Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CDT Tue Jun 28 2022
Valid 011200Z - 061200Z
...DISCUSSION...
Medium-range guidance indicates that blocking with an amplified
split flow will remain prominent across the eastern Pacific into
western North America through next weekend and at least early next
week. While a mid-level high remains centered over the Canadian
Yukon and adjacent Northwest Territories vicinity, large-scale
mid-level troughing is likely to maintained to its south, offshore
through inland of much of the U.S. Pacific coast.
Downstream, after an initially deep embedded mid-level low finally
progresses offshore of the Newfoundland and Labrador coast and
weakens by early next week, broad mid-level troughing is forecast to
be maintained across much of eastern Canada and the Northeast. At
the same time mid-level ridging will also be maintained from the
southwestern Atlantic through the southern Great Plains. And
mid-level ridging within the westerlies to its north is forecast to
expand between the larger scale troughs, from the northern Rockies
eastward along the Canadian/U.S. border vicinity into the upper
Great Lakes region.
A cold front accompanying the deep mid-level low as it migrates
across and east of the southern Hudson/James Bay vicinity appears
likely to progress south of the international border, into the
Northeast by early Saturday. Ahead of the front, it does appear
increasingly probable that at least a narrow corridor of more
substantive low-level moistening, across the northern Mid Atlantic
into southern New England, will contribute to destabilization near
the southern fringe of stronger westerlies (including 30-40+ kt in
the 700-500 mb layer). While it currently appears that CAPE might
be limited by weak mid-level lapse rates, low-level lapse rates may
become fairly steep. If CAPE were a little larger or low-level wind
fields a little stronger, the risk for organized severe thunderstorm
activity would seem a little more certain. As it is currently
forecast, the environment probably will become at least marginally
conducive to thunderstorms capable of producing damaging wind gusts,
and it is possible that this could impact the urban corridor, at
least from the Greater Boston to New York City areas, perhaps into
the Philadelphia and Baltimore/Washington D.C. areas.
Late next weekend through early next week (including the July 4th
holiday), it is possible that one or two perturbations could emerge
from the Pacific coast mid-level troughing, and contribute to
potential for the evolution of organizing convective clusters across
the northern Intermountain region through northern Rockies.
Eventually, this activity may work its way around the northern
periphery of the mid-level ridging near the central Canadian/U.S.
border area. However, the predictability of these features at this
extended range remains low.
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SSzbST
