US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
253 PM EDT Fri Sep 20 2019
 
Valid Monday September 23 2019 - Friday September 27 2019
 
Hazards:
- Heavy precipitation across portions of the Northern Rockies, Fri, Sep 27.
- Heavy rain across portions of the Central Plains and the Middle Mississippi Valley, Tue-Thu, Sep 
24-Sep 26.
- Heavy rain across portions of the Southwest, Mon-Tue, Sep 23-Sep 24.
- Flooding possible across portions of the Plains and Mississippi Valley.
- Flooding occurring or imminent across portions of the Plains and the Upper Midwest.
- Flooding likely across portions of the Middle Mississippi Valley.
- Much above normal temperatures across portions of the Southeast and Southern Appalachians, 
Thu-Fri, Sep 26-Sep 27.
- Heavy rain across portions of the Alaska Panhandle, Mon-Tue, Sep 23-Sep 24.
 
Detailed Summary:

The synoptic flow pattern during the medium range period (Monday to Friday) should remain quite 
amplified with several areas of potential weather hazards. A deep upper level low dropping into the 
Southwest Mon - Tues may stall for a day or two before ejecting eastward into the Plains. This 
would support a period of heavy rainfall across parts of the Southwest in combination of possible 
leading moisture flow from what is currently tropical storms Mario and Lorena in the east Pacific. 
Once the low ejects eastward into the Plains late next week, heavy rainfall may try to develop 
across parts of the eastern Plains into the Midwest along a nearly stationary frontal boundary. 
There remains some uncertainty with how much and the location of the heaviest rainfall, but given 
much of this area is forecast to receive very heavy rainfall in the short range period, a heavy 
rainfall area seemed reasonable for todays outlook. At the end of next week, another deep upper 
level low should drop into the Northwest U.S. supporting enhanced precipitation along the favorable 
terrain of the Northwest. The best chance for heavy precipitation appears at this point over the 
northern Rockies of western Montana. There is plenty of uncertainty for snow levels, though 
ensemble guidance does suggest at least the highest terrain could see several inches of snow.

Meanwhile, across the eastern U.S., upper level ridging will build through the period resulting in 
much above normal temperatures (+10 degrees above normal) for much of the Southeast and into parts 
of the Southern Appalachians. By next Thursday-Friday (and even beyond), daytime highs could 
approach record high values and so this warranted a much above normal temperatures area on the 
hazards outlook today.

Beginning of the medium range period in Alaska should be active also as a deep surface low moves 
over/just south of the Aleutians and into the Gulf by Monday. This will likely bring a round of 
potentially heavy rainfall to much of the Alaskan Panhandle Monday-Tuesday, Sep 23 and 24. This low 
may also bring a round of enhanced precipitation to parts of the eastern Aleutians through Monday, 
though amounts appear to be marginal for a heavy rain area on the hazards chart.

Santorelli