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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made September 29, 2016

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
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Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Sunday October 02, 2016 to Thursday October 13, 2016

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 29 2016

Synopsis: An area of upper-level low pressure is expected to weaken as it progresses slowly north into southeast Canada early in the period. A strong area of upper-level low pressure is forecast to enter the western U.S. this weekend, resulting in a cold front pushing east across the Great Plains to the Mississippi Valley on October 4 and 5. An area of upper-level high pressure is forecast to persist across mainland Alaska through the early part of Week-2. Tropical Storm Matthew, currently over the Caribbean Sea, is forecast to strengthen and turn north during the next five days and could eventually result in multiple hazards along the East Coast.

Hazards Detailed Summary

For Sunday October 02 - Thursday October 06: The closed 500-hpa low, initially centered over the Ohio Valley and central Appalachians, is forecast to gradually fill as it moves north into southeast Canada. Rainfall intensity over the eastern U.S. is likely decrease in time, but river flooding may linger into the beginning of this period across parts of the mid-Atlantic. Elsewhere, heavy rainfall prior to this period triggered moderate to major flooding along the Cedar, Iowa, and Wapsipicnic Rivers in southeast Iowa, middle Mississippi River, and Nueces River in south Texas.

Model guidance remains in reasonably good agreement with the evolution of an amplifying 500-hpa trough entering the western U.S. during the weekend. As the vigorous trough aloft progresses inland to the Rockies, heavy snow (more than 6 inches in 24 hours) is most likely above 6,000 feet across the mountains of Montana and Wyoming on October 3 and 4. Heavy rain (around 1 inch per 24 hours) associated with the surface low is expected across the northern high Plains at the same time. The deterministic 0Z GFS and 0Z ECMWF model indicate 48-hour precipitation amounts, ending at 12Z October 5, of 1 to 4 inches (liquid equivalent) centered on southeast Montana and northern Wyoming on October 3 and 4.

A lee side surface low is expected to develop across the north-central high Plains on Monday, October 3, due to the approaching 500-hpa trough. Although a few severe thunderstorms may affect the Dakotas and Nebraska on Monday afternoon and evening, coverage is expected to be limited by marginal instability. On October 4, instability is expected to be sufficient to support severe thunderstorms along the dryline, extending from Kansas south to the Texas Panhandle and southwest Texas. The amplifying trough and the development of the lee side low pressure system are likely to result in high winds (gusts above 40 mph) across parts of the Great Basin, Rockies, and high Plains on October 3 and 4.
As of 5am EDT on September 29, Tropical Storm Matthew is located at 14.1N/65.5W in the Caribbean as it nears hurricane strength. Matthew is expected to turn north as it moves to the western edge of a subtropical ridge and perhaps begins to be influenced by a mid-level trough over the Gulf of Mexico. Model solutions continue to differ on where and how fast this northward turn occurs. Regardless of the exact track of Matthew, an increase in surf and wave heights is expected from the Atlantic coast beaches of Florida north to at least Long Island, beginning on October 4. A tight pressure gradient between a 1032-hpa surface high over New England and tropical cyclone Matthew is forecast to bring the potential of high winds (gusts above 40 mph) to coastal areas of the Southeast and mid-Atlantic. A heavy rain hazard is not posted due to the continued large differences on the track of Matthew. Please refer to the latest statements and forecasts from the National Hurricane Center at www.nhc.noaa.gov.

For Friday October 07 - Thursday October 13: To be completed later.

Forecaster: Brad Pugh


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Please consult local NWS Forecast Offices for short range forecasts and region-specific information.