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Climate Prediction Center

U.S. Hazards Outlook - Made Jul 27, 2015

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Day 3-7 Outlook Day 8-14 Outlook Day 8-14 Probabilistic Temperature Hazards

Valid Thursday, July 30, 2015 to Monday, August 10, 2015

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 27 2015

Synopsis: Upper-level high pressure is forecast to build across the western U.S. this week, while upper-level low pressure becomes centered near the Great Lakes. A cold front is expected to shift south across the eastern U.S. on Thursday and become stationary near the Gulf Coast this weekend. Upper-level low pressure is expected to persist across Alaska early in the period.

Hazards
  • Periods of heavy rainfall across parts of the Southeast, Fri-Mon, Jul 31-Aug 3.
  • Excessive heat across the lower Mississippi Valley, Thu, Jul 30.
  • Much above-normal temperatures for parts of the Pacific Northwest, Thu-Mon, Jul 30-Aug 3.
  • A slight risk of much above-normal temperatures for parts of the Pacific Northwest, Tue-Wed, Aug 4-5.
  • Ongoing flooding across parts of the middle and lower Mississippi Valley.
  • Severe drought for parts of the western third of the CONUS, southern Georgia, and southern Florida.
Detailed Summary

For Thursday July 30 - Monday August 03: The upper-level pattern is likely to become more amplified during the next week as 500-hpa heights increase (decrease) across the western (eastern) U.S. On Thursday, a cold front is forecast to progress towards the East Coast and then become stationary across the Southeast. This front, coupled with abundant low-level moisture is expected to result in periods of heavy rainfall (more than 1 inch per 24 hours) across parts of the Southeast from Friday through next Monday. Strong thunderstorms are expected as the cold front pushes across the Northeast and mid-Atlantic on Thursday, but the risk of severe weather is low at this time. Northwest flow aloft is expected to promote another cold front to enter the upper Midwest this weekend which would increase the potential for severe thunderstorms across this region.

A low to moderate grade monsoon is expected across the Southwest. Although locally heavy rain can trigger flash flooding, the lack of a strong monsoon signal precludes a heavy rain hazard on the map.

Excessive heat is anticipated across the lower Mississippi Valley on Thursday when maximum heat index values are likely to exceed 105 degrees F. A decrease in 500-hpa heights is expected to bring heat relief to this region on Friday. Meanwhile, an increase in 500-hpa heights is expected to bring a return of unseasonably hot temperatures to the Pacific Northwest later this week. Much above-normal temperatures are posted for areas where maximum temperatures are forecast to average 12 degrees F or more above-normal from Thursday through Monday.

Flooding along the Illinois River is forecast to recede this week, while moderate flooding persists along parts of the lower Mississippi River. For the very latest stream and river flooding information, please consult the River Forecast Center homepage at: http://water.weather.gov/ahps/rfc/rfc.php

An upper-level trough aloft is expected to maintain a relatively wet pattern across interior Alaska through Friday which will aid firefighting efforts. However, lightning could ignite additional wildfires. According to the Alaska Interagency Coordination Center on July 26, nearly 5 million acres have been consumed by wildfires this season. This value is on par with acreage consumed by wildfires in 2005, and slightly less than 1957. This is in comparison to the year 2004, the most active Alaska wildfire season on record (dating back to 1950), when 6.5 million acres burned.

For Tuesday August 04 - Monday August 10: During Week-2, the GFS and ECMWF ensemble means indicate a persistent upper-level pattern featuring a ridge (trough) over western (eastern) North America. A slight risk of much-above normal temperatures is posted for the Pacific Northwest which maintains continuity with the day 3-7 hazard and is consistent with the position of the upper-level ridge. The upper-level trough centered over the Great Lakes is expected to favor near or below-normal temperatures across the Corn Belt.

The most recent U.S. Weekly Drought Monitor, released July 23, indicates a slight decrease (from 17.49 to 16.74) in the percentage of the CONUS in severe to exceptional drought (D2-D4) from the previous week.

Forecaster: Brad Pugh

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Click here to see a display of the GFS Ensemble Forecasts

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


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Page Author: Climate Prediction Center Internet Team
Page last modified: August 22, 2011
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