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U.S. Hazards Outlook - Made June 19, 2018
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Valid Friday June 22, 2018 to Tuesday July 03, 2018
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EDT June 19 2018
Synopsis: A broad area of high pressure aloft is expected to persist over the lower 48 for the next two weeks. Frontal activity is likely over the central and eastern U.S. in the 3-7 day period, with possible extension into Week-2. Heat is forecast to be a concern for parts of the southern tier of the country and for the Northeast and Upper Mid-West in Week-2. For Alaska, precipitation is expected throughout the 3 to 7 day period associated with mid-level low pressure, though likely will not be hazardous.
Hazards
- Heavy rain across portions of the Great Lakes, the Middle Mississippi Valley, and the Ohio Valley, Fri, Jun 22.
- Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, and the Southern Plains, Sat-Mon, Jun 23-Jun 25.
- Heavy rain across portions of the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, and the Ohio Valley, Sun-Mon, Jun 24-Jun 25.
- Excessive heat across portions of California and the Southwest, Fri-Sun, Jun 22-Jun 24.
- Excessive heat across portions of the southeastern quarter of the CONUS, Fri-Tue, Jun 22-Jun 26.
- High winds across portions of the Central Plains and the Southern Plains, Sat-Tue, Jun 23-Jun 26.
- High winds across coastal portions of California and the Pacific Northwest, Sat-Tue, Jun 23-Jun 26.
- Much above normal temperatures across portions of the Central Rockies and the Central Great Basin, Tue, Jun 26.
- Slight risk of much above normal temperatures for portions of the Great Lakes, the Northeast, the Upper Mississippi Valley, and the Northern Plains, Fri-Tue, Jun 27-Jul 3.
- Slight risk of excessive heat for parts of the Middle and Lower Mississippi Valleys, the Central and Southern Plains, and the Great Lakes, Fri-Sat, Jun 27-Jun 28.
- Slight risk of excessive heat for parts of the Southwest, Sat-Sun, Jun 28-Jul 1.
- Flooding possible across portions of the Central Plains, the Lower Mississippi Valley, the Northern Plains, the Great Lakes, the Northern Rockies, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Southern Plains.
- Flooding occurring or imminent across portions of the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains.
- Flooding likely across portions of the Upper Mississippi Valley, the Northern Plains, and the Northern Rockies.
- Severe Drought across the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Northern Great Basin, the Southern Rockies, the Middle Mississippi Valley, California, the Southern Plains, and the Southwest.
For Friday June 22 - Tuesday June 26: An upper-level ridge over the Southwest is forecast early in the period, before deamplifying and flattening over the weekend. Very warm temperatures are expected over the desert Southwest, resultant from this upper-level pattern. Currently, excessive heat is likely June 22 to 24, where temperatures are expected to exceed 110 degrees F. Temperatures are expected to cool later in the weekend, as the upper-level pattern becomes more zonal over the U.S. 500 hPa riding is anticipated to re-develop over the Southwest early next week, increasing chances for much above normal temperatures across parts of the Central Rockies and the Central Great Basin, June 26. Maximum temperatures are expected to reach 12 Deg F above normal, with temperatures reaching the 90s (Deg F) and triple digits in localized areas.
An active frontal boundary is expected to persist through the 3-7 day period over the eastern and central CONUS and several low pressure systems are likely to move along this front. The front is forecast to progress southeastward as the surface low tracks northeastward to the Northeast over the weekend bringing heavy rain to many parts of the eastern half of the CONUS throughout the 3 to 7 day period. Localized areas within the parts highlighted may receive up to one inch or greater of rainfall in a 24-hour period. As the cold front approaches the East Coast of the CONUS on June 25, localized coastal parts of the Carolinas may receive heavy rain, although there are significant model differences delineating this feature, precluding an additional rain hazard from being included at this time.
The 500 hPa heights over the Southeast are expected to increase toward the end of the 3-7 day period. Dew points in the low to mid 70's and high humidity coincide with the increase in mid-level heights over the region. Excessive heat is forecast for parts of the southeastern quarter of the CONUS, June 22-26; heat index values are likely to exceed 105 degrees F.
A surface trough is predicted to form across the Great Plains throughout most of the 3 to 7 day period. This pattern may support increased chances for high winds across parts of portions of the Central Plains and the Southern Plains, June 23 to 26. Some areas may experience sustained winds reaching 30 knots or greater.
Surface high pressure off the coast of northwestern CONUS favors an increased likelihood for high winds across coastal parts of northern California and the Pacific Northwest, June 23 to 26. Localized areas may experience sustained wind speeds reaching 30 knots or greater.
Widespread mid-level troughing is expected for Alaska through the 3 to 7 day period. Several surface low pressure systems are forecast to move over the mainland and parts of the southern coast; however, all impacts from these systems are currently forecast to remain below hazardous criteria.
For Wednesday June 27 - Tuesday July 03: Amplified mid-level ridging is forecast to build across much of the CONUS at the beginning of Week-2 and persist throughout most of Week-2. A slight risk of much above normal temperatures has been forecast for portions of the Great Lakes, the Northeast, the Upper Mississippi Valley, and the Northern Plains, June 27 to July 3, associated with this ridging. The GEFS probabilistic tool predicts a 20%-30% chance of temperatures surpassing the 85th climatological percentile. Areas of slight risk for excessive heat are highlighted across parts of the Middle and Lower Mississippi Valleys, the Central and Southern Plains, and the Great Lakes (heat values reaching 105 Deg F or gretaer), June 27 to 28, and parts of the Southwest (heat values reaching 100 Deg F or greater), June 28 to July 1.
A surface low is forecast to move over the central Plains and into the Mississippi River Valley, along the frontal boundary from the previous period. Currently, the GEFS probabilistic tool is forecasting a 20 to 40 percent chance of rainfall totals across parts of the Central and Southern Plains, Middle and Lower Mississippi Valley, and Southeast surpassing the 85th percentile; however, the ECMWF tool has no indication of above normal precipitation. Due to this disparity in the model guidance, a risk for heavy precipitation has not been forecast at this time. We will continue to watch the evolution of this system in the models.
The mid-level troughing over Alaska is expected to be isolated to mainly the South Coast, Alaska Peninsula, and Kodiak Island, while a ridge develops over mainland Alaska. No hazards are identified for Alaska at this time.
The US Drought Monitor, valid on June 12, indicates that the coverage of severe to exceptional drought decreased slightly from 17.06 percent to 16.97 percent. Exceptional drought remains entrenched over the Four Corners region. Some improvement in conditions is seen in the Oklahoma Panhandle and into southwestern Kansas.
Forecaster: Melissa Ou
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