US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
359 PM EDT Thu Apr 15 2021
 
Valid Sunday April 18 2021 - Thursday April 22 2021
 
Hazards:
- Heavy rain across portions of the Southeast, Sun-Tue, Apr 18-Apr 20.
- Flooding possible across portions of the Southeast and the Lower Mississippi Valley.
- Flooding occurring or imminent across portions of the Lower Mississippi Valley.
 
Detailed Summary:

There is only one main hazard area during the medium range forecast period (Sunday, April 18 - 
Thursday, April 22). The main concern will be across portions of Florida as a low pressure center 
over the Gulf advects moisture eastward along a quasi-stationary front draped across the the 
northern Florida Peninsula. A multi-day heavy rain event is expected from Sunday to Tuesday for the 
northern and central Florida Peninsula as the front drifts slowly southward. Widespread rainfall 
totals over 3 inches are likely. Some lingering heavy rain is also possible during the day 
Wednesday before a second, stronger cold front pushes in from the northwest bringing drier, 
continental air southward across the Peninsula by Thursday morning. 

Elsewhere, a shortwave trough will sweep through the Rockies and Plains beginning Sunday. The 
associated surface cold front may produce some accumulating snowfall, but the heaviest snow totals 
are expected to be confined to the peaks of the Northern Rockies Sunday into Monday and the Central 
Rockies Monday into Tuesday. As this system progresses across the central and southeastern U.S. on 
Tuesday and Wednesday, high pressure will fill in across the central U.S. This area of high 
pressure will contribute to the potential for a freeze Sunday night for the Northern Plains, and 
spread into the Central Plains and Upper Mississippi Valley for Monday and Tuesday night. While 
these temperatures are not significantly below normal for this time of year, some vegetation may be 
sensitive to the freezing minimum temperatures. To the west of this system, strong ridging along 
the Pacific coast will lead to above normal highs, particularly for northern California and the 
Pacific Northwest on Sunday, but the departure from normal and duration is not considered to be 
hazardous at this time. 

By Thursday, rain chances in the Central and Southern Plains will increase ahead of a shortwave 
approaching from the west. There is general model agreement for potentially heavy rain across the 
Red River Valley northward through Oklahoma and central/eastern Kansas. However, since it is at the 
end of the forecast period, a hazards area will not be introduced at this time until there is more 
consistency seen in additional model runs. 

For Alaska, no weather hazards are expected during this forecast period. Above normal temperatures 
are expected to continue across the North Slope, but are not considered hazardous at this time. 
Precipitation chances along with gusty winds will increase for the Aleutian Islands starting on 
Saturday and spread eastward to the Alaskan Peninsula and Kodiak Island by Monday ahead of back to 
back low pressure systems to the south over the Pacific, but the amounts are expected to remain 
below the hazards threshold.

Putnam