US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 302 PM EDT Thu Jun 20 2019 Valid Sunday June 23 2019 - Thursday June 27 2019 Hazards: - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Sun-Mon, Jun 23-Jun 24. - Flooding possible across portions of the Central Plains, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley. - Flooding occurring or imminent across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Central Great Basin and the Ohio Valley. - Excessive heat across portions of the Southern Plains, Sun-Mon, Jun 23-Jun 24. - Excessive heat across portions of the Southeast and the Mid-Atlantic, Sun-Tue, Jun 23-Jun 25. - Much below normal temperatures across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, the Central Plains, and the Southwest, Sun, Jun 23. Detailed Summary: A strong short wave trough and associated cold frontal boundary progressing across the Plains and Mississippi Valley will bring the potential for heavy rainfall to sections of the central U.S. during Sunday and Monday. Propelled by a southerly low-level jet, there will be plenty of instability and deep Gulf moisture ahead of the front, and as the front moves into the Plains, expect widespread pre-frontal convection to fire during Sunday. The model guidance is in general agreement that the heaviest precipitation will fall over the central Plains into the mid-Mississippi Valley with the strongest mid-upper level dynamics. From Sunday into Monday morning, rainfall totals of 2-3 inches are likely across this region, with locally heavier amounts. The upper trough and main surface low on the front will lift northeastward into the upper Mississippi Valley/western Great Lakes region on Monday. Some guidance is indicating the potential for heavy rain along and west of the low track, but there are enough differences in the models to preclude adding a hazard area at this time. Farther south, the front will tend to slow down or stall out across the lower Mississippi Valley and southern Plains. While the overall lifting mechanisms are bit weaker along this southern end of the front, the continued presence of deep moisture and instability along the front will still support at least scattered showers and thunderstorms. Lighter winds aloft will result in slower-moving cells and the potential for locally heavy rainfall over the lower Mississippi Valley. Farther west, temperatures will remain much cooler than normal over the central Rockies on Sunday, and there may be some residual snow early in the day at the highest elevations of Colorado under the upper trough. With the trough lifting out late Sunday, expect temperatures to quickly moderate during the early part of next week. Over southern Texas, hot and humid weather will continue through the period. Current heat index forecasts show values approaching 115F both Sunday and Monday, and relatively high heat indices will persist through midweek. At the moment, think temperatures may drop off slightly after Monday, but confidence is low, and we may need to extend this hazard beyond the first two days of this forecast period. Over the Southeast and mid-Atlantic region, persistent mid-upper level ridging will maintain very warm and humid conditions from Sunday through Tuesday. Heat indices are forecast to approach 105-110F across eastern South Carolina, southeastern North Carolina and eastern Georgia (inland areas only as the sea breeze should keep the coast cooler). The ridging will break down later Tuesday, so temperatures should moderate somewhat Wednesday through Thursday. No hazardous weather is anticipated for Alaska through the medium-range period. Klein