Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Thu Sep 17 2020
Valid 12Z Thu Sep 17 2020 - 12Z Sat Sep 19 2020
...There is a moderate risk of excessive rainfall and a slight risk of
severe thunderstorms over parts of the Mid-Atlantic into the Southeast...
...Frosts and freezes likely across the Upper Mississippi Valley and Upper
Great Lakes Thursday and Friday mornings. Above average temperatures to
continue from the Great Basin/Rockies into the High Plains...
...Poor air quality will continue across the Pacific Northwest, Northern
Rockies and portions of Central California...
..Cooler air moving into the Pacific Northwest and Northern/Central
California with much needed rains over western portions of Washington
State and Oregon...
Sally is a tropical depression and will continue to weaken then get picked
up by front moving out of the Midwest on Friday, then move out over the
Western Atlantic by Saturday. The storm will still produce heavy rain
while moving very slowly northeast on Thursday across southeast Alabama,
through North-Central Georgia and into Central South Carolina by early
Friday. While the wind speeds associated with Sally are expected to
continue to diminish as it pushes inland, the slow movement of Sally will
continue to produce heavy rain over parts of the Southeast/Mid-Atlantic.
The WPC has issued a moderate risk of excessive rainfall over parts of the
Mid-Atlantic into the Southeast on Thursday into Friday morning. The
heavy rain will produce numerous areas of flash flooding with some of
these being significant. In addition, many streams may flood and flood
waters may affect larger rivers. Furthermore, severe weather is possible
over the Southeast into the Southern Mid-Atlantic where tornadoes and high
winds are possible.
The last rains associated with Sally will be pushed off the Southeast
coast Friday night into early Saturday by a strong cold front. This cold
front will bring below average temperatures to areas east of the
Mississippi river Friday into this weekend. Frosts and freezes likely
across the Upper Mississippi Valley and Upper Great Lakes Thursday and
Friday mornings, while below average temperatures spread across areas to
the east of the Mississippi River by late week and the weekend.
Cooler weather is also on tap for the Pacific Northwest into
Northern/Central California over the next two days. While temperatures
drop, hazardous air quality from on going fires will continue. There is
potential, however, for some much needed rains to move into western
portions of Washington State and Western Oregon late Thursday into Friday.
Additionally, the SPC has issued a slight risk of severe thunderstorms
over parts of Western Oregon on Thursday into Friday morning. The main
hazards associated with the thunderstorms will be frequent lighting,
damaging thunderstorm wind gust, and tornadoes.
In between the cooler temperatures along the west coast and over the East,
above average temperatures expected to continue through the Rockies, Great
Basin and across the Northern to Central High Plains.
Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php