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Valid Friday October 26, 2018 to Tuesday November 06, 2018
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT October 23 2018Synopsis
: Upper-level low pressure is
forecast to dominate the eastern U.S. during the 3-7 day period, before
weakening in Week-2 and being replaced by high pressure. A strong coastal low
moving up the Atlantic coast is expected to impact the Eastern Seaboard through
the upcoming weekend. For Week-2, models indicate that an upper-level trough is
likely to build in the central U.S., leading to a frontal boundary setting up
over the southern Plains. Several surface low pressure systems are forecast to
impact southeast Alaska through the next two weeks. Hazards
Detailed Summary For Friday October
26 - Tuesday October 30:
- Heavy precipitation across portions of the Mid-Atlantic and the
Northeast, Sat-Sun, Oct 27-Oct 28.
- Heavy rain across portions of the Pacific Northwest and the Northern Great
Basin, Sun, Oct 28.
- Heavy rain across portions of the Southeast, the Southern Appalachians, the
Mid-Atlantic, the Northeast, and the Central Appalachians, Fri-Sat, Oct 26-Oct
- Flooding possible across portions of the Southern Plains.
- Flooding occurring or imminent across portions of the Middle Mississippi
Valley, the Southern Plains, and the Upper Mississippi Valley.
- High winds across portions of the Mid-Atlantic and the Northeast, Sat-Sun,
Oct 27-Oct 28.
- Heavy precipitation across portions of the Alaska Panhandle and mainland
Alaska, Fri, Oct 26.
- Heavy precipitation across portions of the Alaska Panhandle, Sat, Oct 27.
- Slight risk of much below normal temperatures for portions of the
Northeast, the Central Appalachians, the Tennessee Valley, the Mid-Atlantic,
the Southern Appalachians, the Southeast, the Great Lakes, and the Ohio Valley,
Wed, Oct 31.
- Slight risk of heavy precipitation for portions of the Central Plains, the
Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley,
the Southern Plains, and the Ohio Valley, Wed-Thu, Oct 31-Nov 1.
- Slight risk of heavy precipitation for portions of the Alaska Panhandle and
mainland Alaska, Fri-Tue, Nov 2-Nov 6.
- Severe Drought across the Central Plains, the Central Rockies, the
Northeast, the Central Great Basin, the Northern Plains, the Southern Plains,
the Northern Great Basin, the Southern Rockies, California, the Northern
Rockies, the Alaska Panhandle, the Pacific Northwest, and the Southwest.
An upper-level trough is forecast to remain over
the eastern U.S. throughout the 3-7 day period. As mentioned in yesterday's
forecast, a coastal low is expected to form along the Gulf coast prior to the
period from the remnants of Hurricane Willa currently in the Eastern Pacific.
This low is expected to move across the Florida Panhandle and southern Georgia
and move northward along the Atlantic coast through the weekend. Widespread
rainfall rates of 1 inch in 24 hours are forecast for the Carolinas and
Mid-Atlantic Oct 26-27, with localized rates of up to 3 inches likely. Model
guidance indicates a better consensus on the track today; the GFS deterministic
now keeps the system closer to the coast through New England, falling more in
line with what the ECMWF has been predicting. With this track, heavy rain and
high winds are likely for the Northeast through the weekend, with rainfall
rates of 1-3 inches forecast and sustained winds of 35 knots along the coast.
Prior to the low moving through, widespread high pressure over the Northeast
will cause colder air to move into the region toward the end of the week, so as
the storm system moves into the Northeast, snow showers are also possible,
especially at higher elevations. In the wake of the coastal low, cold air
advection is forecast over the eastern CONUS. Daytime maximum high temperatures
are likely to be anonymously colder the climatological normal; however, the
minimum temperatures anomalies are not expected to exceed -4 degrees F, which
is below hazardous criteria.
For the western CONUS, an upper-level ridge is forecast to build early in
the period. Model guidance indicates a shortwave trough is likely to move
onshore over the Pacific Northwest next Monday. A surface low pressure system,
supported by this trough, is likely to bring unsettled weather to western
Washington and northern Oregon. Heavy rain is expected for the highlighted
region, 1-2 inches per 24 hours, Oct 28.
An upper-level trough is forecast to deepen in the Gulf of Alaska at the
start of the period, and then weaken through the end of Week-1. With the
deepening trough, an anomalously strong surface low is expected to develop in
the Gulf of Alaska and is forecast to track from the Panhandle northwestward
toward the south coast. As the system shifts closer to land on and tracks
northward on Friday, heavy precipitation is expected for parts of southeastern
Alaska. Another storm system is expected move over the southern half of the
Panhandle on Saturday, Oct 27, causing heavy precipitation for the
region. For Wednesday October 31 -
Tuesday November 06:
The amplified trough over the eastern U.S. is
forecast to remain through the start of Week-2, before being replaced by weak
upper-level high pressure. Temperatures may fall below the 15th percentile for
parts of the Eastern seaboard for the first day of the period, before the
trough weakens and shifts off the coast. A slight risk for much below normal
temperatures has been forecast along the East Coast at the start of Week-2, Oct
Model guidance forecasts that another upper-level trough is likely to
develop and amplify across the central and western CONUS toward mid-period.
This upper-level movement is likely to support cyclogenesis in the central
U.S., with forecasts indicating a front is likely to set up along the central
and southern Plains. Model guidance from the GEFS and ECMWF show better
consensus on the timing of this frontal boundary establishing in comparison
with yesterday's runs. A slight risk for heavy rain is forecast for the parts
of the southern Plains and Lower Mississippi Valley, Oct 31-Nov 1. The
probabilistic extremes tool for both models predicate a 40% chance of exceeding
1 inch for the event. In addition, the pattern supports a risk of severe
weather in the warm sector of the front and upslope snow in the Colorado
At the start of Week-2, an upper-level ridge is forecast to build in the
Gulf of Alaska. This ridge is likely to quiet the active storm track for the
start of Week-2, but as it weakens and shifts eastward, model guidance
indicates the possibility of several surface lows moving through southeastern
Alaska. A slight risk for heavy precipitation has been forecast through the end
of period since with the active storm track, bouts of heavy rainfall or snow at
higher elevations are likely, Nov 2-6. Much of the southern Panhandle currently
remains in a severe drought, and though these periods of precipitation will be
beneficial, the short duration of the events are not likely to cause a drastic
improvement in this classification.
The U.S. Drought Monitor, valid October 16, indicates a decrease in severe
to exceptional drought (D2 to D4) coverage from 14.4 to 13.51 percent during
the past week. Continued improvement occurred across northeast Kansas,
Missouri, Texas, and Arizona.
Forecaster: Christina Maurin
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts