US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
430 PM EDT Tue May 12 2020
 
Valid Friday May 15 2020 - Tuesday May 19 2020
 
Hazards:
- Heavy rain across portions of the central and southern Plains, across the Mid- Mississippi Valley 
into the Ohio Valley, Fri-Sat, May 15-May 16.
- Heavy rain across portions of northern New England, as well as northern California into 
southwestern Oregon, Sun-Mon, May 17-May 18.
- Heavy rain across portions of southeastern Texas, Sun-Tue, May 17-May 19.
- Heavy precipitation along portions of the Sierra Nevada, Tue, May 19.
- Flooding possible across portions of the central Plains and the Mid-Mississippi Valley.
- Flooding occurring or imminent across portions of the lower and middle Mississippi Valley, and 
the northern Plains.
- Much above normal temperatures across portions of the central Rockies eastward into the northern 
and central Plains, Mon-Tue, May 18-May 19.
 
Detailed Summary:

It appears that a gradual change in the synoptic pattern will take place during the medium range 
period (Friday 5/15 to Tuesday 5/19) across the U.S.  Model guidance agrees that a strong ridge of 
high pressure will be establishing across the High Plains by early next week as a deep 
trough/closed low approaches the West Coast.  Prior to this pattern change, moisture streaming 
northward from the Gulf of Mexico will likely interact with a stationary front to result in a 
threat of heavy rain from the eastern portion of the central and southern Plains, across the 
Mid-Mississippi Valley into the Ohio Valley Friday into Saturday.  A low pressure system is 
forecast to develop along the front and then move toward the Great Lakes on Saturday.  Moisture 
ahead of this system will interact with a well-developed warm front to result in a threat of heavy 
rain across northern New England Sunday and Monday.

Meanwhile, a deepening upper-level trough is forecast to approach the West Coast during the 
weekend.  Moisture ahead of this system is forecast to bring a potential for heavy rain across 
portions of northern California into southwestern Oregon from Sunday into Monday.  By next Tuesday, 
heavy wet snow could spread into the Sierra Nevada as the upper trough digs further toward 
California.

While the upper-level trough deepens over the West Coast, a ridge of high pressure is forecast to 
strengthen over the Rockies before moving east into the Great Plains early next week.  This will 
bring a warming trend across the northern and central Plains early next week with afternoon 
temperatures likely to soar well up into the 80s.

Underneath this strengthening upper ridge, a couple of atmospheric disturbances are of note during 
the medium-range period.  One noteworthy feature would be in the vicinity of eastern Texas as a 
piece of upper-level energy may become trapped underneath the upper ridge and begin interacting 
with moisture from the Gulf of Mexico.  The GFS shows the system spinning closer to the Texas coast 
and result in a better-defined system along with heavier rainfall amounts.  On the other hand, the 
ECMWF sends the system farther to the northeast before the strong upper ridge in the central Plains 
pushes it back into eastern Texas.  The predictability regarding a mesoscale system of this nature 
is generally rather low for the medium-range.  However, the potential for heavy rainfall cannot be 
ruled out especially if the system meanders closer to the Gulf Coast as suggested by the GFS.

Another noteworthy feature is a low pressure system that is forecast to form to the east of Florida 
this weekend.  This system is being monitored by the National Hurricane Center for the potential of 
tropical/subtropical cyclogenesis.  It appears that this system will move further out to sea at 
this point in time.

Over the Pacific Northwest, a frontal system moving onshore could bring localized areas of heavy 
precipitation this coming weekend.

Over Alaska, low pressure system moving across the southern portion of the state should result in 
weather impacts below hazards criteria.  Above normal temperatures are forecast to continue over 
western and much of the southern portions of the state, in contrast with colder than normal 
temperatures over the north and northeast portions of the state.

Kong