Latest Seasonal Assessment -
The northern part of the Southeastern drought region should continue to see improvement, while the odds for drought relief
diminish farther south, resulting in persisting drought from south-central Alabama eastward and northward through the Carolinas
into southeastern Virginia. Even where improvement is anticipated, many reservoirs and wells will remain low due to lingering
impacts from the extreme rainfall deficits incurred last year. Peninsular Florida will see relatively less rain over both the
short and seasonal time frames, so persisting drought is still expected there, with the chance for expansion toward the east
coast due to the dry 3-month forecast, and also across northwest parts of the Peninsula. Significant rains over the next
several weeks will likely be focused over the Ohio and Tennessee Valleys, as well as over the Pacific Northwest. Elsewhere,
expanding drought is likely across the southern Plains, extending back over eastern and southern New Mexico. During the first
five weeks of 2008, very dry and windy weather has resulted in more acres burned across Texas than during the entire year of
2007. To the north, some improvement is likely for most of the northern Plains from the Dakotas into central Montana, with the
exception of north-central North Dakota, while more significant improvement is expected across the remaining drought areas in
the interior Northwest and Great Basin. However in the Southwest, below normal precipitation is forecast during the February
to April period, so the odds favor little or no improvement from southern California into western Arizona.
Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for February – April 2008, the updated monthly precipitation forecast for February (issued January 31), the four-month drought termination and amelioration probabilities, various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the soil moisture tools based on the GFS model and the Constructed Analogue on Soil moisture, the CFS seasonal precipitation and soil moisture forecasts, and La Niña.
A narrow line of showers and thunderstorms were moving across the Southeast drought area as the Drought Outlook was being completed on Wednesday, February 6. Weather forecasts for the next 2 weeks indicated that rains would be more concentrated over the Ohio and Tennessee Valleys, with little precipitation expected for the Southern Atlantic coastal plain. The 5-day rainfall forecast (QPF) for February 6-11 showed between 0.5 inch and 1.0 inch of rain over eastern and southern Alabama, the western Florida Panhandle and western Georgia. Between 0.25 inch and 0.50 inch of rain was expected east of there across the Southern Atlantic coastal plain. Wednesday's raw GFS model accumulated rainfall forecasts for the next two weeks are showing significant differences across Alabama and Georgia, resulting in considerable uncertainty. Nevertheless, forecasts for the first 2 weeks are more consistent with the seasonal forecast for February-April than last month, and this Outlook shows the area of persistent drought from south-central Alabama to the Carolinas where forecasts for all time frames are mostly in agreement in showing below-normal rainfall. It should be noted that 9 to 12 inches of rain are needed to bring the Palmer Drought Index to near zero (normal) over east-central Tennessee, northern Georgia, and northwestern South Carolina, with even higher amounts of 12 to 15 inches needed over parts of northeastern Alabama, so drought impacts are likely to linger for a long time in these areas despite short-term relief. It also will be very difficult to bring the lowest reservoirs up to full storage in coming months. Lake Lanier levels in northern Georgia remain over 14 feet below normal as of February 4th. Nevertheless, the rains expected during the first 2 weeks will boost soil moisture, raise river levels and benefit groundwater and surface supplies.
Florida is expected to see less relief from both the short-term rains and the Feb-Apr rains, though up to an inch of rain is predicted across the western Florida panhandle during the first 2 weeks. The odds still favor drought persistence and even expansion across central and southern Florida in addition to northwest portions of the Peninsula into April, based on expected La Niña impacts over the longer term and the medium range forecasts for the shorter term. Both the 6-10 day and 8-14 day forecasts issued on February 6th indicate below-normal rains for Peninsular Florida.
The development area across Texas has been expanded from the last outlook because of recent dryness. Little to no rain fell across north-central and western Texas during the past 30 days. The wildfire season is off to an early start this year, with more acres burned during the first five weeks of 2008 than for the entire year of 2007 (127,000 vs. 122,000 acres). The development area in central Texas and also far southwestern Kansas into eastern and southern New Mexico is consistent with the drop in soil moisture forecast by the CFS model by April for these areas. Very recent snowfall over parts of western Kansas has helped to keep the drought expansion area at bay over that area. The University of Washington’s 3-month runoff and soil moisture forecasts based on historical La Niña events were used to tweak some of the areas on the outlook map, including expansion of the development area in eastern and southern New Mexico as well as the persisting area in central North Dakota.
In the Southwest, with the big snow-producing Pacific storms of January now history, and the seasonal forecasts still indicating below-normal precipitation across the region, the Outlook is somewhat less optimistic, especially over interior portions of southern California, although the improved mountain snow pack should benefit water supplies.