Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Thu May 18 2017 Valid 00Z Fri May 19 2017 - 00Z Sun May 21 2017 ...A late-season snowstorm should continue through Friday over the central Rockies... ...Heavy downpours associated with strong to severe thunderstorms could lead to flash flooding over the central Plains through tonight... ...Near record high temperatures over the mid-Atlantic to the Northeast will give way to much cooler conditions during the weekend... A developing low pressure system coupled with upper-level cold air is bringing a late-season snowstorm over the central Rockies. Moderate to locally heavy snow together with near record cold daytime temperatures should continue into Friday as the low pressure system is expected to move very slowly over the central Plains. Meanwhile, warm and moist southerly flow ahead of the low pressure center will promote strong to severe thunderstorms through tonight across the central Plains. Areas in Kansas, located just north of a stationary front, will have the best chance of seeing the heaviest rainfall overnight, which could lead to flash flooding. Farther away from the low pressure system, deep-layer southerly flow associated with a Bermuda high is bringing near record warmth from the mid-Atlantic northward into New England. The early-season heat will end Friday night as a strong cold front sweeps across these areas, bringing much cooler conditions during the weekend. Meanwhile, the low pressure system will consolidate over the central Plains and will begin to move steadily northeastward, reaching the upper Midwest on Saturday. Snow over the central Rockies will taper off on Saturday as the storm moves away but showers and thunderstorms will be on the increase from the southern Plains up through much of the Mississippi Valley and into the Great lakes on Saturday as the storm and the associated cold front approach. The eastern edge of the thunderstorms could reach the western slopes of the Appalachians by Saturday evening. Out West, an upper-level disturbance should promote showers and thunderstorms with high-elevation snow showers across the Intermountain West and northern Rockies on Saturday. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php