An active mid-July weather pattern is forecast throughout much of the Nation, which will include chances for heavy rain and severe thunderstorms, as well as dangerous heat.
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Through tonight, two east-west oriented frontal boundaries are expected to focus chances for heavy rain across parts of the Midwest and Lower Mississippi Valley.
Along the southernmost boundary stretching from the Southeast to the southern Plains, numerous thunderstorms that could include slow forward motions may result in heavy rain leading to flash flooding chances.
A Slight Risk (level 2/4) of Excessive Rainfall is in effect for this region between the Arklatex and southwest Mississippi.
Farther north, a quasi-stationary boundary across the Midwest and extending into the central Plains when combined with an approaching upper level shortwave will produce clusters of strong to potentially severe thunderstorms.
These storms are most likely to impact areas from eastern Montana to Iowa, with damaging wind gusts and very large hail possible through tonight.
A few inches of rainfall over the eastern Missouri Valley and western Iowa may lead to scattered instances of flash flooding.
This same system is anticipated to continue the shower and thunderstorm chances on Wednesday from the Mid-Mississippi Valley to the Great Lakes, with the threat remaining on Thursday from the Ohio Valley to central Plains.
The greatest risk will once again be for damaging wind gusts, large hail, and scattered flash floods.
Upper ridging over the Southwest that also stretches into the southern Plains will allow for above average temperatures to span from the Southwest to the central Plains/Mid-Mississippi Valley through midweek.
Highs throughout the Southwest and southern High Plains are forecast to reach into the triple digits, with daily maximum temperature records possible across southeast New Mexico and the Texas Panhandle on Wednesday.
High afternoon temperatures into the upper 90s and low 100s, with heat indices near 110 degrees are forecast throughout the remainder of the central/southern Plains, while also expanding eastward into the lower/middle Mississippi Valley through Thursday.
Excessive Heat Warnings remain in effect throughout the Desert Southwest, with Heat Advisories spanning from southern New Mexico to southwest Louisiana and into the Mid-South.
Additionally, high heat and humidity when combined with well above average sea-surface temperatures over the Gulf of Mexico will continue to create oppressive daytime and overnight heat throughout the immediate Gulf Coast and Florida Peninsula.
Elsewhere, hot but not necessarily hazardous heat is expected to build into the Mid-Atlantic and Northeast on Wednesday.
Highs into the the upper 80s and low-90s are forecast from Virginia to Maine.
An approaching cold front entering New England on Thursday along with elevated atmospheric moisture content will allow for showers and thunderstorms to develop over a region still recovering from recent flooding.
A Slight Risk of Excessive Rainfall is in effect for Thursday across much of Vermont, eastern New York, and neighboring New Hampshire as a few additional inches of rainfall are possible and could locally exacerbate flooding concerns. ■
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.