607 FXUS01 KWBC 040811 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Fri Sep 04 2026 Valid 12Z Fri Sep 04 2026 - 12Z Sun Sep 06 2026 ...Rounds of strong to severe thunderstorms with locally heavy rain across the lower Great Lakes to the Mid-Atlantic will slowly shift southward during the Labor Day weekend... ...Monsoonal moisture could trigger scattered flash flooding in parts of Arizona/New Mexico for the next few days... ...Heat persists across the midsection of the country as cooler air expands further into the West Coast and the Northeast... An upper-level trough deepening over southeastern Canada will sustain a corridor of strong to severe thunderstorms stretching from the upper Midwest to the Mid-Atlantic through the next couple of days. The cool air mass associated with the trough is forecast to advance gradually into the northeastern U.S. against the heat dome anchored over the midsection of the country through the Labor Day weekend. This will shift the best chance of severe weather and heavy rain southward from the lower Great Lakes to the Mid-Atlantic today, mainly across the southern Mid-Atlantic on Saturday. By Sunday morning, temperatures will dip into the 40s and 50s across much of the interior Northeast. Across the South, ample moisture stretching across the Gulf Coast region to Florida, where weak disturbances travel along a trough of low pressure, will trigger scattered thunderstorms that could cause instances of flash flooding into the Labor Day weekend. Meanwhile, monsoonal moisture will be prevalent across mainly Arizona and New Mexico where showers and thunderstorms will be most active during the late-day hours with locally heavy rain over the next several days. WPC maintains a Slight Risk (level 2/4) of excessive rainfall straddling the Arizona-New Mexico border for today. Urban areas and also dry washes and burn scars will be most vulnerable to flooding. Farther north, a relatively deep upper-level low for this time of year will continue to push cool and unsettled weather through the Northwest, where widespread showers and embedded thunderstorms have a nonzero chance of causing locally flooding issues by Saturday and into early Sunday. Temperatures continue to be well above average for September across most areas east of the Rockies into the Labor Day weekend as an upper-level ridge remains anchored over the midsection of the country. Heat Advisories are widespread from the south-central Plains into the Mid-Atlantic, with Extreme Heat Warnings centered in the Mid-Mississippi Valley, for temperatures and heat indices well into the 90s and 100s. Warm low temperatures will cause added heat stress to vulnerable people and infrastructure, while also setting widespread records for warm minimums. Major to Extreme HeatRisk is widespread. See WPC's Key Messages for more information on the heat. The Northeast to Mid-Atlantic should gradually see some heat relief as a cold front progresses south late week into the weekend, but the central U.S. will remain hot. Meanwhile, temperatures will be below average across the West given the upper low overhead. In fact, below freezing morning temperatures are expected across the higher elevations as far south as northern California. Kong/Tate Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php Extreme Heat Key Messages available at: https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png $$