The first, which extends from the Northeast, through the Great Plains and Southwest, will be responsible for a swath of appreciable snowfall extending from the Southern Rockies through the interior Eastern US over the coming days.
Upper level shortwave energy, an abundance of atmospheric moisture, and large-scale forcing for ascent will fuel moderate to heavy snowfall from the Southern Rockies to the Central plains along and behind the front.
Much of the heavy snow, with accumulations of 6 to 8+ inches, is forecast to fall over higher terrain along the Colorado/New Mexico border including the San Juan and Sangre de Cristo mountains.
Lesser totals of 2 to 4 inches are expected further east over the Central/Southern Plains, though isolated higher amounts will be possible near the Kansas/Missouri border.
As the frontal boundary progresses south and east on Friday the snowfall area will follow suit, producing light to moderate accumulations from eastern New Mexico to the western Ohio Valley.
To account for the aforementioned snowfall, Winter Weather Warnings and Winter Weather Advisories are in effect from the Southern Rockies through the western Ohio Valley.
Behind the frontal boundary surface high pressure is forecast to descend and build over the Great Plains and Upper Midwest, carrying with it a frigid Arctic airmass that is expected to drop daily high and low temperatures as much as 20 to 30 degrees below normal for much of the Central US/Midwest Friday and Saturday.
For areas out of reach of the invading oppressive cold, temperatures are forecast to remain at or near normal into the weekend.
The second of the two high-impact frontal boundaries can be found over the Southeast and is forecast to remain there into the weekend.
Instability along the front will allow for moderate to heavy showers and thunderstorms with rain rates potentially reaching 1.5 inches per hour to develop over southeast Georgia and northern Florida.
These high rain rates over already moist soils has prompted the Weather Prediction Center to issue a Marginal Risk of for Excessive Rainfall for portions of the Southeast through Friday morning.
A marked increase in atmospheric moisture and instability over the Southeast on Friday is expected to fuel higher rain rates and associated rainfall totals over the region.
With 24 hour rainfall accumulations expected to fall somewhere between 2 to 4 inches over increasingly moist soils, thereby heightening the risk of flash flooding, the Weather Prediction Center has hoisted a Slight Risk of Excessive Rainfall over portions of northern Florida and southern Georgia effective Friday morning into Saturday morning.
Environmental conditions conducive for the development of severe thunderstorms are expected to accompany the heavy rainfall over the Southeast into the weekend.
Given the potential for damaging wind gusts, isolated hail, and a tornado or two to develop within these thunderstorms, the Storm Prediction Center has issued a Slight Risk of Severe Thunderstorms for portions of central Florida through the evening hours.
By Friday the severe weather threat is forecast to encompass a much wider and substantially more atmospherically unstable area from the central Gulf Coast states to North Carolina.
Thunderstorms that develop over these areas have the potential to produce damaging wind gusts, isolated hail, and a few tornadoes.
Portions of northern Florida and southern Georgia have the highest probability for these hazards to occur, prompting the Storm Prediction Center to issue an Enhanced Risk of Severe Thunderstorms over these areas effective Friday morning into Saturday morning.
Overnight Friday and into Saturday morning an upper-level shortwave trough is expected to amplify, subsequently forcing the two frontal boundaries to merge into a very strong low pressure/frontal system over the Eastern US.
Strong cold air advection on the backside of this system will result in any precipitation from the Tennessee and Ohio Valleys through the interior Eastern US to fall as snow, with snow rates potentially reaching 1 to 2 inches per hour in some areas.
These heavy snows, in combination with gusty winds, could severely reduce visibility and create difficult to hazardous travel conditions.
While 4 to 6 inch snowfall accumulations are generally expected over the affected portions of the Tennessee and Ohio Valleys, much higher totals that are likely to exceed 12 inches are forecast for the interior Northeast.
Ahead of this impactful winter storm, Winter Storm Watches have been raised from the northern Tennessee Valley through the interior Northeast.
Elsewhere, gusty winds associated with a low pressure wave are expected pass over moderately dry fuels in the Southwest.
With ambient relative humidity values forecast to remain low through the mid to late afternoon hours, the Storm Prediction Center has highlighted an Elevated Fire Weather threat area from far southeast Arizona to far western Texas.
Red Flag warnings are currently in effect for portions of southeastern Arizona and southwestern New Mexico.
Over the Desert Southwest, a tight pressure gradient will lead to the development of high winds today and Friday that could gust up to 55 miles per hour, prompting the issuance of Wind Advisories throughout the region.
Furthermore, these winds could kick up and blow around dust, reducing visibility and making driving hazardous.
As such, Blowing Dust Advisories have been raised for areas along the California/Arizona border. ■