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U.S. Hazards Outlook - Made September 27, 2016
Valid Friday September 30, 2016 to Tuesday October 11, 2016
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EDT September 27 2016
Synopsis: A weakening cold front is expected to move off the Gulf and Atlantic Coasts early in the Outlook period. Broad low pressure at the surface and aloft, associated with the cold front, is forecast to linger over the Ohio Valley before finally lifting out to the north this Sunday. Another cold front is predicted to move across the western and into the central contiguous U.S. during this same period. In the Alaska domain, several frontal systems are anticipated to affect the western portion of the state during the first half of the Outlook period. A well-organized tropical wave currently about 350 miles away from the Windward Islands continues to move west-northwest. This system may have a significant impact on the Southeast CONUS early next week.
Hazards
- Lingering heavy rain from Ohio to Pennsylvania, Fri, Sep 30.
- Heavy rain for southwestern Alaska, Sat-Sun, Oct 1-2.
- Flooding is likely, imminent, or occurring in portions of the Midwest, and southern Texas.
- Slight risk of much below-normal temperatures for much of the west-central CONUS, Wed-Thu, Oct 5-6.
- Severe Drought across parts of the Eastern CONUS, Missouri River Valley, Great Plains, Northern Rockies, Intermountain West, Arizona, California, and Hawaii.
For Friday September 30 - Tuesday October 04: A pronounced cut-off Low at 500-hPa is forecast to bring cloudy and cool conditions to areas primarily east of the Mississippi River, at least into Sunday, Oct 2. By then, the cut-off Low is predicted to weaken and lift northward into southern Quebec. At the surface, a cold front is expected to push off the Atlantic and Gulf Coasts early in the period, though associated low pressure (and attendant cloudiness) over the Ohio Valley and mid-Atlantic is predicted to linger across this region for several more days. Though most of the precipitation is expected to fall prior to the beginning of the Hazards period, there is still the possibility of heavy rain continuing across portions of Ohio and Pennsylvania on Friday, Sep 30. The cold front is forecast to get as far south as central or southern Florida before stalling, enhancing the chances for showers and thunderstorms in that area from Oct 2-3.
A tropical wave 350 miles east of the Windward Islands (as of 2pm EDT 9/27) is predicted to continue its west-northwest heading towards the southern portion of the Caribbean Sea. A track this far south is unusual. Then the track of this system becomes highly uncertain, with the ECMWF taking the system over western Cuba or the Yucatan Channel, and the GFS and Canadian models recurving it a bit earlier over/near Haiti. Much will depend on the exact evolution of the upper-tropospheric flow pattern across the Gulf of Mexico and western Caribbean. At this time, it is recommended that residents of central and southern Florida keep an eye on this system, which the National Hurricane Center predicts has a 90 percent chance of developing into a tropical cyclone in the next 5-days.
Flooding is likely, imminent, or occurring in portions of the Midwest and southern Texas from Sep 30-Oct 2. This is primarily due to rain that recently fell across these areas.
A cyclonic system is predicted to bring heavy rain (2 inches or greater) to southwestern Alaska on Oct 1-2. The deterministic 0z ECMWF and 6z GFS runs forecast in excess of 4 inches during this period across the vicinity of the eastern Alaska Peninsula.
For Wednesday October 05 - Tuesday October 11: There is a slight (20 percent) chance of much below-normal temperatures (at or below the 15th percentile of the historical temperature distribution) across much of the west-central CONUS on Oct 5-6, in association with a strong 500-hPa trough. At the highest elevations, temperatures are expected to be cold enough to support snow.
According to the latest U.S. Drought Monitor (USDM) valid on September 20, the coverage of severe or greater drought (for the CONUS) increased very slightly from 7.72 to 7.76 percent during the past week. Less than 1 percent of the Hawaiian Islands is designated with severe drought.
Forecaster: Anthony Artusa
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