Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 342 AM EDT Tue May 02 2023 Valid 12Z Tue May 02 2023 - 12Z Thu May 04 2023 ...Much below average temperatures expected across Great Lakes/Midwest on Tuesday before spreading eastward into Northeast/Mid-Atlantic on Wednesday... ...Snow to diminish in Upper Peninsula of Michigan on Tuesday, while moderate to heavy snow continues across West Virginia Appalachians through Wednesday... ...Cool and unsettled weather for California and Southwest this week; Warm and dry conditions further north and inland throughout Pacific Northwest and Intermountain West... This week's primary weather headline will be the Omega Block pattern that has set up across North America, with unseasonably cool and damp conditions expected across both lower 48 coasts and much-above-average temperatures throughout the central U.S. As the anomalous upper-level low and associated surface low that has remained nearly stationary across the Great Lakes region begins to meander eastward and weaken on Tuesday, conditions will improve across the Upper Peninsula (U.P.) of Michigan, where localized areas have reported upwards of 12-18 inches of snow over the last 72 hours. In the meantime, an additional 6-10" is possible, especially in the higher terrain of the interior U.P., through Tuesday afternoon. Further east, moderate to heavy snow has also been falling across the West Virginia Appalachians, with localized Winter Storm Warnings and Winter Weather Advisories in effect through Tuesday and Wednesday, respectively, as cold air advects southward across the mountain range, producing high-elevation snowfall amounts up to 12". Furthermore, a broader area of much-below-average temperatures (15-25 degrees F below average), encompassing much of the Great Lakes region, Ohio Valley, and the Appalachians, will be possible on Tuesday, as daytime highs remain in the low 40s and numerous locations approach or break daily record low maximum temperatures. As the upper low begins to push northeastward, the below-average temperatures will spill into the Mid-Atlantic and Northeast on Wednesday, with nighttime lows dipping into the low 40s across nearly the entirety of the I-95 urban corridor. Moreover, conditions will remain damp as showers associated with the upper low continue through Thursday. Elsewhere, a cool and unsettled weather pattern is currently spreading eastward across the West Coast as an upper-level low slowly tracks southward along the California shoreline through Thursday, resulting in increased shower and high-elevation snow chances and below-average temperatures. Daytime temperatures will remain in the 50s and 60s across much of California on Tuesday and Wednesday, with the unseasonably cool weather expanding eastward into the Southwest on Thursday. Further north and inland, gusty southerly winds and well above average temperatures are anticipated for much of the Intermountain West and Pacific Northwest, with warm weather also spreading into the northern and central Rockies and northern High Plains by midweek. Widespread temperature anomalies of 15-25 degrees above average will be possible as daytime temperatures exceed 80F across much of the region. As a result, areas experiencing river flooding due to snowmelt across the Great Basin and Intermountain West can expect more significant snowmelt this week. As the frontal boundary associated with the persistent upper-level troughing pushes inland on Tuesday, showers and thunderstorms will begin to overspread much of the Rockies. Russell Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php