Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 221 PM EDT Wed Sep 29 2021 Valid 00Z Thu Sep 30 2021 - 00Z Sat Oct 02 2021 ...Heavy rain and the threat of isolated flash flooding found across parts of the Central Plains and Lower Mississippi Valley today before the bulk of the activity shifts into the Southern Plains on Thursday... ...Well above average temperatures continue across the Midwest as cooler air surges through the western half of the country and lingers in the Northeast/Mid-Atlantic... The Northeast will be dominated by a compact cold upper-low for the next few days; the cold front has already dropped south into the eastern Carolinas and so below average temperatures will remain entrenched through the short-term forecast period with Wed, Thursday and Friday highs in the 50s and 60s (about 5-15 degrees below normal) for much of New England while upper 60s and 70s return to the Mid-Atlantic. A well defined Pacific cold front continues to track across the Rockies ushering in well below average cold air behind it centered on the central Rockies today and shifting into southern Rockies and southern High Plains Thursday into Friday, respectively. Temperatures will be 10-20 degrees below average for day-time highs, though more moderate/average for lows. In fact, the cold has lead to a few locations with Freeze Warnings across Northern California, Southern Oregon, the western Snake River Plain of Idaho, and portions of the desert of southwest Nevada (northwest of Las Vegas). Along and east of the frontal zone will exist the majority of active and potentially dangerous weather. Strong return flow in response to the approaching upper-level trof and cold front will allow a surge of moisture and well above normal temperatures across the Plains. This is particularly noticeable with near record heat across the Upper Midwest toward the Great Lakes where today's temps of the upper 80s will be 20-25 degrees above normal across eastern Dakotas, Minnesota, and portions of Iowa. While not as anomalous as further north, temps into the low 90s across the Mid-Mississippi River Valley are still 10-20 degrees above normal. Thursday and Friday, the front will be still very slow moving toward the east and temperatures will remain above normal but reducing slightly with highs in the 70s and low 80s Thursday and Friday. Further south, stronger return moisture off the western Gulf, along with mid-level dry air coming out of the Mexican Plateau will support daily rounds of stronger, organized convection along/ahead of the cold front and dry line. Today, convection will remain more focused across the Central Plains where a Marginal Risk (level 1/4) of excessive rainfall suggests heavy rainfall with the potential of isolated flash flooding conditions. A flash flood watch has been issued for a few counties in northwest Kansas based on this risk. By Thursday, the strength of the return flow, moisture increases have resulted in more focused and generally slower moving thunderstorms increasing the heavy rainfall and flash flooding risk to a Slight Risk (level 2/4) across the Edwards Plateau of West Texas into the Hill country of central Texas; though the Marginal extends as far north as Omaha, Neb and southwest Iowa, with similar domains of the Southern Plains under the Marginal and Central Texas at greater level 2 (Slight Risk) for Friday. Another strong storm will impact the Northwest by early Thursday will keep temperatures recharging the cooler temperatures with low to mid-60s expected for the Northwest Thursday into Friday. This storm will also produce several inches of rain across the Olympic Peninsula and northern Cascades, a clear and welcome indicator of the change in season given summer dryness. Gallina Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php