SPC AC 041726
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CST Mon Nov 04 2024
Valid 051200Z - 061200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SABINE
TO LOWER MISSISSIPPI VALLEY...AND OVER PARTS OF WISCONSIN...
...SUMMARY...
A tornado or two and locally damaging winds may occur on Tuesday
across a portion of the Sabine to Lower Mississippi Valleys, and
central to southern Wisconsin.
...Synopsis...
A compact upper shortwave trough will shift northeast across the
Middle and Upper MS Valley and upper Great Lakes vicinity on
Tuesday. As the same time, another upper trough over the northern
Rockies will dig south/southeast through the period, maintaining
broad upper troughing over the West and into the Plains. Moderate to
strong deep-layer southwesterly flow associated with the initial
shortwave trough over the MS Valley will overspread east TX to the
Great Lakes. At the surface, low pressure initially over northeast
KS/northwest MO/southeast NE will lift northeast into southern
Ontario by Wednesday morning. A cold front/composite outflow will
extend from the Mid-MS Valley into east TX and the TX Gulf Coast
vicinity. This boundary will slowly shift east through the period.
Meanwhile, a warm front will be draped across the upper Great Lakes
vicinity. Strong mid/upper level flow and these low-level boundaries
and surface low will focus some potential for strong thunderstorms
on Tuesday, mainly over WI and parts of southeast Texas to the Lower
MS.
...East TX/Lower MS Valley...
Convection will be ongoing Tuesday morning across east TX toward the
TX coast as a cold front slowly progresses east. A corridor of
modest instability will be in place ahead of the front from the TX
coast/Sabine Valley into LA. Midlevel lapse rates are expected to
remain poor. However, a moist boundary-layer (dewpoints in the low
70s F) and moderate low-level and deep-layer shear will support
organized convection. Forecast soundings indicate enlarged, looping
hodographs, becoming elongated above 3 km. This suggests rotation
may accompany convection, and a tornado or two will be possible,
particularly across parts of LA into southwest AR where low-level
shear will be somewhat more favorable compared to points further
south near the TX coast. Otherwise, line segments and cells may also
produce locally strong gusts. The severe risk should move offshore
the TX coast by around midday/early afternoon, while persisting
through the afternoon to early evening further north across LA and
the southeast AR vicinity. Overall, severe risk should be tempered
by poor lapse rates and only modest destabilization, along with
generally weak large-scale ascent further removed from the ejecting
upper shortwave trough.
...WI...
Warm advection ahead of the surface low/cold front moving from IA
into WI will result in showers/thunderstorms and widespread cloud
cover through the morning. This will limit diurnal heating, through
forecast soundings suggest some areas could warm into the mid 50s to
near 60 F by mid afternoon. This could allow for weak
destabilization, though may be ill-timed as low-level winds begin to
veer with time. While this lends to uncertainty in severe potential,
at least a low-end/conditional risk for a tornado or two, or locally
strong gusts appears possible.
..Leitman.. 11/04/2024
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