Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Wed Sep 07 2022

Valid 00Z Thu Sep 08 2022 - 00Z Sat Sep 10 2022

...Dangerous heat continues throughout the West today before gradually
relaxing by the end of the week...

...High impact fire weather forecast over parts of the northern High
Plains...

...Heavy rain and gusty winds associated with Hurricane Kay to begin
entering Southern California and the Desert Southwest by Friday...

...Unsettled weather and flash flood chances to increase over the
Southeast and eastern Gulf Coast by late week...

The weather story for the Lower 48 today remains largely the same, with a
dominant and anomalous upper-level ridge parked over the central Great
Basin supporting widespread oppressive heat through tomorrow, before a
cooling trend begins to usher in relief from the record shattering heat.
Preceding the long awaited relief, well above average temperatures are
forecast once again today from California to the northern/central High
Plains, including much of the Intermountain West and Northern/Central
Rockies. As of early this afternoon, numerous stations in the mid-upper
90's over the central Great Basin have already surpassed their daily
temperature records. Expect to see plenty more daily (and possibly
monthly) records broken today as dangerously high temperatures reach into
the upper 90s and triple digits throughout these regions, with highs up to
110 degrees possible in the interior valleys of California.

A strong cold front entering from southwest Canada will usher in a much
cooler "Fall-like" airmass to the northern Plains and northern Great Basin
Thursday, before reaching the Central Plains on Friday. In fact, high
temperatures are actually forecast to only reach the high 50s-low 60s
throughout the northern High Plains on Friday, which equates to around
20-25 degrees below average. The very cool airmass may actually support
instances of mixed precipitation in higher elevations of the Northern
Rockies on Friday. For California, heat will be much slower to dissipate
as highs will continue to reach into the 100s on Thursday and Friday. More
drastic cooling is possible throughout southern California on Friday as
cloud cover and rainfall associated with Hurricane Kay enters the region.
Residents and visitors within regions impacted by the ongoing heat wave
are urged to continue following proper heat safety and check in on
individuals who may be more susceptible to heat related illnesses.
Meanwhile, deepening low pressure in the lee of the Canadian Rockies will
also aid in producing gusty winds throughout the northern Great Basin and
northern High Plains today. Combined with low relative humidity and very
warm temperatures ahead of the aforementioned cold front, conditions are
likely to support the potential for new wildfires to start and existing
fires to spread uncontrollably. SPC has issued an Extremely Critical
(level 3/3) fire weather area over north-central Montana, where winds
could gust up to 50 mph. Additional dry thunderstorm activity could worsen
the fire weather today, where SPC highlights a Slight Risk (level 2/5) of
elevated thunderstorms producing severe wind gusts (a few of which may be
significant) across the Interior Northwest/Northern Rockies. The Critical
(level 2/3) Fire Weather conditions are forecast to sweep ahead of the
cold front and enter the central Plains on Thursday, while remaining over
parts of the Intermountain West through at least Friday.

Meanwhile in the Eastern Pacific, Hurricane Kay is forecast to begin
producing impacts in the form of heavy rain and gusty winds throughout
Southern California and the Desert Southwest on Friday as the center of
the storm slides northward just to the west of Baja California. Currently,
the main impacts from Kay are anticipated to be from heavy rainfall as
tropical moisture surges into Southern California and Southwest Arizona.
Rainfall amounts of 2 to 4 inches, with maximum amounts of 6 inches
possible through Saturday morning over southernmost California, and 1 to 2
inches of rain (with maxima of 4 inches) are anticipated in southwest
Arizona. This amount of rainfall could to produce numerous instances of
flash flooding in the Peninsular Ranges of Southern California, where a
Moderate Risk (level 3/4) of Excessive Rainfall is in effect on Friday.
For latest track information of Hurricane Kay, refer to the National
Hurricane Center for updated information.

Over the eastern half of the Lower-48, an elongated upper-level trough
extending from the Northeast to the Gulf of Mexico will continue producing
scattered showers and thunderstorms throughout the eastern U.S. today,
with activity relegating to the Gulf Coast and Southeast by Thursday and
Friday. The main threats associated with these storms will be the
potential for downpours and isolated flash floods. Eventually, a
strengthening upper-level low over the northern Gulf of Mexico will help
funnel deep tropical moisture to the eastern Gulf Coast by late week,
creating the threat for additional instances heavy rain and flash
flooding. A Slight Risk (level 2/4) of Excessive Rainfall has been issued
for much of the Southeast and eastern Gulf Coast on Friday as more
widespread thunderstorm activity develops capable of containing intense
rainfall rates.

Asherman/Snell


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