U.S. Drought Monitor - Latest Update

 National Drought Monitor for November 4, 2014

Summary

Early in the period, a cold front moved from the Appalachians to the East Coast. During the latter portions of last week, the pattern amplified, with an intense low pressure system developing over the Great Lakes and another moving into the Pacific Northwest. The storm in the east pushed record cold temperatures as far south as the Everglades and snowfall from the southern Appalachians to New England, while the western storm brought much needed rain to many portions of the West. The western storm system then moved eastward and tapped into moisture from the Gulf of Mexico, spreading rains from Texas to the Great Lakes.

Looking Ahead

During November 6-10, wet weather is forecast for the eastern third of the Nation, Pacific Northwest, and parts of the southern Great Plains. Rainfall totals are likely to exceed 4.0 inches across Texas as the moisture is likely to have a tropical source. Lake enhanced precipitation is also likely near the Great Lakes as a low-pressure system is forecast to move from the Great Lakes to the Canadian Maritime Provinces during the next 3 days. During the early to middle portions of next week, a cold front is forecast to traverse the contiguous 48 states, ushering in drier and cooler conditions.

For the ensuing 5-day period, November 11-15, odds favor below normal temperatures east of the Rockies, with above normal temperatures west of the Continental Divide. Below median precipitation is favored for much of the contiguous 48 states, except near the Great Lakes, New England, and South Texas. Above median rains are favored for most of Alaska, except the interior basin, north of the Alaska range.

New England and mid-Atlantic

A deep low-pressure system moved up the East Coast and spread precipitation (0.5 – 2.4 inches) up across eastern New England. Some of it fell as snow, which has a slower impact on drought reduction, so only a small section of the abnormal dryness (D0) was trimmed from Massachusetts and Rhode Island.

The precipitation associated with the low-pressure system did not spread to the Mid-Atlantic Coast. Dryness is relatively short lived, mainly evident in 30- and 60-day plots of percent of normal precipitation (PnP), which the 30-day PnP of 50 percent or less was used as the demarcation threshold. The National Weather Service Office in Raleigh reported that total rainfall at Fayetteville was about 1.3 inches for the month of October, of which almost 1.1 inches of the monthly total fell on the 14th and 15th. Soil moisture maps presented by the NWS Raleigh office also indicate reductions in the top layers of the soil column. Additionally, across northeastern North Carolina and southeastern Virginia, D0 was expanded down the mainland and across portions of the Delmarva Peninsula. AHPS (Advanced Hydrological Prediction System) 60-day percent of normal precipitation seems to mask the deepening dryness that has settled across this area. However, it was pointed out by the NWS Wakefield that much of the 60-day total is attributed to a storm system on September 9 which produced high amounts of rainfall across that region.

Ohio and Tennessee Valleys

No changes were made to the drought conditions in this region, as precipitation during the past 30 days was at least 50 percent of normal. At longer time periods, precipitation is mostly above average.

Pacific Northwest and California

Moderate to heavy rains fell across the area from northern California to western Washington. Weekly rainfall totals for northern California top out at 2.3 inches, while rains further north, across the Olympic Peninsula and Cascades, exceed 9 inches. Feedback from California included some reports detailing improvements to stream flows while other reports only greening of small plants and grasses, not indicating deeper soil moisture recharge. The rains had an abrupt cutoff across Mendocino County. Northern Mendocino County reported near normal precipitation for October, but Southern Mendocino County was drier (below normal). Local lawns are greening up from the weekend rain which saturated the upper soils. During the past 2 months precipitation amounts for Del Norte, Siskiyou, Humboldt, Trinity and Northern Shasta Counties have been 150-250% of normal. On the north coast Gasquet is at 200% of Sept/October normal (8" over normal). Trinity Reservoir is currently at 106 percent of normal inflow for October. Finally saw some river rises from the weekend storms, after the rises the rivers returned to new elevated baseflow levels. Drought reductions were depicted for areas with rains in excess of 1.5 inches and 30-day PnP greater than 200 percent of normal across Northern California.

AHPS is showing heavy rains across Wheeler County Oregon, but ground reports do not corroborate those estimates. No change was made to the depiction in eastern Oregon.

Across Washington and Northern Idaho, reductions in drought conditions were made. Almost a 1-category improvement was made across the Cascades. Orographically enhanced precipitation fell across portions of Central Idaho, so D1 was removed from near Clearwater County and also around the Boise area. Boise is reporting above-average precipitation for the year, despite below-average snowfall totals. Precipitation missed many portions of northern Idaho, where D0 and D1 were expanded to account for the ongoing dryness, mainly evident in AHPS data out to 60 days and NLDAS Soil Moisture models.

Puerto Rico

Moderate to heavy rains (0.5 – 4.3 inches) were reported across the island. Drought reductions were made where 7-day accumulations were greater than 3 inches, prompting the removal of D0 from northeastern portions of the island. Abnormal dryness was retained anywhere rains measured less than 3.0 inches and 30-, 60-, 90-day precipitation totals were still well below average.

Southeast

Abnormal dryness (D0) and moderate drought (D1) were expanded across portions of Georgia, Alabama, Mississippi, and Louisiana. AHPS precipitation and SPI values (60-, 90-, and 120-day) from the High Plains Regional Climate Center (HPRCC) indicated at least D1 conditions across many portions of Georgia, with an intensification toward the shorter time periods. Dryness increased markedly across western Alabama, southern and eastern Mississippi, and southeastern Louisiana during the past 60 days, with D3 (extreme drought) conditions indicated by HPRCC SPI values across east- central Mississippi, but other tools indicating less severity in the drought.

Southern and Central Plains

Widespread rains (1.0 – 2.1 inches) fell across the area from northwestern Texas to Missouri, prompting some improvements across those areas. The rains were ongoing at the data cutoff time of 12Z on Tuesday, November 4. Some reductions in drought intensity and coverage were made over the Texas Panhandle, partly due to recent rains and partly due to a reassessment of conditions in conjunction with the Texas State Climatologist. Improvements were also made to southwest Missouri, where recent rains have ameliorated any lingering dryness.

Across central and eastern Oklahoma, recent rains (0.5 – 2.6 inches) prompted some small areas of 1-category reduction in drought. No changes were made across southeast Oklahoma. In contrast, dryness continued across Arkansas and northwest Louisiana, so D0 was expanded to cover the areas showing less than 50 percent of normal precipitation at the 30 through 90 day time intervals.

Some reduction in drought coverage was made across eastern New Mexico, as 30-, 60-, and 90-day precipitation totals were well above average. Drought conditions in Colorado showed little signs of change during the past week. The areas around Las Animas and Conejos Counties have competing signals (dry long-term, wetter short-term). If the trend toward wetter conditions continues, the drought conditions will need to be reassessed.

Southwest and Great Basin

No changes were made to the drought depiction across Nevada, Utah, or Arizona. The Nevada State Climatologist requested no changes, pending evaluation of impacts of recent light rains (less than 1.0 inch).


Author(s):
Matthew Rosencrans, NOAA/NWS/NCEP/CPC