Thursday, December 18, 2014
Current U.S. Drought Monitor

NOTE: To view regional drought conditions, click on map above. State maps can be accessed from regional maps

The data cutoff for Drought Monitor maps is Tuesday at 7 a.m. EST. The maps, which are based on analysis of the data, are released each Thursday at 8:30 a.m. Eastern Time.

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The U.S. Drought Monitor is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.

For local details and impacts, please contact your State Climatologist or Regional Climate Center

National Drought Summary for Dec 9, 2014

Summary

During the past week, widespread heavy precipitation (2-6 inches) was reported across much of northern California, and along portions of the central and southern coastline. Moderate to heavy precipitation (0.5-3.0 inches) fell in California’s central Sierras, western portions of both Washington and Oregon, the northern Rockies, the Mogollon Rim area of south-central Arizona, and in a broad band stretching from eastern Kansas and Oklahoma eastward into the Tennessee and lower Ohio Valleys, central Appalachians, the northern mid-Atlantic, and eastern New England. Most other areas of the contiguous United States received less than a half-inch of precipitation during this period. In Hawaii, leeward areas have been fairly dry over the past 5 weeks, while windward areas have received rainfall closer to normal during the same time.

Alaska, Hawaii, and Puerto Rico

In Hawaii, moderate rain (generally 0.5-2.0 inches, locally heavier) fell across windward portions of the Islands this past week, while leeward areas continue to be quite dry. This dryness has persisted for the past 5 weeks, after a relatively wet October. Therefore, abnormal dryness (D0) has either been introduced to, or expanded across, the leeward regions of Hawaii. Neither the Alaska depiction nor the Puerto Rico depiction was modified this week.

California

Locally heavy precipitation fell across portions of the state this past week. Amounts ranged from 1-6 inches (liquid equivalent) across a large portion of northern California, and parts of the central and southern coastal areas. Up to 3 inches of precipitation (liquid equivalent) was reported in the southern Sierras. However, snow pack remains well below-normal in many areas due to the relatively mild temperatures associated with these storm systems. In addition, much more precipitation is needed to replenish lost reservoir storage. There are still deficits in the conservation pool of millions of acre-feet in the Shasta and Oroville reservoirs north of Sacramento. Oroville reservoir gained about 100,000 acre-feet of storage in the recent storm, returning to one million acre-feet in storage capacity. The capacity of this reservoir is 3.5 million acre-feet, with a flood reserve space of 750,000 acre-feet. Well to the south, last week’s storm produced several inches of rain for San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties. However, this was not enough to generate runoff in natural streams and therefore did not provide any benefit to surface reservoirs. Since the start of the Water Year (October 1), almost all precipitation gauges in the area are still running below normal. No revisions were made to the California drought depiction this week. With the anticipation of another significant precipitation event in the short-term, alterations could be required next week, pending resulting impacts.

Mississippi Valley/Delta

Little if any precipitation was observed over the northern half and far southern sections of the Mississippi Valley this past week. The remaining area generally received anywhere from a half-inch to 3 inches of precipitation. Snowpack has been diminishing across portions of the Upper Mississippi Valley. No changes were made to the depiction this week across the Upper Mississippi Valley. However, the Lower Mississippi Valley/Delta region has mounting PNP deficits from 6-months out to the present time, which warrants an expansion of abnormal dryness and drought for southern portions of both Louisiana and Mississippi. Ninety-day PNP deficits become prominent across most of this area (widespread PNP values of 25-75 percent of normal). By 60-days (and up through the present time), PNP deficits of 10-25 percent of normal are showing up in far southeast Louisiana. These values, and consideration of both short and long-term objective drought blends, justifies westward expansion of D0 and D1 conditions across southern Louisiana, and a bit northward across south-central Mississippi. In addition, severe drought (D2) was expanded westward from southern Alabama to include the Mississippi coastal counties of Jackson, Harrison, and Hancock, and into far southeast Louisiana.

Northeast and mid-Atlantic regions

In western New York, precipitation across counties adjacent to Lake Ontario has totaled only up to an inch this past week. Significant deficits during the last 60- and 90-days (Percent of Normal Precipitation (PNP) values range from 25-75 percent of normal across this region) prompted an expansion of abnormal dryness (D0) from Steuben County into Livingston, Monroe, Wayne, Orleans and Niagara Counties. In southeast New York, stream flows are above- and much-above normal, recent precipitation measured 1-2 inches, and portions of this area received about 7 inches of snow from the nor’easter that moved through just prior to Thanksgiving. These benefits are somewhat offset by precipitation deficits of 2-6 inches in Orange County that accumulated over the last 90-days. Even larger deficits of 4-8 inches have mounted in Ulster County just to the north. Accordingly, much of Orange County was improved one-category from D1 to D0.

In New England, significant improvements were rendered to the drought depiction. Stream flows in the CT/RI/MA area are now running near to above normal at USGS stream gauges. In Rhode Island, precipitation totals of 9-10 inches for the combined October-November period bring rainfall to within 90-115 percent of normal. Therefore, moderate drought (D1) was removed from Rhode Island’s depiction. In Connecticut, CoCoRaHS precipitation observing sites (reporting most days from October 1-8am December 9) reported precipitation amounts ranging from 10.4-12.9 inches (liquid equivalent). In the D1 area of eastern Connecticut, COOP observing sites for the same period report precipitation totals of 10.91 inches (Norwich Public Utility Plant), 12.08 inches (Hampton), and 10.83 inches (West Thompson Lake). Connecticut precipitation amounts spanning October 1 to December 9 are now close to normal. Accordingly, moderate drought (D1) was removed from eastern and central Connecticut, and D0 was trimmed out of northern Connecticut, and out of both southern Worcester and western Bristol Counties in nearby Massachusetts.

In northern Virginia, stream flows have improved significantly, and the only substantial precipitation deficits (2-4 inches) are at 90-days. In Strasburg, water restrictions were removed on December 1. No alteration was made to the northern Virginia drought depiction this week, though it appears that some trimming of the abnormal dryness (D0(S)) may be warranted next week.

Northern and Central Plains

The Dakotas, Nebraska, and approximately northwest half of Kansas received little to no precipitation this past week. The southeast half of Kansas reported moderate rainfall (0.5-2.0 inches) during the same period. The regional drought depiction was unaltered this week.

Ohio/Tennessee Valleys

During the past 7-days, most of this region received anywhere from 0.5-3.0 inches of precipitation. This helped to offset the 2-4 inch deficits that accumulated in western portions of both Kentucky and Tennessee during the last 90-days. As a result, no abnormal dryness (D0) was introduced to the region this week.

Pacific Northwest

Moderate precipitation (0.5-3.0 inches, locally heavier) fell across western portions of both Washington and Oregon during the past 7-days. The rain-shadow effect was most pronounced just east of the Cascades, where little to no precipitation fell, but amounts picked up again in far eastern sections of Washington and Oregon (where 0.5-2.0 inches was reported). Snowpack has generally been lacking in this region, and continues to be monitored. No modifications were rendered to the drought depiction in either state this week.

Rockies

Northern and western portions of Idaho received moderate precipitation (0.5-2.0 inches) this past week, as did western portions of Montana and Wyoming. Most of the rest of the Rocky Mountain states received little if any precipitation. Warm, dry weather dominated most of the Upper Colorado River Basin (UCRB) this past week. Most of the region received under 0.10-inch of precipitation, though there were several exceptions. In the Green River Headwaters region, precipitation totals generally ranged between a quarter-inch and one inch, with a swath of 1-2 inch amounts between Lincoln and Sublette Counties in Wyoming. Isolated areas of the San Juan Mountain Range and the central Rockies received over a half-inch of precipitation. Temperatures ranged from about 9-12 degrees F above-normal across a majority of the region, with slightly smaller anomalies to the south. Even though it is still very early in the snow accumulation season, SNOTEL Water-Year-To-Date (WYTD) precipitation percentiles remain very low thus far in the Wasatch and Uintah Ranges.

Across the High Plains of eastern Colorado, generally warm and dry weather prevailed during the past week. The northern Front Range and the northeast Plains received no measurable precipitation, while areas in the foothills and along the Palmer Divide reported up to a quarter-inch of precipitation. The southeast corner of the state received up to a half-inch, which is a bit unexpected at this time of year. The Standardized Precipitation Indices (SPI) on short timescales are low; however, this is a dry time of year and not part of the growing season. In addition, the trend is reversed for longer timescales. Finally, flows along the Arkansas and South Platte Rivers, and reservoirs, are currently in good shape. The drought depiction across this broad region was left unchanged.

Southeast

Northern Alabama continued to receive precipitation from passing fronts, while southern Alabama has been bypassed. Stream flows in coastal Mobile and Baldwin Counties are in D2-D3 status, as are a few others elsewhere in southwest Alabama, intermingled with a majority of stream flows in the D0-D1 range. The 60- and 90-day deficits depicted by the Advanced Hydrologic Prediction System (AHPS) show large areas of southwest Alabama where PNPs are in the 25-50 percent of normal range. This supports the one-category downgrade (from D-nothing to D0) in Wilcox and Dallas Counties, and the expansion of moderate drought (D1) from near the Mississippi border eastward across Marengo and Clarke Counties. In east-central Alabama, the area of severe drought (D2) appeared less justified, especially since conditions are worse southwest of there. As a result, the D2 area was removed.

Ninety-day Departure from Normal Precipitation (DNP) values in west-central, east-central, and southwest portions of Georgia range from 2-6 inches below normal. This factor, combined with little to no precipitation this past week, and near to below-average stream flows favor 1-category deteriorations to the drought depiction in these areas.

In North Carolina, little to no rain fell across much of the state this past week. Still, hydrologic conditions remain fairly good across a large part of the state, with the exception of parts of the central Piedmont and the Sand Hills, where 7- and 28-day stream flows are below-normal at 21 and 7 stream gauges, respectively, in a scattered pattern across these areas. Declining temperatures, decreased evaporation and diminished water demands have helped to maintain overall conditions. No changes were made to the drought depiction in North Carolina this week.

Southern Plains

Most of the region was dry this past week, with the exceptions of the eastern Panhandle of Oklahoma, eastern and southeastern Oklahoma, and a few locales near the Texas Coast, where 0.5-1.0 inch of rain fell. Short-term dryness is emerging across parts of northeast and southeast Texas, and in the Panhandle. The 30-day PNP values range from 10-50 percent of normal in northeast Texas and the Panhandle, and 25-50 percent of normal in interior southeast Texas (Polk and San Jacinto Counties north of Houston). Minor degradations were made to the depiction in these Texas regions (for Polk and San Jacinto Counties, abnormal dryness (D0) was introduced.

In northwestern Oklahoma during the last 90-days, the Oklahoma Climatological Survey reports PNP values between 20-40 percent of normal (1981-2010 base period), and the Daily Averaged Fractional Water Index (FWI, from the Oklahoma Mesonet) 24 inches deep into the soil ranged from 0.1-0.3. The 32-inch Percent Plant Available Water (32PPAW), which considers column soil moisture from the soil surface down to a depth of 32 inches, is running between 18-34 percent in the Counties of Harper and Woods. Most plants experience water stress when less than 50-percent of the maximum plant available water remains in the active root zone. In western Oklahoma (northern Roger Mills County), PNP’s during the past 90-days were about 60 percent of normal, with FWI values ranging from 0.1 in the far west part of the County to 0.6 in the far east. In extreme southeast Oklahoma, the 90-day PNP values range from 60-80 percent of normal, while the FWI bottoms out near 0.2 in southern Bryan County. The relative dryness over the past 3-months roughly coincides with the secondary rainy season in this region and this is on top of at least 4 years of significant drought. As a result, one-category degradations were made to the depiction in northwest Oklahoma (southeast half of Harper County, and Woods County), western Oklahoma (northern Roger Mills County), and extreme southeast Oklahoma (Bryan and Choctaw Counties). Finally, in southwest Oklahoma, extreme and exceptional drought (D3 and D4) was expanded slightly to include more of Comanche County. A COOP site at Lawton reported 89.66 inches of precipitation since October 1, 2010 (normal is 137 inches), when the drought began. This is a deficit of nearly 50 inches during this period.

Southwest

Southern stream energy was attended by moderate to heavy precipitation (0.5-3.0 inches) this week across central and south-central Arizona, and northwest parts of New Mexico. Most other areas of the Southwest remained dry. The regional depiction was not altered this week.

Looking Ahead

For the upcoming 5-day period (December 11-15, 2014) very heavy precipitation (5-9 inches, liquid equivalent) is anticipated across northern and central portions of California, with moderate precipitation (0.5-2.0 inches) predicted from the southern Sierras westward to the coast. Between 4-5 inches of precipitation (liquid equivalent) is also forecast for the Olympic Range of Washington state. Moderate precipitation (0.5-2.0 inches) is also predicted for portions of the northern Rockies, the Wasatch Range in northern Utah, the central and southern Great Plains, upstate New York and northern New England. Most remaining areas are expected to receive light precipitation (up to 0.5-inch), if any.

For the ensuing 5-day period (December 16-20, 2014), above-median precipitation is favored for most areas west of the Continental Divide (about a 60-65 percent chance in central California), the central and southern Plains, most of the Mississippi-, Ohio-, and Tennessee Valleys, and most of the Southeast. Below-median precipitation is favored over the Northeast and mid-Atlantic regions, much of the Great Lakes region, the northern Great Plains, and southern Florida.


Author(s):
Anthony Artusa, NOAA/NWS/NCEP/CPC

View a printable narrative here.

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