SPC AC 080525
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 PM CST Sat Mar 07 2020
Valid 091200Z - 101200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe thunderstorms appears negligible across the
U.S., Monday through Monday night.
Models continue to indicate that the crest of a flattening mid-level
ridge will nose across the northeastern mid-latitude Pacific, into
parts of southern British Columbia and the Pacific Northwest during
this period. As this occurs, a significant mid-level low, initially
digging across parts of the southern mid-latitude and subtropical
eastern Pacific, is forecast to turn/reform eastward, roughly along
30N latitude. The progression likely will be slow and, though the
leading edge of the cyclonic flow may approach the southern
California coast by late Monday night, the mid-level cold core is
still expected remain several hundred miles offshore.
Downstream of the low, broad ridging likely will be maintained
within the southern branch of the split mid-latitude westerlies,
across the Southwest into southern Plains. However, a transition
toward a more zonal regime may continue across much of the nation,
as short wave troughs within both the northern and southern streams
progress east of the Canadian Prairies and south central Plains,
Ahead of the north branch impulse, a surface low may consolidate
across parts of the Upper Midwest and Great Lakes region into
southeastern Ontario and western Quebec. A trailing cold front is
forecast to advance east/southeast of the Upper Midwest, middle
Missouri Valley and central Plains, eventually into parts of the
lower Ohio Valley, Ozark Plateau and southern Plains Red River
Valley by late Monday night, as the southern branch perturbation
accelerates into and through the lower Ohio Valley.
The southern branch perturbation will be preceded by a shield of
rain associated with a plume of mid/high level moisture return from
the lower latitude eastern Pacific. Along the front, weakening
convection, initially over parts of the central Plains and mid
Missouri Valley into the Upper Midwest, will spread northeastward,
to the north/northeast of the mid-level feature.
A moderately strong (30-50 kt) southerly 850 mb jet, initially over
the southern Plains into middle Mississippi Valley, is expected to
shift northeastward (within the generally stable air) in association
with the primary developing surface low. While it does appear that
continuing southerly return flow off a modifying boundary layer over
the Gulf of Mexico may yield more substantive inland moisture
return ahead of the cold front, models suggest that this will occur
mostly south and southwest of the forcing for ascent associated with
the southern branch wave.
A corridor of weak boundary-layer destabilization may occur ahead of
the cold front, across parts of northeast Texas into eastern
Oklahoma, contributing to at least conditional potential for
thunderstorm development Monday. However, attempts at deep
convection may be suppressed by increasing inhibition associated
with warming aloft, as well as the lack of mid/upper support for
...Central Plains into middle Mississippi Valley...
Trailing the initial shield of rain, cooling aloft associated with a
developing center of cyclonic vorticity may contribute to the
evolution of thermodynamic profiles marginally sufficient for
scattered weak thunderstorm activity, particularly across parts of
eastern Kansas into Missouri Monday afternoon and evening.
Additional weak thunderstorm development is possible late Monday
night across southwestern Nebraska and adjacent portions of the
central Plains, aided by lift associated with increasing low-level
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