US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
408 PM EDT Mon Aug 16 2021
 
Valid Thursday August 19 2021 - Monday August 23 2021
 
Hazards:
- Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Fri, Aug 20.
- Heavy rain across portions of the Mid-Atlantic and the Northeast, Thu, Aug 19.
- Flooding occurring or imminent across portions of the Southeast.
 
Detailed Summary:

Tropical moisture pooling along a trough and front will aid in producing heavy rain over parts of 
the northern Mid-Atlantic into parts of Southern New England on Thursday.  A second front over the 
Northern Plains will be quasi-stationary over the region on Thursday and Friday before moving 
eastward on Saturday.  There is a lot of uncertainty associated with this system. Some of the 
models show more significant areas of rain; however, others show less. The stationary front over a 
region for a day or two suggests heavy rain along and near the boundary.  At this time, the 
confidence in an area of heavy rain is low; therefore, a smaller region of heavy rain is depicted 
on the Hazards Chart for Friday. Nevertheless, the heavy rain could extend as far south as Nebraska 
and develop on Thursday, too.

The excessive heat over the country will get a break as a deep upper-level trough is over the West 
that only starts to weaken on Monday. As a result, below-normal temperatures will be over the West 
through Saturday. However, that is not seen as a hazard at this time of the year but more as relief 
from the heat. The temperatures over the East will be close to normal.

For Alaska, the upper-level pattern will be dominated by troughing, which will be conducive to wet 
weather.  At the surface, low pressure and a front will be across the Bering Sea into the Interior 
of Alaska, then into Canada that will move into Canada by Saturday.  Another front, along the Gulf 
of Alaska Coast, moves towards the Panhandle by Friday.  The systems will produce rain over parts 
of the state through Monday.  Yet, the precipitation totals will not reach the criteria for a 
hazard for this time of year.  There is some uncertainty for heavy rain along the Gulf Coast, with 
the ECMWF being the most robust with the precipitation totals.

Ziegenfelder