Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 308 PM EDT Fri Sep 18 2020 Valid 00Z Sat Sep 19 2020 - 00Z Mon Sep 21 2020 ...A developing slow moving tropical storm will threaten the Texas Gulf Coast late this weekend into next week... ...Much needed rains on tap Friday night into Saturday for the Pacific Northwest into the Northern Rockies. Flash flooding and debris flows possible over burn scars... ...Dry conditions, fire weather threat and poor air quality to continue across California... ...Below average temperatures this weekend for areas east of the Mississippi River... ...Frosts likely Saturday and Sunday morning from the Great Lakes into the Northern Mid-Atlantic, western and Upstate New York and interior New England... ...Above average temperatures expected from the Southwest into the Central and Northern Plains... A developing tropical system over the southwest Gulf of Mexico is expected to move very slowly over the weekend. An initial slow northward movement Friday night into Saturday will be followed by an equally slow westward movement for the remainder of Saturday and Sunday. This storm has the potential to be a prolific rain producer for the Texas Gulf coast beginning Sunday and possibly continuing into much of next week across the western Gulf coast given the expected slow movement. In addition to the very heavy rain potential, high winds and storm surge will also be a threat along the western Gulf Coast. Much needed rains are expected to fall Friday night into Saturday across portions of the Pacific Northwest into the Northern Rockies. While these rains will bring some relief from the recent fires and hazardous air quality, they will also pose a of threat of flash flooding and debris flows across the recent burn scar regions. No relief from the dry weather farther to the south across California where a fire weather threat and hazardous air quality from ongoing fires will continue through the weekend. Above average temperatures will continue this weekend from the Southwest, across the Great Basin, Rockies and into the Central and Northern Plains. Below average temperatures likely this weekend for nearly all areas to the east of the Mississippi River. Frosts are likely both Saturday and Sunday morning from the Great Lakes into the Northern Mid-Atlantic, western and Upstate New York and interior New England. Oravec Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php