SPC - No watches are valid as of Mon Sep 24 12:18:02 UTC 2018

No watches are valid as of Mon Sep 24 12:18:02 UTC 2018.


No Mesoscale Discussions are in effect as of Mon Sep 24 12:18:02 UTC 2018.

SPC Sep 24, 2018 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
      
Day 3 Outlook Image
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0224 AM CDT Mon Sep 24 2018

Valid 261200Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
APPALACHIANS ACROSS THE NORTHEAST...

...SUMMARY...
Strong/isolated severe storms will be possible Wednesday across the
Northeast.

...Synopsis...
Long-wave troughing is forecast to remain established over the
central U.S. this period, flanked by ridging across the eastern
Pacific/West Coast states, and over the western Atlantic/Southeast
states.  Within the broader/long-wave cyclonic flow, a
shorter-wavelength trough is forecast to advance quickly
east-northeastward from the Upper Great Lakes/western Ontario, to
the Lower Great Lakes and western Quebec through the daylight hours,
and then across New England and into the Canadian Maritimes by the
end of the period.

Meanwhile, a second short-wave trough is progged to dig quickly
southeastward across the Canadian Prairies, reaching the
north-central U.S. after dark.

At the surface, a seasonably strong cold front is forecast to
continue advancing quickly eastward/southeastward across the
southern and eastern portions of the country.  By the end of the
period, the front will likely have moved off the New England coast,
trailing southwestward from the Mid-Atlantic region to the western
Gulf Coast vicinity by 27/12z.  Progression of this front will be
accompanied by a zone of showers and thunderstorms, which will
likewise traverse the southern and eastern U.S. through the period.

Meanwhile farther north, a second cold front is forecast to advance
southeastward out of Canada and across the northern Intermountain
Region/northern Plains.  However, with a drier pre-frontal airmass
ahead of this front, only isolated shower activity is expected.

...The Northeast...
Modest pre-frontal heating/destabilization is expected Wednesday
across the Northeast, which should support continuation -- and some
intensification -- of the ongoing frontal convective band as it
moves across the upper Ohio Valley and lower Great Lakes region into
the central Appalachians through the day.  With the front serving as
a linear-organizing mechanism and with shear sufficient for
long-lived updrafts, evolution into semi-continuous squall line is
expected.  While flow aloft is not progged to be excessively strong
-- and with a limited across-boundary component to the shear vector,
combined with only modest CAPE, the overall setup is not ideal, with
respect to widespread/significant wind risk.  Still, locally
gusty/damaging winds can be expected along more intense/possibly
bowing line segments -- primarily from early afternoon through early
evening.

..Goss.. 09/24/2018

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SPC Sep 24, 2018 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook
      
Day 4-8 Outlook Image
Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0329 AM CDT Mon Sep 24 2018

Valid 271200Z - 021200Z

...DISCUSSION...
The latest medium-range model runs exhibit remarkable similarity
through the day 6/day 7 time frame, after which some deviation
begins to increase with respect to the large-scale flow pattern
across the country.  Prior to that, however, pattern evolution
suggests limited severe weather risk CONUS-wide, as a long-wave
trough -- whose broad cyclonic flow field will encompass much of the
U.S. initially -- gradual weakens and retreats northward into
Canada.  In its wake, a much more weakly cyclonic -- trending toward
zonal -- flow field is expected to evolve, downstream of a blocking
pattern over Alaska and the eastern Pacific.  Given the lack of
apparent/substantial severe risk at this time, no outlook areas will
be issued.

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