US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 332 PM EDT Wed Jun 02 2021 Valid Saturday June 05 2021 - Wednesday June 09 2021 Hazards: - Flooding possible across portions of the Central/Southern Plains. - Flooding occurring or imminent across portions of the Southern Plains. - Flooding likely across portions of the Northern Rockies and the Northern Great Basin. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Sat-Tue, Jun 5-Jun 8. - Much above normal temperatures across portions of California and the Northern/Central Great Basin, Sat-Sun, Jun 5-Jun 6. - Much above normal temperatures across portions of the Northern/Central Rockies, the Northern/Central Plains, the Upper Mississippi Valley, and the Upper Great Lakes, Sat-Wed, Jun 5-Jun 9. - Much above normal temperatures across portions of the Northeast and the Central Appalachians, Sun-Wed, Jun 6-Jun 9. Detailed Summary: During the medium range period (Saturday, June 5th - Wednesday, June 9th), an upper level cut-off low positioned over the Southern Plains will be the main driving force behind the very active weather forecast for the region. Throughout the weekend and into early next week, moist return flow off the Gulf of Mexico interacting with a stationary boundary will help to enhance instability at the surface over Texas and Louisiana, priming the atmosphere for the development of multiple rounds of convective precipitation. Rainfall totals up to and, in isolated areas, exceeding 2 inches in 24 hours have been forecast for much of southeast Texas and southern Louisiana Saturday and Sunday. As the upper level low tracks to the northeast early next week, the heavy rainfall is forecast to extend northward through eastern Texas on Monday where widespread accumulations of 1 to 2+ inches will be likely. By Tuesday, isolated areas along the Oklahoma/Arkansas, Oklahoma/Texas, and Texas/Louisiana borders are expected to have the greatest chance of heavy rainfall exceeding 1 inch. With the soils heavily saturated in each of these affected locations due to recent above average rainfall, the potential for flash flooding associated with these heavy rain events will be a significant concern. Temperature wise, portions of the western US and an appreciable amount of the Northern Tier will experience much above normal temperatures this weekend and into early next week. Upper level high pressure positioned over the western half of the country will allow daily high temperatures throughout the Intermountain West, Northern Rockies, and the Northern Plains to soar into the 90s and near 100 on Saturday, 15 to 25 degrees warmer than normal. Though a descending upper level trough will moderate temperatures out west after Sunday, the anomalously warm weather is forecast to continue in the Rockies, Plains, and Upper Midwest throughout the remainder of the period. Another area of upper level high pressure is expected to develop over the eastern US on Sunday which will help spread the heat to the Northeast and Central Appalachians where daily highs will likely reach the 80s and, in some areas, the low 90s. Though no hazards have been posted for Alaska, two precipitation events occurring within the medium range period are worth mentioning. The first event is some marginally heavy rainfall over the southwestern portion of the state that is expected to develop Sunday into Monday ahead of a warm front over the Bering Strait. While the current guidance indicates some heavy precipitation with 1 to 1.5 inch rain totals is possible, the models cannot agree as to whether this would occur over the upper Alaskan Peninsula or the southwestern Mainland. Due to the lack of agreement among the models and the fact that these two locations have different thresholds for what is considered hazardous precipitation it was decided that no hazard area would be drawn today. A second event over the southeastern Mainland later in the period has also been decidedly left off of today's graphic because, according to the most recent deterministic model guidance, storm total rainfall may fall short of the hazardous threshold. Seeing that either of these events could become hazardous as the forecast evolves, they will continue to be monitored in the coming days. Finally, it is worth noting that daily high temperatures across the state will hover between 5 and 15 degrees below normal throughout the period. Zavadoff