448
FXUS21 KWNC 231917
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT October 23 2026

SYNOPSIS: An active weather pattern is anticipated for much of the contiguous
U.S. (CONUS) during week-2. A series of mid-level lows approaching the West
Coast is predicted to bring periods of heavy precipitation, high elevation
snow, and high winds across coastal areas, shifting from coastal California to
the Pacific Northwest with time. Additionally, an influx of moisture from the
eastern tropical Pacific favors increased chances for heavy precipitation
across the Four Corners region and heavy snow across the Central Rockies at the
beginning of the period. Enhanced southerly moist flow and surface low
formation in the lee of the Rockies favors an increased risk of heavy
precipitation across the south-central contiguous U.S. into portions of the
Mississippi, Ohio, and Tennessee Valleys, and Southeast with the greatest
likelihood over the Southern Plains and Lower Mississippi Valley at the
beginning of week-2.

HAZARDS

Moderate risk of heavy precipitation for portions of Arizona, adjacent parts of
New Mexico, Sat-Mon, Oct 31-Nov 2.

Slight risk of heavy precipitation for southern portions of the Four Corners,
Sat-Mon, Oct 31-Nov 2.

Slight risk of heavy snow for parts of the Central Rockies, Sat-Mon, Oct 31-Nov
2.

Slight risk of heavy precipitation for coastal portions of central and southern
California, Sat-Mon, Oct 31-Nov 2.

Slight risk of heavy precipitation for coastal portions of Northern California
and southwestern Oregon,  Mon-Fri, Nov 2-6.

Slight risk of heavy precipitation for portions of the Pacific Northwest,
Wed-Fri, Nov 4-6.

Slight risk of heavy snow for the Klamath and Sierra Nevada Mountain Ranges,
Sun-Fri, Nov 1-6.

Slight risk of heavy snow for the Cascades,  Wed-Fri, Nov 4-6.

Slight risk of high winds for coastal portions of the Pacific Northwest,
Wed-Fri, Nov 4-6.

Moderate risk of heavy precipitation for parts of the Lower Mississippi Valley
and Southern Plains, Sat-Mon, Oct 31-Nov 2.

Slight risk of heavy precipitation for parts of the Lower and Middle
Mississippi, Ohio, and Tennessee Valleys, Southern Plains, and Southeast,
Sat-Wed, Oct 31-Nov 4.

DETAILED SUMMARY

FOR MONDAY OCTOBER 26 - FRIDAY OCTOBER 30:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SATURDAY OCTOBER 31 - FRIDAY NOVEMBER 06: A series of mid-level troughs
near or over the West Coast are anticipated to bring enhanced moist flow to
parts of the West during week-2, shifting northward from California and the
Southwest to the Pacific Northwest with time. Additionally, increased tropical
moisture is anticipated into parts of the southwestern CONUS from the eastern
Pacific.  The orientation of the mid-level trough in the GEFS ensemble is less
favorable for heavy precipitation across California than the ECENS and compared
to yesterday.



A moderate risk of heavy precipitation is designated for parts of Arizona, Oct
31-Nov 2 where the ECENS (GEFS) Probabilistic Extremes Tool (PET) indicates at
least a 70% (40%) chance of 3-day precipitation totals exceeding the 85th
percentile climatologically. Uncalibrated guidance and PETs indicate 3-day
totals exceeding anywhere from 0.5 to one inch in the moderate risk area.
Localized flooding is possible across the highlighted region. A broader area of
slight risk is forecast across the southern Four Corners region, Oct 31-Nov 2
where the PETs indicate at least a 30% chance of exceeding the 85th percentile.
Further north, the slight risk of heavy snow has been decreased in spatial
coverage reflecting lowering heavy snow signals in the model guidance and
tools, and is now designated for the Central Rockies, Oct 31-Nov 2, where there
is at least a 20% chance of 3-day accumulated totals exceeding 4 inches (6
inches locally).





Even with the series of mid-level shortwave troughs and accompanying enhanced
moist flow shifting from California to the Pacific Northwest, the GEFS shows a
weaker precipitation response  across California compared to its solutions
yesterday, and compared to todays ECENS. Despite this difference, slight risks
of heavy precipitation are designated for coastal portions of Central and
Southern California, Oct 31-Nov 2, Northern California, Nov 2-6, and the
Pacific Northwest, Nov 4-6. For California, the PETs indicate at least a 20%
chance of 3-day accumulated precipitation exceeding the 85th climatological
percentile, with some discrepancy regarding the totals. The ECENS PET shows the
greatest 3-day totals, exceeding one inch broadly across California, whereas
the GEFS and CMCE indicate totals reaching 0.5 inches. There is significantly
better agreement among models and associated PETs for the Pacific Northwest at
the end of week-2, with good agreement of 3-day precipitation totals exceeding
the 85th percentile and one inch (2 inches locally along the coast).



 Corresponding slight risks of heavy snow are posted for the Klamath and Sierra
Nevada Mountain Ranges, Nov 1-6, and the Cascades, Nov 4-6. These risk areas
may receive 3-day snowfall totals upwards from 4-6 inches. As the mid-level
trough expands from the Gulf of Alaska southward to the Northwest coast, and
adjacent surface pressure further inland, a tight pressure gradient along the
coast is possible. This translates to a slight risk of high winds for coastal
portions of the Pacific Northwest, Nov 4-6. The ECENS PET indicates at least a
20% chance of wind speeds exceeding the 85th percentile and 35 mph, further
supported by uncalibrated GEFS and ECENS ensembles indicating greater than 40%
likelihood of wind gusts exceeding 20 knots (about 23 mph).





Potential lee cyclogenesis east of the Rockies combined with southerly moist
flow associated with surface high pressure over the East supports increased
chances for enhanced precipitation across the south-central and east-central
CONUS. A moderate risk of heavy precipitation is delineated across parts of the
Lower Mississippi Valley and Southern Plains, Oct 31-Nov 2 where PETs indicate
30-40% chances or greater of 3-day precipitation totals exceeding the 85th
percentile and one inch, further supported by uncalibrated guidance. A broader
area is highlighted with a slight risk across parts of the Lower and Middle
Mississippi, Ohio, and Tennessee Valleys, Southern Plains, and Southeast, Oct
31-Nov 4, where PETs are in good agreement indicating at least a 20% chance of
3-day precipitation totals exceeding the 85th percentile climatologically and
one inch.

FORECASTER: Melissa Ou

$$