Tools used in the U.S. Seasonal Drought Outlook (SDO) included the official CPC temperature and precipitation outlooks for December 2013,
the long lead forecast for December 2013 - February 2014, various
short- and medium-range forecasts and models such as the 5-day and 7-day precipitation totals from the Weather Prediction Center,
6-10 day and 8-14 day CPC forecasts, the NAEFS precipitation outlooks, the soil moisture tools based on the Constructed Analog
on Soil (CAS) moisture, dynamical models (CFSv2, NMME, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer
drought termination and amelioration probabilities, DJF climatology, and initial conditions. ENSO conditions continue to be and are forecast to remain neutral.
The 30-day ACIS-based precipitation was less than 50 percent of normal across the central Gulf and Atlantic Coast States (from Alabama northeastward into Maine,
and southern Florida). Deficits of 4 to 8 inches have accumulated during the past 90-days, especially in the Southeast and lower New England. The current 28-day USGS
averaged stream flow values have begun to drop into the below normal (<25th percentile) category in the Southeast, and are below to much below
normal (<10th percentile) in central North Carolina/southern Virginia and from New Jersey into southern New Hampshire. As a result, the latest Drought Monitor has
increased D0 across the region, and expanded D1 in New England. Impacts could have been worse except that the short-term dryness has been offset by longer-term
(6-month) surpluses, lower temperatures, and the end of the growing season. Little or no precipitation is forecast for the upcoming 5-days, however, precipitation is
expected to begin spreading northeastward from the western Gulf during days 6 and 7, with odds for above median precipitation in the 6-10 and 8-14 day outlooks.
Further complicating the situation is that once the ground freezes in northern areas, moisture conditions generally remain locked in place until the spring thaw.
Therefore, the next several weeks will be critical as to whether or not further deterioration or improvement will occur in New England – with the odds slightly
favoring drier weather here. Farther south, with general troughing over the East during late November plus the normal end of the Atlantic hurricane season fast
approaching (Nov. 30), the chances for significant moisture from any tropical system are unlikely over the southeastern U.S. Lastly, the CPC December outlook has
slight chances for below median precipitation along the southern Atlantic Coast while the seasonal outlook (Dec-Feb) depicts probabilities above 40-percent for
below-median precipitation. Therefore, drought development is possible from the central Gulf Coast northeastward into Virginia, in eastern Florida, and southern
New England, where 90-day deficits are the highest, D0 already exists, and stream flows continue to slowly drop.
Forecast confidence for the central Gulf and Atlantic Coast States are low-moderate (Northeast) to moderate (Southeast).
Above normal precipitation fell on most of the Midwest and Great Lakes region since Oct. 21, providing some drought relief. Unfortunately, some of the precipitation
was accompanied by severe weather on Nov. 17, with Illinois especially hard-hit with numerous tornadoes. In contrast, under half of normal precipitation was observed
over the northern Great Plains and upper Midwest (less than an inch); however, late autumn and winter are climatologically dry for the upper Mississippi Valley, so
accumulated deficits were rather small. Similar to New England, the soils, streams, and lakes will eventually freeze as the winter progresses, so the amount of
precipitation during the next several weeks will be influential toward impacting the drought. Therefore, in the absence of well above normal precipitation, it is
difficult to realize significant drought improvements during this period. Additional light accumulations, generally under a half inch, are anticipated during the
upcoming 7-days across most of the region, except for somewhat heavier totals (0.5-2 inches) in southern Missouri. The CPC 6-10 and 8-14 day outlooks indicate
enhanced chances of below-median precipitation over the Midwest. The CPC monthly and seasonal outlooks both maintain equal chances for below, near, or above-median
precipitation. But with similar conditions to surrounding D1 areas and expected minimal precipitation the next several weeks, development was added to northeastern
Missouri and western Illinois. Elsewhere, based on the time of year climatology, persistence is forecasted for lingering drought areas in Missouri, Illinois,
Minnesota, Iowa, and Wisconsin.
Forecast confidence for the upper and middle Mississippi Valley is moderate.
During the previous 30 days, surplus rains overspread eastern Texas and western Louisiana, but missed areas to the east. The moisture brought localized drought
relief to parts of eastern Texas and western Louisiana, but increasing 90-day deficits expanded D0 across southern Arkansas, central Mississippi, and central
Louisiana. During the next 7 days as a slow-moving upper-air disturbance tracks eastward out of the Southwest, it will tap Gulf moisture and drop significant
rains (2-4 inches) on the western and central Gulf Coast states, and northward into southern Missouri. The CPC 6-10 and 8-14 outlooks tilt the odds towards
above-median rainfall, indicating a continuation of the wet pattern during the remainder of November. The CPC official monthly and seasonal outlooks generally
maintain equal chances for below, near, or above-median precipitation, although the December outlook hints at slight odds for below-median precipitation in western
areas. Climatological rainfall slightly increases during the winter months across the lower Mississippi Valley as the mid-latitude storm track shifts southwards
towards the Gulf Coast. Given the wet short-term forecast and climatology, drought improvement is anticipated over the lower Mississippi Valley.
Forecast confidence for the lower Mississippi Valley is moderate-high.
During the previous 30 days, surplus rains fell across eastern, southwestern, and extreme southern Texas, easing drought conditions. In contrast, the remainder of
the state measured subnormal rainfall. Over the past 3-months, the largest deficits (3 to 6 inches) have accumulated in the Panhandle and in the Red River Valley,
and drought persisted or intensified. Rainfall was spottier in Oklahoma, but southern and eastern Kansas recorded 2 to 6 inches, or 1.5 to 3 times above normal. Above
normal precipitation also fell on eastern Nebraska. Late autumn and winter months are climatologically dry across the Plains, making significant reductions in
drought less likely during this period. However, a slow-moving storm tracking across the southern tier of states during the next 7 days is expected to drop
significant precipitation on eastern sections of Texas, Oklahoma, and Kansas, possibly easing drought along the Plains eastern drought area. The CPC 6-10 and 8-14 day
outlooks tilt the odds towards abnormal wetness across the southern two-thirds of Texas, with abnormal dryness more likely over the remainder of the southern and
central Plains. The CPC monthly outlook for December indicates enhanced chances for below-median precipitation across the southern Plains, and the winter outlook
indicates favorable odds for below-median precipitation and above-normal temperatures across western Texas, the Oklahoma Panhandle, and New Mexico. Based on the dry
climatology and outlooks, therefore, drought persistence is forecast for the central and southern High Plains, with areas of development possible across southwestern
Texas, western Oklahoma, and southern New Mexico. In contrast, the near term rainfall is forecast to continue improving drought conditions across parts of eastern
Texas, particularly in areas that have shallower drought conditions due to recent rains and short-term surpluses.
Forecast confidence for the central and southern Plains is moderate.
After an early October storm brought widespread heavy precipitation to the northern Rockies and adjacent Plains, more tranquil conditions have occurred since then.
Since Oct. 21, above normal precipitation was limited to northern Montana and western Wyoming. Fortunately, this early October precipitation eased drought conditions
across Wyoming, with only lingering long-term D0 and a small D1 area left. Little or no precipitation is forecast during the upcoming 7-day period across Montana and
the Dakotas, while Wyoming can expect light to moderate totals (0.5 to 1.5 inches). The CPC 6-10 day outlook favors dry weather, but the 8-14 day outlook indicates
above-median precipitation for Montana and the Dakotas. Climatologically, the winter months are normally dry in the northern High Plains, but normal do increase as
one travels west (northern Rockies). Additionally, the CPC monthly and seasonal outlooks tilt the odds towards above-median precipitation across the northern Rockies
and northern Plains. Based on the wet guidance in the medium and long range, and additionally the fairly shallow drought conditions in Wyoming and parts of Idaho
(surpluses at 60- and 90-days), drought improvement or removal is forecast.
Forecast confidence for the northern Rockies and northern High Plains is moderate-high.
Mostly dry weather dominated the southwestern U.S. as the monsoon season came to a close in mid-September. Portions of southern California, western Arizona, and
southern Nevada received little or no rainfall the past 30 days, while subnormal precipitation was common across the region the past 60 days. The lone exception with
surplus 2-month rainfall was northern New Mexico. As an upper-air low develops in the Southwest during the next 5 days, significant precipitation (1 to 2 inches,
locally to 5 inches) is forecased for most of Arizona, southern California, southern Utah, southern Colorado, and western New Mexico. Then, during the 6-10 and 8-14
day periods, the probabilities call for near to above median precipitation. In contrast, the CPC seasonal outlook tilts the odds toward below-median precipitation
across much of New Mexico and Arizona, while the December outlook calls for below-median values in eastern New Mexico (and equal chances elsewhere). Although the
short-term forecast favors some improvement, the existing short term dryness, long-term hydrological drought impacts, and the monthly and seasonal outlooks skew the
forecast toward persistence of existing drought areas, with additional development possible over parts of New Mexico and Arizona at the end of February 2014.
Forecast confidence for the Southwest is moderate.
California, Oregon, and Washington receive a significant percentage of their annual precipitation during the winter months due to Pacific winter storm activity.
Therefore, precipitation anomalies during this period play a large role in the amelioration or development of drought. Light precipitation is forecast during the
upcoming 7-days for the Pacific Coast, with some moderate amounts (an inch) possible in the Sierra Nevada and southeastern California. The CPC 6-10 and 8-14 day
outlooks indicate enhanced odds for below-median precipitation during the remainder of November. Several climate models forecast abnormal dryness during December,
but the seasonal signal becomes mixed, with some models suggesting above normal precipitation later in the winter period (e.g. January and February). The CPC
monthly and seasonal outlooks both maintain equal chances for below, near, or above-median precipitation; therefore this outlook is based primarily on the impact of
climatological rainfall, and the enhanced odds for above-median monthly and seasonal precipitation in the northern Rockies and Plains. Based upon this, some
reduction in drought is possible across northwestern California and southern Oregon, and into the north-central Rockies. The improvement areas of the outlook were
not extended into Sierra Nevada due to the possibility of a slow start to the winter wet season.
Forecast confidence for the Pacific Coast States is moderate.
Precipitation rates normally drop during the autumn months in interior Alaska as cold, dry Arctic air masses dominate, but to date the opposite conditions have
prevailed. A very wet and mild October lingered into November, easing D1 conditions across central Alaska by mid-November. The easternmost D1 area remained as
deficits were higher and recent precipitation was lower. As this region enters winter, the remaining D1 should persist as colder and drier air should envelop the
interior. Therefore, drought persistence is forecast during the December through February period.
Forecast confidence for Alaska is high.
Precipitation rates increase during the winter months across Hawaii due to influence from mid-latitude winter storms. With recent rainfall increasing along the
windward sides, some drought relief has occurred. The CPC winter outlook tilts the odds toward above-median rainfall. Precipitation amounts near or above normal
across the islands would ease or erase existing drought conditions. Therefore, improvement or removal is indicated in this outlook.
Forecast confidence for Hawaii is high.
Forecaster: D. Miskus
Next Seasonal Drought Outlook issued: December 19, 2013 at 8:30 AM EDT