New Orleans, LA...Atlanta, GA...Fort Wayne, IN...Baton Rouge, LA...Mobile, AL...
SPC AC 061726
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CST Mon Feb 06 2017
Valid 071200Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OH VALLEY
TO THE CENTRAL GULF COAST STATES...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA...
Showers and scattered thunderstorms are forecast to affect the mid
Mississippi, Ohio, and Tennessee Valleys and central Gulf Coast
States Tuesday, eventually spreading eastward across the
Appalachians. Isolated strong to severe thunderstorms will be
possible across these areas.
Within broadly cyclonic flow across the CONUS, a lead shortwave
trough is forecast to be located over the upper Midwest to lower MS
Valley at the start of the period (12Z Tuesday). This trough will
advance quickly eastward across the OH/TN Valleys and the central
Gulf Coast States through Tuesday evening, before continuing to move
across the East Coast and into Quebec overnight. At the surface, a
low initially over northern IL should develop northeastward across
the lower Great Lakes while deepening, before moving into Canada
late Tuesday evening. A trailing cold front will shift
eastward/southeastward across the OH/TN Valleys into the Southeast,
as low-level moisture return ahead of the front supports some
convective risk across these regions.
...OH Valley to the Southeast...
Confidence in the evolution of the severe threat Tuesday is lower
than usual for a Day 2 forecast given a wide range of possible
scenarios regarding convective development through the latter
portion of the Day 1 period (Monday). At this time, it appears that
mainly elevated thunderstorms posing an isolated large hail threat
may be ongoing Tuesday morning from the OH Valley to the Mid-South
in association with a southwesterly low-level jet and the previously
mentioned mid-level shortwave trough. This convection, if it
develops, would shift quickly eastward across much of the
Marginal/Slight Risk area by early Tuesday afternoon. It is possible
that with time and modest diurnal heating this activity could pose
some strong to locally damaging wind threat if it can become surface
based. Better low-level moisture and corresponding instability will
be in place across the lower MS Valley into the central Gulf Coast
States Tuesday morning, although stronger large-scale forcing for
ascent should become increasingly displaced farther to the north
Behind the morning/early afternoon activity, thunderstorm
development along the surface cold front appears highly
uncertain/conditional. The lead shortwave trough and its associated
ascent will be departing the OH/TN Valleys and Southeast by Tuesday
afternoon. Most guidance suggests little in the way of convective
redevelopment given the nebulous forcing for ascent and perhaps even
some subsidence behind the initial shortwave trough. However, if any
isolated thunderstorms were able to form along or just ahead of the
front Tuesday afternoon/evening, they would pose a severe risk given
steep mid-level lapse rates and the forecast combination of
instability and shear.
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z