Latest Seasonal Assessment -
Excluding the widespread drought areas of the West, only minor changes were made to the previous outlook, released on December 18,
2008. During December, significant drought relief occurred across the upper Ohio Valley and Southeast. Additional improvement can
be expected across the upper Ohio Valley and southern Appalachians. In contrast, the moderate drought has recently expanded in
west-central Florida. During the next three months, the expansion of drought should continue across the Florida peninsula and into
southeast Georgia. As the wildfire season approaches, the expected drought development should be closely monitored. Across the
Great Lakes region, frequent periods of snowfall have occurred during the past month. Improvement is forecast across southeast
Minnesota, Wisconsin, and the upper peninsula of Michigan. Improvement is also forecast in southern and eastern Oklahoma, while
drought should persist in south-central Texas and may expand. Persistence is forecast for the small drought areas in southeast
Colorado, the northern high Plains, and northwest Montana. The forecast remains a challenge across the western drought areas. The
wet, cold pattern during mid-December increased snow-water content values to near average for this time of year. With signals from
La Niña composites favoring dryness during the next three months, persistence is forecast for central and southern California,
southeast Oregon, and Nevada. Improvement or some improvement is forecast for parts of northern California where climatology is
quite wet, while some improvement is forecast for southern Idaho, northwest Utah, and southwest Wyoming. It should be noted that
any improvement in the western drought areas may not be realized until the spring snow melt commences. Due to a wet climatology,
improvement should continue across the Hawaiian Islands.
Discussion for the Seasonal Drought Outlook
Tools used in the Drought Outlook included the
official CPC precipitation outlook for January 2009 and January – March 2009, various short and medium-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 (CAS) moisture, the CFS seasonal precipitation forecast, La Niña composites, climatology,
and initial conditions.
During December, substantial drought relief has occurred across the
southern Appalachians and drought was eliminated in middle Tennessee, Alabama, and central Georgia. The watershed of Georgia’s
Lake Lanier has received abundant rainfall, resulting in a two foot rise of the lake’s level since December 1. However, Lake
Lanier remains 18 feet below full pool stage and the protracted hydrological drought will likely continue. The 6-10/8-14 day
outlooks call for above normal precipitation in the upper Ohio Valley and southern Appalachians. Seasonal precipitation tools
indicate that drought improvement should continue during the remainder of the winter, especially in Kentucky and eastern
Tennessee. Odds for improvement decrease slightly farther south in northeast Georgia and the upstate of South Carolina, but
climatology favors continued improvement. It should be noted that February and March are two of the wettest months in the
Confidence for the upper Ohio Valley: High
Confidence for the southern Appalachians: Moderate
In southeast Georgia and the Florida peninsula, climatology along
with the CPC seasonal precipitation forecast indicates drought persistence or development. If drought development occurs, an
increase in wildfire activity would likely occur during the spring. With La Niña composites strongly favoring dryness,
confidence is relatively high in this forecast.
Confidence for southeast Georgia and Florida: High
In the Great Lakes region, the short and medium-range forecasts are
fairly wet while the seasonal tools are noncommittal. La Crosse, Wisconsin established a record for most snow measured during
December, dating back to 1908. The outlook calls for improvement due to the heavy snowfall during the past month with
additional snow expected in the short and medium-range.
Confidence for Great Lakes region: Moderate
In southern and eastern Oklahoma, the January – March 2009 seasonal
outlook calls for above normal precipitation. Also, precipitation normals increase during March across southeast Oklahoma.
Therefore, the outlook indicates improvement.
Confidence for southern and eastern Oklahoma: Moderate
In Texas, drought should persist in south-central areas and may
expand to the south towards the lower Rio Grande and to the northwest. Climatology is quite dry for this time of year,
especially across the western half of the ongoing drought area. The January – March 2009 seasonal outlook calls for a tilt in
the odds towards below normal precipitation across western and southern Texas. Drought development is forecast for areas of
western and southern Texas that are currently experiencing abnormal dryness.
Confidence for Texas: High in western areas; moderate in eastern areas
In the high plains of North Dakota and southeast Colorado,
climatology favors persistence.
In northwest Montana, the 6-10 Day forecast along with the CPC January precipitation forecast favors above normal
precipitation. However, snow-water content values are near record lows for this time of year. Since the odds for recovery from
these current values are low, persistence is forecast.
Confidence for northwest Montana: Moderate
Across the widespread drought areas covering California and the
Great Basin, significant changes were made to the previous outlook, released on December 18. Heavy rain and mountain snow
brought drought relief to southern California in December. Despite the recent pattern featuring wet and cold conditions,
snow-water content values are near or even remain slightly below-average in California and Nevada. Based on La Niña composites
and the latest model guidance for the medium-range, prospects for improvement are slim for the southern half of California and
Nevada. In addition, no forecast tools indicate wetness during any time range. Therefore, drought persistence is now forecast
for central and southern California, southeast Oregon, and Nevada. The forecast for some improvement remains unchanged in
southern Idaho, northwest Utah, and southwest Wyoming, due to mixed signals from the tools. In northwest California, the
forecast for improvement is maintained from the previous outlook as La Niña has less of a signal across northern California
compared to the remainder of the state.
Confidence for the West: Low
Across the Hawaiian Islands, relief has occurred during the past
several weeks. Improvement should likely continue with the wet season underway.
Confidence for Hawaii: High