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Climate Prediction Center

U.S. Hazards Outlook - Made Jul 01, 2016

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

Valid Monday, July 04, 2016 to Friday, July 15, 2016

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 01 2016

Synopsis: At the beginning of the forecast period, a stationary front is anticipated to extend from the Central Plains eastward through the Mid-Atlantic. A surface low pressure system is forecast to move eastward along this boundary, bringing heavy rainfall to the Ohio Valley and Mid-Atlantic early in the week-1 period. Mid-level high pressure is generally forecast for the Western and Central CONUS during week-2. Periodic weak disturbances are expected to impact Southern Alaska during weeks 1 and 2, with no associated hazards currently anticipated.

Hazards
  • Heavy rain across portions of the Mid-Atlantic, the Central Appalachians, and the Ohio Valley, Mon, Jul 4.
  • Flooding possible across portions of the Central Plains, Midwest, and Ohio Valley, Mon-Tue, Jul 4-Jul 5.
  • Flooding occurring or imminent across portions of the Southern Plains, Mon-Tue, Jul 4-Jul 5.
  • Excessive heat across portions of South Texas, Mon-Fri, Jul 4-Jul 8.
  • Excessive heat across portions of the Central Plains, the Middle Mississippi Valley and the Midwest, Wed-Fri, Jul 6-Jul 8.
  • Excessive heat across portions of the Southeast and Carolinas, Wed-Fri, Jul 6-Jul 8.
  • Much above-normal temperatures across portions of the Northern and Central Plains, Tue-Wed, Jul 5-Jul 6.
  • Moderate risk of much above-normal temperatures for portions of the Southeast, Sat-Sun, Jul 9-Jul 10.
  • Slight risk of much above-normal temperatures for portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Sat-Mon, Jul 9-Jul 11.
  • Slight risk of much above-normal temperatures for portions of the Central Plains, the Central Rockies, the Central Great Basin, the Southern Rockies, the Southern Plains, and the Southwest, Tue-Fri, Jul 12-Jul 15.
  • Severe Drought across the Central Great Basin, the Northern Plains, the Tennessee Valley, Hawaii, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, California, and the Southwest.
Detailed Summary

For Monday July 04 - Friday July 08: At the beginning of the forecast period, 500-hPa ridging is forecast through the Central CONUS, with adjacent troughing over the Pacific Northwest and New England. Over the course of week-1, expectations are for the pattern to progress eastward with ridging becoming established over the eastern half of the CONUS and troughing across the west, before anticipated flattening of the flow pattern late in the week. Both the GEFS and ECMWF feature this general progression over the course of the week, with the GEFS being slightly more amplified relative to the European solution.

A wave of low pressure moving along a stationary front stretching from the Central Plains through the Mid-Atlantic will bring a threat of heavy rainfall (exceeding 1" in 24 hours) shifting eastward from the Ohio Valley through the Mid-Atlantic on Monday, July 4. Strong to possibly severe thunderstorm potential also exists with this system for the Central Appalachians on Independence Day, but no hazard is shown on the map due to predictability concerns associated with the modest forecast flow amplitude. Flooding is possible behind this system across portions of the Mid-Mississippi Valley and Ohio Valley.

To the south of and behind the aforementioned cyclone, ridging is expected to build with associated heat-related hazards. Excessive heat is forecast across much of South Texas from Monday, July 4 through Friday, July 8, where maximum heat index values could exceed 105-115 degrees Fahrenheit due to the ridge presence coupled with moist low-level flow off the Gulf of Mexico. Further north, much above-normal temperatures are forecast for parts of the Northern and Central Plains Tuesday, July 5 and Wednesday, July 6, where maximum temperature anomalies are anticipated to exceed 12 degrees Fahrenheit above normal. Another region of excessive heat is forecast for portions of the Mid-Mississippi Valley, Midwest, and Central Plains on Wednesday, July 6, through Friday, July 8. Here southerly flow, antecedent rainfall increasing the soil moisture, and seasonal evapotranspiration in the Corn Belt are anticipated to help drive heat index values above 105 degrees Fahrenheit. A final region of excessive heat is forecast across portions of the Southeast and Carolinas for Wednesday, July 6, through Friday, July 8, where the heat index could surpass 105-110 degrees Fahrenheit.

Moderate flooding is predicted to continue for the Trinity River at Liberty near Houston, Texas, at least until July 6th.

Throughout week-1 periodic disturbances are anticipated to impact Southern Alaska, though none currently justify an associated hazard depiction.

For Saturday July 09 - Friday July 15: For week-2 the initial 500-hPa flow pattern is forecast to be relatively flat, although some increases in the amplitude are anticipated late in week-2 with preferences for ridging in the West and troughing across the East. The ECMWF also attempts to bring a trough onshore in the Pacific Northwest early in week-2 that the GEFS keeps further north over Canada. The strongest ridging during week-2 is anticipated to be established over the Four Corners region by the middle of the forecast period.

Given the ridging tendencies favored during week-2 across the southern tier, much above-normal temperatures are possible across the Southern Plains and Southeast early in week-2. The greatest risk of much above-normal temperatures is currently from the Central Gulf of Mexico extending North and East through much of South Carolina during Saturday, July 9 and Sunday, July 10 where the GEFS probabilistic extremes tool gives a greater than 40% chance of exceeding the 90th percentile of climatological maximum temperatures. With ensemble guidance forecasting 594 dm ridging across the Four Corners region by the middle of week-2, a slight risk of much above-normal temperatures exists for this area through the end of the week-2 period.

According to the U.S. Drought Monitor (USDM), valid on June 28, severe, or greater intensity, drought covers 4.56 percent of the U.S. Drought Monitor areas (including Alaska, Hawaii, and Puerto Rico), up slightly from 4.24 percent on June 21.

Forecaster: Daniel Harnos

$$

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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