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
- 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
- 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.
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.
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