Scientific Forecaster Discussion

000 fxus63 kmkx 192318 afdmkx Area forecast discussion National Weather Service Milwaukee/Sullivan WI 618 PM CDT Fri Apr 19 2019 Update... No change to the short term forecast. Winds will remain elevated close to Lake Michigan, but will decouple farther inland. && Aviation(00z tafs)... VFR conditions are expected through the taf period with clear skies across the region. North to northeast winds near Lake Michigan will remain elevated into Saturday, but will be much lighter farther inland. && Previous discussion... (issued 245 PM CDT Friday Apr 19 2019) Short term... Tonight through Saturday night - confidence...high. Some gustiness will continue tnt into Sat over far se WI as cyclogenesis occurs into the evening from Tennessee nwd to ern Kentucky and wrn WV. The low will then occlude and fill late tnt-Sat. During this time, the sfc ridge over Minnesota will slowly move ewd across WI. As the high moves ewd and an upper ridge builds, light sly winds will develop Sat nt. The very dry airmass over srn WI will cool nicely tnt as the high approaches, but warm into the middle to upper 60s well inland on Sat. Low temps in the lower to middle 40s for Sat nt with weak warm advection beginning. Sunday through Monday - confidence...medium. The trend continues for Sunday to be a very pleasant day across southern Wisconsin. A slowly sagging cold front will move across northern Wisconsin during the day with pockets of low level warm air advection focused in its vicinity, and also well to the southwest of southern WI during the day. Expecting breezing south to southwest winds and warm 925h temps in the 16 to 18c range by the afternoon. The low to mid levels of the atmosphere will remain dry, with only some passing sct-bkn cirrus passing by from time to time. Hence daytime temperatures should warm well into the 70s to around 80. The pressure gradient will be weak enough to allow a lake breeze to develop later in the morning and afternoon. Lakeshore areas in Sheboygan and Ozaukee counties will be the coolest, longest, due to the shore orientation. Record high for both Madison and Milwaukee is 84 for April 21st. For Sunday night, expecting an increase in mid-high level clouds as protective mid-level ridge shifts off to the east and increasing south to southwest low level winds begin to pull deeper column moisture into the area from the south. Precipitable water increases to around 1.25 inches on Monday ahead of approaching weak short wave trof in the central and northern plains. Low level jet focus remains to the south of WI Sunday night but a few showers and storms may develop later on as forecast soundings show the elevated cap weakening late in the night with MUCAPE of 500-1000 j/kg with weaker low level convergence. There will be a better chance for showers and storms later Monday into Monday night as low level jet reinvigorates and brushes southern WI ahead of approaching deepening low pressure. Guidance lacks agreement on this system for early next week, as European model (ecmwf) has remained weaker and more progressive with an open wave moving through Wisconsin Monday and Monday night, while GFS/NAM slower with the main sfc low circulation moving slowly northeast through WI on Tue. At this point, most favored time for convection is later Monday into early Tuesday morning. Should still be mild on Monday, and a bit more humid Long term... Monday night through Friday...forecast confidence...medium. Differences continue in the medium range guidance Monday night as European model (ecmwf) and Gem remain more progressive with weaker, open wave moving off to the east. Meanwhile, GFS has a bit more amplitude and corresponding slower eastward movement of the short wave, with the chance for showers and storms continuing Monday night into Tuesday. The GFS ensembles are showing large variability of the track and timing of the passing associated surface low during this period, so wl need to continue pops into Tuesday at this point. Otherwise, guidance in general agreement on developing split flow across the Continental U.S. For the remainder of the work week with cut-off low pressure developing over the Southern Plains, while mild zonal flow sets up over the northern Continental U.S.. after a slight cool-down on Tuesday, daytime temperatures should rebound back into the 60s for the final days of the week. A weakening front passing through the upper Midwest may bring a few showers to the area by Friday. Aviation(21z tafs)...mostly clear skies and VFR conditions this afternoon through Saturday night. Gusty nly winds will continue late this afternoon especially over far se WI where wind gusts of 30-35 kts are expected. The brisk nly winds will weaken tonight but gust to 25 kts over far se WI on Saturday. Marine...a Gale Warning continues for the south half of Lake Michigan and the nearshore waters south of Port Washington into early this evening. 8 to 12 foot waves occasionally to 16 feet can be expected over the open waters and 5 to 8 feet over the nearshore waters. A Small Craft Advisory is in effect for the same time period from Port Washington to Sheboygan for brisk north winds and high waves. The entire nearshore waters will need a Small Craft Advisory after the Gale Warning expires for tnt-Sat for continued brisk nly winds and high waves. Light winds and low wave heights are then expected for late Saturday afternoon and Sunday. && Mkx watches/warnings/advisories... WI...none. Lm...Gale Warning until 7 PM CDT this evening for lmz080-644>646-669- 671-673-675-777-779-870-872-874-876-878. Small Craft Advisory until 7 PM CDT this evening for lmz643. &&

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