453
FXUS21 KWNC 171815
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT October 17 2024

SYNOPSIS: A generally quiet pattern is predicted across the contiguous U.S.
(CONUS) during week-2, with mid-level high pressure over the East into portions
of the Southwest favoring above-normal temperatures. An exception is in the
Pacific Northwest where enhanced onshore flow may bring rounds of precipitation
into the Pacific Northwest but precipitation is unlikely to reach hazardous
thresholds. Flooding in the wake of Hurricane Milton remains a concern over
parts of Florida. Conversely, Rapid Onset Drought remains a risk across
portions of the Southern Plains and Lower Mississippi Valley. In Alaska, two
areas of low pressure are forecast in week-2 that may bring high winds and
heavy precipitation to portions of western Mainland Alaska and the Bering and
Chukchi Seas.



HAZARDS

A slight risk of high winds for portions of western Mainland Alaska, Fri-Sat,
Oct 25-26, and Mon-Wed, Oct 28-30.

A slight risk of heavy precipitation for portions of western Mainland Alaska,
Fri-Sat, Oct 25-26.

A slight risk of heavy snow for portions of western Interior Alaska, Fri-Sat,
Oct 25-26.

Possible flooding for the parts of Withlacoochee River, Peace River, and St.
Johns River in the central Florida Peninsula.

Risk of Rapid Onset Drought (ROD) across portions of eastern Texas, northern
Louisiana, and southwestern Mississippi.

DETAILED SUMMARY

FOR SUNDAY OCTOBER 20 - THURSDAY OCTOBER 24:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY OCTOBER 25 - THURSDAY OCTOBER 31: Anomalous ridging and unseasonably
warm temperatures are forecast to be widespread across much of the CONUS,
excluding portions of the West Coast and Northern Rockies. The anomalous warmth
may be in decline by the end of week-2 but temperatures are likely to remain
above-normal throughout the period.



In Alaska, a progressive mid-level height pattern is forecast with mid-level
ridging forecast across the Aleutian Islands and North Pacific at the start of
the period to progress southeast over time and weaken. Multiple waves of
mid-level troughing are forecast to move through Mainland Alaska from eastern
Siberia and the North Pacific. An area of surface low pressure is forecast to
impact western Alaska early in the period. This may potentially set up a strong
pressure gradient across western Alaska bringing high winds to the region with
surface high pressure forecast across the North Pacific. The Probabilistic
Extremes Tools (PETs) from the GEFS and ECENS forecasts elevated chances of
high winds across much of western Alaska and is supported by the mid-level flow
pattern. Therefore, slight risk of high winds is posted for western Mainland
Alaska for Oct 25-26. Following a brief break, a second area of low pressure is
forecast to move into the same area by Oct 28, once again increasing chances
for high winds along coastal portions of western Alaska. Therefore, a second
risk period is forecast from Oct 28-30.



Any low pressure system that does develop may bring chances for heavy rain and
snow to portions of western Alaska. The GEFS and ECENS PETs forecast 20-30%
chances of 3-day precipitation amounts to exceed the 85th percentile for days
8-10. Therefore, a slight risk of heavy precipitation is posted for portions of
western Alaska for Oct 25-26. In portions of the central Interior much of this
precipitation would likely fall as snow and a slight risk of heavy snow is
posted for Oct 25-26. Near the western coast the heavy snow is favored across
higher elevations with more mixed precipitation chances at lower altitudes and
so there is some overlap of the heavy snow and heavy precipitation slight risks
in this area. There remains too much uncertainty regarding precipitation
amounts with any secondary low pressure system to forecast a hazard for the
middle to end of the period.



Along the West Coast of the CONUS, a mid-level trough is forecast to be along
the coast at the start of week-2. The trough may bring a period of unsettled
weather to portions of the Pacific Northwest and Northern California. The PETs
from the ECENS and GEFS forecast 20-30% chances for 3-day precipitation amounts
to exceed the 85th percentile across the Pacific Northwest. However, the tools
generally forecast a 20-40% chance of 3-day precipitation amounts reaching 1.5
inches across portions of western Washington with a 20-40% chance of 3-day
precipitation amounts of 1 inch across portions of Oregon and Northern
California. This would be unlikely to reach hazardous thresholds and in many
ways would be beneficial to this area, therefore, no corresponding hazard is
posted today.



Hurricane Milton made landfall on Oct 9 near Siesta Key, Florida leaving behind
extensive ongoing flooding and is forecast to continue through week-1 and
possibly into week-2. Therefore, the flooding possible area remains posted
across portions of the St. Johns River and the Withlacoochee River. These
rivers are in a region of flat terrain and sandy soils and this will slow river
recession.



The Rapid Onset Drought (ROD) risk has been updated today to reflect the new
Drought Monitor with reduced coverage across portions of eastern Texas,
Louisiana and Arkansas. There remains a risk of ROD for portions of eastern
Texas and northern Louisiana. The ROD hazard has also been expanded into
portions of southwestern Mississippi. These areas remain favored to have near-
to below-normal precipitation during week-2, along with the potential for
temperatures in the 80s deg F supporting higher evapotranspiration rates.

FORECASTER: Ryan Bolt

$$