Drought Outlook Seasonal: Increased Dryness in the West, Central U.S. Improvements

With sub-median precipitation and above-normal temperatures favored during March and MAM, drought should persist in the southwestern quarter of the Nation, along with development in most of California and Nevada, south-central Oregon, and southern Texas.

The odds for California to get to near-normal precipitation this Water Year are rapidly diminishing as the wet season normally ends in April. In central Oregon, below- to near-median precipitation during the next 1-2 months will probably not be enough to significantly increase the mountain snowpack that stood at 28-35 percent of normal as of February 14.

Subnormal winter precipitation, minimal snow cover, and a dry climatology (until late April) in eastern sections of the northern Plains does not bode well for adequate soil moisture recharge, hence persistence was left there. In contrast, recent precipitation and the forecast for additional rainfall from the southern Great Plains and lower Mississippi Valley northeastward into New England tilts the odds toward improvement in the eastern third of the Nation.

Similarly, improvement is likely in the western sections of the northern Plains where surplus fall and winter precipitation has built a decent snow pack to aid in soil moisture recharge during spring snow melt while March and MAM precipitation favor above-median totals.

Removal is forecast for western portions of the Big Island of Hawaii while development is possible along the southeastern Alaskan Panhandle.

Forecast confidence for the Southeast is moderate to high in northern areas (northern AL, VA, NC) and moderate in southern areas (southern AL, southern GA, and eastern SC).

United States Seasonal Drought Outlook Graphic - click on image to enlarge

Click Image to Enlarge

  • After relatively dry weather occurred during the late fall and early winter, precipitation began to increase in intensity and coverage across the Southeast in late January and continued into mid-February, providing widespread improvement of short-term drought in most areas of the region – which also extended northward into the Northeast.
  • A few areas of D1 remained as of the February 13 U.S. Drought Monitor, but similar to the short-term forecast for the Northeast, the 7-day QPF has moderate to heavy precipitation from the southern Great Plains and lower Mississippi Valley northeastward into southern New England. Similarly, the 6-10 and 8-14 day ERFs also favor above-median precipitation in a similar area as the QPF, while Week 3-4 odds tended toward above-normal precipitation in the Deep South.
  • In addition, LLF precipitation for March also tilted toward above-median precipitation in the Southeast, while the MAM was EC. Therefore, most of the remaining D1 areas in the Southeast are forecast for removal.
  • A notable exception to the wetness was a band of below-median rainfall at all time periods (QPF to MAM LLF) across most of Florida, southeastern Georgia, and coastal South Carolina.
  • With some of this area already in D0, development was added in southeastern Georgia and coastal South Carolina while the D1 area in northern Florida and southern Georgia should persist.

Forecast confidence in the South is moderate in far eastern sections, and low to moderate in southern and western areas.

  • Consistent with the La Niña signal, enhanced chances for subnormal March and MAM 2018 precipitation cover southern and western sections of the Southern region. However, in the short-term (QPF, ERFs, and Week 3-4), moderate to heavy precipitation or above-median precipitation is favored from south-central Texas and central Louisiana northeastward, including eastern Oklahoma and southeastern Kansas.
  • Farther west and north, however, QPF totals are much lower (QPF), and odds more likely for sub- to near-median precipitation (ERFs, Week 3-4). In addition, the past 3-4 months have been extremely dry in the southern High Plains (numerous TX and OK Panhandle locations have observed no measurable precipitation for more than 90 consecutive days), leading to areas of D2 and D3. Another factor is the climatology of the southern Plains – where the winter months are typically dry, but a sudden uptick in rainfall usually occurs in May and continues into the summer.
  • Although the MAM LLF precipitation favors below-median precipitation in the southern High Plains, even normal precipitation during May could lead to improvement from extreme drought (e.g. D3 to D2) by May 31 in the Panhandles of Texas and Oklahoma.
  • With this possibility and the mixed signals in the short-term vs medium-term, improvement was limited to eastern areas with the greatest QPF totals, highest odds of above-median ERF precipitation, and less intense drought, while the more severe western drought areas were left to persist or to develop where D0 existed (southern Texas) based on the March and MAM LLFs (La Niña dry and warm signal).

Forecast confidence in the Midwest is moderate to high in the middle Mississippi Valley and northern Minnesota, and moderate in western Minnesota.

  • In the Midwest, drought was limited to parts of Minnesota and portions of the middle Mississippi Valley, although in the most recent USDM drought intensified to D3 in parts of southern Missouri.
  • Fortunately, the short-term forecasts (QPF, ERFs), and somewhat the Week 3-4 and March LLF, favor above-normal precipitation for the next 1.5 months for much of the region.
  • Climatologically, after a fall and winter minimum, precipitation gradually increases in the Midwest as spring arrives and peaks during the summer. In addition with the ongoing La Niña, the Tennesse and Ohio Valleys typically observe above-median MAM precipitation, and this is the official CPC 3-month precipitation outlook.
  • So with both the short- and medium-term forecasts pointing toward above-median precipitation, improvement was made for the drought areas of Missouri, Iowa, and Illinois. Additionally, the small D1 area in extreme northern Minnesota was expected to be removed due to ample snow cover (spring snow melt for soil moisture recharge) and above-median MAM precipitation odds.
  • In contrast, snow cover was minimal in western Minnesota (extending into the eastern Dakotas), and with a rather dry and snowless winter to date, the lack of soil moisture recharge from snow melt would be a concern by May.
  • Therefore, without any strong evidence for above-median precipitation over the next 3 months, persistence was left here.

Forecast confidence for the High Plains is moderate to high in the west, and low to moderate in the east.

  • In the High Plains, the winter months are a relatively dry time of year, but precipitation normally increases as the period progresses, with April slightly wetter than the average and May quite wet, especially in the northern High Plains.
  • So far this Water Year, precipitation (and snowfall) has been above-normal in western areas (including Montana), but less so toward the east (eastern Dakotas). Most of Wyoming, Nebraska, northeastern Colorado, and western Iowa have seen above-normal winter precipitation, and drought is lacking there.
  • During the rest of February, precipitation amounts should be greatest in Montana and Wyoming, and unremarkable in the Dakotas, so the outlook for current drought areas are based on the longer-term indicators and climatology.
  • For March, there are enhanced chances for above-median precipitation in Montana, Wyoming, and the western Dakotas, while MAM favors above-median precipitation throughout the northern Rockies and Plains, with EC in the north-central Plains. However, with the meager snow cover across the eastern Dakotas (and western Minnesota), there is concern for soil moisture recharge from spring snow melt if new snowfall is lacking.
  • Therefore, continued slow improvement is forecast for the western areas (eastern Montana and the western Dakotas) while persistence is expected for the eastern Dakotas (unless May is particularly wet).

Forecast confidence for the West is high except in Oregon where confidence is moderate.

  • In the West, drought intensified the past 30 days (from the south-central Plains) across the Four Corners Region, the Great Basin, and in California and Oregon. The Water Year to Date (WYTD) has been exceptionally dry and mild across the southern half of the West (particularly in the Southwest), with basin average precipitation ranging from 5-70% of normal, and basin average snow water content (SWC) even lower (between 0-50%) as of February 14.
  • With California’s wet season typically ending in April, time is running out for bringing the state’s WYTD totals close to normal. With cold and dry weather expected in the short-term (QPF and ERFs), and above-normal temperatures and sub-median precipitation expected in southern sections during March and MAM (with the opposite in northern areas), the outlooks favor continued deterioration and expansion of drought through May in the Southwest, California, and the Great Basin.
  • Oregon is in the EC precipitation area, so it is possible for enough precipitation to occur to bring the state out of D1 by May.
  • The northern edge of the drought in the West marks the boundary between above- (north) and below-median (south) precipitation odds in the LLFs, thus this northern drought boundary will stay where it currently exists.

Forecast confidence for the Northeast is moderate to high in Maryland.

  • A small area of D1 in central Maryland (which extended southward into parts of central Virginia) was all that was left of drought after wet weather during the past 30 days.
  • With the wet weather pattern expected to continue as shown in the 7-day QPF and 6-10 and 8-14 day ERFs, and even at 3-months (e.g. MAM LLF favors above-median precipitation; March LLF EC precipitation), the small remaining D1 area in Maryland should be gone soon.

Forecast confidence for Hawaii is moderate to high, and moderate in Alaska.

  • In Hawaii, moderate drought was limited to parts of the western coast on the Big Island. La Niña conditions and the official CPC outlooks favor surplus precipitation for the forecast period statewide, thus Hawaii is expected to be drought-free by the end of May.
  • In Alaska, areas of D0 were found in the southwest and along the southeastern Panhandle. Although the short-term (ERFs and Week 3-4) outlooks indicate EC or slightly elevated odds for above-median precipitation along the southern coast, the March and MAM LLFs indicated favorable chances of subnormal temperatures and sub-median precipitation in the southeast. Therefore, by the end of May, D1 development is possible in the southeastern Alaskan Panhandle.
  • In Puerto Rico, there is no drought, and none is expected to develop.

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