The U.S. drought outlook for March 2018 calls for drought to persist across most areas west of the Continental Divide. Unseasonably wet and cold conditions are expected across much of the West in March.
However, since the Water-Year-To-Date season has been so dry and mild, leading to low snow packs, the anticipated surplus precipitation and subnormal temperatures most likely will not be enough to show marked improvement in Oregon and California, but should be enough to preclude any drought development there during March.
Most forecast tools and March precipitation climatology favor drought persistence over the southern half of the High Plains region, with fairly regionalized areas of drought development expected in western Texas.
Farther north, the official CPC precipitation outlook for March favors above normal precipitation over the northern Plains, supporting improvement and/or removal of drought across eastern Montana and nearby portions of the Dakotas. For the remainder of the Dakotas, it appears less likely that enough precipitation will be received to warrant an improvement in overall conditions.
Elsewhere, precipitation received during the past few weeks, and the expected continuation of a wet pattern over the eastern portions of the southern Plains, the Lower and Middle Mississippi Valley, interior portions of the Southeast, and the Washington, D.C. vicinity, favor improvement and/or removal of drought.
Drought persistence is considered most likely in south-central Virginia and near the eastern Gulf Coast, which is expected to be sufficiently distant from the primary storm track. Prospects for drought development are elevated for the Florida peninsula, southeastern Georgia, and along much of the South Carolina coast.
There is currently no drought in Hawaii, Alaska, or Puerto Rico, and these regions are anticipated to remain drought-free throughout the month of March.
Forecast confidence for the Western region is moderate in California and Utah, and moderate to high elsewhere.
- Most drought areas of the West are expected to persist during March 2018. The Advanced Hydrologic Prediction Service (AHPS) Water-Year-To-Date (WYTD) map shows California is lagging well behind in their wet season precipitation.
- For about the northern half of California, WYTD totals average between 25-75 percent of normal, while the southern half of the state received only about 10-50 percent of normal precipitation (PNP) since the start of the Water Year last October. Below average stream flows are noted over most of the state.
- The Snow Water Content (SWC) map from the Western Regional Climate Center’s Desert Research Institute in Reno, Nevada, shows SWC values of only 27-39 percent of average across much of the Sierras.
- CPC’s updated 30-day precipitation outlook favors above normal precipitation for most of California and Oregon, and the temperature outlook calls for enhanced odds of subnormal temperatures. March precipitation climatology also favors wetness for much of this area.
- However, despite these factors, the WYTD season has been very dry and mild leading to low snow packs (snow water equivalent values), and the anticipated surplus precipitation and subnormal temperatures are most likely not going to be enough to show marked improvement in the drought across Oregon and California. Still, the anticipated precipitation, and hold-over water from the previous Water Year should be enough to offset any potential drought development.
- In some areas across southern California, there are reports of rangeland foraging being very compromised due to very limited precipitation with the past year, record-breaking heat, and wind patterns that appear to be unusually active.
- Elsewhere across the West, drought removal is anticipated over northern Utah, including the Great Salt Lake region. This is based upon SWC values of 56-77 percent of average (suggestive of sufficient snowpack across the higher terrain), precipitation outlooks for Weeks 1 and 2, and the GFS predicted soil moisture anomaly change of nearly +0.5-inch within the first two weeks of March.
- This forecast for northern Utah also has limited support from March precipitation climatology, and from CPC’s updated 30-day precipitation outlook for March. On the other hand, the Constructed Analog on Soil moisture (CAS) tool predicts very little precipitation during the period.
- Finally, eastern Montana (and neighboring parts of the Dakotas) are predicted to experience drought improvement and/or removal during March, despite the fact that the 121-year historical record shows only 3.5-7.0 percent of the annual precipitation in this region is typically received in March.
- CPC’s 30-day accumulated PNPs from 29 Jan-27 Feb 2018 (rain gauge based) depicts values of 200-400 percent of normal in western Montana, and 400-800 percent of normal over eastern parts of Montana. SWC values range from about 131-152 percent of average.
- These factors, and CPC’s updated 30-day outlook favoring above normal precipitation (probabilities between 50%-59%), form the basis for this prediction.
Forecast confidence for the High Plains region is moderate.
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- With the exception of the previously mentioned extreme western Dakotas, the current drought areas across the High Plains region are predicted to persist.
- Precipitation amounts are forecast to be fairly low in this area, and climatology favors relatively dry conditions for this time of year.
Forecast confidence for the South is moderate to high.
- March climatology favors a drier pattern over the western part of the South (southern High Plains), a wetter pattern over the eastern part of the South (much of the Lower Mississippi and Lower Tennessee Valleys), and conditions close to average in-between these two regions.
- During the past two weeks, PNP values of 300-600 percent of normal were noted over much of the Lower southern Plains, and approximately the northwestern half of the Lower Mississippi Valley. In contrast, the Oklahoma/Texas Panhandle region received PNPs within the lowest quartile of the historical distribution, and in many cases, the lowest 10 percent of the distribution.
- Incidentally, CFS precipitation forecasts from Feb 20-28 (valid for March) all depict below normal precipitation across the southern High Plains/southern Rockies region. Current stream flows generally mirror the precipitation pattern of the past two weeks.
- WPC’s Week-1 precipitation outlook, and CPC’s Week-2 precipitation outlook indicate a very persistent pattern across this region, with the same areas that already received heavy precipitation during the past two weeks expected to continue receiving heavy precipitation (during Week-1, 3-7 inches is predicted from the Arklatex region to Tennessee).
- The 30-day updated precipitation outlook predicts enhanced odds of above normal precipitation (50%-59%) across some of these same areas.
Forecast confidence for the Midwestern region is moderate to high.
- The only remaining larger-scale drought area over the Midwestern region is located over the Middle Mississippi Valley.
- March precipitation climatology favors drier conditions (3.5-7.0 percent of annual average) north of a line that extends approximately from Kansas City to Detroit, with conditions closer to average south of this line. The exception is Kentucky, where approximately half of the state is favored to receive a significantly higher proportion of their annual precipitation (9.5-11.5 percent of average).
- According to AHPS, much of the Midwestern region has received PNPs on the order of 300-600 percent of normal over the past two weeks. CPC’s updated 30-day precipitation outlook tilts the odds toward above normal precipitation in March.
- Improvement and/or removal of drought conditions seems to be the best bet.
Forecast confidence for the Southeast region is moderate to high.
- A significant fraction of the Southeast region is experiencing abnormal dryness (D0) or moderate drought (D1) at this time, and the only location that is climatologically favored to be dry is the Florida peninsula. It is during March and April that the Florida peninsula typically experiences the height of their dry season, along with significantly elevated wildfire activity.
- Drought development is therefore anticipated over this area, and parts of southeastern Georgia, and portions of the South Carolina coast, perhaps as far north as the Charleston area.
- This general region is expected to miss out on a large portion of the precipitation during the next two weeks, with drought likely to persist across south-central Virginia.
- Elsewhere, in Alabama and parts of Georgia, anticipated proximity to the mean storm track favors the removal of drought conditions.
Forecast confidence for the Northeast region is moderate.
- Lingering drought over the Washington, D.C. area is likely to be removed during March. Drought is not expected to develop in the Northeastern region during March.
Forecast confidence for Hawaii, Alaska, and Puerto Rico, is moderate to high.
- There is no drought currently in Hawaii, Alaska, or Puerto Rico, and none is anticipated during March.