California and National Drought Summary for March 10, 2015
Summary
Two low-pressure systems brought significant rains to portions of the contiguous U.S. from the Southern Great Plains to the mid-Atlantic. Elsewhere, most of the rest of the reporting stations around the country reported little to no precipitation, continuing the dry conditions across much of the western states. Moderate rains have brought much needed drought relief to Hawaii, which much of central Alaska remained without precipitation. The eastern portions of Puerto Rico continued to receive light rains, while western portions of the island remain dry.Alaska, Hawaii and Puerto Rico
Only light precipitation fell over northeastern Puerto Rico, while the western end of the island remained without significant precipitation. The rains that did occur did not fall over the currently depicted, abnormally dry area.Recent wet weather across Hawaii led to a reduction in drought and dryness. The rains have fallen primarily over the eastern areas of Molokai, east-facing slopes of Maui, and portions of the Big Island. As a result, drought conditions were paired back and the designation has been changed from short-term to long-term, reflecting the longer-term issues with water storage and the recent, wetter period.
Middle and Lower Mississippi Valleys, and Gulf Coast
The two low-pressure systems that impacted the eastern portions of the contiguous 48 states brought significant rains to these regions, although some portions of northwest Arkansas and neighboring states largely missed out on the heaviest rains. The ongoing dryness continued across northwest Arkansas, eastern Kansas, and northeast Oklahoma. Moderate drought is now indicated in the SPI values at many time frames, United State Geologic Survey (USGS) streamflow gauges, and North American Land Data Assimilation System (NLDAS) soil moisture models. This area will need to be monitored closely in the coming weeks.Reports from Oklahoma suggest localized effects from the dry conditions. Areas of Oklahoma are still almost 4 inches behind in overall rainfall and the subsoil has not completely recovered from the past droughts. There are some areas in Sequoyah County, locally, near the river that have soils holding water and those are the lowest areas and prone to flood. Adair County is the driest of the three counties covered by the FSA representative for that region. Some of the ponds started to decrease in levels the last month or so in Adair, Cherokee and northern Sequoyah Counties.
With rains of up to 6.51 inches reported across eastern Texas, drought conditions have improved, so some of the D0-D3 areas were trimmed back across northeastern Texas. Across southeastern Texas, recent rains prompted the removal of severe drought (D2) and some trimming of the moderate drought (D1) and abnormal dryness (D0).
Heavier rains farther east also helped alleviate ongoing dryness across Louisiana and Mississippi. Rainfall totals ranged from 0.6 inch to over 2.5 inches across southwest and central Louisiana, while precipitation amounts were generally lighter across Mississippi. Due to the generally more entrenched drought conditions across southern Mississippi and southern Alabama, only small reductions in coverage were made to the moderate drought (D1) areas over Mississippi and Alabama.
Northern Plains and upper Midwest
No precipitation fell last week and temperatures were below average (1.0 to 6.1 degrees F). The cold temperatures and frozen soil continue to mitigate most impacts from no precipitation, as does the 2-5 inches of snow water equivalent (SWE) that is locked in the snowpack. Abnormal dryness was expanded across northeastern Iowa and most of Wisconsin to reflect the ongoing lack of precipitation, but tempered by the snowpack considerations across northern Michigan and Wisconsin.Across Minnesota, precipitation totals since 1 Oct 2014 are 2.5 to 3.5 inches below average. The accumulated total values would rank somewhere between the 5th and 25th percentile, supporting anywhere from a D2 to a D1 classification, but mitigated by the frozen soils and lack of moisture demand during this time of year.
Southwest
A few stations in New Mexico reported light precipitation (0.01 to 0.15 inch), but most of the Southwest remained dry this week. Westwide SNOTEL reports of SWE much below average across southwest New Mexico and eastern Arizona prompted the expansion of severe drought (D2) across Navajo and Apache Counties in Arizona and Catron County in New Mexico.The High Plains, Rockies, and Intermountain West
No significant precipitation fell across much of this region during this past week, through the data cutoff time on Tuesday morning. The past week was slightly cooler than average for the Upper Colorado River Basin, and fairly seasonal in terms of precipitation. Another large slug or two of moisture like what was realized at the end of February will be necessary in order for basin-wide snowpack numbers to achieve median status by peak season. East of the divide conditions were much cooler than average and mostly dry with less than a tenth of an inch of precipitation across most of the region. On short timescales eastern Colorado is not at a deficit precipitation-wise with the exception of the northeast corner of the state, which is still holding onto average soil moisture conditions. With the cold temperatures keeping things dormant, lack of substantial winds, and recent snowfall events the recent dryness east of the divide this week should be relatively inconsequential. No changes were made to the drought depiction as precipitation was not far off of normal.The lack of winter storms across the Great Basin prompted the intensification of drought conditions across eastern Nevada and western Utah. SPI values out through 9 months indicate conditions at least as intense as D1, with shorter time period SPI values indicating even more intense conditions.
The mid-Atlantic and Northeast
Light to moderate rains (1.0 – 3.5 inches) fell across portions of the Central Appalachians and southern portions of the Northeast. As a result, abnormal dryness (D0 from West Virginia to central Pennsylvania was reduced in coverage. Farther south, the same storm systems spread between 1.0 and 2.3 inches of precipitation over the western Virginia, prompting the removal of D0 along the Virginia-West Virginia border counties on the Virginia side.The Ohio and Tennessee River Valleys
Significant rain and frozen precipitation (1.0 – 3.3 inches, liquid and liquid equivalent) fell across southern Indiana, Ohio, and Kentucky. Streamflows are now above average and the only remaining, significant deficits are evident in 3-month Standardized Precipitation Index (SPI-3) values. Soil moisture models also indicate a saturated soil profile, so a complete amelioration of drought was prudent over that region.The Pacific Northwest and California
The winter continues to be dry for much of this region as no significant rains fell this past week. Abnormally dry conditions expanded across northwest Oregon to near Tillamook. The rest of the area remained unchanged, but will be monitored closely in the coming weeks.Looking Ahead
Through March 17, two low-pressure systems are forecast to impact the contiguous 48 states during the next 5 days. One is forecast to move across the northern tier while another is forecast to bring significant rains (more than 3.0 inches) to the Gulf Coast and Lower Mississippi Valley. These two systems are forecast to phase over the northeast, with precipitation spreading from west to east across that region. Some flow into the front range of the Rockies, with upper-level support is likely to bring some spring snows to southwest Colorado.For the ensuing 5 days (Mar 17 -21), below median precipitation is favored along the west coast, and from the Great Lakes to the Southeast, while an upper-level trough supports above median precipitation over the Southwest, most of the Rockies, and portions of the southern and central Great Plains. Western and Southern Alaska are expected to experience an active weather pattern with above median precipitation.
Author(s):
Matthew Rosencrans, NOAA/NWS/NCEP/CPC
Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.Drought Intensity Categories
D1 ... Moderate DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
