221 FXUS63 KGRB 211959 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 259 PM CDT Thu Mar 21 2019 Forecast discussion for routine afternoon forecast issuance .SYNOPSIS... Issued at 257 PM CDT Thu Mar 21 2019 Relatively quiet weather is expected through the middle of next week. Temperatures will be reasonably close to seasonal normals, with just some scattered light precipitation at times. The blocky pattern over western North America and the eastern Pacific will remain in place throughout the forecast period, though it will undergo some changes in structure. A southern stream of energy undercutting the block will strengthen through early next week, though it is expected to remain south of the forecast area through that time. A westward shift in blocking is possible during the middle to latter part of next week. If that occurs, it would open the door for a stronger southern stream system to affect the area toward the end of next week. Temperatures will undergo day to day variation as polar air masses surge into the area and then modify under the insolation of the springtime sunshine. The forecast area remaining between the main branches of the flow or dominated by the northern stream favors only scattered light precipitation through early next week, though a wetter period could develop thereafter. && .SHORT TERM...Tonight and Friday Issued at 257 PM CDT Thu Mar 21 2019 A shortwave and upper level speed max with strong QG forcing will dig southeast from Canada tonight. The strongest QG forcing will shift through before the low-level convergence and better moisture arrive. So delayed the precipitation chances into the evening, still going with chance PoPs across the north overnight, and lower PoPs for a trace event across most of the rest of the area. Winds will stay up all night, and combined with the incoming cloud deck that should again keep temps from falling too far. Pushed mins toward a blend of the top performing guidance products, which were warmer than the previous forecast. Colder air will be pushing into the area Friday. But when combined with decreasing clouds, still anticipating an 8-12 F degree diurnal rise. .LONG TERM...Friday Night Through Thursday Issued at 257 PM CDT Thu Mar 21 2019 The latest medium range models and ensemble means continue to indicate that a relatively high amplitude split flow pattern will remain in place across North America over the next week. Most of our weather will be dominated by the northern stream, though the southern stream tries to have some impact in our conditions by late in the weekend. Forecast concerns generally revolve around this system as well as temperatures. Friday night through Saturday night...Canadian high pressure will be sliding southeast across the area during this period. After a blustery Friday, winds will likely diminish on Friday night as the center of the high passes directly over the area. Very dry air will accompany the high, which will lead to nearly ideal radiational cooling conditions. Will lower min temps on Friday night where deep snow pack remains. Otherwise, mostly clear skies will be present across the region during the period. High temperatures on Saturday will rebound into the lower 50s over parts of east-central WI and the upper 40s across the north. Rest of the forecast...Clouds will be on the increase on Sunday when a southern stream low pressure system moves into the mid-Mississippi Valley while a cold front drops in from the north. Because of the abundant dry air from the departing airmass, remain skeptical that the low pressure system will have much impact on our weather. However, decent mid-level fgen will accompany the front, and could lead to a band of light snow arriving into northern WI by late Sunday afternoon and will pass across the rest of the region on Sunday night. This front will also be moisture-starved, so not expecting a significant amount of precip or snowfall. High pressure will settle over the area behind the front for early next week, leading to a brief period of below normal temps. Temps and chances of precip rebound somewhat by next Wednesday. && .AVIATION...for 18Z TAF Issuance Issued at 1254 PM CDT Thu Mar 21 2019 A cold front and upper level disturbance dropping south from Canada will bring a period of MVFR clouds and some snow showers to the north overnight. Clouds should decrease Friday as high pressure builds into the area. && .HYDROLOGY... Issued at 257 PM CDT Thu Mar 21 2019 Favorable conditions for a slow snowmelt across the north will remain in place through early next week. There is some support on the medium range models for a warmer and wetter southern stream system to affect the area late next week. That could lead to a sharp uptick in flooding potential across the north. But the system will be developing as large scale changes are occurring, so predictability will be low and there may very well be significant changes in the forecast track and intensity of the system during the coming days. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS.......Skowronski SHORT TERM.....Skowronski LONG TERM......MPC AVIATION.......Skowronski HYDROLOGY......Skowronski