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U.S. Hazards Outlook - Made July 29, 2014
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Valid Friday August 01, 2014 to Tuesday August 12, 2014
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EDT July 29 2014
Synopsis: A strong area of upper-level low pressure is forecast to persist across the eastern U.S. through the end of July before it begins to weaken. An area of upper-level high pressure is expected to remain centered over the western U.S. A surface low is expected to cross mainland Alaska this weekend.
Hazards
- Much above-normal temperatures for parts of the Pacific Northwest and Northern Intermountain West, Fri-Tue, Aug 1-Aug 5.
- Heavy rain for coastal areas of the Southeast, Fri-Sun, Aug 1-3.
- Flash flooding possible for parts of the Southwest, Fri-Sun, Aug 1-3.
- Severe drought for parts of the Great Plains, Southwest, Pacific Northwest, Great Basin, and California.
For Friday August 01 - Tuesday August 05: Flash flooding is likely to remain the major hazard across the Southwest as southeast flow increases monsoon moisture and results in thunderstorms with locally heavy rainfall through the weekend. The 6z GFS model indicates that the potential for precipitable water values to exceed 1 inch across much of Arizona by Sunday. Beyond the weekend, model solutions vary on whether the mid-level flow remains southeasterly or becomes more westerly across the desert Southwest. In addition to the flash flooding hazard, outflow from thunderstorms is capable of causing blowing dust across southern Arizona.
Unseasonably low 500-hpa heights, enhanced low-level convergence along a stationary front, and abundant moisture are expected to result in heavy rainfall across coastal areas of the Southeast from Friday through at least Sunday.
Maximum temperatures are forecast to average around 10 degrees F below-normal across the southern Great Plains from Friday through Monday. Meanwhile, the amplified ridge over the western U.S. is likely to maintain much above-normal temperatures through at least Tuesday across the interior Pacific Northwest and northern intermountain West. Numerous wildfires continue to burn across these areas along with California, Nevada, and Utah. Currently, the largest wildfire with nearly 400,000 acres burned is located in southeast Oregon. A few dry thunderstorms could ignite additional wildfires across the northern Great Basin and Pacific Northwest.
The coverage of showers is expected to increase across mainland Alaska by early next week, but precipitation amounts are likely to remain below hazards criteria.
For Wednesday August 06 - Tuesday August 12: Spread amongst the 0z GFS ensemble members increases regarding the amplitude of the ridge (trough) over the western (eastern) U.S. during Week-2. A slight risk of above-normal temperatures for parts of the Pacific Northwest on August 6 and 7 is posted on the Probabilistic Week-2 Hazards Outlook. This Week-2 hazard area is based on the potential that the upper-level ridge may not weaken as quickly as forecast by the models. Also, the slight risk is consistent with increasing spread among the 0Z GFS ensemble members.
As of 2pm EDT on Tuesday, a tropical wave is located near 10N/40W. This well organized tropical wave should be monitored as it tracks into the central Atlantic.
Based on the latest Drought Monitor valid on July 22, severe to exceptional drought continued to decrease and now covers 23.9 percent of the continental U.S.
Forecaster: Brad Pugh
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