…A brief spell of record heat expected to spread from the Midwest to the
East Coast…
…Active showers and severe thunderstorms this morning across the
northern Plains and upper Midwest/Great Lakes will shift eastward into the
northern Mid-Atlantic/southern New England by late Wednesday into early
Thursday…
…First snowflakes of the season could reach the higher elevations of
northwestern Montana on Wednesday followed by a chance of severe
thunderstorms across North Dakota Wednesday night/early Thursday…
The closed upper high currently centered over the mid-Mississippi Valley
will be expanding eastward over the next two days, spreading into large
portions of the East Coast from the Mid-Atlantic southward. This will
send a quick spell of potentially record high temperatures from the
Midwest into the Ohio Valley, Tennessee Valley, southern to central
Appalachians and into the Mid-Atlantic. The combination of hot
temperatures in the mid to upper 90s to near 100 degrees together with
high humidity levels will produce maximum daily heat indices of between
105 and 115 degrees across these regions, with heat risks reaching major
to extreme levels today across the Midwest into lower Great Lakes.
Excessive Heat Warnings and Heat advisories are currently in effect across
the mid to upper Mississippi Valley, the Midwest and southern New England,
affecting nearly 61 million people, with further expansion of these
warnings and advisories possible into portions of the Mid-Atlantic for
Wednesday. This spell of record heat will be relatively short-lived as a
cool high pressure system settling into southern Canada is forecast to
send a cool and damp air mass into the Great Lakes on Wednesday and will
quickly overspread New England Wednesday night, reaching into the
Mid-Atlantic by Thursday morning behind a sharp cold front.
Around the peripheries of the above mentioned upper high, precipitation is
likely to be active along the Gulf Coast and from portions of the
Southwest, northeastward into the Central Plains, upper Mississippi
Valley, upper Great Lakes into northern New England in this “ring of
fire”. In these regions, moisture values are forecast to remain above
average, supporting the potential for areas of active thunderstorms, heavy
rains and flash flooding. Active showers and severe thunderstorms this
morning across the northern Plains and upper Midwest/Great Lakes could
result in areas of heavy rains and flash flooding. Some of these
thunderstorms are expected to shift eastward into the northern New England
by early Wednesday, before some additional strong to severe thunderstorms
and heavy rain possible across portions of the upper Ohio Valley, central
Appalachians and into the Mid-Atlantic later on Wednesday into early
Thursday ahead of the sharp cold front.
While much above to record high temperatures dominate portions of the
central to eastern U.S. into mid week, another strong front will be
pushing inland into the Pacific Northwest followed by the northern Rockies
and into the northern High Plains by this evening. Much below average
temperatures in the wake of this front will likely spread across the
Pacific Northwest for today and into the northern Rockies/northern High
Plains on Wednesday with high temperatures 10 to 20 degrees below average.
There is not expected to be a lot of precipitation with this front over
the Northwest, but the falling temperatures could bring the first
snowflakes of the season for the higher elevations of northwestern Montana
on Wednesday. By Wednesday night into early Thursday, a chance of severe
thunderstorms will be moving eastward across North Dakota ahead of the
strong cold front.
Kong/Oravec
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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