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Climate Prediction Center

U.S. Hazards Outlook - Made Jul 01, 2015

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

Valid Saturday, July 04, 2015 to Wednesday, July 15, 2015

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 01 2015

Synopsis: A series of cold fronts are forecast to impact the central and eastern part of the Lower 48, while upper-level high pressure is expected to impact regions from the Southwest U.S. to mainland Alaska, especially early in the period. Low pressure is expected to bring active weather to the Aleutians and far western Alaska lasting into Week-2. Parts of the Southwest are expected to see more active weather associated with the start of the monsoon season over the next one to two weeks.

Hazards
  • Much above-normal temperatures for parts of the Northwest, Sat-Wed, Jul 4-8.
  • Heavy rain for parts of eastern Oklahoma, Arkansas, and the Tennessee River Valley, Sat, Jul 4.
  • Heavy rain extending from parts of the Southwest northeastward to Kansas, Mon-Tue, Jul 6-7.
  • Enhanced wildfire risk for parts of mainland Alaska, Sat-Wed, Jul 4-15.
  • Slight risk of much above-normal temperatures for parts of the interior Northwest and Northern Rockies, Thu-Wed, Jul 9-15.
  • Ongoing, likely, or possible flooding across parts of the Midwest, mid-Mississippi Valley, and the Southern Plains.
  • Severe drought for parts of the western third of the CONUS, and southern Florida.
Detailed Summary

For Saturday July 04 - Wednesday July 08: At the beginning of this period, an upper-level ridge is forecast over the western third of the CONUS, with a trough downstream centered near the Great Lakes. This pattern favors much above-normal temperatures across parts of the Northwest for this entire period. Some of these areas may experience temperature anomalies approaching 16 degrees F or greater above climatology, especially early in the period. Because of the long duration of these anomalously warm temperatures, people outdoors or without air conditioning should take precautions.

Over the central and eastern CONUS, a stalled frontal boundary at the beginning of the period is expected to focus locally heavy rainfall over parts of the Tennessee Valley, extending westward to eastern Oklahoma. The threat for heavy rain is greatest on Saturday where the hazard is depicted, with increased uncertainty beyond that, as the frontal zone is forecast to slowly move north as a warm front ahead of the next shortwave trough and associated surface low. Within the depicted hazard, some areas could receive up to 2 inches of rain in 24 hours.

Over the southwestern CONUS, a combination of remnant cold fronts and increased monsoonal flow out of the south is likely to lead to periods of locally heavy rain, spreading northward later in the period. Today's model guidance is in better agreement depicting an area where over 2 inches of rain is likely on Monday and Tuesday. This region extends from the New Mexico/Arizona border northeastward to Kansas where surface low pressure development is forecast along a stalled frontal zone. After Tuesday, uncertainty increases, though the pattern remains favorable for near- to above-median precipitation across parts of the Southwest extending into the central Plains.

The southeastern CONUS is expected to remain near or southeast of the frontal zone, meaning hot and humid conditions are likely. The latest guidance continues to suggest that heat index values will not warrant a depicted hazard at this time.

As a forecast upper-level trough swings through southern Canada during the period, surface low pressure and an associated cold front are expected to impact the northern Plains, upper Midwest, and Great Lakes, resulting in cooler-than-normal temperatures and increased rain chances during the middle and latter parts of the period. Currently there is insufficient model support for a heavy rain hazard.

Warm and dry conditions are anticipated across much of mainland Alaska, increasing chances for wildfire risk across parts of this area during this period as well as Week-2. Active weather is likely over the Aleutians during the period, though no additional hazard depiction is warranted.

For Thursday July 09 - Wednesday July 15: Little change is needed from yesterday's Week-2 hazards outlook, with the low-frequency tendency toward warm conditions in the Northwest continuing through the period. However, only a slight risk is depicted as the pattern is forecast to deamplify toward climatology fairly early in the period. Some of this deamplification, however, is likely due to ensemble averaging at longer lead times.

The enhanced fire weather hazard in Alaska continues during this period, despite a notable deamplification by both deterministic and ensemble forecasts. This is due in part to the potential for increased convection due to falling mid-level heights, which can contribute to an increased risk of wild fires caused by cloud to ground lightning strikes.

The most recent U.S. Drought Monitor, valid on June 23, indicates a small increase (from 13.62 to 14.31) in the percentage of the CONUS in severe to exceptional drought (D2-D4).

Forecaster: Stephen Baxter

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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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