SPC AC 211731
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 PM CDT Thu Sep 21 2023
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHERN NE AND SD AS WELL AS OVER THE COASTAL MID-ATLANTIC...
...SUMMARY...
Severe thunderstorms will be possible across parts of the central
and northern Plains, mainly Friday afternoon into Friday night. A
few tornadoes are also possible along the Mid-Atlantic Coast early
Saturday morning.
...Synopsis...
A mid/upper cyclone will likely be centered near the OR/ID/NV border
intersection early Friday morning, before then gradually shifting
eastward throughout the day. This cyclone is forecast to be centered
over eastern WY by early Saturday morning. Enhanced mid-level flow
will accompany this cyclone, spreading across the Great Basin and
into the central Plains as the cyclone progresses eastward. Surface
lee troughing across the High Plains will likely deepen ahead of
this system, and cyclogenesis along this troughing may lead to the
development of a pair of surface lows, one over the central Plains
and the other farther north across southeast MT.
Elevated showers and thunderstorms will likely be ongoing at the
beginning on the period from the Mid MO Valley into eastern OK and
northeast TX. Evolution of these storms and their attendant cloud
cover and outflow will influence the surface pattern across the
Plains. General expectation is that the resulting combination of
cloud cover and storm outflow will lead to a sharpening of the warm
front across central and southern Plains. Strong heating is
anticipated west of this warm front across the warm sector, but the
warm temperatures aloft will likely keep most of OK and KS capped
throughout during the afternoon and evening. The only exception is
across southwest TX, where the combination of heating and low-level
moisture could erode all the convective inhibition. A conditional
risk for storms capable of strong gusts and large hail exists in
this area.
Higher thunderstorm chances are expected farther north across NE and
SD during the evening and overnight. Much of this activity will
likely be elevated, fostered by a strengthening low-level jet over
the warm front and aided by increasing large-scale ascent attendant
to the approaching cyclone. Environmental conditions support the
potential for some stronger storms capable of large hail and a
strong gust or two. There is a low-probability chance that
development occurs close enough to the warm to support a
surface-based (or at least near-surface-based) storm, with limited
tornado potential. Additional development is possible early Saturday
morning closer to the low, with some severe potential with this
activity as well.
...Mid-Atlantic Coast...
A developing tropical cyclone, recently deeded Potential Tropical
Cyclone 16 by NHC, is forecast to track northeastward. Wind fields
are expected to strengthening considerably, elongating hodographs
over the Mid-Atlantic states. Highest tornado potential is
anticipated closer to the center of this system, where the best
low-level moisture and resulting instability will exist. Based on
the current forecast, this appears it will occur over coastal NC
around 06Z to 12Z.
..Mosier.. 09/21/2023
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