SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1137 AM CST Thu Mar 09 2023
Valid 101200Z - 111200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS
PARTS OF SOUTHERN GEORGIA...SOUTHEASTERN ALABAMA AND NORTHERN
FLORIDA...
CORRECTED FOR OUTLOOK GRAPHIC
...SUMMARY...
A couple of strong thunderstorms are possible across parts of
southern Georgia, adjacent southeastern Alabama and northern Florida
Friday, accompanied by some risk for severe weather.
...Synopsis...
Models suggest that flow in the mid- and higher latitudes of the
eastern Pacific through western Atlantic will remain amplified, with
generally weak westerlies, as blocking highs are generally
maintained near the Aleutians and across the Canadian Arctic through
this period. Lower amplitude flow will prevail in the southern mid-
and subtropical latitudes, with broad mid-level troughing across the
central Pacific transitioning to broad ridging across the eastern
Pacific through the southern tier of the western into central U.S.,
and broad troughing farther downstream into the western Atlantic.
Within this regime, one vigorous shortwave impulse is forecast to
progress inland across the northern U.S. Pacific coast and northern
Rockies by late Friday night. This will be accompanied by a
weakening surface cyclone and inland advancing cold front across the
interior Northwest and Rockies, and deepening surface troughing to
the lee of the Rockies. It appears that a plume of higher moisture
content air emanating from the subtropical Pacific, initially
impinging on the Sierra Nevada, before spreading into the Great
Basin, will gradually be suppressed southward, ahead of the front.
East of the Rockies, a weak initial surface low is forecast to
gradually migrate northeastward through the Allegheny Plateau
vicinity, before much more substantive cyclogenesis takes place off
the Mid Atlantic coast, in response to a significant short wave
trough digging southeast of the Great Lakes region. As this occurs,
low-level cooling and drying, in the wake of a trailing cold front,
will overspread much of the Southeast through central Gulf coast.
...Pacific Northwest into northern Rockies...
Models indicate that the inland migrating short wave will be
accompanied by a compact mid-level cold core, including 500 mb
temperatures of -30 to -35C. This will contribute to weak
boundary-layer destabilization, which may become supportive of
scattered low-topped convection capable of producing lightning near
Oregon coastal areas at 12Z Friday, inland toward the Montana
Rockies through the day.
...California coast through the Great Basin...
Forecast soundings suggest that lower/mid-tropospheric moistening,
coupled with weak mid-level cooling, will be sufficient to
contribute to layers of weak conditional instability. It appears
that this will mostly be rooted at higher altitudes, as cloud cover
and precipitation hinder surface heating and boundary-layer
destabilization at lower elevations, particularly to the west of the
Sierra Nevada. Aided by 40 to 70 kt westerly flow in roughly the
4,000-10,000 foot layer, strong orographic forcing for ascent may
contribute to convection capable of producing lightning across the
western slopes of the Sierra and Wasatch.
...Southeast...
Scattered thunderstorm activity is possible Friday near the
southeastward advancing cold front. The general tendency may be for
this activity to form to the cool side/above the front. However,
near peak afternoon instability, a window of opportunity may develop
for sustained thunderstorm activity rooted within the
boundary-layer, just ahead of the front across parts of southern
Georgia into northern Florida. Forecast soundings suggest that the
environment might become conducive for a couple of strong storms
posing at least some risk for severe hail and wind, before activity
weakens by Friday evening.
..Kerr.. 03/09/2023
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