The upper-level pattern over the CONUS will remain rather stagnant the next couple of days with lows over the Northeast and California and ridging in between.
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This will keep temperatures for many locations from New England southwest into the Mid-Atlantic, Appalachians, and Ohio Valley, as well as California and the Southwest, as much as 10-20 degrees below average Wednesday and Thursday.
Highs for portions of New England will only be in the 50s and 60s, with 70s generally expected further to the south.
Similarly, most of coastal California should remain in the 60s while highs will be warmer, but still below average, into the interior valleys and Desert Southwest, with 80s to low 90s expected.
In contrast, under the ridging stretching northwestward over the Plains and Northwest, temperatures will be running as much as 10-20 degrees above average.
Highs Wednesday and Thursday in the Northern Plains and interior Pacific Northwest will be in the upper 80s to low 90s, with 80s to near 90 for the I-5 urban corridor as well on Thursday.
Another notable event in this pattern, with northwesterly flow around the northeastern upper-level low, is the recurring, widespread smoke streaming into the Great Lakes and Northeast due to wildfires in Canada.
Numerous Air Quality Alerts remain in effect throughout the region late Tuesday, with the expectation that not much will change about the pattern over the next couple of days.
While not quite as thick or widespread, smoke has also continued to spread further over portions of the central and eastern CONUS, with Air Quality Alerts for many of the regional urban areas.
In addition, breezy winds and low humidity over portions of the Lower Great Lakes into the Mid-Atlantic, where conditions remain very dry due to a recent lack of rainfall, have prompted an Elevated Risk of Fire Weather from the Storm Prediction Center for Wednesday.
Showers and thunderstorms will be possible along a backdoor cold front sinking southwestward through portions of the Missouri/Mississippi Valley and into the Southeast.
Rainfall totals should generally remain light to moderate, expect for South Florida where more abundant tropical moisture will lead to heavier downpours.
Scattered to widespread showers and thunderstorms will also continue along the High Plains and into the Rockies.
Anomalously moist southeasterly upslope flow will contribute to the risk for locally heavy downpours and rainfall totals, with Slight Risks of Excessive Rainfall in effect for portions of the central/southern High Plains into the central Rockies Wednesday and for portions of Montana and Idaho Wednesday and Thursday.
Scattered instances of flash flooding will be possible with wet antecedent conditions in place from recent episodes of heavy rainfall.
Storms will also continue over portions of northern California into the northern Great Basin as the upper-level low slowly shifts northward.
There will be an attendant risk for a few isolated instances of flash flooding, particularly for terrain sensitive areas as well as burn scars. ■