Valid Tuesday October 03, 2023 to Monday October 09, 2023
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT September 25 2023Synopsis
: During the week-2 period,
mid-level troughs are predicted over the western and southeastern contiguous
U.S. (CONUS), and mid-level ridges are forecast from the Southern Great Plains
northeastward across approximately the northeastern quarter of the CONUS, and
over Alaska. A coastal storm system is predicted off the Southeast coast during
at least the first half of week-2, with accompanying heavy precipitation.
- Slight chance (20%) of much below-normal
temperatures over Utah, southwestern Wyoming, and northern Arizona, Tue, Oct 3.
- Slight chance of much below-normal temperatures for a large fraction of the
northwestern quarter of the CONUS, Fri-Mon, Oct 6-9.
- Slight chance of much below-normal temperatures for south-central and
Southeast Alaska, Tue-Wed, Oct 3-4.
- Slight chance of heavy precipitation for the Southern Plains, Tue-Fri, Oct
- Slight chance of heavy precipitation along the Carolina coast, Tue-Thu, Oct
- Rapid Onset Drought (ROD) risk across the vicinity of south-central
Tennessee and most of Alabama.
Thursday September 28 - Monday October 02: WPC Days 3-7 U.S.
Hazards For Tuesday October 03 - Monday
A mid-level trough over the western CONUS early in week-2
warrants a slight chance for much below-normal temperatures for Utah,
southwestern Wyoming, and northern Arizona, on Oct 3. This means temperatures
are expected to fall to (or below) the 15th climatological percentile, and
overnight temperatures are forecast to drop to (or below) 32 deg F. Renewed
troughing across the northwestern quarter of the CONUS during the middle and
latter stages of week-2 results in the posting of a slight risk area for much
below-normal temperatures for interior sections of Washington and Oregon, far
northern California, Northern Intermountain region and Northern Rockies, and
the Northern High Plains, Oct 6-9. The lowlands of western Washington, and the
Willamette Valley of western Oregon are expected to remain substantially above
freezing during this period, so no cold hazard is posted for these areas. An
amplified ridge and well above-normal 500-hPa heights supports a strengthening
surface high and an associated slight risk for much below-normal temperatures
over south-central and Southeast Alaska, Oct 3-4. This ridge over Alaska is
consistent with anomalously cold temperatures for western and north-central
sections of the Lower 48 states, especially during the second half of week-2.
A slight risk of heavy precipitation is indicated for the Southern Great
Plains, Oct 3-6, in advance of a predicted mid-level trough. This means at
least a 20% chance that expected precipitation amounts will reach or exceed the
85th climatological percentile, and at least 1-inch of precipitation is
forecast to fall during a 3-day period. Although this highlighted area of heavy
precipitation is supported by the various reforecast precipitation tools, its
greatest support comes from the ECMWF reforecast tool. A mid-level trough and
surface low pressure system are predicted near the Southeast coast, during at
least the first half of week-2. A slight risk for heavy precipitation is posted
for the Carolina coast, Oct 3-5. With the storm anticipated so close to the
Southeast coast, it is unclear as to how much precipitation may affect coastal
areas or remain just offshore, though projected amounts are close to 1 inch.
These coastal storms are often accompanied by gusty winds, but at this time,
the probabilistic extremes wind tool does not show a specific wind hazard.
30-day precipitation deficits, little to no precipitation during the next
week, and above normal temperatures and near to below normal precipitation
favored during week-2 continue to support the possibility of rapid onset
drought (ROD) across south-central Tennessee and most of Alabama.
In recent weeks, most storms that formed within the Main Development Region
(MDR) of the tropical Atlantic have recurved early, and remained well off the
East Coast of the United States. At this time, little if any tropical activity
is expected to influence the Gulf or Atlantic coasts. through the next two
Forecaster: Anthony Artusa
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts