Valid Saturday September 05, 2015 to Wednesday September 16, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT September 02 2015Synopsis
: Surface high pressure is
predicted to move from eastern Canada into the eastern United States with a
strong low pressure moving through the High Plains. This pattern favors
precipitation from the southwestern states into the Dakotas. Below normal
temperatures are forecast for the western states with above normal temperatures
favored for the eastern states. Hazards
Detailed Summary For Saturday
September 05 - Wednesday September 09:
- Severe drought
for parts of the western third of the CONUS, southern Great Plains, lower
Mississippi Valley, Southeast, and Hawaii.
- Flooding possible for parts of west-central Florida and Iowa.
- Heavy rain for southeastern Alaska, Wed-Thu, Sep 9-10.
This forecast period is expected to
begin with an upper-level trough amplifying along the West Coast, with an
upper-level ridge from eastern Texas to the northern Gulf Coast. This pattern
favors below normal temperatures in the western states with above normal
temperatures in the eastern states. The greatest chance of significant
precipitation extends along the western periphery of the upper-level high from
the mountains in the Southwest to the High Plains and the Dakotas.
By the end of this period, moisture from the remnants of TD 14E south of
Baja California could get drawn into the CONUS, increasing the potential
amounts of precipitation in the Southwest. At this time, no large-scale
hazards are denoted on the map, but localized flooding is possible in any heavy
downpours that might occur.
Surface low pressure in the Plains combined with high pressure in Canada is
expected to lead to strong northeasterly upslope flow from Idaho through
Montana into the Dakotas. While significant precipitation is likely, the
forecast amounts do not reach hazardous criteria, although some localized
flooding is possible.
In the West, as individual shortwaves rotate around the base of the trough,
enhanced winds are possible, and given the dry conditions, an enhanced wildfire
risk from Nevada into Utah cannot be ruled out. However, there is too much
model uncertainty in regards to the magnitude of the surface winds, thus no
hazards are denoted on the map. For Thursday September 10 -
Wednesday September 16:
By the time this forecast period begins, the
remnants of Hurricane Ignacio are expected to merge into the mid-latitude
westerly flow. How this will impact the downstream flow is uncertain. At this
time, models are forecasting the amplification of an upper-level trough south
of the Aleutians. This pattern favors continued chances of heavy rain for the
southern and southeastern coasts of Alaska for the middle and end of this
period. However, because numerical models have a notoriously hard time in
forecasting the curvature of tropical systems into the mid-latitude jet stream,
no hazard is placed on the map. If the models continue to forecast heavy rain
over the next few days, a hazard could be introduced with more certainty.
According to the U.S. Drought Monitor map, valid on August 25, the coverage
of severe to exceptional drought (D2 to D4) decreased from 18.21 to 18.07
percent across the contiguous U.S. since 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.