SPC AC 281730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CST Tue Feb 28 2017
Valid 011200Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
MISSISSIPPI AND NORTHERN ALABAMA ACROSS PARTS OF
TENNESSEE...KENTUCKY...SOUTHERN OHIO AND WEST VIRGINA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED RISK FROM THE SOUTHEAST STATES INTO THE MID-ATLANTIC REGION
AND SOUTHERN NEW ENGLAND...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK....
...SUMMARY...
Strong to severe thunderstorms will be possible from the lower
Mississippi Valley northeastward across the Tennessee Valley and
Appalachians, and northward into parts of the Mid-Atlantic states
into southern New England. Damaging winds are forecast to be the
predominant severe hazard. However, a few tornadoes will be
possible, especially during the day, from the Tennessee Valley into
the middle and upper Ohio Valley.
...Synopsis...
An energetic progressive flow pattern is forecast to persist through
Wednesday as the current full-latitude western US upper trough moves
eastward into the Plains tonight and then lifts east-northeastward
across the northeast states through Wednesday night. Very strong
winds aloft accompany this system with 100+ kt maxima at 500 mb and
60-65 kt at 850 mb which will provide intense low-level and
deep-layer vertical shear supportive of severe storms.
At the surface, a low over southeast lower Michigan at the start of
the period is expected to deepen as it moves across the lower Great
Lakes during the day, reaching northern Maine by the end of the
period. A trailing cold front initially extending southwest from
the low across the middle Mississippi Valley to the upper Texas
coast will progress eastward and southeastward during the period,
crossing the Appalachians by 00Z and moving offshore into the
Atlantic between 06-09Z and extending across northern Florida into
the eastern Gulf of Mexico by the end of the period.
...Tennessee Valley into the middle/upper Ohio Valley...
Strong to severe storms are likely to be ongoing early in the period
in association with several pre-frontal convective systems from
parts of Ohio southwestward into parts of the mid-South region. The
mesoscale/near-storm environment west of the Appalachians is
expected to be characterized by 60-65F surface dew points, MUCAPE
ranging from 750 J/kg in Ohio to 1200 J/kg in the mid-South, and an
expansive region of very strong vertical shear of 50-70 kt in the
lowest 6 km AGL will support some rotating updrafts, especially if
more discrete cells can be maintained. Nevertheless, strongest
storms will have potential to produce all severe hazards including a
few tornadoes, especially during the daytime hours, as cells move
rapidly eastward/northeastward along and ahead of the advancing cold
front.
...East of the Appalachians from southern New York/New England into
the Carolinas and Georgia...
Over the northern part of this area, several rounds of strong/severe
storms may spread eastward across the region before the threat ends
with passage of the cold front. Farther south, the primary
convective threat is expected to remain closer to the cold front
where a line of storms is likely to develop and progress
eastward/southeastward through the afternoon into the overnight
hours.
Low-level moisture is expected to gradually increase, especially
from the Atlantic, with surface dew points of 60-65F from the
Delmarva region southward, and 50-60F extending northward into
southern parts of New York and New England. The limited moisture
will be offset to some extent by an plume of modestly steeper
mid-level lapse rates spreading over the area, with MUCAPE of
500-1000 J/kg possible over the area. Strong winds aloft and
associated vertical shear will enhance storm organization, with
potential for some rotating updrafts and bowing line segments to
develop through the night. Damaging wind gusts are expected to be
primary severe threat, although a tornado cannot be ruled out given
the large clockwise low-level hodograph structure indicated in
forecast soundings.
..Weiss.. 02/28/2017
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