12/18 Drought Monitor - Slight Easing In Mountain West, No Change N Plains, W TX, OK Worse

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National Drought Summary -- December 18, 2012

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilized include the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14 Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast web page used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

Over the last 7 days, much of the eastern United States has received some precipitation, with the greatest amounts at the end of the period over portions of Louisiana, Mississippi, Alabama and Georgia, where up to 3 inches of rain was recorded. Portions of the central Plains and Midwest recorded light precipitation from Nebraska and Iowa into South Dakota, Minnesota and Wisconsin, where amounts were generally less than 1 inch and most fell on unfrozen soils. This allowed for good infiltration into the top layers of the profile. An active pattern continued in the Pacific Northwest, where precipitation amounts of 2 to 4 inches were common along the coast and several feet of snow fell in the upper elevations. Central Arizona also received some good rain over several days with amounts from 1.5 to 3 inches.

The Northeast: Some scattered precipitation events occurred, with some amounts over 1 inch in Maine, Pennsylvania, New York, Massachusetts, and Connecticut. With the region being drought free and just a few areas of abnormally dry conditions currently, no changes were made in the region this week.

Mid-Atlantic: This was a dry week in the region, with very little precipitation. The last 30 to 60 days have been dry in the region, but the time of the year has allowed for very few impacts. No changes were made this week to the United States Drought Monitor depiction.

Southeast: Dry conditions through much of Virginia and the Carolinas continued this week, as the last few months have been dry with well below normal precipitation. This week, D2 was expanded out of South Carolina and into North Carolina. In Georgia, D2 was also expanded in the northeast portion of the state, where ponds continue to dry up. In areas of Mississippi, Alabama, and Georgia, a large area of precipitation amounts from 2 to 3 inches was recorded. This helped to bring amounts near normal for the month, but the last 30 to 60 days still show large deficits in many areas. In Alabama, D1 and D2 were improved in the northeast portion of the state where conditions warranted.

South: Dry conditions prevailed over much of the region this week, with only east Texas and Louisiana recording significant precipitation amounts. Improvements to the drought depiction were made in east Texas and Louisiana, with D1 and D2 areas being reduced. Degradation to the drought status in Oklahoma and Texas was made, with D3 expanding in central Oklahoma and along the border with Texas. In central Texas, a new area of D4 was introduced and D3 expanded, D0 was expanded in west Texas, and D3 was expanded in north central Texas.

Midwest: Widespread precipitation over much of the area was welcomed with the continuing dry conditions for the region. Amounts were generally less than 1 inch for most places and no changes were made this week.

The Plains: Rains over eastern Nebraska and into north Central Kansas were welcomed, but generally less than 1 inch for the total amounts. Most other locations were again dry for the week and no changes were made on the Plains for this week.

The West: A wet week over central Arizona and along the west coast allowed for some improvements to the drought status. In central Arizona, D2 conditions were improved where the most rains were recorded. In southern Nevada and into southern California, some improvements to the D1 and D2 conditions were made where indicators were improved out to 12 months. Areas of the central and northern Rocky Mountains have had a slow start to the snow season and lower elevations remain dry. In response to the dryness, D3 was expanded in central Wyoming and a small area of D4 was added near Rock Springs. In southwest Wyoming, D3 was improved as this area has received some recent precipitation, easing conditions. For Montana, some degradation was noted in the southeast and south central areas where dryness has persisted.

Hawaii, Alaska and Puerto Rico: The northeast slopes of the Hawaiian Islands have received enough precipitation recently to allow for some improvements on the Big Island, Maui, Molokai, and Oahu. No changes were made for Alaska and Puerto Rico this week.

Looking Ahead: Over the next five days (December 19-23) the weather pattern should stay active, with multiple storm systems impacting the country. A vigorous system will be moving out of the Plains and into the Midwest and Great Lakes region and finally into New England over the next 5 days. Precipitation amounts are expected to be in the 0.50 to 2.40 inch range, with the greatest amounts expected over New England. A second system will be coming into the Pacific Northwest with projected precipitation amounts of up to 9.00 inches in southern Oregon and northern California along the coast. Temperatures during this time look to be above normal over much of the eastern half of the country and below normal along the west coast. Extremes will range from 9 degrees Fahrenheit above normal in Oklahoma and Arkansas to 6 degrees Fahrenheit below normal in southern Oregon.

The CPC 6-10 day forecast (December 24-28) is showing a good chance for below normal temperatures over much of the United States, from the northern Rocky Mountains all the way to the southeast. The coldest temperatures are expected over the central Plains to Montana. The best chances for temperatures above normal are in Alaska and the northern Great Lakes into New England. The precipitation pattern stays active, but much of the country will have good chances of above normal precipitation, with the best chances over the southeast and Great Basin.

Author: Brian Fuchs, National Drought Mitigation Center

Dryness Categories

D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1 ... Moderate Drought
D2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought

Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)
L ... Long-Term, typically >6 months (e.g. hydrology, ecology)



Updated December 19, 2012