US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
416 PM EDT Tue Apr 21 2020
 
Valid Friday April 24 2020 - Tuesday April 28 2020
 
Hazards:
- Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, 
Sun-Mon, Apr 26-Apr 27.
- Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the 
Great Lakes, and the Ohio Valley, Fri-Sat, Apr 24-Apr 25.
- Heavy rain across portions of the Mid-Atlantic, the Northeast, and the Central Appalachians, 
Sun-Mon, Apr 26-Apr 27.
- Flooding possible across portions of the Northern Plains.
- Flooding occurring or imminent across portions of the Middle Mississippi Valley, the Lower 
Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains.
- Flooding likely across portions of the Southeast and the Tennessee Valley.
- Much above normal temperatures across portions of the Central Plains, the Central Rockies, the 
Central Great Basin, the Southern Plains, the Northern Great Basin, the Southern Rockies, 
California, the Pacific Northwest, and the Southwest, Fri-Tue, Apr 24-Apr 28.
- Much below normal temperatures across portions of the Northeast, the Central Appalachians, the 
Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Great Lakes, and the Ohio 
Valley, Sun-Mon, Apr 26-Apr 27.
- Much below normal temperatures across portions of mainland Alaska, Fri-Sun, Apr 24-Apr 26.
 
Detailed Summary:

The medium-range period from Friday, April 24 to Tuesday April 28 in the West is headlined by a 
deep upper level trough in the Gulf of Alaska while a strong ridge of high pressure takes control 
of the Southwest. A dome of much above normal temperatures originating in the Desert Southwest to 
start the period will spread north and east into central California, the Great Basin, and Four 
Corners region throughout the period. High temperatures are forecast to soar into the triple digits 
for the first time this year in portions of the Desert Southwest by week's end and continue into 
early next week, making it the first heat wave of the season for the region. To the north, a steady 
stream of Pacific moisture will be aimed at the Pacific Northwest. The heaviest round of 
precipitation looks to arrive Sunday and continue into Monday as a frontal system tracks across the 
region. The primary precipitation type will be rain but some heavy higher elevation snowfall in the 
Washington Cascades is also possible. As a result, a heavy precipitation area has been added to the 
chart.

Further east, a series of upper level disturbances will rotate through the eastern half of the 
Lower 48. The first on Friday morning will cause wet and dreary conditions across the Northeast and 
Mid-Atlantic on Friday with scattered showers and storms dotting The Sunshine State. Meanwhile, a 
new upper level feature exiting the Rockies should track east and deepen while doing so. The result 
will be blossoming areas of showers and thunderstorms in the middle Mississippi Valley and western 
Ohio Valley. The axis of the heaviest precipitation is still not agreed upon by guidance, but there 
is plenty of moisture and vertical motion to work with, making it increasingly likely for heavy 
rain in these regions. The storm will intensify as it tracks into the Ohio and Tennessee Valleys 
late Saturday with periods of rain over the Lower Great Lakes and the potential for strong 
thunderstorms in the Southeast. Eventually by Sunday a coastal low will form off the Northeast 
coast making for a wet, dreary, and gusty Sunday. Look for rain and perhaps some mountain snow in 
the northern Appalachians to stick around into Monday before the storm exits late day. The 
prolonged fetch of Atlantic moisture has led to model guidance keying in on an area of heavy rain 
over the Northeast, but there are discrepancies on exact placement of heaviest rainfall either 
further inland or over the I-95 corridor.

Over Alaska, a deep upper-level trough will move over the eastern part of the Alaska mainland, 
followed by an area of cold high pressure from the North Pole. This air will linger in some form 
over the region Friday and into the weekend. Temperatures will moderate across the eastern mainland 
next week. To the south, a pair of occluded storm systems will slam into the Panhandle both at the 
start and ends of the period. Plenty of precipitation is in the forecast but precipitation rates 
are not forecast to become excessive at this time. Should trends become wetter, there may be a need 
for a heavy rain or precipitation area in the future forecasts.

Mullinax