US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
255 PM EST Wed Mar 03 2021
 
Valid Saturday March 06 2021 - Wednesday March 10 2021
 
Hazards:
- Heavy precipitation across portions of California and the Pacific Northwest, Mon-Tue, Mar 8-Mar 9.
- Heavy snow across portions of California, Mon-Wed, Mar 8-Mar 10.
- Flooding possible across portions of the Southeast.
- Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, 
and the Ohio Valley.
- Flooding likely across portions of the Mid-Atlantic and the Ohio Valley.
- Heavy precipitation across portions of mainland Alaska and the Alaskan Peninsula, Mon-Tue, Mar 
8-Mar 9.
- High winds across portions of mainland Alaska, Sun-Mon, Mar 7-Mar 8.
 
Detailed Summary:

During the medium range period (Saturday, March 6th - Wednesday, March 10th) much of the activity 
over the lower 48 will be isolated to the west of the Rockies where persistent upper-level 
troughing will set the stage for multiple rounds of precipitation, while ridging over the remainder 
of the CONUS will keep activity to a minimum. On Saturday, a moisture-rich cold front is expected 
to pass through California and the Great Basin, leaving a trail of light to moderate rain and high 
elevation snow in its wake. Dry and quiet conditions on Sunday will precede the arrival of a pair 
of low pressure/frontal systems that will bring a mix of heavy coastal rain and mountain snow to 
the northern California/Oregon border as well as the Sierra Nevada on Monday. Shortly after these 
systems progress further inland a shortwave is forecast to sweep through, prolonging the heavy 
precipitation near and along the coast into Tuesday and the heavy snow in the Sierra Nevada through 
Wednesday.

After passing through and bringing moderate snowfall to the Northern and Central Rockies on 
Tuesday, the two low pressure/frontal systems will coalesce into one and continue moving eastward 
into the Great Plains. Current model guidance is still too uncertain at this time to make any 
definitive comments about the potential hazards associated with this storm system, however, the 
guidance does indicate the potential for heavy precipitation to develop over the Northern Great 
Plains and Upper Midwest. Additionally, a tight pressure gradient surrounding this system may 
produce high winds and wind gusts from the base of the Rockies to the Mississippi Valley. Updates 
will be provided in the coming days as the guidance evolves and the details come into better focus.

Elsewhere, an upper-level trough working in tandem with a low pressure/frontal system at the 
surface is forecast to bring moderate rain to Florida's Space Coast on Saturday. Current model 
guidance suggests 24 hour rainfall totals reaching or exceeding an inch will be possible in some 
isolated areas, but most, if not all, of the significant rainfall is expected to remain offshore.

For the entire length of the medium range period, minimum and maximum temperatures are forecast to 
sit 10 to 20 degrees above normal for the Northern/Central Plains, the Upper Mississippi Valley, 
and around the Upper Great Lakes. These temperature departures translate into highs that will reach 
the 50s and 60s, while lows will generally remain above freezing through Tuesday. This is 
particularity significant as states in the Upper Midwest still possess a snowpack and these high 
temperatures combined with a prolonged lack of re-freezing will lead to widespread, though gradual, 
snow melt. Along the East Coast both maximum and minimum temperatures are forecast to be slightly 
below normal throughout the weekend before moderating at the beginning of next week. Out West, 
temperatures are expected to remain close to average until Monday when maximum temperatures are set 
to take a marginal drop below normal.

In Alaska, a series of storm systems are expected pass through the Bering Sea, the stronger of 
which will occur at the beginning of the period. Tight pressure gradients associated with these 
strong systems are forecast to set up and generate hazardous wind gusts over the western mainland 
Sunday into Monday. While high winds are also possible along the Aleutians during the same time 
frame, they are not expected to reach hazardous levels. As the second of these systems propagates 
east towards the mainland, a wave of low pressure and its fronts are expected to pass through and 
bring heavy precipitation to the Southwestern and Southcentral mainland Monday into Tuesday. Above 
normal maximum and minimum temperatures are forecast to affect portions of the Far North and 
Southwestern mainland Sunday through Tuesday, with the highest temperatures expected to occur on 
Monday. Though warmer than usual, actual temperatures in the region will still remain well below or 
near freezing and are thus expected to be non-hazardous.

Zavadoff