Valid Thursday July 30, 2015 to Monday August 10, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT July 27 2015Synopsis
: Upper-level high pressure is forecast
to build across the western U.S. this week, while upper-level low pressure
becomes centered near the Great Lakes. A cold front is expected to shift south
across the eastern U.S. on Thursday and become stationary near the Gulf Coast
this weekend. Upper-level low pressure is expected to persist across Alaska
early in the period. Hazards
Detailed Summary For Thursday July 30 - Monday August 03:
- Periods of heavy rainfall
across parts of the Southeast, Fri-Mon, Jul 31-Aug 3.
- Excessive heat across the lower Mississippi Valley, Thu, Jul 30.
- Much above-normal temperatures for parts of the Pacific Northwest, Thu-Mon,
Jul 30-Aug 3.
- A slight risk of much above-normal temperatures for parts of the Pacific
Northwest, Tue-Wed, Aug 4-5.
- Ongoing flooding across parts of the middle and lower Mississippi Valley.
- Severe drought for parts of the western third of the CONUS, southern
Georgia, and southern Florida.
pattern is likely to become more amplified during the next week as 500-hpa
heights increase (decrease) across the western (eastern) U.S. On Thursday, a
cold front is forecast to progress towards the East Coast and then become
stationary across the Southeast. This front, coupled with abundant low-level
moisture is expected to result in periods of heavy rainfall (more than 1 inch
per 24 hours) across parts of the Southeast from Friday through next Monday.
Strong thunderstorms are expected as the cold front pushes across the Northeast
and mid-Atlantic on Thursday, but the risk of severe weather is low at this
time. Northwest flow aloft is expected to promote another cold front to enter
the upper Midwest this weekend which would increase the potential for severe
thunderstorms across this region.
A low to moderate grade monsoon is expected across the Southwest. Although
locally heavy rain can trigger flash flooding, the lack of a strong monsoon
signal precludes a heavy rain hazard on the map.
Excessive heat is anticipated across the lower Mississippi Valley on
Thursday when maximum heat index values are likely to exceed 105 degrees F. A
decrease in 500-hpa heights is expected to bring heat relief to this region on
Friday. Meanwhile, an increase in 500-hpa heights is expected to bring a return
of unseasonably hot temperatures to the Pacific Northwest later this week. Much
above-normal temperatures are posted for areas where maximum temperatures are
forecast to average 12 degrees F or more above-normal from Thursday through
Flooding along the Illinois River is forecast to recede this week, while
moderate flooding persists along parts of the lower Mississippi River. For the
very latest stream and river flooding information, please consult the River
Forecast Center homepage at: http://water.weather.gov/ahps/rfc/rfc.php
An upper-level trough aloft is expected to maintain a relatively wet
pattern across interior Alaska through Friday which will aid firefighting
efforts. However, lightning could ignite additional wildfires. According to the
Alaska Interagency Coordination Center on July 26, nearly 5 million acres have
been consumed by wildfires this season. This value is on par with acreage
consumed by wildfires in 2005, and slightly less than 1957. This is in
comparison to the year 2004, the most active Alaska wildfire season on record
(dating back to 1950), when 6.5 million acres burned. For Tuesday August 04 - Monday
During Week-2, the GFS and ECMWF ensemble means indicate a
persistent upper-level pattern featuring a ridge (trough) over western
(eastern) North America. A slight risk of much-above normal temperatures is
posted for the Pacific Northwest which maintains continuity with the day 3-7
hazard and is consistent with the position of the upper-level ridge. The
upper-level trough centered over the Great Lakes is expected to favor near or
below-normal temperatures across the Corn Belt.
The most recent U.S. Weekly Drought Monitor, released July 23, indicates a
slight decrease (from 17.49 to 16.74) in the percentage of the CONUS in severe
to exceptional drought (D2-D4) from the previous week.
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.