California and National Drought Summary for March 28, 2017

Summary

PLEASE NOTE – The Drought Monitor reflects observed precipitation through Tuesday, 1200 UTC (8 am, EDT); any rain that has fallen after the Tuesday 1200 UTC cutoff will be reflected in next week’s map (in particular, Tuesday’s and Wednesday’s heavy rain on the central and southern Plains).

March 30, 2017 - During the 7-day period (ending Tuesday morning), renewed Pacific storminess brought increasingly wet, mild weather to a large swath of the country. Precipitation was heaviest from the central and northern Pacific Coast into the central and northern Rockies, while a secondary area of locally heavy rain and wet snow developed over the central High Plains and environs. Farther east, an influx of Gulf moisture led to widespread moderate to heavy rain from the lower and middle Mississippi Valley into the interior Southeast, while somewhat lighter precipitation was observed across the Midwest (mostly rain) and New England (wintry mix). As a result, widespread reductions in drought intensity and coverage were made where the heaviest precipitation fell, although the lower Southeast (including Florida) remained unfavorably dry.

Northeast

A pair of storm systems generated rain and snow from western New York into southern and eastern Maine, though the bulk of the heaviest precipitation (greater than an inch, liquid equivalent) missed the region’s lingering long-term (denoted by an “L” on the map) Moderate to Severe Drought (D1 and D2); in these locales, precipitation over the past 12-months has averaged less than 75 percent of normal.

Mid-Atlantic

Drought depiction was largely unchanged during the period, with a small westward expansion of D0 in western Virginia to account for increasing short-term dryness (less than 50 percent-of-normal rainfall over the past 60 days). However, the region was beginning to feel the effects of the increasingly warm, wet weather pattern that has unfolded over the nation’s mid-section by the end of the period, with locally heavy showers and thunderstorms spreading over the region after the Tuesday morning data cutoff for inclusion in this week’s Drought Monitor.

Southeast

Locally heavy rain facilitated additional widespread drought reduction across the interior, while persistent dryness led to additional drought expansion and intensification over southern portions of the region. Rain totaled 1 to 4 inches (locally more) from western Tennessee into the western Carolinas as well as northern portions of Alabama and Georgia. Significant reductions in Abnormal Dryness (D0) as well as Moderate, Severe, and Extreme Drought (D1, D2, and D3) were made where the heaviest rain fell. Despite this week’s heavy rain, precipitation totals in many of the Southeastern drought areas are averaging 45 to 65 percent of normal over the past 6 months, and streamflows remained unfavorably low from northern Georgia into western and northern North Carolina, indicating the need for additional rainfall over the upcoming weeks to prevent rapid declines into more severe drought. In contrast, rain bypassed most areas along the Gulf and southern Atlantic Coasts, with 60-day deficits in excess of 6 inches (30-50 percent of normal) encompassing a large area from central and northern Florida and southeastern South Carolina westward into southern Alabama. D2 was added to northern Florida where 90-day rainfall stood at a meager 25 to 30 percent of normal, with totals out to 6 months less than 40 percent of normal. Likewise, D1 was expanded over south-central Florida, coincident with 90-day rainfall averaging 30 to 40 percent of normal.

Delta

Widespread heavy rain eased or eliminated drought in northern portions of the region, while showers and thunderstorms provided localized relief closer to the Gulf Coast. Rainfall totals of 2 to 5 inches led to 1-category reductions in drought in northern Arkansas and environs, though 6-month deficits lingered (50-70 percent of normal) in Arkansas’ northwestern drought areas. Amounts were highly variable farther south, with totals in Louisiana ranging from less than one-tenth an inch in the interior northwest to more than 3 inches near Baton Rouge. As a result, improvements in the southern Delta were more modest and confined to locales where weekly rain approached or topped 2 inches.

Midwest and lower Ohio Valley

Rain in southern and western portions of the region afforded some relief from drought, though the bulk of the heaviest rainfall remained south and west of the region. From central and southern Missouri into southwestern Kentucky, 1 to 3 inches of rain (locally more) led to reductions of Abnormal Dryness (D0) and Moderate to Severe Drought (D1 and D2). Nevertheless, drought improvements were tempered by lingering deficits, with precipitation over the past 180 days averaging locally less than half of normal in the remaining D2 area and immediate environs.

Northern Plains

There were no changes to this region’s drought depiction, with light to moderate showers (locally more than 0.5 inch) bypassing the lingering long-term Moderate Drought (D1) area.

Central and Southern Plains

Locally heavy precipitation in western- and eastern-most portions of the region afforded some drought relief, while mostly dry weather prevailed during the period elsewhere. Moderate to heavy rain and wet snow (1-3 inches, liquid equivalent) led to reductions in Abnormal Dryness (D0) as well as Moderate to Severe Drought (D1 and D2) from central Colorado northeastward into central Nebraska. A secondary precipitation maximum (1-4 inches) likewise led to reductions of D0 and D1 across eastern Kansas. The remainder of the region was mostly dry, though heavy rain (1-3 inches, locally more) was recorded during the 24-hour period from Tuesday into Wednesday morning over southern and central Kansas into central and western Oklahoma; as this rain fell after the 1200 UTC Tuesday cutoff, the impacts will be incorporated into next week’s analysis.

Texas

There were minor changes to the drought depiction in Texas, with minor improvements in eastern portions of the state contrasting with subtle expansion of dryness farther west. Rain amounts across eastern Texas were highly variable, with amounts of 1 to 3 inches affording some reduction of Abnormal Dryness (D0) or Moderate Drought (D1). Meanwhile, D0 was expanded north of Midland after another dry week left precipitation over the past two months less than 60 percent of normal. It should be noted the recent heavy rain (1-4 inches) over north-central Texas fell after the Tuesday 1200 UTC cutoff, and will be incorporated into next week’s drought assessment.

Western U.S.

Despite renewed heavy locally heavy rain and mountain snow across central as well as northern portions of the region, the precipitation largely bypassed the lingering long-term drought areas (denoted by an “L” on the map) across southern California and the Southwest.

Alaska, Hawaii, and Puerto Rico

In Alaska, there were no changes made to the state’s Abnormal Dryness (D0), as mostly dry but cold (up to 10°F below normal) weather prevailed. In Hawaii, locally heavy rain (more than 3 inches) on the southern coast of the Big Island led to a modest reduction of Moderate Drought (D1). More notably, Severe Drought (D2) was expanded over the western third of the Big Island – the leeward side – which remained dry (locally less than one-third of normal rainfall over the past 90 days); impact reports regarding the locally severe short-term drought have started to come in across different aspects of the agriculture sector. Conversely, the lingering D0 was removed over the over southern Puerto Rico where rain totaled 1 to 4 inches, pushing the 90-day rainfall to above-normal levels over most of the island.

Looking Ahead

The storm responsible for the heavy rain that has fallen since Tuesday morning over the southern and central Plains will move slowly east, bringing welcomed showers and thunderstorms to the eastern third of the nation. The greatest likelihood for an inch or more of rain will be from the Midwest into the Northeast, with the more appreciable rainfall totals bypassing the lower Southeast’s drought areas. Meanwhile, another moisture-laden Pacific storm will track from the Northwest across the northern Great Basin, emerging onto the central High Plains before reorganizing and strengthening over eastern Texas. This latter system will produce a swath of rain and mountain snow from the Pacific Northwest into the central Rockies, while moderate to heavy rain (2-6 inches) develops across the south-central U.S. by early next week. Moisture from this second system is expected to reach the Ohio Valley, Mid-Atlantic, and Southeast by Tuesday morning. The NWS 6- to 10-day outlook for April 3 – 7 calls for above-normal temperatures nearly nationwide, with the greatest likelihood of warmth occurring in the southern Atlantic States. Meanwhile, near- to above-normal precipitation across most of the country will contrast with drier-than-normal weather from parts of California to the Rio Grande Valley.

Author(s):
Eric Luebehusen, U.S. Department of Agriculture

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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 Drought

D2 ... 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)
Source: National Drought Mitigation Center