043
FXUS21 KWNC 131820
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 13 2025

SYNOPSIS: Mid-level high pressure remains forecast across the western
contiguous U.S. during the first half of the week-2 period. This leads to
enhanced chances for extreme heat for portions of the West. Above-normal
temperatures across the Interior West may lead to enhanced winds along parts of
the West Coast. In the East, Tropical Storm Erin may track close enough to the
U.S. East Coast to bring periods of high winds early in week-2. However,
uncertainty remains high with the eventual track of this tropical system.

HAZARDS

Moderate risk of extreme heat for parts of the Great Basin, Southwest, and
Central and Southern Rockies, Thu-Fri, Aug 21-22.

Slight risk of extreme heat for many parts of the Interior West, Thu-Sat, Aug
21-23.

Slight risk of extreme heat for the California Central Valley, Thu-Sun, Aug
21-24.

Slight risk of episodic high winds for coastal portions of most of the East
Coast, Thu-Sat, Aug 21-23.

Slight risk of episodic high winds for coastal portions of California, Thu-Wed,
Aug 21-27.

DETAILED SUMMARY

FOR SATURDAY AUGUST 16 - WEDNESDAY AUGUST 20:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY AUGUST 21 - WEDNESDAY AUGUST 27: The 0Z GEFS, ECENS, and Canadian
ensemble means predict amplified mid-level ridging over the west-central CONUS
at the beginning of week-2, with maximum 500-hPa heights near 595 dm centered
near the Four Corners. This pattern supports the increased likelihood of
extreme heat over the Interior West. A moderate risk (40-60% chance) of extreme
heat is posted for parts of the Great Basin, Southwest, and Central and
Southern Rockies, Aug 21-22. Multiple Probabilistic Extremes Tools (PETs) show
at least a 40% chance of temperatures exceeding the 85th percentile
climatologically, with values exceeding 95 deg F across the designated risk
area (greater than 110 deg F across the Desert Southwest).  A broader area is
highlighted with a slight risk for much of the Interior West throughout August
23rd. A slight risk of extreme heat is also indicated over the California
Central Valley for Aug 21-24 with PETs indicating at least a slight chance of
temperatures exceeding the 85th climatological percentile and 100 deg F across
much of the Valley. Anticipated dry, hot conditions and moderate winds may
support increased wildfire risk. The National Interagency Fire Center (NIFC)
indicates moderate risk for significant fire potential at the end of week-1 and
there are currently active wildfires across the Interior West.



Thermal low pressure near the California-Arizona border combined with surface
high pressure off the West Coast may lead to a tight pressure gradient over the
coast of California. This pattern supports a slight risk of periodic high winds
for portions of coastal California, Aug 21-27. The ECENS and GEFS PETs indicate
at least a 20% chance of wind speeds exceeding the 85th percentile and 25 mph
further increasing confidence.



As of 2pm EDT, the National Hurricane Center (NHC) analyzed Tropical Storm Erin
over the low-latitudes of the central Atlantic. The NHC forecasts Erin to
become a Major Hurricane by the end of the 5 day period and with the storm
moving northeast beyond day 4. There is still considerable uncertainty
regarding the forecast track beyond the NHC forecast with ensemble guidance
indicating a number of solutions. A mid-level trough predicted near the
Mid-Atlantic coast along with a secondary shortwave trough forecast to dig
southward on the western edge of this trough. This could lead to amplification
of the Mid-Atlantic trough which would keep the Tropical Storm east of the U.S.
However, if the trough remains less amplified the Storm could progress further
west and impact portions of the East Coast. Therefore, a slight risk of high
winds is posted for much of the East Coast, Aug 21-23. Residents living near
the Atlantic coast are encouraged to keep updated with the latest forecast
information from the National Hurricane Center and their local forecast offices.

FORECASTER: Ryan Bolt

$$