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. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php