Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 334 AM EDT Sat Jul 17 2021 Valid 12Z Sat Jul 17 2021 - 12Z Mon Jul 19 2021 ...Severe thunderstorms and numerous instances of flash flooding possible across the Northeast today... ...Excessive heat found throughout the Northern Plains and Intermountain West... ...Potential for dry lightning over central and northern California on Sunday could lead to conditions capable of producing new wildfires... A slow moving cold front is continuing to meander eastward between the Lower Great Lakes and Southern Plains this morning, while producing scattered showers and thunderstorms. As it reaches the Northeast today it is expected to run into a very warm and humid airmass, sparking numerous thunderstorms. Much of the Northeast has experienced a waterlogged first half of July, leaving many low-lying areas extremely susceptible to flash flooding. Thunderstorms will be capable of producing 1 to 3 inches of rain, with locally higher amounts across areas that have seen triple their normal rainfall so far this month. A Moderate Risk (level 3/4) of Excessive Rainfall has been issued for portions of southern New England and the Northeast, where the combination of wet soil and heavy rain is most likely to cause flash flooding. Additionally, a few storms may turn severe between western Connecticut and northeast Maryland with damaging wind gusts and isolated tornadoes possible. For the most part, the heavy rain threat is expected to come to an end on Sunday for the Northeast as the system reaches the coastline. Isolated downpours and flash flooding are expected to remain possible further south across the Southeast, Lower Mississippi Valley, and Southern Plains through the end of the weekend. For the Southwest, additional showers and thunderstorms associated with the summer monsoon could produce an isolated flash flood threat this weekend, but activity is forecast to be slightly weaker than earlier this week. A building upper-level ridge over the western U.S. will lead to temperatures soaring well above average across the Northern Plains and Northern Great Basin for the next several days. Highs into the triple digits can be expected throughout eastern Montana and lower elevations of the Intermountain West. Excessive Heat Warnings/Watches and Heat Advisories have been issued. Meanwhile, high temperatures into the low-to-mid 90s are forecast throughout the Northern Plains and into parts of northern/central Minnesota. This heat wave will exacerbate the severe to exceptional drought currently found across the region, which in combination can make for an environment ripe for wildfires to spread uncontrollably. Speaking of wildfires, dry lightning could be a concern for parts of northern and central California on Sunday as monsoonal moisture enters from the south, but produces very little rain. If thunderstorms do form, extremely dry fuels struck by lightning could produce new fires. Fire Weather Watches have been issued. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php