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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made July 02, 2015

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
TemperatureNo Hazards
SoilsNot Available

Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Sunday July 05, 2015 to Thursday July 16, 2015

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 02 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 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 Detailed Summary

For Sunday July 05 - Thursday July 09: At the beginning of the period, a cold front is forecast to propagate eastward across the northern tier of the CONUS. This is expected to bring heavy rain over parts of the northern Plains on Sunday, where 24-hour rainfall amounts are forecast to exceed one inch in many areas.

Much above-normal temperatures are forecast over parts of the Northwest from Sunday through Tuesday. Beyond that, maximum temperature anomalies are forecast to moderate to less than 12 degrees F above normal. Given the recent record heat over much of the area, the depicted hazard is discontinued at that point, as the perceived relief is likely to be significant. Temperatures are, however, forecast to remain above normal through the end of the period into Week-2.

500-hPa heights are forecast to fall across parts of the central U.S. early next week as a fairly deep trough swings through southern Canada. An associated cold front is expected to impact parts of the central Plains, with a pressure trough extending southwestward to parts of New Mexico. This in combination with increased precipitable water associated with the monsoon onset leads to a large area favoring heavy rain from the mid-Mississippi Valley extending southwestward to parts of New Mexico. Over the two-day period, widespread rainfall amounts of 1-3 inches are expected, with the highest amounts likely over the central Plains region. Local amounts exceeding 4 inches are not out of the question.

As the cold front shifts eastward later in the period, it is expected to bring active weather farther east. At the same time a second cold front is forecast to impact parts of the northern Plains. However, model uncertainty precludes specific hazard depictions with respect to either of these regions at this time.

Warm and dry conditions are anticipated across much of mainland Alaska, maintaining chances for enhanced 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 Friday July 10 - Thursday July 16: Today's Week-2 ensemble mean forecasts show some significant differences from yesterday's. Anomalous troughing off the West Coast during Week-1 is forecast to progress eastward in the mean, with negative height anomalies now forecast over much of the western U.S. in the mean for Week-2. This is part of a forecast pattern with very low-amplitude height anomalies over much of the CONUS. However, the deterministic runs of the GFS continue to show fairly high-amplitude patterns over North America. This highlights the fact that the official height forecast is largely a product of large ensemble spread, as evidenced by the spaghetti diagrams.

A slight risk for much above-normal temperatures exists for Day 8 over the Pacific Northwest, continuing from the preceding period. (Note: probabilities of much above-normal temperatures over this region are less than 50% for Days 6-7, thus no hazard is depicted at that time on the 3-7 day hazards map.) Beyond this, however, temperature appear to be only marginally above-normal.

Today's Week-2 forecasts from various models have trended toward a warmer solution for the Southeast CONUS, thus increasing the risk of much above-normal temperatures for part of the period. Based on the calibrated GEFS guidance, the most likely period for much above-normal temperatures is Day 9-11, when a slight risk is depicted.

The enhanced fire weather hazard in Alaska continues during this period, despite forecast 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 30, indicates an increase (from 14.31 to 15.54) in the percentage of the CONUS in severe to exceptional drought (D2-D4). Drought intensification (improvement) was observed over parts of the Northwest and Southeast (Mid-Atlantic and Northeast).

Forecaster: Stephen Baxter

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Please consult local NWS Forecast Offices for short range forecasts and region-specific information.