Valid Sunday July 31, 2016 to Thursday August 11, 2016
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT July 28 2016Synopsis
: During week-1, two frontal boundaries
are anticipated to impact the lower 48 states: a cold front dropping south
across the eastern half of the country and another cold front pushing eastward
from the Pacific Northwest to the Northern Plains. Low-level high pressure is
expected to dominate southern portions of the U.S. throughout week-1. For
week-2 mid-level low pressure is expected build across the Northeast with
mid-level high pressure in control further west. Two cold fronts are forecast
to influence Alaska during week-1, impacting the interior and northern portions
of the state. During week-2 Alaska is favored to experience mid-level high
Summary For Sunday July 31 - Thursday August 04:
- Heavy rain across eastern portions of
the Mid-Atlantic and Carolinas, Sun-Mon, Jul 31-Aug 1.
- Heavy rain across portions of Interior Alaska, Sun, Jul 31.
- High winds across portions of the North Slope of Alaska, Sun-Mon, Jul
- Slight risk of much above-normal temperatures for portions of the Great
Lakes, the Mid-Atlantic, and the Northeast, Fri, Aug 5.
- Slight risk of much above-normal temperatures for portions of the Lower
Mississippi Valley, the Carolinas, the Southern Appalachians, the Southeast,
and the Southern Plains, Fri-Mon, Aug 5-Aug 8.
- Severe Drought across the Mid-Atlantic, the Lower Mississippi Valley, the
Central Great Basin, the Northern Plains, the Tennessee Valley, the Great
Lakes, Hawaii, the Northeast, California, the Southern Appalachians, the
Southeast, the Southern Plains, and the Southwest.
Heavy rainfall (exceeding 1" in 24 hours) is forecast for southeastern
Virginia and the eastern Carolinas on July 31 and August 1 associated with a
cold front expected to slowly descend through the region. The region of
rainfall indicated on the map is anticipated to shift towards coastal regions
for the second day of the event.
Another area of heavy rainfall associated with a cold front is forecast for
portions immediately west and north of the Alaska Range on July 31. Antecedent
wet conditions could lead to flooding concerns, supporting the hazard
delineation on the forecast map despite rainfall amounts generally being below
regional hazard levels (2" in 24 hours), but are supported via coordination
with NWS Alaska Region and Alaska-Pacific River Forecast Center. Flood watches
have been issued for the Seward Peninsula and Western Interior of Alaska that
currently end prior to day 3, but may be extended into the forecast period. A
second cold front is forecast to push through the North Slope of Alaska on July
31-August 1, and while not forecast to bring substantial rainfall, may yield
possible high winds (exceeding 25 knots) in advance of, and immediately behind,
the frontal passage.
While not displayed on the forecast map, marginal fire weather concerns are
forecast by the Storm Prediction Center across portions of the West early in
week-1. They suggest dry thunderstorm chances are elevated for portions of the
Great Basin and Central Rockies on July 31. Presence of dry fuels is also
anticipated along with low relative humidity, warm temperatures, and somewhat
windy conditions for parts of the Great Basin, Northern Intermountain region,
and Northern Rockies for July 31-August 2. For Friday August 05 - Thursday
The 500-hPa pattern at the beginning of week-2 is forecast to
feature ridging across the Central CONUS, with the greatest positive height
anomalies across the Great Lakes. As the week progresses, dynamical model
ensemble guidance supports 500-hPa troughing building across the Northeast and
modest amplification a ridge focused over the Rockies and Central CONUS.
Two areas are highlighted for a slight risk of much above-normal
temperatures during week-2. The first region is for portions of the Northeast
and New England on August 5th, where the GEFS probabilistic extremes tool
indicates at least a 20% chance of exceeding the 85th percentile of
climatological maximum temperatures. The second area is adjacent to the Gulf
of Mexico and up the eastern seaboard through the Carolinas for August 5-8.
The GEFS probabilistic extreme guidance supports similar circumstances for this
warmth relative to the former region. GEFS, European Ensemble, and NAEFS
guidance also indicate this portion of the Southeast as the most likely CONUS
area to experience above-normal temperatures during the 6-10 day period.
Two easterly waves near 10N-20W and 12N-35W bear continued monitoring for
tropical cyclogenesis throughout the two week forecast period. Currently the
National Hurricane Center (NHC) gives these systems a 40% and 30% chance
respectively of forming a tropical cyclone through August 2. GEFS guidance has
difficulty today tracking these systems beyond the Lesser Antilles, however
some CFS members track the more eastern disturbance through Hispaniola in
week-2. Dynamical model guidance has trended weaker relative to yesterday in
regards to the easternmost system's forecast intensity, with unfavorable
environmental conditions expected across the Central Tropical Atlantic. Even
if these systems do not impact U.S. interests as tropical cyclones, they may
still bring heavy rain to Puerto Rico. Additional information on these systems
are available through the NHC (http://www.nhc.noaa.gov) or Global Tropical
According to the U.S. Drought Monitor (USDM), released on July 28, severe,
or greater intensity drought covers 5.97 percent of the U.S. Drought Monitor
areas (including Alaska, Hawaii, and Puerto Rico). This is a nearly
three-tenths of a percent increase compared to the prior week. This increase
is due to an expansion of short-term severe drought across the eastern CONUS,
primarily across the Lower-Mississippi Valley.
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.