US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 414 PM EDT Tue Jun 23 2020 Valid Friday June 26 2020 - Tuesday June 30 2020 Hazards: - Heavy rain across portions of the Central Plains, the Great Lakes, the Middle Mississippi Valley, the Southern Plains, and the Upper Mississippi Valley, Fri, Jun 26. - Heavy rain across portions of the Great Lakes, the Northeast, the Central Appalachians, and the Ohio Valley, Sat, Jun 27. - Heavy rain across portions of the Central Appalachians and the Ohio Valley, Sat-Sun, Jun 27-Jun 28. - Heavy rain across portions of the Northern Plains, the Northern Rockies, the Middle Mississippi Valley, the Northern Great Basin, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Sun-Mon, Jun 28-Jun 29. - Heavy rain across portions of the Northern Plains, Tue, Jun 30. - 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 Mid-Atlantic, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Middle Mississippi Valley and the Upper Mississippi Valley. - High winds across portions of the Central Rockies, the Central Great Basin, California, the Northern Great Basin, and the Southwest, Sun, Jun 28. - Much above normal temperatures across portions of California, the Central Great Basin, the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Fri, Jun 26. - Much above normal temperatures across portions of the Central Plains, the Upper Mississippi Valley, and the Northern Plains, Sun-Mon, Jun 28-Jun 29. - Heavy rain across portions of northwest mainland Alaska, Sat-Sun, Jun 27-Jun 28. - High winds across portions of northwest coastal Alaska, Sat-Sun, Jun 27-Jun 28. Detailed Summary: The last five days of June are shaping up to be quite wet from the northern Rockies to the northern Appalachians. The period starts with heavy thunderstorms in south-central Texas and portions of the central Plains on Friday. Farther north, an area of low pressure over the Midwest on Friday heads east to the northern Great Lakes and southern Ontario on Saturday. Rounds of showers and thunderstorms should sweep across these regions with localized flash flooding and severe weather possible from eastern Iowa to northern New York. The cold front associated with this low pressure system could also trigger strong thunderstorms and heavy rain in the Ohio Valley on Saturday. Showers and thunderstorms remain in the forecast over western Pennsylvania and northern West Virginia due to a nearby frontal boundary and upslope flow on Sunday. By Sunday and Monday, a weak upper-level disturbance will cut beneath a building upper level ridge over southern Canada. This feature may lead to more opportunities for heavy rainfall and strong thunderstorms from the Midwest to the Ohio Valley. To the west, abnormally hot conditions will continue in parts of the Pacific Northwest and northern California on Friday before temperatures begin to cool off this weekend. This is because of an intensifying upper-level low tracking over the Pacific Northwest that looks to move southeastward to parts of the Northern Rockies early next week. The upper-level low will pull in moisture from the Pacific and the Plains into the Northern Rockies. Heavy rain with embedded thunderstorms should develop over the region. Temperatures aloft are so cool for the time of year, however, that some precipitation may fall in the form of snow in the higher elevations of northern Idaho, western Montana, and northwestern Wyoming. To the south, a strong southwesterly jet sets the stage for potential high winds in the Great Basin and Intermountain West. Given recent history with dry humidity levels and wildfires, there could also be a heightened risk for fire weather in these regions early next week. Downstream of the upper trough, much above normal temperatures are possible in the Northern Plains and Upper Midwest by the end of the month, along with a threat for heavy rain and thunderstorms in the Dakotas. Over Alaska, a low pressure in the Gulf of Alaska will dissipate as it moves eastward to the Alaska Panhandle on Friday. Expect rain over parts of the Aleutians with some showers as far north as the Alaska Ridge, but totals look to remain below thresholds. However, guidance is gravitating towards a more robust upper trough diving from the East Siberian Sea to the northwest coast this weekend. Rainfall totals have increased on most of model guidance with the Baird mountains most at risk for heavy rainfall. In addition, a tight pressure gradient could lead to strong winds along the Seward Peninsula coast. There will be more chances for showers across much of the mainland as the upper trough tracks over the state, while simultaneously ushering in a fairly chilly air-mass for late June. Mullinax