Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 404 PM EDT Fri Aug 27 2021 Valid 00Z Sat Aug 28 2021 - 00Z Mon Aug 30 2021 ...Severe thunderstorms and flash flooding will be possible across parts of the Northern Plains and Upper Midwest through Sunday morning... ...Parts of the Mid-Atlantic may experience flash flooding and severe weather this evening... ...Excessive and dangerous heat likely throughout much of the Southwest over the weekend... ...Hurricane Ida is forecast to intensify into a major hurricane as it approaches the Central Gulf Coast with landfall likely on Sunday evening, bringing heavy rain to the region and a Moderate Risk of Excessive Rainfall... For a majority of the short-range period one long frontal boundary is expected to remain quasi-stationary as it drapes over the Northeast, Great Lakes, Plains, and central Rockies/Great Basin through Sunday morning. A majority of the activity for the next couple of days along this boundary will be focused on the Upper Midwest and Mid-Atlantic regions. This evening a pair of surface lows over Nebraska and Minnesota are expected to lift northeast into the Upper Midwest along with an associated warm front. As storms develop along the front favorable wind shear and rising dewpoints are expected to be in place to support some of these storms becoming severe with the potential to produce high winds, large hail, and a few tornadoes. Furthermore, high atmospheric moisture will allow for heavy rain rates that could possibility lead to flash flooding. As such, the Storm Prediction Center has issued a Slight Risk of Severe Thunderstorms for portions of Iowa, Minnesota, and Wisconsin, while the Weather Prediction Center has issued a Slight Risk of Excessive Rainfall for a similar area, but extended east to include parts of western Michigan. Both issuances are valid through Saturday morning. With the help of an upper-level trough an occluded boundary is forecast to propagate along the quasi-stationary boundary from the Northern Plains into the Upper Midwest on Saturday. As the upper trough and occlusion interact with parts of the quasi-stationary boundary as they move through these regions, heavy rain and severe weather are expected to impact both the Central Plains and Upper Midwest. Similar to the previous day, strong surface instability, high atmospheric moisture values, and favorable wind shear will create conditions within which flooding, high winds, large hail, and a few tornadoes will be possible. To account for this the Storm Prediction Center has issued an Enhanced Risk of Severe Thunderstorms for portions of southern Minnesota and western Wisconsin within a larger Slight Risk Area extending from Nebraska to the Michigan Upper Peninsula, effective Saturday morning through Sunday morning. Additionally, the Weather Prediction Center has issued a Slight Risk of Excessive Rainfall for portions of northern Iowa, southern Minnesota, and western Wisconsin, valid for the same time period. On top of the activity in the Upper Midwest, severe weather is also expected this evening ahead of a cold front passing through the Mid-Atlantic and the aforementioned occluded boundary in the Northern Plains. In the Mid-Atlantic a well defined Mesoscale Convective Vortice moving slowly through southwest Pennsylvania/western Maryland will encounter an unstable surface layer that will allow for the development of severe thunderstorms that may produce damaging winds. Additionally, high atmospheric moisture values fueling heavy rainfall and wet soils due to the recent passing of Henri earlier this week will make flash flooding possible. These conditions have prompted the Storm Prediction Center to issue a Slight Risk of Severe Thunderstorms and the Weather Prediction Center to issue a Slight Risk of Excessive Rainfall for portions of the Mid-Atlantic through tomorrow morning. Meanwhile, storms capable of producing high winds and large hail will also be possible over the Northern Plains due to modest low-level moisture and strong deep-layer shear, prompting the issuance of a Slight Risk of Severe Thunderstorms for portions of eastern Montana and the western Dakotas through tomorrow morning. Along the central Gulf Coast, high precipitable water values will allow showers and thunderstorms that develop due to shortwave energy at the surface to produce high rain rates with accumulation totals of 3 to 6 inches in isolated areas. These high totals have prompted the Weather Prediction Center to issue a Slight Risk of Excessive Rainfall for parts of eastern Louisiana and extreme southern Mississippi through tomorrow morning. Dangerously hot conditions are forecast to persist in the Desert Southwest throughout the weekend, prompting the issuance of Excessive Heat Warnings for much of south/western Arizona, extreme southeast California, and southern Nevada. With temperatures hitting triple digits and the mid to high 110s in some areas, residents are urged to take precautions to avoid the onset of heat-related illness. Such precautions include: drinking plenty of fluids, staying out of the midday sun, seeking air-conditioned locations, and avoiding outdoor activities. Heat Advisories are also in effect for portions of the Middle Mississippi and Western Ohio Valleys, where high temperatures are forecast to be in the upper 90s and low 100s on Saturday. At the end of the period all eyes will be on the Gulf Coast as Hurricane Ida moves northwestward through the Gulf of Mexico towards its projected landfall location of Louisiana, intensifying into a major hurricane along its way. According to the latest forecast from the National Hurricane Center, Ida is expected to make landfall Sunday evening, bringing extremely heavy rainfall and dangerous maximum sustained winds around 120 miles per hour to coastal Louisiana and the surrounding area. Hurricane and Storm Surge Watches are currently in effect for much of southern Louisiana and extreme southern Mississippi.The Weather Prediction Center has also issued a Moderate Risk of Excessive Rainfall for southeast Louisiana and extreme southern Mississippi effective Sunday morning. Widespread life-threatening flash and urban flooding will be very likely. For the latest information on Hurricane Ida, visit nhc.noaa.gov. Zavadoff Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php