US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
440 PM EDT Mon Aug 10 2020
 
Valid Thursday August 13 2020 - Monday August 17 2020
 
Hazards:
- Heavy rain across portions of North Dakota into northern Minnesota, Thu-Fri, Aug 13-Aug 14.
- Heavy rain across portions of the Mid-Atlantic into the central Appalachians, Thu-Sun, Aug 13-Aug 
16.
- Flooding occurring or imminent across portions of the Middle Mississippi Valley.
- Excessive heat across portions of the Desert Southwest, Fri-Mon, Aug 14-Aug 17.
- Excessive heat across portions of the southern Plains, Thu-Fri, Aug 13-Aug 14.
- Excessive heat across portions of the lower Mississippi Valley, Sat-Sun, Aug 15-Aug 16.
- Much above normal temperatures across portions of the southern High Plains, Thu-Fri, Aug 13-Aug 
14.
- Heavy rain across much of the Alaska Panhandle, Sun-Mon, Aug 16-Aug 17.
 
Detailed Summary:

The medium range period (Thursday, Aug. 13 to Monday, Aug. 17) will feature a slow-moving front 
stretching across the eastern U.S.  Models are showing increasing support for heavy rain to fall 
over portions of the Mid-Atlantic into the central Appalachians through the medium range period.  
In addition, remnant energy associated with a decayed front could be reinvigorated as a low 
pressure center possibly forms near the Carolina coast and then tracks toward the Outer Banks.  The 
National Hurricane Center has begun watching for any signs of tropical cyclone formation regarding 
this system.  In any event, the presence of the slow-moving front together with the alleged 
development of the new low pressure system will keep a good chance of showers and thunderstorms for 
the Mid-Atlantic for late this week into the weekend.  It appears that daytime heating will enhance 
the thunderstorm chances each day during the late afternoon to early evening hours while lulls in 
the precipitation will tend to occur at night.  By next Monday, the low pressure system should be 
moving off the Mid-Atlantic coast but a cold front moving in from the Ohio Valley may bring some 
heavy rainfall into southern New England.

A cold front dipping into the northern Plains on Thursday will possibly interact with a low 
pressure wave associated with another frontal system just to the south.  This will increase the 
threat of heavy rainfall associated with strong thunderstorms across eastern North Dakota into 
northern Minnesota Thursday and Friday.  The threat of heavy rain is expected to decrease as the 
front moves into the Great Lakes during the weekend. 

Meanwhile, the upper-level ridge over the Southwest is forecast to strengthen and move westward 
during the medium-range period.  This will increase the threat of excessive heat in the desert 
areas where afternoon temperatures of 115 degrees or higher are forecast from Friday through next 
Monday, with record daily high temperatures likely by Sunday.  Temperatures in the southern High 
Plains will also soar well into the 100s on Thursday and Friday under the strong upper ridge.   
Humidity will be sufficiently low to keep the heat from being too oppressive there.  On the other 
hand, high humidity across the southern Plains into the lower Mississippi Valley will allow heat 
indices to possibly soar above 105 degrees in the afternoon, where a couple areas of Excessive Heat 
are highlighted.

As for Alaska, models are showing increasing support for a fairly vigorous occluded cyclone to 
approach and make landfall over southeastern part of the state during the weekend and into next 
Monday.  Therefore, heavy rain will appear possible next Sunday to Monday for the Panhandle.  
Elsewhere, rather warm high temperatures into the 70s are forecast for southern Alaska as the next 
occluded cyclone tracks into the Aleutians.

Kong