Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Thu Sep 08 2022

Valid 12Z Thu Sep 08 2022 - 12Z Sat Sep 10 2022

...Hazardous weather associated with Hurricane Kay to begin entering
southern California and parts of the Desert Southwest on Friday...

...Dangerous heat continues throughout central and northern California
through the end of the week, with well above average temperatures building
into the Pacific Northwest by the weekend...

...Critical Fire Weather conditions forecast throughout portions of the
Intermountain West and Central Plains...

...Unsettled weather and flash flood chances forecast over parts of the
Southeast and eastern Gulf Coast...


Hurricane Kay currently churns off the coast of Baja California and
continues to track north-northwest along the Pacific coastline, with
gradual weakening expected to occur as Kay treks northward over cooler
waters. However, impacts are still likely throughout parts of the Desert
Southwest and southern California as a surge of tropical moisture slides
northward. Rainfall amounts potentially adding up to around 6 inches
throughout the mountainous terrain of southern California will likely lead
to areas of flash and small stream flooding. Additionally, heavy rain is
possible over parts of southwest Arizona between Friday night and Saturday
morning. Moisture is expected to reach farther north along the southern
California coastline and reach the greater Los Angeles region by Friday
night as well. A Moderate Risk (level 3/4) of Excessive Rainfall is in
effect for Friday over portions of southern California and far southwest
Arizona, with a larger Slight Risk (level 2/4) encompassing more of
southern California, western Arizona, and far southern Nevada by Saturday.
In addition to the heavy rain threat, gusty winds are possible on Friday
across far southern California. In fact, before rain onset the high winds
could create increasing fire danger. Residents throughout these regions
are urged to plan for dangerous driving conditions and heed warnings
issued by local forecast offices.

Dangerous heat also continues to impact the Golden State as high
temperatures are once again forecast to reach well into the triple digits
both today and Friday, particularly over interior valley regions. The
upper-level ridge responsible for this week's heat wave is fortunately
dissipating and will allow for cooler weather to enter the region by this
weekend, but offshore flow will allow for scorching heat to stick around
for a few more days and eventually spread northward along western Oregon
and Washington. Excessive Heat Warnings remain in effect for much of
California and southern Nevada. For the Intermountain West, central
Rockies, and central Plains one additional day of well above average
temperatures are forecast until a powerful cold front ushers in cooler and
even below average temperatures. Highs today are forecast to reach into
the upper 90s throughout the central Great Basin/Rockies, with triple
digits possible throughout the central High Plains. The above average
temperatures combined with low relative humidity and gusty winds ahead of
the cold front will allow for conditions supportive of new wildfires to
form and existing fires to spread uncontrollably. SPC has issued a
Critical Fire Weather area for today over central Idaho, as well as
portions of central Nebraska and southeast South Dakota. Red Flag Warnings
have also been issued from Idaho to the central Plains, as well as
throughout the Pacific Northwest, where elevated fire weather conditions
exist on Friday.

For the Southeast and Gulf Coast States, a strengthening upper-level low
over the north-central Gulf of Mexico will help funnel deep tropical
moisture into the Southeast and eastern Gulf Coast over the next few days.
A stationary boundary extending along the Gulf Coast will provide a focus
for developing thunderstorms to tap into the increasing moisture content
and potentially lead to numerous downpours. As a result, flash flooding is
possible each day through the beginning of the weekend between the central
Gulf Coast and coastal South Carolina. A slightly higher risk for flash
flooding exists across the Southeast coast today, which is where a Slight
Risk of Excessive Rainfall has been issued. As moisture begins to stream
farther inland on Friday, heavy rainfall chances are likely to spread
north toward the southern Appalachians before reaching into western North
Carolina and Upstate South Carolina by Saturday. In total, widespread
rainfall amounts by this weekend may add up to 2 to 4 inches, with locally
higher totals possible where thunderstorms repeat over similar locations.

Elsewhere, an advancing cold front may lead to scattered thunderstorms
over the Upper Midwest and into northeast Wyoming today. The main threat
with these storms are likely to be associated with isolated damaging winds
gusts. The powerful cold front will bring well below average temperatures
to the northern and central Plains on Friday and Saturday, with highs only
reaching into the 50s and 60s. The cold airmass may also support light
snow across parts of the northern Rockies residing above 10000 feet.


Snell


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