US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
417 PM EDT Fri Oct 23 2020
Valid Monday October 26 2020 - Friday October 30 2020
- Heavy precipitation across portions of the Southern Rockies, the Central Plains, and the Southern
Plains, Mon-Wed, Oct 26-Oct 28.
- Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Southern
Plains, the Middle Mississippi Valley, the Great Lakes, and the Ohio Valley, Mon, Oct 26.
- Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the
Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Wed-Thu, Oct
- Heavy rain across portions of the Lower Mississippi Valley, the Central Appalachians, the
Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, and
the Ohio Valley, Thu-Fri, Oct 29-Oct 30.
- Heavy snow across portions of the Central Plains, the Central Rockies, the Central Great Basin,
the Southern Rockies, the Southern Plains, and the Southwest, Mon-Tue, Oct 26-Oct 27.
- Heavy snow across portions of the Southwest, Mon, Oct 26.
- High winds across portions of California, Mon, Oct 26.
- Much below normal temperatures across portions of the Central Plains, the Central Rockies, the
Lower Mississippi Valley, the Central Great Basin, the Northern Plains, the Great Lakes, the
Northern Rockies, the Southern Rockies, the Middle Mississippi Valley, the Northern Great Basin,
the Upper Mississippi Valley, the Southern Plains, and the Southwest, Mon-Thu, Oct 26-Oct 29.
- Enhanced wildfire risk across portions of California, Mon, Oct 26.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Oct 26.
A dome of Arctic high pressure encompassing much of the Northwest, the Rockies, and Plains will
lead to very cold conditions across these regions through mid-week. Latest NDFD forecast suggests
numerous daily record cold max/min temperatures are likely to be broken. Sub-zero temperatures are
a good bet across the northern Rockies and High Plains Monday morning where bitterly cold wind
chills of -10 to -20 degrees are also possible. The coldest temperatures are likely to occur where
fresh and deep snow pack is present. Speaking of which, a late October snow storm looks to blanket
much of the mountainous terrain of the Four Corners region (including some low lying valleys) in
snow with the higher elevations most at risk for significant snow accumulations. Expect numerous
travel delays in these areas which combined with gusty winds may lead to near whiteout conditions
Sunday and into Monday.
How long the snow threat lasts in the Four Corners region is dependent upon what happens when the
jet stream pattern lifts north and how influential an intense ridge builds over the Northwest. A
cut-off upper low will develop and keep mountain snow and inclement weather in the forecast through
mid-week. A heavy precipitation area remains in place over parts of the southern High Plains and as
confidence is increasing in a combination of heavy snow and/or ice. Free-falling temperatures near
or breaking record cold levels for late October combined with over-running southwest flow aloft
looks to support a heavy wintry mix across eastern New Mexico, western and central Oklahoma, and
the Texas Panhandle. On the southeast flank of the upper-low, heavy showers and thunderstorms could
cause excessive rainfall rates in portions of northern and central Texas Tuesday and Wednesday.
Farther west in California, as the base of the trough swings through the Great Basin Sunday night,
intense low-mid level winds embedded within the base and the backside of the upper trough pass over
the region. A strong surface high pressure diving south over the Northwest along with a surface
trough off the California coast, high winds will develop in the northern Sierra Nevada and
potential for downsloping winds in the Sacramento Valley and Bay Area. Southern California is also
at risk for strong winds and favorable fire weather conditions. As a result, High Winds and Fire
Weather hazards are in place in these areas.
In the East, upper level ridging over the Southeast is likely to keep most of the region under the
influence of a persistent above normal temperature regime. Some rain and mountain snow is possible
in across northern New England on Monday, but the primary precipitation type ahead of an
approaching cold front from the mid-Mississippi Valley to the Ohio Valley and northern
Mid-Atlantic. As the upper low in the Southwest gradually advances east into the South Central U.S.
around mid-week, rich moisture from the Gulf of Mexico should stream north from Texas and the Lower
Mississippi Valley to the Mid-South and Mid-Atlantic the second half of the week. In fact, moisture
from a tropical disturbance in the Caribbean Sea (NHC gives a 70% chance of development over the
next 48 hours) may become incorporated into the moist southerly flow, adding even more moisture to
an already wet pattern. Timing and totals are still subject to change in the days 5-7 time frame
due to the lower confidence in when the upper trough exits the Four Corners region and how slowly
it progresses through the southern Plains.
Across Alaska, an area of low pressure in the Gulf of Alaska heads toward the southeast mainland
and be preceded by a southwesterly flow of very moist Pacific air. Expect heavy precipitation from
southeastern portions of the mainland (Prince William Sound eastward) through Yakutat starting on
Monday. Some heavy rainfall may linger in portions of the lower Panhandle early Tuesday before
drier conditions arrive throughout the region later in the day. Heaviest rainfall will generally be
along the coast with snow over higher elevations. A second round of heavy precipitation is possible
across the Panhandle towards mid-late week but ensemble guidance suggests a good amount of
uncertainty presides in the pattern from Alaska to the North Pacific.
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