Scientific Forecaster Discussion

000 fxus63 kmkx 221447 aaa afdmkx Area forecast discussion...updated National Weather Service Milwaukee/Sullivan WI 847 am CST Fri Feb 22 2019 Update... No change to the forecast for today. && Marine... There is a gale watch in effect for late Sat night through Sunday night. Might have to consider an upgrade to a storm watch/warning given gusts to 50 knots possible, particularly for the open waters. Less of a chance for storm force gusts across the nearshore waters, though not out of the question. Heavy freezing spray will be also possible Sunday night into Monday. The highest waves through this event will be across the eastern half of the lake in ice free areas. Lighter winds will return for early next week. && Previous discussion... (issued 546 am CST Fri Feb 22 2019) Update... The forecast is on track for the upcoming day. Aviation(12z tafs)... VFR conditions and light winds are expected through today under high pressure. Mid level clouds will move through the forecast early this morning, with mostly sunny skies then into the afternoon. Will eventually see lower ceilings/visibilites later tonight as low pressure and precip head for the area. Mixed precipitation is likely by late tonight, with a pretty good chance for freezing rain most places by daybreak Saturday. Previous discussion... (issued 438 am CST Fri Feb 22 2019) Short term... Today and tonight...forecast confidence is high: Scattered mid to high level clouds will be possible into early morning...but otherwise high pressure should bring plenty of sunshine today. Temps will be near normal. Strengthening low pressure will approach the area tonight, bringing a mix of precipitation later in the night. Precip may start off as snow, especially in areas northwest of Madison. A warm layer aloft will move in quickly though, with precip quickly changing to freezing rain. There are sizable differences among models with how much precip will arrive with this first round of forcing. Some of the more aggressive models would suggest more icing by daybreak than in the current forecast, but either way, icing is expected to occur later tonight. Best chance of a quick glaze of ice by early morning will be from the Madison area southwestward. Saturday through Sunday night...forecast confidence is medium. Cyclogenesis will ensue over the Texas/OK panhandles Fri nt as a strong shortwave trough approaches from the desert SW. The deepening low will track to se Iowa by 00z sun. Well ahead of the low, a sly 30-40 kt low level jet and associated warm, moist advection and frontogenesis will shift ewd across the region Sat am. Fairly strong lift and steepening mid level lapse rates will lead to a large area of moderate pcpn moving east across srn WI. A strong warm layer aloft of 2-6c will move nwd into srn WI by late Sat am. Initial pcpn chances will be mixed, but transitioning to freezing rain as the column becomes saturated and relatively warm aloft. Some models produce relatively heavy qpf totals but looks overdone. Went with a blend of quantitative precipitation forecast which gives 0.25-0.45 over south central WI and .15-.30 over east central and se WI. Ice accums are .10-.25 inches with lesser amounts toward central WI. Sfc temps will warm above freezing over all of S WI by noon with areas of light rain expected the remainder of the day. A winter wx advisory has been issued for Sat am. The 994 mb low over se Iowa at 00z sun will then track to the nrn end of Lake Michigan by 12z sun and deepen to 979 mb. Widespread moderate rainfall will arrive Sat eve on the nose of a strong llj, and strong upper level divergence via positive vorticity advection and warm advection at the jet level. Strong cold advection will then ensue from west to east after midnight. Much of the pcpn will move out before changing to snow so only an inch or less is forecast toward central WI. The occluded low will continue to deepen as it moves into Ontario on sun. A strong pressure gradient and well mixed atmosphere should be a slam dunk for a Wind Advisory with wly wind gusts of 45-55 mph. Higher wind gusts cannot be ruled out and will depend on the details of the cyclogenesis and pressure gradient. A high wind watch may eventually be needed for Sunday into Sunday evening. In addition to the winter weather and high winds, minor river flooding and lowland flooding will be possible due 0.5-1.0 inches of rain along with several inches of snow melt. Ice jams will be possible. Long term...Monday through Thursday...forecast confidence is low. The European model (ecmwf) drops another reinforcing upper trough and cold temps into the nrn Great Lakes and srn Canada for Mon-Wed while the GFS is weaker and farther north with this feature. Thus, the GFS produces more warm advection and frontogenesis with chances of light snow for this period. Overall, below normal temps are expected with chances of light snow Mon-Wed. High pressure and dry for Thu. Aviation(09z tafs)... VFR conditions and light winds are expected through today under high pressure. Will eventually see lower ceilings/visibilites Friday night as low pressure and precip head for the area. Mixed precipitation is likely by late tonight, with a pretty good chance for freezing rain most places by daybreak Saturday. Marine... Kept the gale watch timing as is for now for late Sat night through Sunday night. Might have to consider an upgrade to a storm watch/warning given gusts to 50 knots possible...particularly for the open waters. Less of a chance for storm force gusts across the nearshore waters...though not out of the question. Heavy freezing spray will be also possible Sunday night into Monday. The highest waves through this event will be across the eastern half of the lake in ice free areas. Lighter winds will return for early next week. && Mkx watches/warnings/advisories... WI...Winter Weather Advisory from 3 am to noon CST Saturday for wiz046-047-056-057-062-063-067>069. Winter Weather Advisory from 6 am to noon CST Saturday for wiz051-052-058>060-064>066-070>072. Lm...gale watch from late Saturday night through late Sunday night for lmz080-261-362-364-366-563-565-567-643>646-669-671-673- 675-777-779-868-870-872-874-876-878. &&

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