Valid Sunday July 05, 2015 to Thursday July 16, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT July 02 2015Synopsis
: 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:
- Much above-normal temperatures for parts of the Northwest, Sun-Tue, Jul
- Heavy rain for parts of the Northern Plains, Sun, Jul 5.
- Heavy rain extending from parts of the southern High Plains northeastward
to the central Plains and mid-Mississippi Valley, Mon-Tue, Jul 6-7.
- Enhanced wildfire risk for parts of mainland Alaska, Sun-Thu, Jul 5-16.
- Slight risk of much above-normal temperatures for parts of the Pacific
Northwest, Fri, Jul 10.
- Slight risk of much above-normal temperatures for parts of the Southeast,
Sat-Mon, Jul 11-13.
- Ongoing, likely, or possible flooding across parts of the Midwest,
mid-Mississippi Valley, and the Southern Plains.
- Severe drought for parts of the western third of the CONUS, and southern
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
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
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
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
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
Forecaster: Stephen Baxter
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.