US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 314 PM EDT Mon Jun 03 2019 Valid Thursday June 06 2019 - Monday June 10 2019 Hazards: - Heavy rain across portions of the Central/Southern Plains, the Lower and Mid-Mississippi Valley, the Tennessee and Ohio Valleys, the Central and Southern Appalachians into the Mid-Atlantic and parts of the Southeast, Thu-Mon, Jun 6-Jun 10. - Heavy rain across portions of the Northern Plains and central Florida, Sat-Sun, Jun 8-Jun 9. - Heavy snow across portions of the Northern Rockies, Fri-Sat, Jun 7-Jun 8. - Flooding occurring or imminent across portions of the Central Plains, the Lower Mississippi Valley, the Central Great Basin, the Northern Plains, the Great Lakes, the Northern Great Basin, the Middle Mississippi Valley, the Upper Mississippi Valley, the Southern Plains, and the Ohio Valley. - Excessive heat across portions of the Southern Texas, Sat-Mon, Jun 8-Jun 10. - Excessive heat across portions of the Southeastern Plains, Thu-Mon, Jun 6-Jun 10. - Much below normal temperatures across portions of the Northern High Plains, the Northern Rockies, parts of the Great Basin, including parts of Northern California and parts of the Pacific Northwest, Fri-Sat, Jun 7-Jun 8. Detailed Summary: Models and ensemble means are in excellent agreement on depicting an upper-level trough exiting the southern Rockies on Day 3 (Thu Jun 6) and then moving rather slowly eastward into the mid-Mississippi by the weekend. This pattern by itself would represent a heavy rain threat for the central Plains and the lower to mid-Mississippi Valley. The more uncertain part of the forecast has to do with a tropical system currently organizing in the southern Gulf of Mexico that could be drawn northward into the western Gulf coast region ahead of the slow-moving upper trough. The GFS has been taking this system on a more northwesterly track toward northeastern Mexico. On the other hand, the ECMWF and particularly the Canadian model have been taking the system northward, tracking it near/along the Texas coast. Since the forecast track would favor convection to develop on the eastern half of the circulation over the Gulf of Mexico, the eastern track solution (as depicted by the ECMWF for example), cannot be ruled out. This would likely enhance the rainfall amounts near and just east of the eventually track of the system. In any event, a heavy rain threat is expected to associate with the slow-moving upper trough from the central Plains eastward into the lower and mid-Mississippi Valley including parts of the Ohio Valley for late this week into the weekend. From Sunday into Monday, the heavy rain could spread into much of the Mid-Atlantic region although the confidence is not high at this point. This heavy rain potential is related to the slow-moving upper trough beginning to interact with a back-door cold front arriving from New England during the weekend. This is a scenario that has been introduced by the ECMWF in the most recent runs but not yet apparent in the GFS runs. In the western U.S., a rather cold and deep upper-level trough for June is indicated by the guidance for the Northwest through much of the medium-range period. This upper trough will likely bring much cooler than normal temperatures for a large portion of the Northwest into the northern Rockies and the Great Basin through next Monday (Jun 10). In fact, temperatures will appear to be cold enough to support snow in June for the higher elevations of the northern Rockies. The ECMWF has been the more consistent model in forecasting this upper trough. Elsewhere, excessive heat is forecast to spread from far southern Texas northeastward into eastern Texas during the weekend behind the potential tropical system. Heat indices are forecast to exceed 105 degrees in these area through the weekend. By next Monday, the excessive heat might retreat somewhat back into southern Texas. No hazardous weather is anticipated for Alaska through the medium-range period. Kong