be attributed to a
more robust mass response during the afternoon/early evening hours.
This results in a pronounced shortwave trough which can be seen at
700 and 850mb and reflected as a significant confluence zone at the
surface. Not only does this act as a forcing for storm development,
but it also acts as moisture convergence with a more broad region of
70+F dewpoints. In this scenario, numerous strong tornadoes would be
likely, with the potential for several intense tornadoes. Despite
being the most aggressive, this solution does not seem unreasonable
as similar low-level confluence features can been on both the 00Z
GFS and the 18Z ECMWF.
As is often the case, the severity of the tornado threat across the
moderate risk will be modulated by mesoscale influences in the
region. As the event approaches, these mesoscale effects may become
more clear and allow the greatest risk corridor to become better
defined.
..Bentley/Weinman.. 03/24/2023
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
Friday, March 24, 2023
SPC Mar 24, 2023 0600 UTC Day 1 Convective Outlook
Wednesday, March 22, 2023
SPC Mar 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
1259 AM CDT Wed Mar 22 2023
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
NORTHEASTERN KANSAS EASTWARD TO NORTHERN INDIANA...
...SUMMARY...
Isolated/elevated strong to severe thunderstorms -- capable of large
hail -- are possible from far northeast Kansas eastward to northern
Indiana late tonight.
...Synopsis...
An upper trough across the western U.S. will move gradually eastward
with time, with the broader cyclonic flow field to encompass roughly
the western half of the country through the period. As this trough
advances, downstream ridging centered over the Gulf of Mexico will
amplify a bit, with a trend toward a bit of anticyclonic curvature
within the westerlies across the central and eastern U.S. with time.
At the surface, a low initially over the northern Minnesota vicinity
is forecast to shift quickly northeastward into -- and then across
-- Ontario through the period. Meanwhile, the trailing cold front
will become an increasingly west-to-east quasi-stationary front from
the central Plains into the Midwest. This boundary -- or more
specifically, a zone of warm advection focused to the cool side of
the front -- will focus a zone of elevated convection through the
period.
...Northeastern Kansas to northern Indiana...
Elevated showers and isolated/embedded thunderstorms are forecast to
be ongoing at the start of the forecast period across the northern
Missouri vicinity -- i.e. portions of the MRGL risk area. This
convection is forecast to shift eastward across the Midwest region
through the day.
Meanwhile, as a southwesterly low-level jet redevelops later this
evening, a gradual increase in new, elevated convection is expected,
in tandem with the increase in low-level warm advection atop a
surface-based stable layer.
With continued low-level theta-e advection within the 900 to 700 mb
layer, and some steepening of lapse rates aloft, the elevated
destabilization will likely be sufficient to support locally
strong/vigorous updrafts. This, combined with favorably strong
speed shear through the cloud-bearing layer, will likely support
locally severe storms, capable of producing large hail. With time,
an expanding convective cluster is forecast to spread eastward,
crossing central Illinois and eventually northern Indiana through
the end of the period.
..Goss/Lyons.. 03/22/2023
Read more CHECK UPDATE ZOOM GRAPHIC
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Sunday, March 19, 2023
SPC Mar 19, 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
1153 PM CDT Sat Mar 18 2023
Valid 191200Z - 201200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected on today.
...Discussion...
As an upper low crosses Quebec and shifts into the Canadian
Maritimes today, remnant troughing extending southwestward across
the eastern U.S. will weaken/advance slowly through the period.
Upstream, ridging will generally prevail over the West, though
short-wave troughing over the West Coast states early will be
replaced by a stronger short-wave trough that should approach/reach
the Pacific Northwest Coast overnight.
At the surface, a cold front is forecast to continue moving
southward across Florida early in the period, clearing the southern
coast/Keys by early afternoon. Meanwhile, in the wake of the front,
high pressure will shift eastward across the south-central and into
the southeastern U.S. through the period.
Little lightning potential is evident onshore through Monday
morning. A few flashes may occur across southern Florida or the
Keys early, as the front progresses southward. A couple of flashes
will also be possible over portions of the Sierra of
central/northern California. No severe weather is expected.
..Goss/Lyons.. 03/19/2023
Read more CHECK UPDATE ZOOM GRAPHIC
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Saturday, March 18, 2023
SPC Mar 18, 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
1232 AM CDT Sat Mar 18 2023
Valid 181200Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not forecast Saturday.
...Florida...
Strong northern-stream upper trough will shift east across the Great
Lakes during the day1 period as 100+kt 500mb speed max translates
off the southern New England Coast, increasing to near 140kt by
19/12z. In the wake of this feature, strong surface anticyclone will
build south across the Plains, ultimately dominating the CONUS east
of the Rockies. Leading edge of this air mass will force a cold
front into the central FL Peninsula later this afternoon, then to
the Keys by the end of the period.
Early this morning, most concentrated convection extends ahead of
the front across southeast GA along with a nearly north-south band
approaching the central FL Gulf Coast. Scattered convection will
likely persist along/ahead of the boundary into the early part of
the period, but aside from a few strong updrafts, this activity is
not expected to be severe. Latest model guidance suggests modest
boundary-layer heating ahead of the cold front by late morning with
surface temperatures forecast to rise into the lower 80s by 18z.
Convective temperatures will be breached shortly thereafter and
isolated thunderstorms should develop along the boundary. While
SBCAPE values could exceed 1000 J/kg, modest lapse rates and
seasonally weak surface-6km bulk shear do not favor organized
updrafts, especially given the expected weak low-level convergence.
While a few robust updrafts could evolve, the prospect for severe
wind, and/or hail appear too low to warrant severe probabilities.
..Darrow/Lyons.. 03/18/2023
Read more CHECK UPDATE ZOOM GRAPHIC
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