Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000 FXUS63 KMKX 191405 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 905 AM CDT Mon Apr 19 2021 .UPDATE... (Issued 905 AM CDT Mon Apr 19 2021) Surface cold front has shifted off to our east. Still may see a few sprinkles/drizzle yet this morning. Otherwise plenty of cloud cover will prevail with the post-frontal cold advection regime underway. Going forecast has instability showers this afternoon/early evening handled pretty well. Collar && .SHORT TERM... (Issued 340 AM CDT Mon Apr 19 2021) Today through Tuesday Night: Strong cold front over southern WI will be exiting the far southeast early this morning. Scattered showers will accompany the frontal passage, but should be brief, with only light amounts if any. Drier low level air surging into the area with the colder air will end the scattered showers quickly this morning. A period of gusty northwest winds will accompany the frontal passage, with gusts of 20 to 25 knots possible. Isolated rain showers may redevelop this afternoon across the northern CWA as a short wave trof rotates around the parent low pressure system located near Lake Superior. The strongest forcing and deeper low to mid level moisture looks to remain over northern WI this afternoon. High temperatures in some areas will be reached early this morning before colder air overspreads the area. The frontal boundary passing through this morning will continue to sag southward into the southern Plains arcing northeast into the eastern Great Lakes tonight. However lagging behind will be a strengthening low level thermal gradient and baroclinic zone which is expected to orient from Oklahoma northeast through central IL into the northern OH Valley late tonight into Tuesday. Weak low pressure around 5k feet and a amplifying mid-level trof will move along this thermal gradient on Tuesday and Tuesday evening. The short term guidance and GFS and ECMWF ensembles continue to show the main forcing and axis of heavier precipitation with this system remaining south of Wisconsin, but affecting parts of northern IL. While the NAM has lowered QPF across southern WI, several ensembles do show light precipitation grazing southern WI on Tuesday. The low level thermal profile continues to favor a rain and snow mix or all light snow for a time, if precipitation were to develop. Also, although the low level flow is weaker, the Delta-T does increase to 13 degrees along the lakeshore on Tuesday with some low level lake induced Cape. Can not rule out some lake effect light rain and snow showers developing closer to the lake on Tuesday, with the best chance from Milwaukee south to the state line. With pavement temps likely to be above freezing, expecting little to no snow accumulation on Tuesday into Tuesday evening. Kavinsky && .LONG TERM... (Issued 340 AM CDT Mon Apr 19 2021) Wednesday through Sunday: A shortwaves will move across the Great Lakes Region Wednesday. As it moves through there will be a chance for some cold air advection showers across southern Wisconsin. Air aloft will be cooling faster than the air near the surface, which will cause the surface based parcels to become buoyant. During the morning, lapse rates are rather steep which could lead to some more convective showers. Regardless, lift and lingering moisture should be enough to bring some light and scattered showers during the day. High pressure returns to much of the central CONUS Thursday. Thus dry conditions are expected to return to southern Wisconsin. This high pressure and dry conditions will be short lived as a more active pattern is expected over the weekend. Multiple shortwave troughs are expected to move through the area bringing with them, chance for more precipitation. Patterson && .AVIATION... (Issued 905 AM CDT Mon Apr 19 2021) Gusty northwest winds will continue in the wake of the departed cold front. A few showers may still yet pop up again this afternoon, but latest HRRR is focusing this activity more towards central WI. Plenty of MVFR cigs upstream so this should persist today into tonight. Collar && .MARINE... (Issued 340 AM CDT Mon Apr 19 2021) Strong cold front knocking on the door of Lake Michigan and will move across the lake early this morning. The front will exit the far south later this morning, with gusty west to northwest winds in its wake. Low pressure will move across Lake Superior into southern Canada today and tonight. Far northern Lake Michigan is still susceptible to some gale force gusts later today into tonight since the pressure gradient will be a little stronger closer to the low pressure center. Hence left the Gale Warning in effect for the far north. Otherwise, a 1-3 hour period of gusty winds will affect the near shore waters early this morning, immediately after frontal passage. Gusts to 25 knots will be possible, but wl hold off on issuing a Small Craft Advisory for now due to brief nature of gusts reaching 22 knots or higher. Possible gusts to 25 knots may reoccur later this morning and afternoon so wl be watching closely for whether a longer term Small Craft Advisory may be needed. Kavinsky && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Gale Warning...LMZ261-LMZ362...1 PM Monday to 5 AM Tuesday. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee

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