US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
355 PM EDT Mon May 11 2020
 
Valid Thursday May 14 2020 - Monday May 18 2020
 
Hazards:
- Heavy precipitation across portions of California, Sat-Mon, May 16-May 18.
- Heavy rain across portions of California and the Pacific Northwest, Sat-Mon, May 16-May 18.
- Heavy rain across portions of the Central/Southern Plains, the Mississippi Valley, the Great 
Lakes, the Ohio Valley, and the Northeast, Thu-Sun, May 14-May 17.
- Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Fri-Sat, May 
15-May 16.
- Heavy rain across portions of the Southeast, Thu-Fri, May 14-May 15.
- Flooding occurring or imminent across portions of the Middle/Lower Mississippi Valley, the Great 
Lakes, and the Northern Plains.
- Much above normal temperatures across portions of the Central/Southern Rockies and the 
Central/Southern Plains, Mon, May 18.
 
Detailed Summary:

The main threat over the medium range period (Thursday 5/14 to Monday 5/18) will be the potential 
for multiple rounds of heavy rainfall across portions of the central and eastern U.S. A frontal 
boundary is expected to meander across the Central Plains, Middle Mississippi Valley, and Ohio 
Valley through the weekend, and moisture flowing into the vicinity of the front plus support from 
upper-level energy will combine to create the heavy rainfall potential. Portions of the Plains to 
the Ohio Valley and Great Lakes can expect rain events from Thursday through Sunday before the 
front finally moves eastward on Monday, while the Southern Plains and western parts of the Lower 
Mississippi Valley region appear to see the bulk its rain on Friday and Saturday. Severe weather 
may be a possibility with thunderstorms that occur.

A persistent stationary front near southern Florida could lead to heavy rain there through Friday, 
before a low develops and moves northeastward away from the state. This low could have tropical 
characteristics and is being monitored by the National Hurricane Center.

Precipitation is forecast across the Northwest Thursday into Friday, and the Northern Rockies and 
Wind River Mountains/Tetons could see a few inches of snow. Then as a deep upper-level low 
approaches, precipitation is expected to increase across the Pacific Northwest and northern 
California over the weekend and into Monday. Once again northern California and southwestern Oregon 
can expect the highest precipitation totals, in the form of rain along the coast and some snow in 
higher elevations of the Shasta/Sierra Nevada. Rain which could be heavy is also possible along the 
Pacific Northwest coast and into the Cascades (with snow possible in the highest elevations).

Temperature anomalies are not expected to be significant through the weekend, though Thursday 
morning could be cool across the Northeast before a warmup Friday and Saturday. As the upper-level 
low approaches the West, temperatures there are forecast to be below average by Sunday and Monday. 
But east of the upper low, a strengthening upper-level ridge is expected to cause much above 
average temperatures across the High Plains on Monday, and this warmth will likely move eastward 
through next week.

Over Alaska, above normal temperatures are forecast to continue over western portions of the state, 
but areas with anomalies over 20 degrees above normal should be pretty localized. Meanwhile, Arctic 
surface high pressure should keep northern areas cool. Ice jam and snowmelt flooding will continue 
to be threats across some central and northern areas of the mainland where rivers have not yet 
opened up.

Tate