Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 410 AM EDT Mon Apr 24 2023 Valid 12Z Mon Apr 24 2023 - 12Z Wed Apr 26 2023 ...Mountain snow and coastal/valley showers over the Pacific Northwest will continue to spread into the northern and central Rockies... ...Heavy wet snow can be expected over central Colorado by late Tuesday/early Wednesday... ...March-like cold temperatures with additional morning frosts/freezes across much of the eastern two-thirds of the country.. ...Damp and dreary conditions to linger in New England with high-elevation wet snow at times... ...More showers and storms to develop Tuesday and Wednesday in the south-central U.S.... As a lingering low pressure system brings additional rounds of showers, high-elevation wet snow, and some thunderstorms across New England for the next couple of days, moisture ahead of the next weather maker has already moved into the Pacific Northwest with a solid round of mountain snow and lower elevation moderate to locally heavy rain. In contrast to the slow-moving low over the Northeast, the system moving into the Pacific Northwest will move relatively quickly and steadily inland, bringing widespread mountain snow and valley rain across the northern Rockies today, reaching into the central Rockies by Tuesday. It appears that heavy wet snow will develop from late Tuesday into early Wednesday morning over the Colorado Rockies, the foothills, and possibly spreading east into the Front Range, as a cold front races across the Intermountain West and a low pressure system develops over the central High Plains on Tuesday. This system will also be responsible for triggering and expanding the next round of showers and thunderstorms across the central to southern Plains beginning on Tuesday, with the threat of flash flooding increasing later on Tuesday. Some of the thunderstorms are expected to turn severe, especially farther south in the warm sector across eastern Texas. Meanwhile, a large dome of Canadian high pressure has taken hold of the Nation's Heartland and will spread east into the Mid-South and Mid-Atlantic during the first half of the week. Accompanying this large high pressure system is an even more extensive area of below normal temperatures. Today's daily low temperatures from the Middle Mississippi Valley on east into the Ohio/Tennessee Valleys and northern Mid-Atlantic will plunge near or below freezing, prompting the issuance of Freeze Warnings and Frost Advisories in some of these areas. A handful of daily record low minimum and maximum temperatures are possible as well. Temperatures east of the Rockies and into the Mid-Atlantic are likely to average 10-15 degrees below normal through mid-week, making it feel more like March outside rather than late April. The unusually chilly temperatures will be cold enough to where some precipitation in the upper Great Lakes will fall in the form snow at times on Monday, but little in the way of accumulation is expected. Farther west, an upper level ridge strengthening off the coast tomorrow and into mid-week will foster warmer than normal temperatures in California and the Desert Southwest. By Tuesday, portions of California's Great Valley will rise well into the 80s with desert areas of southern California and Arizona eclipsing the 90 degree mark. One of the reasons for the cooler than normal temperatures regime in the eastern and central U.S. is a large, spiraling upper low over the Great Lakes and Ontario being blocked by a ridge of high pressure over Quebec and the Davis Strait. This ridge is forcing a storm system off the Northeast coast to become stationary, making for a dreary and unsettled weather to continue for much of New England into midweek. Kong/Mullinax Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php