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Climate Prediction Center

U.S. Hazards Outlook - Made Apr 29, 2016

Composite Images

Day 3-7 Outlook Day 8-14 Outlook Day 8-14 Probabilistic Temperature Hazards

Valid Monday, May 02, 2016 to Friday, May 13, 2016

Summary of Forecasts and Hazards

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 29 2016

Synopsis: A series of low pressure systems are expected to develop along a front near the East Coast through mid-week. An area of upper-level high pressure is expected to briefly build across the west-central U.S. during the beginning of May. An area of upper-level low pressure is forecast to move inland from the east Pacific prior to the Week-2 period. Multiple surface lows are expected to affect southern Alaska and the Alaska Panhandle during the next two weeks.

Hazards
  • Heavy rain for the lower Mississippi Valley and southeast Texas, Mon, May 2.
  • Heavy rain for the eastern Carolinas, Tue-Wed, May 3-4.
  • Flooding occurring, imminent, likely, or possible across parts of the central U.S., Mon-Tue, May 2-3.
  • Flooding possible across parts of Washington, Mon-Tue, May 2-3.
  • Much below-normal temperatures for parts of the Rockies and high Plains, Mon, May 2.
  • Much above-normal temperatures for parts of the Pacific Northwest, Mon, May 2.
  • Much above-normal temperatures for parts of eastern Washington, Tue-Wed, May 3-4.
  • Much above-normal temperatures for the desert Southwest, Wed, May 4.
  • Heavy precipitation (rain and high-elevation snow) for parts of the Sierra Mountains, Great Basin, north-central Rocky mountains, and north-central high Plains, Sat-Sun, May 7-8.
  • Slight risk of much-above normal temperatures for much of the Great Plains, Sat, May 7.
  • Severe drought across parts of California, the Great Basin, Southwest, Wyoming, southern Great Plains, Hawaii, and Puerto Rico.
Detailed Summary

For Monday May 02 - Friday May 06: The risk of heavy rainfall (locally more than 2 inches) along a trailing front is expected to persist across the lower Mississippi Valley and southeast Texas through Monday, May 2. The deterministic 6Z GFS and 0Z ECMWF models on April 29 indicate precipitable water values remaining around 1.75 inches across this region until drier northerly flow arrives on Tuesday, May 3. Meanwhile, waves of low pressure are expected to develop along a front near the East Coast and result in heavy rainfall across the eastern Carolinas on Tuesday and Wednesday, May 3 and 4. The heaviest rainfall amounts (2 inches or more in the 48-hour period) are expected across the Outer Banks of North Carolina.

An upper-level trough is expected to bring a brief period of much-below normal temperatures to parts of the south-central Rockies and high Plains on Monday, May 2. Maximum temperatures are forecast to average more than 20 degrees F below-normal and minimum temperatures could fall below freezing in the highlighted area on the map.

A strong ridge aloft is expected to promote much above-normal temperatures (10 to 20 degrees F) across the Pacific Northwest from May 2 to 4. The anomalous warmth is expected to accelerate snow melt and may trigger river flooding across parts of Washington. The summer-like warmth, with maximum temperatures into the 80s, is expected to end later in the week when 500-hpa heights decrease.

Elsewhere, much above-normal temperatures are posted for the desert Southwest on Wednesday, May 4, when maximum temperatures are forecast to peak near 10 degrees F above-normal and could reach 100 degrees F in the lower deserts.

Model guidance remains consistent that a vigorous upper-level trough shifts east into the western U.S. by Friday, May 6. The deterministic 6Z GFS model on April 29 is most progressive with this upper-level trough and indicates heavy rain and high-elevation snow developing over the north-central Rockies on May 6. However, the deterministic 0Z ECMWF model is slower with the progression of this upper-level trough and delays the risk of heavy rain and high-elevation snow across the interior West until Week-2. Due to these model differences, a heavy precipitation hazard is posted in the Week-2 period.

Antecedent heavy rainfall results in areas of flooding occurring, imminent, likely, or possible across portions of the central U.S. Multiple rivers are currently in minor to moderate flood stage from Louisiana and Texas north to the Missouri River Valley.

A series of low pressure systems are expected to bring periods of rain to the southern coastal areas of Alaska and the Alaska Panhandle. However, rainfall amounts are forecast to remain below hazards criteria.

For Saturday May 07 - Friday May 13: A vigorous upper-level trough is likely to be centered over the Rocky Mountains early in the Week-2 period. Based on excellent model consistency, heavy precipitation (rain and high-elevation snow) is most likely across parts of the Sierra Mountains, Great Basin, north-central Rocky Mountains, and high Plains on May 7 and 8. The 0Z ECMWF ensemble mean on April 29 indicates a 48-hour max of more than 1 inch (liquid equivalent) in Wyoming from May 7-8.

Downstream of the upper-level trough entering the western U.S., a slight risk of much above-normal temperatures is posted for parts of the Great Plains where the GEFS reforecast temperature tool indicates that maximum temperatures have at least a 20 percent chance of exceeding the 85th percentile compared to climatology.

According to the U.S. Drought Monitor valid on April 26, severe, or greater intensity, drought covers 5 percent of the U.S. Drought Monitor areas with a continued decrease in coverage during the past six months.

Forecaster: Brad Pugh

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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.


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