Valid Thursday March 19, 2026 to Wednesday March 25, 2026
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM
EDT March 11 2026
Synopsis: Very strong mid-level high pressure
is expected to develop over the Interior West to promote unseasonably warm
temperatures for much of the western U.S. next week. Spring extreme heat
conditions are possible over parts of Desert Southwest as well as into parts of
southern California where there is also an increased risk of Santa Ana winds
through the middle of the period. This anomalously warm pattern is likely to
accelerate spring snowmelt where seasonal snowpack over the higher elevations
has been well below normal. Across the Pacific Northwest, there are increased
chances for episodes of wind speeds underneath an enhanced onshore flow regime
to the north over southwestern Canada. Persistent mid-level high pressure to
the west of the Bering Strait remains favored to usher in below normal and
potentially impactful temperatures, with this threat gradually easing for much
of Alaska later in week-2.
Hazards - Moderate risk of
much above-normal temperatures for portions of the Great Basin, Rockies,
California, and Desert Southwest, Thu-Fri, Mar 19-20.
- Slight risk of much above-normal temperatures for much of the western
CONUS, Thu-Mon, Mar 19-23.
- Slight risk of extreme heat for portions of southern California and the
Desert Southwest, Thu-Fri, Mar 19-20.
- Slight risk of high winds for portions of southern California, Thu-Sun, Mar
19-22.
- Slight risk of high winds for portions of the Pacific Northwest, Northern
Intermountain, and Northern Rockies, Thu-Sat, Mar 19-21.
- Slight risk of much below normal temperatures over much of southern and
western Mainland Alaska and parts of the Southeast, Thu-Wed, Mar 19-25.
- Slight risk of high winds over the southern coast of Alaska and Southeast
Alaska, Thu-Wed, Mar 19-25.
Detailed SummaryFor
Saturday March 14 - Wednesday March 18:
WPC Days 3-7 U.S.
Hazards For Thursday March 19 -
Wednesday March 25: Towards the middle of next week, both the latest 0z
GEFS and ECMWF ensembles feature a highly amplified ridge centered over the
Interior West, with a weakening 500-hPa trough downstream over the eastern U.S.
Since yesterday, the GEFS has become more amplified with the western ridge, and
the ECMWF remaining stronger, continuing to favor >591 dam heights peaking over
the southwestern U.S translating to 3 standard deviations above climatology
extending into the Four Corners region early in the period. There continues to
be good model agreement in the evolution of this mid-level feature gradually
sliding eastward into the Central High Plains. A larger coverage of positive
height departures is favored to overspread the Mississippi, Tennessee, and Ohio
Valleys to support an eastward expansion of above-normal temperatures later in
week-2. However, as this mid-level feature deamplifies, one novel development
featured in the latest ensemble guidance is more of a flattening of the 500-hPa
ridge, with decreasing heights encroaching from southern Canada. Such a
transition would favor cooler temperatures the northern tier of the CONUS, as
well as the potential for the return of enhanced onshore flow over the Pacific
Northwest in conjunction with a mean 500-hPa trough digging southward from the
Gulf of Alaska.
Underneath the amplified ridge center over the Interior West, there is an
uptick in warm signals in percentile space in both the GEFS and ECMWF
Probabilistic Extreme Tools (PETs) compared to yesterday. The GEFS remains
comparatively weaker than the ECMWF, but these tools indicate at least 40-50%
chances for maximum daytime temperatures exceeding the 98th percentile focused
over eastern Four Corners region. Additionally, the National Blend of Models
(NBM) continues to show a higher number of locations nearing record breaking
daytime temperatures across the Northern Intermountain, Rockies, Great Basin,
California and the Desert Southwest early in week-2. In consideration of these
factors, as well as better support in the Canadian ensemble favoring stronger
mean ridging over the West since yesterday, a moderate risk of much
above-normal temperatures is issued for Mar 19-20 before the ridging aloft
begins to deamplify. A broader slight risk area remains posted for much of the
western CONUS, valid through Mar 23, where PETs maintain at least a 20% chance
for maximum temperatures exceeding the 95th climatological percentile. Across
the Sonoran Desert, the NBM forecasts have also trended slightly higher in the
daytime temperatures, now nearing 105 deg F, which is also supported in the
uncalibrated ECMWF ensemble with 10-30% chances for exceeding this threshold
for springtime heat. The NWS heat risk tool also depicts increasing orange
(moderate) level values developing across this region and across southern
California late in week-1, where the potential for higher maximum temperatures
heading into week-2 could lead to heat driven illnesses for vulnerable
populations as well as other heat related impacts. Therefore, a slight risk of
extreme heat is introduced in the updated outlook for portions of southern
California and southwestern Arizona, valid for Mar 19-20. While actual
temperatures forecast for other areas of the West (70 to 80 deg F) are not in
themselves hazardous, the unseasonable warmth looks to contribute to an early
onset of spring snowmelt where high elevation snowpack has already been well
below normal across the West. Snowmelt is expected to significantly increase
this week and lead to increased flows. Combined with elevated chances for
below-normal precipitation, any persistence of this level of warmth over the
Interior West later in March may have longer-term implications in terms of
declining soil moisture and drought development.
Accompanying the warmth throughout the West, strong mid-level ridging
centered over the Great Basin also supports an increased risk of offshore flow
and Santa Ana winds for portions of southern California. Ensembles continue to
grow stronger with the development of surface high pressure over the Four
Corners and Great Basin, with better indications for the development of
thermally induced low pressure in the Sonoran Desert to support this flow
setup. Therefore, a slight risk of high winds remains posted for southern
California, and is extended through Mar 22 before the surface high pressure
over the West begins to relax.
Due to a more expansive coverage of positive mid-level height departures
extending into southwestern Canada early in week-2, any enhanced onshore is
expected to be displaced to the north with drier conditions prevailing across
much of the northwestern CONUS in proximity to the ridge further south.
Although parts of northwestern Washington may receive above-normal
precipitation during the period, both raw and calibrated precipitation tools
have become less supportive of the heavy precipitation potential (<20% chances
for amounts exceeding 2 inches) since yesterday, and a corresponding slight
risk area is removed over western Washington in the updated outlook. However,
based on the PETs maintaining at least a 20% chance of wind speeds exceeding
the 85th percentile, a slight risk of high winds is posted (Mar 19-22) over
portions of Washington, Oregon, Idaho, and Montana as these areas may
experience episodes of elevated wind speeds associated with the enhanced
onshore flow regime to the north. Tied to the eastward progression of the
strong mid-level ridging to allow for the troughing upstream to dig further
south over the northeastern Pacific, increased precipitation is favored over
parts of western Oregon and northern California by mid week-2, however amounts
remain unsupportive of any corresponding hazards at this time.
With the downstream troughing favored to deamplify, and surface high
pressure shifting farther eastward into the Atlantic to induce more return flow
from the Gulf, a moderation of temperatures is expected to be underway over the
eastern U.S. heading into week-2. This is reflected in the raw temperature
tools showing the strongest negative temperature anomalies timing off into
week-1 as well as the PETs where there is reduced chances for minimum
temperatures falling below freezing over the Southeast. As a result, the
slight risk of much below normal temperatures is removed in the updated
outlook, but it is worth noting that any residual cold looks to be more locally
confined to the Carolinas, where any lingering frost or freezes may impact
emerging spring vegetation towards the middle of next week.
Over Alaska, anomalous 500-hPa ridging west of the Bering Strait with
downstream troughing over the Mainland and Gulf of Alaska is favored to bring
well below-normal temperatures for the state. Ensembles continue to show a
gradual breakdown of the mid-level troughing over the state, however PETs
indicate elevated chances for minimum temperatures falling below the 15th
percentile throughout the entirety of week-2 associated with the prevailing
northerly flow. Therefore, a slight risk of much below normal temperatures is
maintained for much of Alaska, and now valid through Mar 25. The mid-level
troughing favored over the northeastern Pacific also supports the continuation
of a slight risk of high winds, also valid through Mar 23. Within the
highlighted wind risk area, freezing sea spray remains a concern due to the
colder temperatures favored during the period.
Following a Kona low event ongoing over the Central Pacific that looks to
bring heavy rains, high winds and flooding for Hawaii this week, ensembles
favor the potential for a reloading mid-level trough to the west of the state
next week, which may induce additional Kona low development. PETs continue to
highlight at least 20% chances for 3-day precipitation amounts exceeding the
85th percentile and 1 inch over much of the island chain during week-2. Given
little to no relief from the persistently wet pattern, any additional rainfall
is anticipated to further saturate grounds.
Forecaster: Nick
Novella
$$
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts
www.nws.noaa.gov
