Valid Friday July 29, 2016 to Tuesday August 09, 2016
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT July 26 2016Synopsis
: 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.
Summary For Friday July 29 - Tuesday August 02:
- Heavy rain across portions of the Central
Appalachians and Mid-Atlantic, Fri-Sat, Jul 29-Jul 30.
- Much above normal temperatures across portions of the Central Great Basin,
the Northern Rockies, California, the Northern Great Basin, the Pacific
Northwest, and the Southwest, Fri-Sat, Jul 29-Jul 30.
- Heavy rain across portions of mainland Alaska, Fri-Sat, Jul 29-Jul 30.
- Slight risk of much above-normal temperatures for portions of the Central
Plains, the Northeast, the Central Appalachians, the Northern Plains, the
Middle Mississippi Valley, the Mid-Atlantic, the Upper Mississippi Valley, the
Great Lakes, and the Ohio Valley, Wed-Fri, Aug 3-Aug 5.
- Moderate risk of much above-normal temperatures for portions of the
Northeast and the Great Lakes, Wed-Thu, Aug 3-Aug 4.
- Slight risk of much above-normal temperatures for portions of the
Southeast, the Mid-Atlantic, the Lower Mississippi Valley, and the Southern
Appalachians, Wed-Mon, Aug 3-Aug 8.
- Severe Drought across the Mid-Atlantic, the Lower Mississippi Valley, the
Central Great Basin, the Northern Plains, the Tennessee Valley, Hawaii, the
Northeast, California, the Southern Appalachians, the Southeast, the Central
Appalachians, the Great Lakes, and the Southwest.
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.
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.