Drought intensification and development occurred during May across the central to southern Great Plains due to insufficient rainfall coupled with periods of above normal temperatures.
According to the U.S. Drought Monitor valid on May 26, drought coverage across Kansas increased from 6.85 to 27.46 percent since late April with Oklahoma experiencing an increase from 3.94 to 14.44 percent.
Additional development is likely across the central to southern Great Plains during early to mid-June with the combination of above normal temperatures and below normal precipitation. Development is also favored across parts of New Mexico and Wyoming.
Much of the eastern U.S. remains drought-free, but development is forecast across parts of New England where short-term precipitation deficits are increasing and the updated June outlook calls for elevated probabilities of above normal temperatures and below normal precipitation.
Heavier rainfall during mid to late May resulted in improving drought conditions across southern Texas along with much of the Gulf Coast and Florida. Continued improvement or removal of drought is forecast for these areas, based on the likelihood of above normal precipitation through at least the first half of June.
Meanwhile, drought persistence is most likely across ongoing drought areas of the West and North Dakota. Persistence is also favored for drought across Puerto Rico and Hawaii, while Alaska is likely to remain drought-free through the end of June.
Forecast confidence is high for the Western Region.
- Above-normal precipitation along with slightly below normal temperatures during the latter half of May slowed the expansion and intensification of drought across the Pacific Northwest.
- Development remains unlikely during the next month due to an unseasonably wet, cool start to June.
- Although above-normal precipitation is favored across the Pacific Northwest during June, precipitation amounts are not expected to be enough to result in broad-scale improvement.
- Drought expanded or intensified across the Great Basin during May, while abnormal dryness increased in coverage across eastern New Mexico.
- This region is primed for development during early to mid-June due to 30 to 60-day precipitation deficits, the likelihood of above normal temperatures, and little or no rainfall.
Forecast confidence is high for development across the central Great Plains with low to moderate confidence for the remainder of the High Plains region.
- Drought developed or worsened across western Kansas and North Dakota during May, while improving conditions occurred across South Dakota and northeast Colorado.
- Based on increased chances of below normal precipitation and above normal temperatures during June, drought is likely to continue expanding in coverage across the central Great Plains and western Corn Belt. The development is forecast for areas with ongoing 30 to 60-day precipitation deficits.
- Since maximum temperatures are forecast to be in the middle to upper 90s (degrees F) during the first week of June, intensifying drought is likely across western Kansas with rapidly developing drought across northern Kansas.
- Development is also favored across parts of Wyoming where short-term precipitation deficits are increasing.
- Short-term drought is most likely to persist across North Dakota, but elevated probabilities of above normal precipitation during the 6-10/8-14 day time periods preclude additional development across the northern Great Plains.
Forecast confidence is high for the Southern Region.
- Insufficient rainfall, above normal temperatures, and high evapotranspiration rates led to intensifying drought and expansion of abnormal dryness across the southern Great Plains during the spring.
- Additional drought development is favored from Oklahoma southwest into the Texas Panhandle where 30-day precipitation deficits exist.
- Little or no rainfall to start the month along with above normal temperatures are likely to cause this development early in June.
- During May, above normal precipitation (surplus of 2 to 4 inches, or more) resulted in improving drought conditions along the Texas Gulf Coast, southern Texas and the lower to middle Rio Grande Valley.
- Above normal precipitation is likely to persist through at least the first half of June and continue the decrease in drought coverage across those areas of Texas. Also, the GFS ensemble members on May 31 indicate an increasing chance of tropical cyclone development over the western Gulf of Mexico during early June.
- Regardless of TC development, model solutions are in good agreement that the Texas Gulf Coast and southern Texas remain anomalously wet during early to mid-June.
- Although mostly dry weather along with above normal temperatures are likely to increase concern for rapidly developing drought across western Tennessee and northern Mississippi, the GEFS and ECMWF reforecast tools during Week-2 indicate increased chances of above normal precipitation. Therefore, development is not forecast for these areas.
Forecast confidence is low for the Midwest Region.
- Pockets of abnormal dryness have recently developed across parts of Iowa, Minnesota, and Wisconsin.
- However, due to increased chances of above normal precipitation during early June, forecast confidence is not high enough to designate development for any of these abnormal dryness areas.
- Farther to the south across Missouri, there are elevated chances of development where the updated monthly outlook calls for increased chances of above normal temperatures and below normal precipitation. However, precipitation surpluses dating back 90 days and current soil moisture conditions preclude forecasting development across Missouri.
Forecast confidence is high for the Southeast Region.
- Heavy rainfall (2 to 6 inches, locally more) brought drought amelioration to parts of the Florida’s Big Bend along with central and southern portions of the Florida Peninsula.
- A wet start to the month and an increasingly wet climatology during June strongly favor removal of drought across the Florida Peninsula.
- Removal or improvement of drought is forecast from the Florida Panhandle west to Louisiana is consistent with the updated monthly precipitation outlook and a relatively wet climatology.
- A majority of GFS ensemble members (May 31) continue to indicate a tropical cyclone tracking north into the northwest Gulf of Mexico during early June.
- Although 30-day precipitation deficits exist across northwest Alabama and above normal temperatures are likely during June, development is not forecast due to 1 to 3 inches of rainfall during late May and signs that the second week could become wetter.
Forecast confidence is moderate for the Northeast Region.
- Abnormal dryness has recently developed across parts of upstate New York and New England where 30-day precipitation deficits exceed 2 inches.
- Soil moisture is beginning to dry out due to the lack of rainfall and also a brief period of above normal temperatures during the final week of May.
- Based on a likely dry start to the month and above normal temperatures favored during June, development is forecast for southern areas of New Hampshire and Vermont along with northwest Massachusetts.
Forecast confidence is high for Alaska.
- Alaska has remained drought-free since March. Since the updated monthly outlook calls for increased chances of above normal precipitation across southern mainland Alaska and the Alaska Panhandle, drought development is unlikely through the end of June.
Forecast confidence is low for Hawaii.
- Abnormal dryness (D0) expanded to all the Hawaiian Islands during May. Since the updated CFS model at the end of May indicates that suppressed rainfall is most likely across the equatorial Central Pacific, forecast confidence is not high enough to designate any development areas at the monthly time scale.
- The lack of a strong wet signal among the model guidance favors persistence for ongoing drought areas across the Big Island and Molokai.
Forecast confidence is low for Puerto Rico.
- According to the U.S. Drought Monitor (valid May 26), nearly half of Puerto Rico is designated with abnormal dryness (D0) and moderate drought (D1).
- During early June, the heaviest rainfall is likely to be over the western Caribbean Sea. Based on the updated CFS model at the end of May, persistence is favored for ongoing drought areas.