US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 403 PM EDT Fri Jun 26 2020 Valid Monday June 29 2020 - Friday July 03 2020 Hazards: - Heavy rain across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Mon, Jun 29. - Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Tue-Wed, Jun 30-Jul 1. - Flooding possible across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley. - Flooding occurring or imminent across portions of the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Middle Mississippi Valley and the Upper Mississippi Valley. - Much above normal temperatures across portions of the Upper Mississippi Valley and the Northern Plains, Mon-Tue, Jun 29-Jun 30. - Much above normal temperatures across portions of the Great Lakes and the Upper Mississippi Valley, Wed-Fri, Jul 1-Jul 3. - Enhanced wildfire risk across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, and the Southwest, Mon, Jun 29. Detailed Summary: An unusually intense upper level low closing off over the western U.S. will be the primary driver for hazards across the contiguous U.S. during this Day 3-7 period. This system will amplify as it slides from the Pacific Northwest on Sunday into the northern Rockies and northern Intermountain Region by early Monday. Strong winds rotating through this trough combined with a very dry air mass ahead of a cold front will support an enhanced risk of wildfires over the Southwest and central Great Basin/Rockies during Monday. Conditions should improve on Tuesday as the system lifts into southern Canada. To the north and west of the upper low, moderate to heavy rainfall that starts on Sunday is likely to continue through much of Monday across sections of western Montana and northern Idaho. Maximum rainfall amounts will generally range from 1-1.5 inches on Monday, and combined with Sunday's totals, 2 day amounts of up to 3 inches are possible. A lack of significant air mass instability should keep rainfall rates from being excessive, but the amounts support at least some local flood threats. On Tuesday, the upper low will lift into southern Canada and slowly drag a trailing trough into the Plains states. Moisture streaming northward from the Gulf of Mexico combined with a a well-defined surface front will bring an increasing threat for heavy showers and thundershowers to far eastern Montana and the Dakotas, with this activity only slowly pushing eastward through Wednesday. There have been some differences among the model guidance with the degree of eastward progression, so confidence is lower for the heavy rainfall hazard in this region versus the one over Montana/Idaho for Monday. Upper ridging out ahead of the trough will bring much above normal temperatures (on the order of 12-15 degrees) across the eastern Dakotas on Monday before the rains become organized on Tuesday. Above to much above normal temperatures will extend into northern/central Minnesota through Wednesday, though increasing clouds and a threat for showers will allow temperatures to moderate across much of western Minnesota by Wednesday. However, farther east over Michigan's Upper Peninsula and northern sections of the Lower Peninsula, strong upper ridging extending southward from James Bay should result in mostly dry and very warm conditions (upper 80s to near 90 degrees) through the middle to latter part of next week. Elsewhere, a combination of temperatures near or above 100 degrees and dew points in the 70s will push heat indices to near 110 degrees across portions of southern Texas late this weekend through early next week. Was debating on adding a threat area, but opted against since the temperatures are fairly close to normal. Over Alaska, a fairly strong upper level low will push across the mainland early next week, bringing cool and unsettled conditions. Temperatures were not quite cool enough (10-15 degrees below normal) and rainfall not heavy enough (.75-1 inch) to meet criteria, but it's still a fairly anomalous pattern. By mid-late week, there are signs that a storm system will move through the Aleutians or Bering Sea, which could bring locally heavy rain to the Aleutian chain and breezy conditions to the western mainland. However, with fairly notable differences among the models, confidence in strength and placement of any system is very low this far out. Klein