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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made July 26, 2016

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
Temperature
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Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Friday July 29, 2016 to Tuesday August 09, 2016

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 26 2016

Synopsis: At the beginning of week-1 a stationary front is forecast to extend eastward across the Ohio Valley through the Mid-Atlantic, before expectations of it slowly dropping south and east later in the week. Across the western CONUS, mid-level high pressure is forecast early in week-1 that is anticipated to weaken throughout the forecast period. Week-2 for the CONUS is forecast to be dominated by mid-level high pressure across the central portion of the country. A cold front is expected to impact western and northern Alaska during week-1 before an anticipated transition to mid-level high pressure for the following week.

Hazards Detailed Summary

For Friday July 29 - Tuesday August 02: As the forecast period begins an initially stationary front across the Mid-Atlantic is expected to lift northward into New England. Heavy rainfall (exceeding 1" in 24 hours) is anticipated to accompany the frontal passage across the Central Appalachians and Mid-Atlantic on July 29-30. ECMWF precipitation solutions are more progressive and push the heaviest accumulations offshore for July 31 while the operational GFS and GEFS linger precipitation across the Mid-Atlantic. The hazard depicted is in line with WPC's QPF guidance which appears more in line with the European solutions.

Another focus for heat early in week-1 is expected across much of the West on July 29-30 associated with a 594-dm ridge forecast at 500-hPa. Forecast maximum temperatures are anticipated to be 8-12 degrees F above normal on these dates, with expectations of the focal region shifting north and east across the two days. The Storm Prediction Center is also highlighting elevated fire weather-related risks across the west for July 29-31, although at criteria below hazard depiction. Marginal dry thunderstorm risks are forecast for portions of the Great Basin on July 29-31, while marginal fire weather conditions (prolonged warmth, elevated winds, and low humidity) for portions of the Great Basin and Northern Intermountain Region on July 30-31.

Rainfall is also forecast for portions of Western Alaska and the Interior Basin on July 29-30 associated with a cold front expected to sag south and east across the state. While widespread precipitation amounts are unlikely to meet Alaska hazards criteria (2" in 24 hours), antecedent wet conditions that could lead to flooding concerns result in this hazard being depicted on the map. Rainfall is likely to be ongoing beyond the hazard forecast, however the ECMWF (further south) and GFS (further north) diverge substantially in their solutions focus precipitation beyond the 30th.

For Wednesday August 03 - Tuesday August 09: Similar thinking exists to yesterday regarding week-2 hazards being focused on heat-related events across the eastern CONUS. 500-hPa ridging is forecast to be focused across the Central CONUS during the period, with strongest height anomalies expected through the Great Lakes early in week-2. The GEFS is slightly more amplified than the ECMWF with forecast ridge amplitudes, yet the feature is consistent between the two.

Reforecast guidance from the ECMWF, GFS, and NAEFS all focus on two areas of warmth: the first across the Great Lakes and vicinity early in week-2 and the second across the Southeast for most of week-2. The greatest risk of much-above normal temperatures appears to be across the Great Lakes August 3-4 associated with the strongest 500-hPa height anomaly forecasts, while the GEFS probabilistic extremes tool gives this region a 40% chance of exceeding the 85th percentile of climatological maximum temperatures which is consistent with a moderate risk. A slight risk of much above-normal temperatures extends through interior New England and the Upper Mississippi Valley for August 3-5 consistent with a 20% chance reflected by the GEFS probabilistic extremes tool. Across the southeast anomalous 500-hPa heights are expected to be weaker, but a 20% chance of exceeding the 85th percentile of maximum temperatures indicated by the GEFS probabilistic extremes tool for August 3-8 supports a slight risk of much above-normal temperatures.

According to the U.S. Drought Monitor (USDM), released on July 21, severe, or greater intensity, drought covers 5.68 percent of the U.S. Drought Monitor areas (including Alaska, Hawaii, and Puerto Rico), an increase of a half percent since the previous week. This increase is due to an expansion of short-term severe drought east of the Rockies.

Forecaster: Daniel Harnos

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