Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Mon Oct 23 2023 Valid 12Z Mon Oct 23 2023 - 12Z Wed Oct 25 2023 ...Heavy rain chances and flash flood potential increases across the Southern Plains early this week... ...Some locally heavy rainfall possible for the Upper Great Lakes Tuesday... ...Impactful snow to enter parts of the Northwest, Northern Rockies, and northern High Plains on Tuesday... After a generally quiet period of weather for much of the country, the pattern gets more active this week including a couple regions of locally heavy rainfall with flash flood potential and an early season winter storm. An initial upper-level low dropping well southward into northern Mexico as a ridge amplifies over the Southeast will help to focus southerly flow over the Southern Plains. The potent upper-level dynamics as well as ample moisture advecting northward, enhanced by the remnants of Norma from the eastern Pacific, are expected to trigger numerous showers and thunderstorms from the Texas Big Bend vicinity northeastward through northwest Texas into Oklahoma and eastern Kansas Monday and Tuesday. Slight Risks for Excessive Rainfall (level 2/4) are in effect both days as the anomalously high moisture, as well as the stagnant pattern with storms repeating over the same area, will lead to the threat of locally heavy downpours/rainfall totals and the risk of some scattered flash flooding. Rain chances look to continue this week beyond the current forecast period as the upper low is forecast to progress slowly and a stormy pattern remains in place. High temperatures will generally be above average from the Southern Plains into the Southeast under the influence of the upper-level ridge, with 70s and 80s forecast. Temperatures will be around average to the west under the upper-low, with 60s and 70s for California and the Great Basin and 80s for the Desert Southwest. Meanwhile, further north, some lighter showers are expected Monday along a cold front pushing southward across the Northern Plains and Upper Great Lakes. As the noted broad southerly flow over the Plains helps to advect more moisture northward, some more potent storms will locally heavy downpours are possible Tuesday for portions of the Upper Great Lakes, with an isolated risk of flash flooding. Temperatures will be running as much as 10 to 20 degrees above average ahead of the front, with the anomalies centered on the Central Plains Monday and the Mississippi Valley into Great Lakes Tuesday. Highs well into the 80s and even a shot at 90 are possible for the Central Plains Monday. To the west, some rain and higher elevation, mountain snow is expected along the frontal boundary as it extends into the Northern Rockies Monday. Then, another upper-level system upstream over the northeastern Pacific will drop southward Tuesday, enhancing precipitation chances along and behind the frontal boundary. This will also bring much colder air southward, dropping snow levels and lead to an early season winter storm beginning in the northwest and Northern Rockies by late Tuesday. This storm will continue beyond the current forecast period, and spread further eastward into the Northern High Plains by Wednesday. Winter storm watches are out for portions of the Cascades and Northern Rockies as storm total snow of 8-12" will be possible. Snow levels will drop overnight Tuesday, allowing rain to change over to snow for lower elevations, with accumulations of a few inches possible through Wednesday. Highs in the 50s and 60s Monday will drop into the 40s and 50s Tuesday, with much chillier winter-like temperatures expected by Wednesday. Elsewhere, after a chilly Monday morning with temperatures dropping near freezing for the Lower Great Lakes/Upper Ohio Valley, conditions will remain a bit below average broadly across the Northeast , with highs mainly in the 50s to low 60s. Temperatures will moderate a bit Tuesday with some low 70s possible. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php