Since mid-June, drought coverage and intensity increased across the Plains and Southwest, especially in eastern Montana and the Dakotas, exacerbated by periods of intense heat, windy conditions, and low humidity. Drought also increased in southwestern Alaska and on the Big Island of Hawaii. In contrast, ample rains and near- to sub-normal temperatures in the eastern half of the Nation eliminated drought (D1 or drier) east of the Mississippi River.  With a mixture of drought improvement and deterioration during the past 4 weeks, coverage increased to 9.1% in early July, which is still low by historical standards, while D3 coverage went from 0% to almost 2%. As of July 11, there were still no areas of D4.
The latest ENSO Advisory favors ENSO-neutral conditions into the Northern Hemisphere winter 2017-18 (50-55% chance). In addition, this period (summer into fall) is notoriously difficult to predict due to variable summertime convection and the wild card Atlantic hurricane season. Furthermore, there was little guidance in the longer-term statistical and dynamical precipitation models as they were limited in their probability, areal coverage, and consistency, therefore much of this SDO was based upon climatology, current conditions, and short-term forecasts, along with any slight tilts in the 1- and 3-month precipitation and temperature outlooks. In the Southwest, late July, August, and early September are climatologically wet due to the southwest monsoon, with some parts of Arizona and New Mexico receiving up to 50% of its annual rainfall during July and August.  With recent rainfall, wet short-term (7-day QPF, 6-10 and 8-14 day ERFs) forecasts, and the August precipitation outlook favoring enhanced rains, improvements were made in the Four Corners region. Persistence was left in southern California and extreme southwestern Arizona as the first area is typically dry while the latter region is experiencing long-term drought and lower probabilities for enhanced August rainfall. In the southern Plains, a favorably wet climatology during September into October plus a tilt toward above-median ASO rainfall was enough for a forecast of improvement in Texas and Oklahoma. Farther north, with no signal (EC) in the 1- and 3-month precipitation outlooks, climatology, recent conditions, and short-term forecasts were used in the northern half of the Plains and upper Midwest, resulting in a mixed forecast with low confidence. Accordingly, improvement was more likely in southern and eastern areas (KS, NE, IA, eastern Dakotas, MN) while persistence was forecast for northern and western sections (MT, western Dakotas), along with development in western Montana where D0 existed and the ASO precipitation outlook tilted slightly below-median while odds for above-normal ASO temperatures were good. In Alaska, the summer months are typically wet, and with the ERFs, 1- and 3-month precipitation outlooks favoring enhanced totals, drought removal is likely. In Hawaii, rainfall normally increases during the fall along windward sites, and with an active Pacific hurricane season and a wild card for enhanced rainfall on eastern sides, improvement was forecast for windward areas with persistence in leeward locations.

Forecaster: David Miskus

Next Seasonal Outlook issued: August 17, 2017 at 8:30 AM EDT