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Climate Prediction Center

U.S. Hazards Outlook - Made Jul 25, 2016

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

Valid Thursday, July 28, 2016 to Monday, August 08, 2016

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 25 2016

Synopsis: At the beginning of the forecast period a pair of surface fronts are expected to be relatively stationary across the Great Lakes and Mid Atlantic where they are expected to remain for the majority of week-1. By late in the week some minimal progression of the pattern may shift these only slightly south and east of the region. Mid-level high pressure is expected to dominate the west during week-1 before shifting eastward during week-2. A cold front is forecast to drop southeast across Alaska during week-1 before an anticipated shift to mid-level high pressure during week-2.

Hazards
  • Heavy rain across portions of the Upper Mississippi Valley and Great Lakes, Thu, Jul 28.
  • Heavy rain across portions of the Mid-Atlantic, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Northeast, and the Ohio Valley, Thu-Fri, Jul 28-Jul 29.
  • Heavy rain across portions of Central Alaska, Fri-Sun, Jul 29-31.
  • Excessive heat across portions of the Southeast and the Mid-Atlantic, Thu-Sun, Jul 28-Jul 31.
  • Much above normal temperatures across portions of the interior Northeast, Thu, Jul 28.
  • Much above normal temperatures across portions of the Central Great Basin, the Northern Plains, the Northern Rockies, the Central Rockies, California, the Northern Great Basin, the Pacific Northwest, and the Southwest, Thu-Sat, Jul 28-Jul 30.
  • Moderate risk of much above-normal temperatures for portions of the Great Lakes, Tue-Wed, Aug 2-Aug 3.
  • Slight risk of much above-normal temperatures for portions of the Central Plains, the Northeast, the Northern Plains, the Middle Mississippi Valley, the Mid-Atlantic, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Tue-Fri, Aug 2-Aug 5.
  • Slight risk of much above-normal temperatures for portions of the Southeast and Mid-Atlantic, Tue-Sun, Aug 2-Aug 7.
  • Severe Drought across the Mid-Atlantic, the Lower Mississippi Valley, the Central Great Basin, the Northern Plains, the Tennessee Valley, Hawaii, the Northeast, California, the Southern Appalachians, the Southeast, the Central Appalachians, the Great Lakes, and the Southwest.
Detailed Summary

For Thursday July 28 - Monday August 01: Much above-normal temperatures are forecast to continue for portions of the Northeast through the outset of the forecast period, with expectations of maximum temperature anomalies exceeding 8 degrees F on July 28. Further south, excessive heat is possible July 28-31 across interior portions of the Carolinas where comparable maximum temperature anomalies are forecast, with expectations of overnight lows being near 80 degrees F and heat index values exceeding 105 degrees F.

Further to the west, heavy rainfall (exceeding 1" in 24 hours) is forecast across portions of the Middle Mississippi Valley and Great Lakes on July 28 where Mesoscale Convection System activity may build over top of the ridge. However, the primary focus for heavy rainfall is expected on July 28-29 further south and east stretching from the Southern Mississippi Valley northeast through Southern New York associated with the primary stationary front. The GEFS is generally further south with this precipitation, while the ECMWF ensembles are focus precipitation through the Mid-Atlantic. This boundary is expected to linger across this region for the remainder of week-1, although uncertainty around position and shortwave timing limits any further hazards being depicted.

The heat focus in week-1 will shift from the east to across the west, with a 594 dm 500-hPa ridge expected across the Great Basin early in the forecast period. A broad region of much above-normal temperatures are forecast for July 28-30 where maximum temperature anomalies could exceed 8 degrees F. Hazards associated with this shape are expected to shift north and east over the course of week-1. Anticipated deamplification of the flow by July 31 limits any further heat hazard depiction. Increased dry thunderstorm chances are also anticipated across portions of the Great Basin and Northern Intermountain Region on July 29-30, however current forecast probabilities fall below criteria for depiction on the forecast map.

A cold front is forecast to drop south across Alaska during week-1, with the GFS being further south and more progressive relative to the ECMWF which is slower and keeps the boundary further north. While precipitation amounts should generally be below the 2" of rain in 24 hours criteria used for Alaska during July 29-31, antecedent wet conditions may lead to flooding concerns associated with this frontal passage, thus resulting in a hazard depiction.

For Tuesday August 02 - Monday August 08: For week-2, ridging is generally forecast across the Central CONUS, with the strongest positive 500-hPa height anomalies favored through the Great Lakes during the early part of the forecast period. A moderate risk of much above-normal temperatures is co-located with these expected strongest height anomalies for August 2-3. A slight risk of much above-normal temperatures extends from the Upper Mississippi Valley through the Great Lakes to interior New England for August 2-5. The GEFS probabilistic extremes tool highlights these two areas as exceeding 40% and 20% during the respective periods mentioned. ECMWF ensembles also feature the heat for this area, albeit a bit further south than the GEFS.

A second region highlighted for a slight risk of much above-normal temperatures is across portions of the Southeast for August 2-7. Both the GEFS and ECMWF reforecast tools highlight this region for likelihood of much above-normal temperatures during the 8-14 day period. The GEFS probabilistic extremes tool also isolates this region for having a 20% chance of exceeding the 85th percentile of climatological maximum temperatures during the aforementioned period.

According to the U.S. Drought Monitor (USDM), released on July 21, severe, or greater intensity, drought covers 5.68 percent of the U.S. Drought Monitor areas (including Alaska, Hawaii, and Puerto Rico), an increase of a half percent since the previous week. This increase is due to an expansion of short-term severe drought east of the Rockies.

Forecaster: Daniel Harnos

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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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