LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 PM CST Sun Feb 19 2023
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk for thunderstorms appears likely to remain generally low
across much of the U.S. today through tonight.
...Synopsis...
As the center of a broad, deep mid-level low emerging from the
Arctic turns southward through Hudson Bay, models indicate that the
leading edge of broad mid-level troughing (within the mid-latitude
westerlies to the south) will begin to shift offshore of the north
Atlantic Seaboard during this period, while the trailing edge shifts
east of the Rockies. This regime will include a couple of
smaller-scale perturbations accompanied by deepening surface
cyclones: one across the lower St. Lawrence Valley/Canadian
Maritimes vicinity and another across the Upper Midwest/Great Lakes.
Cold fronts trailing the cyclones are forecast to overspread much of
the Northeast and the Upper Midwest/Northern Great Plains through
much of the Ohio, middle Mississippi and lower Missouri Valleys by
12Z Tuesday.
At the same time, upstream, models indicate that the westerlies will
begin to undergo considerable amplification, including mid-level
ridging building from the mid-latitude Pacific (near 150-160 W)
north-northwestward through western Alaska. As this proceeds, a
vigorous downstream short wave impulse is forecast to dig near the
British Columbia coast, into the Pacific Northwest by the end of the
period, around the northeastern periphery of a blocking mid-level
high. Initially centered over the southern mid-latitude eastern
Pacific, the high may begin to reform to the west-northwest, while
an initially positively tilted trough to its southeast slowly begins
to accelerate inland across the Baja California vicinity. This may
lead to some suppression of ridging on the western flank of a
persistent subtropical high, gradually becoming centered over the
Caribbean.
...Southwest...
Within the mid-level troughing across the subtropical eastern
Pacific, the most significant embedded perturbation and mid-level
cold core are forecast to initially pivot southwestward, then
southward, away from the coastal areas, before accelerating eastward
toward northern Baja California Sur by early Tuesday. As this
occurs, any appreciable risk for thunderstorm activity is expected
to generally become focused well to the south of the international
border vicinity.
...Gulf States into southern Appalachians...
An initial influx of low-level moisture off the Gulf of Mexico, as
far northeast as the southern Appalachians vicinity by late this
afternoon, may contribute to weak destabilization supportive of
scattered showers. Aided by forcing for ascent associated with weak
perturbations on the southern fringe of the westerlies,
thermodynamic profiles may become marginally conducive for a few
lightning flashes with some of this activity.
The somewhat better/deeper low-level moisture appears likely to
remain capped by warm layers aloft as it initially spreads northeast
and east of Texas/Louisiana coastal areas. However, as the more
prominent short wave trough digs southeast of the Upper Midwest late
this evening into the overnight hours, suppression of the mid-level
inhibition in a corridor across southeastern Arkansas through the
northern Mississippi/Alabama vicinity may allow for weak
thunderstorm development.
..Kerr/Wendt.. 02/20/2023
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