An active weather pattern will begin to take shape later today and extend into early this weekend as a multifaceted weather system develops over the central United States.
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Before this system develops, there is the chance for isolated instances of flash flooding and severe weather along a quasi-stationary boundary extending from the middle Mississippi Valley to the Central Plains.
A Marginal Risk (level 1/4) of excessive rainfall is in effect for today from southeast Nebraska and eastern Kansas into much of Missouri, where rainfall amounts over an inch could pose isolated flash flooding concerns.
The Storm Prediction Center has issued a Slight Risk (level 2/5) of severe weather over western Nebraska, and a larger Marginal Risk (level 1/5) that extends southward and just east of dryline throughout the central and southern Plains today.
An isolated tornado, large hail, and a damaging wind gust are possible with thunderstorm activity in the aforementioned area.
By early this evening, a negatively tilted upper-level trough crossing the Intermountain West will facilitate lee-cyclogenesis and lead to a developing precipitation shield over the northern Rockies.
Heavy snow is forecast across parts of Montana, Idaho, and northwest Wyoming, with moderate snowfall accumulations confined to regions above 5000 feet in elevation.
In advance of the wintry weather, Winter Storm Warnings are in effect through Friday night over portions of central Montana.
South of the winter weather, a few damaging wind gusts and some hail can't be ruled out across southeast Idaho, northern Utah, and southwest Wyoming as elevated thunderstorms develop overhead.
A strong low pressure system will emerge over the central Plains by Friday afternoon as the upper-level trough begins to close off while propagating eastward.
This will lead to an expanding precipitation shield over the northern Plains and Mid-Mississippi Valley.
Widespread rainfall amounts up to, and locally exceeding, 2 inches within a developing commahead region of the low may produce scattered areas of flash flooding from south-central North Dakota to central South Dakota, where sensitive hydrologic conditions reside.
Accordingly, a Slight Risk (level 2/4) of excessive rainfall is in effect for this region.
Over the central Plains, there is higher confidence that severe thunderstorms capable all hazard types will impact an area extending from southeast Nebraska to north-central Oklahoma, prompting SPC to issue an Enhanced Risk (level 3/5) of severe weather.
Thunderstorms forming ahead of a dryline and approaching cold front in a sheared and unstable airmass may contain tornadoes and produce significant hail.
With multiple strong storms, heavy rainfall rates are also likely and could lead to isolated flash flood concerns.
By Saturday, the maturing low pressure system will support additional locally heavy rain over the northern Plains, with wet snowflakes mixing into the northern High Plains and Black Hills.
Heavy rain and severe thunderstorms will also remain possible along the advancing cold front forecast to extend from the Midwest to the Southern Plains.
Fire weather is also a potential hazard across the Southwest, southern Rockies, and southern High Plains over the next few days.
The combination of gusty southwesterly winds, low relative humidity, above average temperatures, and dry terrain will lead to critical to extreme fire weather conditions today and Friday.
More specifically, SPC has issued an area of extreme fire weather danger over parts of southeast Colorado on Friday where an outbreak of dangerous fire weather conditions is anticipated.
Any new wildfires could start with ease and new/existing fires may spread uncontrollably.
Red Flag Warnings and Fire Weather Watches are in effect over southern Nevada, northern Arizona, the entire state of New Mexico, parts of southern Colorado, West Texas and the Texas Panhandle, as well as western Oklahoma.
A period of favorable fire weather condtions this weekend is noted over the southern Plains in the SPC extended fire weather outlook as well, which will need monitored over the next few days.
Elsewhere, a wobbling upper-level low located over the Gulf of Maine will maintain unsettled weather over northern New England over the next few days.
Northern Maine in particular will experience the greatest impacts, with snowfall accumulations up to 5 inches and gusty winds possible throughout northern portions of the state, where a Winter Weather Advisory remains until tomorrow morning.
Conditions will finally begin to improve on Saturday as the system gradually slides further into the Atlantic.
Meanwhile, an attached cold front is currently found near south-central Florida, with increasing thunderstorm activity noted ahead of the front.
A targeted Marginal Risk of excessive rainfall remains along the southeastern Florida Atlantic coastline for urban flash flood concerns.
Behind this cold front much of the eastern U.S. will experience a chilly end of the workweek.
In fact, lows into the upper 20s and low 30s will likely lead to frost/freeze concerns over parts of the Ohio Valley and Mid-Atlantic through tomorrow morning.
The combination of post-frontal dry air and gusty winds over the Mid-Atlantic will also lead to elevated fire weather concerns.
Fire Weather Watches and Red Flag Warnings have been issued for parts of eastern Pennsylvania and New Jersey through this evening.
Lastly, a frontal system entering the Pacific Northwest early Saturday will spread lower elevation/coastal rain and mountain snow into the region.
Precipitation amounts are expected to remain under an inch. ■