Tools used in the U.S. Monthly Drought Outlook (MDO) included the official Climate Prediction Center (CPC) updated temperature and precipitation outlooks for July 2016, various short- and medium-range forecasts and models such as the 7-day precipitation totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC Extended-Range Forecasts (ERFs), Weeks 3 and 4 experimental outlooks, the NAEFS precipitation outlooks, dynamical models including the CFSv2 and GFS, climatology, and initial conditions.

During the past several weeks, mostly dry weather continued to reduce streamflow levels, leading to the expansion of abnormal dryness (D0) in northwestern California, southwestern Oregon, and most of Washington, with D1 expansion into northeastern Oregon. July is normally dry in the Northwest, but with the early and rapid snow melt that occurred in the Cascades this Spring, drought impacts have gradually increased during the summer months. Little precipitation is anticipated during the next week, and the CPC 6-10 and 8-14 day outlooks also indicate enhanced chances for sub-median precipitation, as well as the July updated precipitation outlook. One bit of good news is that temperatures are expected to average below normal during the first part of July which may somewhat temper the effects of anticipated dry weather. However, with nearly all the precipitation tools pointing toward dryness and the early snowpack melt off has led to much below normal stream flows, drought development is likely for western (coastal) areas that have higher precipitation normals (and larger deficits) than central and eastern (interior) areas - which have also received recent unseasonably heavy rains. 
Forecast confidence for the Northwest is moderate to high.

July is a dry and warm time of year across much of California and the western Great Basin, but farther to the southeast, the onset of the summer monsoon typically brings abundant showers to the Southwest, especially in Arizona, New Mexico, and southwestern Texas. In particular, southeastern Arizona and southwestern New Mexico receive 15-25% of their annual precipitation during July, and 50-67% of their annual rainfall during July-September. During June, unseasonably heavy rains fell on most of southern and eastern Nevada that allowed for some improvement to this area. Showers have recently increased across the Southwest, and the 7-day QPF is forecasting decent rains for Arizona, western New Mexico, Utah, and Colorado. The CPC 6-10 and 8-14 day forecasts call for equal chances (normal) of precipitation, while weeks 3-4 and the updated July precipitation outlooks have enhanced odds for above-median precipitation in Arizona and New Mexico. In addition, temperatures should be tempered by the increased cloudiness, humidity, and showers. With the tilt toward near and above-median rainfall and the high July climatology totals for Arizona and New Mexico, improvement is expected by the end of July for most of Arizona and New Mexico, while persistence is highly-likely for California and western Nevada. 
Forecast confidence for the Southwest quadrant of the CONUS is high (California and western Nevada) and medium to high (Arizona and New Mexico).

Abnormal dryness and drought has lingered across the northern Rockies (northwestern and south-central Montana), and expanded in the north-central High Plains (southeastern Montana, northeastern Wyoming, western South Dakota, southwestern North Dakota) and north-central Great Plains and upper Midwest (northeastern South Dakota, southeastern North Dakota, and western Minnesota). In the latter two regions, the sudden expansion was due to the combination of heat and dryness (30-day precipitation less than half of normal and temperatures averaging more than 5 degF above normal) and an uptick in impacts (wild fires and declining agricultural conditions). July is a climatologically wet time of year for the northern Plains and upper Midwest, but drier toward the west (northern Rockies). Little precipitation and above normal temperatures are anticipated during the next week, while the 6-10 and 8-14 day outlooks favor above-median precipitation in eastern areas and below-median rainfall in western regions, and near normal in-between. ERF temperatures favor above-normal readings except in northwestern Montana (subnormal). During the Week 3-4 period, the dynamical model guidance is mixed, with the CFS wetter than the ECMWF, but also warmer than the European. The updated July outlook maintains enhanced chances for sub-median precipitation in the northern Rockies. Therefore, based on climatology and the forecasts for drier conditions in the west and somewhat wetter weather in the east, persistence and expansion (development) is favored for the northern Rockies and north-central High Plains, and improvement for the drought area in the eastern Dakotas and western Minnesota.  
Forecast confidence for the northern Rockies, north-central Plains, and upper Midwest is moderate.

During the past 30 days, less than 50 percent of normal precipitation fell on eastern Nebraska, western and southern Iowa, eastern Kansas, northern Missouri, and western Illinois, while temperatures also averaged more than 4 degF above normal. This led to the expansion of abnormal dryness (D0) on the U.S. Drought Monitor released June 28, with D1 in southeastern Iowa and northeastern Missouri and small D1 areas in south-central Nebraska and western Illinois. Abnormal dryness had also developed in Indiana and Ohio by mid-June, raising concerns of a possible Midwest and Plains flash drought, but recent rains erased much of this. During the next week, a band of heavy rain (2-6 inches) is expected to fall from eastern Colorado into the central Appalachians, with northern Missouri expected to receive the greatest amounts (more than 5 inches). The 6-10 and 8-14 day ERFs maintain favorable odds of above-median precipitation in the Midwest, while there was no help from the weeks 3-4 and updated July precipitation outlooks (both EC). Based on the potential for heavy rains during the first week of July and into mid-month, improvement is forecast for central Nebraska, southeastern Iowa, northwestern Missouri, and western Illinois. Accordingly, a Midwest July flash drought that looked possible in mid-June now appears unlikely.
Forecast confidence for the central Great Plains and Midwest is moderate to high.

As mentioned above, the recent dryness and warmth also extended southward into parts of the south-central Great Plains and lower Mississippi Valley, with D0 added to the USDM during the past 2 weeks in southeastern Kansas, east-central Oklahoma, and western Arkansas, along with a small D1 in central Oklahoma. The 7-day QPF band of heavy rain sharply cut off across northern Oklahoma and southern Missouri, while the 6-10 and 8-14 day ERFs had slight tilts toward sub-median rainfall for the south-central Plains, but high odds for above-normal temperatures. However, if this band shifts southward, improvement would be quite likely, raising the uncertainty in this drought outlook. But for this forecast, the assumption is that the heaviest rains will stay north of Oklahoma, thus additional development was expanded in Oklahoma. In Texas (currently drought-free), the QPF was basically dry the first week of July, with the ERFs both favoring sub-median rainfall (highest odds in the southeast) and greatly enhanced above-normal temperatures. Although Texas has been quite wet most of this year, parts of south-central Texas were below normal at 30-days, and only slightly above-normal at 60-days. With such dry and warm weather expected during the first half of July and maybe longer, the possibility of flash drought in Texas would be greatest where surpluses are lowest, namely in south-central sections, thus development was added here.
Forecast confidence for the southern Great Plains is low to moderate. 

Precipitation shortages extended out to 6-months in the Tennessee Valley, Southeast, and southern Appalachians, with the driest conditions (50-75% of normal) at 60-days found from Mississippi eastward into northern Georgia and southwestern North Carolina. Recent heavy rainfall in Tennessee trimmed away some of the drought there, but drier conditions to the south expanded abnormal dryness and drought across central sections of Mississippi, Alabama, and Georgia, and the western Carolinas. The 7-day WPC rainfall forecast has the heaviest totals mainly north and east of the drought area. A similar pattern is forecast for the Week-2 period, with above-median precipitation likely for northern and eastern portions, and equal chances in southern and western areas. Temperatures, however, are strongly tilted toward above-normal throughout the region. During the Week 3-4 period, dynamical model solutions are mixed, with the CFS maintaining a dry pattern and the ECMWF forecasting surplus rainfall across the Southeast and Delta. The updated CPC monthly outlook has EC for the Southeast. Therefore, with the best chances for sub-median precipitation in southern and western sections and lower odds (or above-median chances) in northern and eastern areas, drought development is forecast for eastern Louisiana and south-central Mississippi, while remaining areas of drought are forecast to persist. The best chances for any improvement would be across Tennessee and the western Carolinas, but with too much uncertainty and the longer time frame of the drought (out to 6-months, with 5-10 inch deficits), persistence remains the favored outcome through the end of July.
Forecast confidence for the Southeast and lower Mississippi Valley is moderate.

During the last month, subnormal precipitation fell on most locations in the northeastern quarter of the Nation, expanding abnormal dryness across much of New England and the eastern Great Lakes region, while moderate drought (D1) also developed in parts of New York, New Jersey, Connecticut, Massachusetts, Vermont, New Hamshire, and Maine. USGS 7-, 14-, and 28-day average stream flows dropped below the tenth percentile, with several sites in eastern New England experiencing record low values.  In contrast, ample rains improved conditions by one category in the mid-Atlantic (southern Pennsylvania, western Maryland, and northern West Virginia), but also caused devastating and deadly flooding in central West Virginia. The recent dryness and drought in New England actually goes back to much longer time scales (1-2 years) as long-term deficits have not been completely erased. If it were not for the near to subnormal temperatures since April resulting in low evapotranspiration rates, drought impacts probably would have been more severe and widespread. During the next week, light rainfall (less than 0.5 inches) is expected across the region, with larger totals to the south (mid-Atlantic). The 6-10 day precipitation outlook also favors sub-median totals, but the 8-14 day ERF tilts toward above-median rainfall. The weeks 3-4 (CFS and ECMWF) have no tilt either toward dry or wet, as does the update July precipitation outlook (EC). Temperatures at all time scales favor somewhat above-normal readings. With the growing short-term deficits (5-10 inches at 90-days), very low stream flows, warmer time of year (with above-normal temperatures favored), and expected dry start to the month, development was expanded in the eastern Great Lakes region and across eastern New England, with persistence in the existing D1 areas. However, a factor that reduces forecaster confidence in the Northeast is the evenly-distributed precipitation climatology which usually makes it difficult for a drought to become widespread, extreme, and long-lasting.
Forecast confidence for New England and eastern Great Lakes region is moderate to high.

No drought development is anticipated across Alaska, although northern portions were depicted as D0 in the latest June 28 DM. But with the 6-10 and 8-14 day ERFs and the updated July precipitation outlook favoring increased odds for above-median precipitation, it is possible the D0 areas may be gone by July 31. In Hawaii, increased June shower activity led to improvement across the islands, and with a summer rainfall maximum on the leeward side of the Big Island, continued improvement is forecast there. However, drought on the remaining islands leewards are expected to persist. Across Puerto Rico, the past 30-days brought surplus rains to western and eastern areas, but south-central sections received about half of normal. As the Caribbean and Atlantic tropical season continues and approaches its early September peak, shower activity should also increase across the island during July now that El Nino has faded. This expected increased rainfall should be enough to remove the D1 on Puerto Rico. 
Forecast confidence is moderate for Alaska, Hawaii, and Puerto Rico.

Forecaster: David Miskus

Next Monthly Drought Outlook issued: July 31, 2016 at 3:00 PM EDT