Tools used in the U.S. Monthly Drought Outlook (SDO) included the official Climate Prediction Center (CPC) temperature and precipitation outlooks for November 2017, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), Weeks 3-4, the daily runs of the CFSv2 monthly precipitation and temperature probability forecasts, the 384-hour total precipitation forecasts from several runs of the GFS, 240-hour total precipitation forecasts from the ECMWF, climatology for November including median soil moisture changes, and initial conditions (the U.S. Drought Monitor valid on October 24, 2017). There is an increasing chance (~55-60%) of La Nina during the boreal fall and winter 2017-18.

According to the U.S. Drought Monitor (USDM) valid on October 24, moderate drought (D1) covered nearly 12 percent of the Northeast. A couple of strong low pressure systems brought drought busting rainfall (2 to 5 inches, or more) to much of the region during the final week of October. Rainfall amounts with the latest storm on October 29 and 30 included: 4.58 inches at Danbury, Connecticut, 3.15 inches at Bethel, Maine, 3.30 inches at Worcester, Massachusetts, 4.70 inches at Manville, Rhode Island, and 4.92 inches at West Halifax, Vermont. Given the recent heavy rainfall and favorable time of year for soil moisture recharge, drought removal is likely. There could be a few lingering spots of D1 but broad scale removal is expected. 

Confidence for the Northeast is high.

Hurricanes Irma and Nate resulted in above-normal rainfall across parts of the Southeast during the past 60 days. Abnormal dryness (D0) and moderate drought (D1) were designated on the USDM, valid Oct 24, extending from southwest Georgia northeast to the Piedmont region of the Carolinas and Virginia. Heavy rainfall (2 inches or more) on October 28 and 29 is expected to result in the removal of D1 and a large reduction in coverage of D0 across Virginia and northern North Carolina on subsequent USDMs. Below normal precipitation is favored at all time scales through November with the next two weeks likely to be especially dry across Alabama, Georgia, and the Florida Panhandle. Based on these precipitation forecasts, development is expected for western Alabama, the Big Bend of Florida, Georgia, and South Carolina where 30 to 60-day precipitation deficits are the largest.

Confidence for the Southeast is high.

Abnormal dryness (D0) and moderate drought (D1) recently expanded across the lower Mississippi Valley during late October. 30-day precipitation deficits of 3 to 5 inches exist across southwest Arkansas, northeast Texas, and northwest Louisiana. Based on these large short-term precipitation deficits and the CPC monthly outlook, persistence is most likely for the ongoing drought areas in the lower Mississippi Valley and northeast Texas. Closer to the Ozarks region, there is a slight tilt in the odds for above normal precipitation during days 6-10/8-14 along with the monthly time scale. Therefore, removal is forecast for northern Arkansas. Development is most likely for northeast Texas and parts of west Texas, including the Big Bend region, where 30 to 90 day precipitation deficits exist. These areas of development are consistent with the CPC monthly outlook. The excessive rainfall from Harvey continues to preclude a larger area of development across Texas.

Confidence for the South is moderate.

Drought removal is likely for the small moderate areas in Iowa, Illinois, Indiana, and Ohio where 30-day precipitation has averaged at or above normal. Parts of Iowa and Illinois have averaged more than 2 inches above normal during the past 30 days. Precipitation averaged below normal during the past 30 days across southeast Missouri where soil moisture ranks in the lowest 30th percentile. The WPC 7-day precipitation forecast indicates an axis of 0.5 to 1.5 inches of precipitation from southeast Missouri northeast to the eastern Corn Belt. The CPC 6-10/8-14 day and monthly outlooks call for increased chances of above normal precipitation throughout the Midwest. Given these relatively wet forecasts during the first half of November and a favorable time of year for soil moisture recharge, drought removal is expected for Iowa, Illinois, Indiana, and Ohio. Persistence is forecast for northern Minnesota where short-term precipitation may not be enough to result in removal of the long-term drought area.

Confidence for the Midwest is high in Iowa, Illinois, Indiana, and Ohio but low in Missouri and Minnesota.

Long-term drought continues across the western Dakotas. According to the U.S. Drought Monitor, valid on October 24, 37 and 49 percent of North and South Dakota are covered by drought, respectively. Soil moisture is currently in the lowest 20th percentile. Only 2 to 3.5 percent of the annual precipitation occurs during November across the Dakotas. Although upslope snow is expected across the high Plains during early November, total precipitation amounts are forecast to remain less than 0.5 inch, liquid equivalent. Due to the dry climatology and only light precipitation amounts expected in the short-term, persistence is most likely for the high Plains.

Confidence for the High Plains is high.

Long-term drought also continues across much of Montana with extreme drought (D3) over northeast parts of the state. Soil moisture currently ranks in the lowest 10th percentile across northeast Montana, close the U.S.-Canada border. Although the monthly outlook calls for enhanced odds for above normal precipitation, the largest precipitation amounts are expected to occur across the western two-thirds of Montana. For example, the WPC 7-day forecast indicates widespread amounts of 1 to 3.5 inches (liquid equivalent) across that part of the state. The heavy precipitation during early November favors improvement and removal of drought over western and central Montana. Precipitation amounts during the first week of November are forecast to be much lower (less than 0.5 inch, liquid equivalent) across eastern Montana. Although the CPC monthly outlook indicates a slight tilt in the odds for above normal precipitation, lower precipitation amounts in the short-term coupled with a relatively dry climatology during November favor persistence for eastern Montana. 

Confidence for the West is moderate for Montana.

Frequent heavy rain and high-elevation snow since mid-September resulted in drought removal across parts of Idaho, Oregon, and Washington. Another round of heavy precipitation is likely during the next five days. The Pacific Northwest and northern Idaho typically receives 11.5 to 17 percent of its annual precipitation during November. Based on this wet climatology and short-term heavy precipitation forecasts, removal is likely for the lingering drought areas of northern Idaho and Washington by the end of November.

Confidence for the West is high for northern Idaho and Washington.

Although an amplifying trough is expected to bring locally heavy precipitation to the favored terrain areas of southern California, long-term drought impacts related to the multi-year drought are likely to persist through the end of November across southern California. 60 to 90-day precipitation deficits increased across Arizona and adjacent areas of western New Mexico due to a rather dry end to the monsoon season. The lack of rainfall since mid-August led to a decrease in reservoir levels, low soil moisture levels, and brush fires. Precipitation that occurs with the amplifying trough during early November is forecast to be limited to the higher elevations of northwest Arizona. The CPC 6-10/8-14 day outlooks favor below-normal precipitation across Arizona and New Mexico. Persistence is forecast for the ongoing drought areas across Arizona with development most likely throughout southern/eastern Arizona and western New Mexico, given the worsening impacts.   

Confidence for the West is moderate for California, Arizona, and New Mexico.

Moderate drought currently exists across parts of Colorado and Utah. An amplified upper-level trough is expected to bring heavy snow to the central Rocky Mountains early in the month. Since the heaviest amounts are forecast to occur outside the ongoing drought areas and there is not a strong wet signal during the remainder of November, persistence is expected for Colorado and Utah. 

Confidence for the West is low for Colorado and Utah.

Heavy rain during late October resulted in drought improvement across the Hawaiian Islands. Additional widespread improvement is not forecast by the end of November, but the climatology becomes increasingly wet beyond November. Alaska and Puerto Rico are likely to remain drought-free through the end of November.

Confidence for Hawaii is moderate and high for Alaska and Puerto Rico.

Forecaster: Brad Pugh

Next Monthly Outlook issued: November 30, 2017 at 3 PM EST