(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 270857
SPC AC 270857
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Mon Jun 27 2022
Valid 301200Z - 051200Z
...DISCUSSION...
Medium-range guidance suggests that a more prominent blocking regime
developing during the middle to latter portion of this week may
persist into the July 4th holiday, with a mid-level high becoming
centered over the Yukon/Northwest Territories vicinity and mean
mid-level troughing to its south closer to and perhaps somewhat
inland of the U.S. Pacific coast. Downstream mid-level troughing
may become entrenched across much of eastern Canada into the
Northeast, with a deep embedded low, emerging from the Canadian
Arctic latitudes, gradually turning across the southern Hudson/James
Bay vicinity through northern Quebec by the end of the period.
In association with this perturbation, surface cyclogenesis may
proceed across northwestern Ontario into southern Hudson Bay on
Thursday, before occluding with secondary wave development across
northern Quebec late this week into the weekend. While a belt of
stronger southwesterly deep-layer mean flow may linger across parts
of the Upper Midwest/Great Lakes region on Thursday, destabilization
along and ahead of the associated cold front may remain relatively
modest due to the lack of more substantive low-level moistening.
It is appearing more probable that potential for thunderstorm
development in peak pre-frontal boundary layer instability may
remain mostly north of the international border (near the St.
Lawrence Valley) late Friday afternoon, before tending to diminish
while advancing southward into Friday evening. Better pre-frontal
low-level moistening appears possible by Saturday as the front
advances southward into the northern Mid Atlantic and southern New
England vicinity. While this could support considerable afternoon
and evening thunderstorm activity, more modest deep-layer wind
fields and weak mid-level lapse rates may only contribute to an
environment marginally supportive of strong to severe gusts.
Late next weekend into the July 4th holiday, it is possible that
areas with at least some severe weather potential could develop
across parts of the West into the northern Great Plains, downstream
of the large-scale mid-level troughing. However the predictability
of the shorter wavelength perturbations within this regime remains
low at this time.
..Kerr.. 06/27/2022
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