Valid Sunday June 25, 2017 to Thursday July 06, 2017
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT June 22 2017Synopsis
: A cold front is predicted to stretch
across the Southern Tier of the lower 48 states at the beginning of the period,
evolving into a stationary front across Florida on June 28th. Meanwhile,
surface low pressure is expected to dominate most of the western third of the
Contiguous U.S. during the 3 to 7 day period. Surface low pressure is
anticipated to develop over the Bering Sea and Gulf of Alaska during the 3 to 7
day period. Southerly flow associated with surface low pressure may bring
unsettled weather to the Kenai Peninsula by the end of the 3 to 7 day period.
Summary For Sunday June 25 - Thursday June 29:
- Heavy rain across portions of the Southern
Rockies and Southern Plains, Central and Western Gulf Coast, and coastal parts
of the Southeast and southern Mid-Atlantic, Sun-Mon, Jun 25-Jun 26.
- Much above normal temperatures across portions of the Great Basin, the
Pacific Northwest, and the Northern Rockies, Sun-Mon, Jun 25-Jun 26.
- Excessive heat across portions of the Desert Southwest, Sun-Tue, Jun 25-Jun
- Heavy rain across portions of the Central Plains, the Middle Mississippi
Valley, and the Upper Mississippi Valley, Wed-Thu, Jun 28-Jun 29.
- Heavy rain across coastal portions of the Kenai Peninsula, Wed-Thu, Jun
- Flooding possible across portions of the Central Plains, the Lower
Mississippi Valley, the Central Appalachians, the Northern Plains, the
Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the
Upper Mississippi Valley, the Southeast, the Great Lakes, and the Ohio Valley.
- Flooding occurring or imminent across portions of the Southeast and the
Northern Great Basin.
- Flooding likely across portions of the Central Rockies, the Southeast, the
Lower Mississippi Valley, the Central Great Basin, and the Northern Rockies.
- Severe Drought across California, Hawaii, the Northern Plains, and the
- Heavy rain across portions of the Central Plains, the Southern Plains, the
Middle Mississippi Valley, the Upper Mississippi Valley, the Great Lakes, and
the Ohio Valley, Fri-Sun, Jun 30-Jul 2.
On Jun 25, a frontal system is expected to stretch from along coastal
sections of the southern tier of the CONUS from the Mid-Atlantic to the
Southwest. This will serve to act as a focusing mechanism for showers and
thunderstorms. Heavy rain is anticipated for parts of the Central and Western
Gulf Coast June 25 to 26. Surface troughing across the Southwest is also
expected to support strong moist southerly flow, bringing heavy rainfall to the
Southern Rockies and Southern Plains June 25 and 26. In addition, moisture
associated with the remnants of Tropical System Cindy are forecast to interact
with the frontal system leading to heavy rain for coastal portions of the
Southeast and southern Mid-Atlantic June 25 to 26. As the front moves
southeastward and stalls over the Florida Peninsula Jun 27, heavy rain is
possible for parts of the state. However, due to significant model uncertainty
regarding the amount of rainfall, an additional heavy rain hazard is not
included at this time. Rainfall amounts in excess of 1 inch in 24 hours are
possible for the aforementioned areas.
Heat-related hazards continue to be forecast across parts of the western
third of the CONUS during the 3-7 day period, due in part to subsidence
associated with 500-hPa ridging that is anticipated over the western CONUS.
Much above normal temperatures (positive anomalies of 16-20 degrees F) are
expected for parts of the Great Basin, the Pacific Northwest, and the Northern
Rockies, Jun 25-26. Maximum temperatures are expected to be in the triple
digits across parts of western Oregon and southern Washington. Excessive heat
(heat index values above 105 F) is forecast across portions of the Southwest
Surface low pressure is predicted to form across a frontal boundary
stretching from the northern Plains southwestward to the Southwest by June 29.
As this storm moves eastward, parts of the Central Plains, the Middle
Mississippi Valley, and the Upper Mississippi Valley may receive heavy rainfall
(1.5 inches or greater in 24-hours) June 28 to 29.
A surface low is anticipated to form over the Gulf of Alaska by June 28.
Strong onshore flow associated with this system may support heavy rainfall
across coastal portions of the Kenai Peninsula June 28 to 29. Localized areas
may receive up to 2 inches of rainfall in a 24-hour period. Besides this
feature, Alaska is forecast to be relatively warm and dry throughout both weeks
with high pressure forecast to the south of the state and mid-level ridging in
the Gulf of Alaska. This scenario suggests increased risks for fire activity
for the state which bear monitoring throughout the period, despite some
initially moist conditions from antecedent rains across the interior. For Friday June
30 - Thursday July 06:
The aforementioned surface low pressure along a
frontal boundary across central CONUS from the 3 to 7 day period is expected to
move eastward across the CONUS into the beginning to middle of week-2. Passage
of this cold front may bring heavy rainfall to parts of the Central Plains, the
Southern Plains, the Middle Mississippi Valley, the Upper Mississippi Valley,
the Great Lakes, and the Ohio Valley June 30 to July 2. The GEFS Reforecast
Tool indicates a 20% chance or greater of rainfall reaching the 85th percentile
of accumulated 3-day precipitation compared to climatology in highlighted
areas. The GEFS shows the greatest chance for heavy rainfall over the upper
Mississippi Valley and Upper Great Lakes, whereas the ECMWF ensemble indicates
the axis of heavy rainfall shifted southeastward, mainly across the Middle
Mississippi Valley. The highlighted heavy rainfall area incorporates a broad
risk area taking into account these model differences. Beyond this possible
area of unsettled weather, a mostly zonal flow pattern is forecast across most
of the CONUS during the week-2 period, with weak troughs over the Northeast,
western CONUS and Aleutians, and a weak ridge over the interior western CONUS.
The U.S. Drought Monitor released on June 22nd shows D2-D4 drought coverage
over the CONUS now at 2.13%, a slight increase from 1.57% one week
Forecaster: Melissa Ou
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.