The stifling heat that enveloped much of the Northeast and Mid-Atlantic this weekend will be on its last leg today as daytime highs make one last run at the low-mid 90s from central Virginia on north to southern New England.
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Some areas could still see heat indices in the triple digits, supporting Heat Advisories and Excessive Heat Warnings being posted in portions of southern New England, the Philadelphia metro area, and on south to the DelMarVa Peninsula.
In the Heartland, an even larger footprint of Heat Advisories and Excessive Hear Warnings are in place in the Southern Plains and Lower Mississippi Valley today.
Unlike their neighbors in the Northeast, where a cold front will bring about the return of more seasonal temperatures on Tuesday, sizzling temps will stick around in the South Central U.S..
In the Northwest, a strengthening upper level ridge over the northeast Pacific and western Canada sets the stage for a heat wave to engulf the Pacific Northwest through mid-week.
Daytime highs will surpass the 90s each day and even eclipse the century mark in the Columbia River Gorge and Columbia River Basin.
This prompted the issuance of numerous Excessive Heat Warnings/Watches and Heat Advisories throughout much of the region.
Daily record highs will likely be broken from northern California to the Portland and Seattle metro areas on Tuesday.
Record warm minimum temps are also expected in similar parts of the Pacific Northwest through Wednesday.
A quasi-stationary frontal boundary draped across the nation's mid-section from the Central Plains to the Mid-Atlantic coast becomes the focus for daily rounds of showers and thunderstorms.
Southerly flow emanating out of the Gulf of Mexico will provide storms with the necessary moisture to produce copious amounts of rainfall from the Midwest to the Tennessee Valley and central Appalachians.
In response to this threat for heavy rainfall, a pair of Slight Risks (threat level 2/4) for Excessive Rainfall have been issued for parts of these regions today.
In addition to the flash flood threat in these areas, there is also a Slight Risk (threat level 2/5) for severe weather up and down the Northeast/Mid-Atlantic I-95 megalopolis today with damaging winds the most prominent severe threat.
By Tuesday, the front does not make much progress across the Ohio Valley, which is where a Slight Risk for Excessive Rainfall is in place.
Come Wednesday, the front shifts slightly to the south, but after multiple days of heavy rain and another rich plume of moisture delivering more excessive rainfall, a Day 3 Moderate Risk (threat level 3/4) has been issued for much of West Virginia.
Meanwhile, in the Southwest, the monsoon remains in full swing with plenty of moisture aloft and numerous showers and thunderstorms each afternoon and evening.
Both Monday and Tuesday, there are Slight Risks for Excessive Rainfall in parts of the Four Corners region, which includes Arizona, New Mexico, Utah, and Colorado.
Areas most at risk for flash flooding are areas near burn scars, within slot canyons, and in locations with abnormally saturated soils.
Elsewhere, a cold front tracking across the Northern Plains Monday night and into the Upper Mississippi Valley on Tuesday will spark scattered showers and storms across these regions.
In the Southeast, diurnally driven showers and thunderstorms will dot the Gulf Coast on east to the Southeast coast today. ■
A clipper system will move quickly across the northern Plains into the Midwest Friday and the Northeast by Saturday, bringing a wintry mix of rain and snow showers ahead of a sweeping cold front.