SPC AC 220505
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1205 AM CDT Sat Sep 22 2018
Valid 221200Z - 231200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe thunderstorms appears negligible across the U.S.
today through tonight.
A deep surface cyclone and associated vigorous short wave trough
appear likely to progress east of Newfoundland and Labrador into the
northwestern Atlantic during this period. In their wake, broad
troughing within the mid-latitude westerlies is forecast to linger
across southeastern Canada, the Great Lakes and Northeast.
Upstream, models indicate that troughing will progress inland across
the Pacific Northwest coast. To the south of the mid-latitude
westerlies, much of the southeastern U.S., and the northern Mexican
Plateau and adjacent portions of the Southwest, may remain under the
influence of modest subtropical ridging. To the north of the ridge
axis, one perturbation is expected to slowly continue shifting from
the southern Plains into the lower Mississippi Valley, while a wave
in the easterlies migrates from just west of the Florida peninsula
toward the north central Gulf of Mexico.
In lower levels, a cold front trailing from the cyclone appears
likely to stall and begin to weaken across the southern Mid Atlantic
Coast, southern Appalachians, Tennessee Valley and Ozark Plateau.
However, it is forecast to maintain a southeastward progression from
the southern Plains into the Sabine Valley and Texas Gulf coast.
Seasonably high moisture content will remain confined to areas along
and southeast of the front, with the front providing the primary
general focus for thunderstorm development today through tonight.
With this mostly south of the stronger westerlies, in an environment
characterized by relatively warm mid-levels and modest to weak
lower/mid tropospheric lapse rates, the risk for storms capable of
producing severe wind and/or hail still appears negligible at this
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z