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U.S. Week-2 Hazards Outlook - Made September 25, 2023 | About the Hazards Outlook
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| Composite Map Day 8-14 |
Experimental Probabilistic Outlooks |
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Valid Tuesday October 03, 2023 to Monday October 09, 2023
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EDT September 25 2023
Synopsis: 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.
Hazards
- 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 3-6.
- Slight chance of heavy precipitation along the Carolina coast, Tue-Thu, Oct 3-5.
- Rapid Onset Drought (ROD) risk across the vicinity of south-central Tennessee and most of Alabama.
For Thursday September 28 - Monday October 02: WPC Days 3-7 U.S. Hazards
For Tuesday October 03 - Monday October 09: 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 weeks.
Forecaster: Anthony Artusa
$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts