Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
445 AM EDT Fri Sep 09 2022

Valid 12Z Fri Sep 09 2022 - 12Z Sun Sep 11 2022

...Tropical Storm Kay to bring excessive rainfall and flash flooding to
portions of Southern California and the Desert Southwest this weekend...

...Dangerous heat begins to wane in central California as Northwest warms
up...

...Cold air surges through Rockies and Plains behind powerful cold front...

...Heavy rainfall likely from Gulf Coast to Mid-Atlantic...


Tropical Storm Kay will begin impacting Southern California and the Desert
Southwest today. Upper ridging in the West will aid in steering the system
out into the eastern Pacific today, but convective bands with heavy
rainfall potential will still work their way into the Southwest. A
moderate risk of excessive rainfall (level 3/4) is in effect from southern
California to southwestern Arizona as a result. Loaclized flash flooding
is also possible over other parts of the Southwest where another slight
risk area is in place. The upper ridge is also responsible for the ongoing
heat wave gripping parts of the Sacramento and San Joaquin Valleys this
week. This record breaking heat will begin to weaken today as clouds and
rain and general troughing roll into the region thanks to T.S. Kay.
Overnight lows will continue to rival records this weekend as the
increased cloud cover traps warm air at the surface. Approximately 29
million Americans are currently under an Excessive Heat Warning. Elevated
fire risk is in effect for portions of the Pacific Northwest as warm/dry
air and increased winds create favorable conditions for fires. Red Flag
warnings are also in effect from Washington state to west-central Oregon.

A powerful, yet slow moving, cold front will traverse the Plains and
Midwest this weekend. Showers and thunderstorms will focus along this
boundary, while a significant surge of cold air follows on the backside.
Heavy snow may develop over the highest peaks of the Bighorn Mountains of
Wyoming today thanks to the convergence of moisture and cold air along the
base of an amplified upper-level trough. Localized flash flooding is
possible along the cold front from eastern Iowa to southern Wisconsin on
Saturday.

Shortwave energy will lift north across the Florida Panhandle this
weekend, sending moisture streaming into the Southeast between an upper
low over the Central Gulf coast and an upper high a stationed just off the
Southeast coast. This dipole pattern will allow for a continuos stream of
showers and thunderstorms to develop around a stationary front draped from
the western Atlantic through the Gulf coast. A moderate risk of excessive
rainfall leading to flash flooding is in effect for portions of the South
Carolina coast down to the central Georgia coast where 2-4 inches of rain
with pockets of locally higher amounts are possible. A broad slight risk
area is also in effect for much of the same area as well as much of the
central/Florida Gulf coast. The heavy rain threat shifts into the North
Carolina/Virginia Blue Ridge and Piedmont on Saturday as Gulf moisture
surges into those areas.


Kebede


Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php