Valid Monday September 15, 2014 to Friday September 26, 2014
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT September 12 2014Synopsis
: Upper-level high pressure is
forecast to dominate the western U.S. for much of the period, while surface
high pressure brings relatively tranquil weather to most of the U.S. A
stationary front is expected to focus precipitation across the Southeast and
Gulf Coasts, while surface low pressure brings active weather to parts of
southeastern Alaska throughout the period. The Pacific Northwest is expected to
see more active weather later in the period. Hazards
Detailed Summary For Monday
September 15 - Friday September 19:
- Heavy rain for parts of Southeast Coast, Mon-Wed, Sep 15-17.
- Much above-normal temperatures for parts of the Pacific Northwest, Mon-Tue,
- Flooding likely with areas of ongoing flooding for parts of northern
Missouri, Iowa, and the middle Mississippi Valley, Mon-Tue, Sep 15-16.
- Flooding ongoing across parts of northern Florida.
- Flooding possible across parts of eastern North Carolina, Mon-Tue, Sep
- Locally heavy rain could produce localized flash flooding over parts of the
Southwest, Thu-Fri, Sep 18-19.
- Severe drought for the Central and Southern Great Plains, Southwest,
southern Georgia, Pacific Northwest, Great Basin, and California.
Below-normal temperatures are expected
across most of the eastern part of the CONUS for this period, due to persistent
Canadian high pressure. However, forecast temperatures are not hazardously low
at this time.
By this weekend, the cold front that ushered in the below-normal
temperatures across much of the CONUS before the start of the period is
expected to stall across the far southeastern CONUS, increasing chances for
heavy rain over the Southeast and Gulf Coasts. Rainfall totals exceeding 3-5
inches of rain are possible over a three day period, especially along the
immediate coast. Locally heavy precipitation is also possible across other
parts of the Gulf Coast, especially due to uncertainty with respect to a
tropical system that could develop early next week in the Gulf of Mexico. While
a strong tropical storm is unlikely, locally heavy rainfall is likely in some
areas. This tropical feature will serve to enhance rainfall along the
stationary front, in any case.
Upper-level ridging is forecast to build rapidly across western North
America, downstream of a strong trough over Alaska. This will likely lead to
much above-normal temperatures for parts of the interior Pacific Northwest
early next week, where temperatures could exceed 90 degrees in some locations.
After that, some shortwave energy is likely going to attempt to break down the
ridge, leading to moderating temperatures over the Pacific Northwest, while
500-hPa heights rise farther east. Wetter conditions are likely for the Pacific
Northwest late next week, though nothing hazardous is expected at this time.
Tropical Storm Odile is forecast to strengthen to hurricane status while
moving northwestward off the coast of Baja. There is still some chance that
deep tropical moisture from this system could impact parts of the Southwest.
While a repeat of the event observed in that region earlier in the week is
unlikely based on the forecast midlatitude circulation, an abundance of caution
leads to the depiction of a flooding shape on today's map, due to the increased
risk of flash flooding in that area late next week.
Active weather is expected for Southeast Alaska, with large negative height
anomalies forecast over the Northeast Pacific/Gulf of Alaska. Given the
increasingly stormy climatology for that region, especially hazardous
conditions are not currently favored. For Saturday September 20 -
Friday September 26:
The latest model guidance for Week-2 is in good
agreement, forecasting a deep trough continuing over Alaska and extending
southeastward into the Gulf of Alaska. Above-average 500-hPa heights are
forecast for much of central North America, with below-average heights forecast
over the immediate East Coast and Southeast. Such a pattern favors above-normal
temperatures over much of the CONUS, though there is little confidence in
hazardously high temperatures, especially given the rapidly falling climatology
this time of year.
Active weather is forecast to continue for southeastern Alaska, though
there is not enough confidence pertaining to an individual event to warrant a
hazard depiction at this time. Heavy rainfall could also impact parts of the
far northwestern CONUS, though model uncertainty precludes a hazard depiction
at this time. Likewise, the mean frontal position through the Gulf of Mexico is
expected to continue into Week-2, and could serve to focus locally heavy
The most recent U.S. Drought Monitor, released today, indicates the
percentage of the CONUS in severe to exceptional drought decreasing from the
previous week's (September 4) 20.93 percent to 20.31 percent. This is also down
substantially from both 2013 and 2012 at this time of year (32.40 and 42.48
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.