Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000 FXUS63 KMKX 020339 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1039 PM CDT Wed Apr 1 2020 .UPDATE... A narrow band of mid level clouds will continue to affect the region into the overnight hours, though they should slowly dissipate with time. Temperatures remain on track to bottom out in the low to mid 30s east and mid to upper 30s west. && .AVIATION(06Z TAFS)... Conditions are expected to remain VFR through the next 24 hours. A narrow band of mid level clouds will continue to slowly dissipate overnight, though some cloud cover may stick around north and west of Madison. High level clouds will then stream into the area on Thursday. Winds will be light from the southeast, becoming light and variable at times. Southeast winds are expected through the day on Thursday. && .PREV DISCUSSION... (Issued 840 PM CDT Wed Apr 1 2020) MARINE... Areas of dense fog will continue to impact the far southern portion of the lake through the overnight hours. Otherwise, quiet weather is expected as high pressure remains in place over the region. Winds will be light and variable tonight, before shifting to the east and then southeast on Thursday. A front will eventually pass through the lake on Friday and Friday night, turning winds to the northwest. High pressure builds back into the area later Saturday, bringing quiet weather through the remainder of the weekend. PREV DISCUSSION... (Issued 340 PM CDT WED APR 1 2020) SHORT TERM... TONIGHT THROUGH THURSDAY - Forecast Confidence...High. An upper level ridge remain over the Great Lakes Region and the sfc high pressure will prevail through the Thursday. The sun will begin to peak through the dissipating cloud layer this afternoon into the late evening hours, before clouds return during the overnight hours. Tonight`s low temperatures will be in the 30s with the coldest temperatures found along the lake shore due to the persistent easterly winds. Temperatures will be warming into the low 40s along the lake shore to the low 60s out west for Thursday. THURSDAY NIGHT THROUGH SATURDAY - Forecast Confidence...Medium to High. Sharp mid-level ridge over the western Great Lakes gets nudged eastward Thursday night into Friday into the central Great Lakes. Upper level pattern shifting only very slowly east because of large low pressure area over western Atlantic. Meanwhile, a slow moving low pressure trof over the central and northern Plains will edge slowly eastward and eventually cross Wisconsin later Friday and Friday night per more progressive GFS/ECMWF scenario. The bulk of the synoptic scale forcing associated with the associated mid-level short wave will remain northwest of the area. However enough warm air and moisture advection spreads across southern WI along and behind the front to warrant continuing higher level Pops Fri night. Precipitable water increases to around 1" on Friday. The showers may linger into Saturday morning before shifting off to the east with dry conditions returning for the afternoon. GFS soundings show considerable drying during the day Saturday with sunshine returning. For now leaning toward the more progressive GFS/ECMWF solution. NAM considerably slower with eastward movement of system and keeps the chance for showers lingering through more of Saturday across eastern areas. For now, can`t completely rule out this slower solution due to that large system affecting the east coast. LONG TERM... SATURDAY NIGHT THROUGH WEDNESDAY - Forecast Confidence...Medium. Protective high pressure ridge remains over the Great Lakes through the latter part of the weekend resulting in a period of quiet and dry weather. However low level winds will remain east to northeast which will keep lakeshore areas significantly cooler than areas inland. Also, some difference in extended guidance on how much low level moisture lingers over southern WI and areas to the east later in the weekend. For now, wl remain more optimistic for partial sunshine for most of the day on Sunday, which would result in temps in the 50s to around 60 well away from Lake Michigan. Ridge moves off to the east Sunday night as upstream long wave trof amplifies across the western CONUS. In response, upper level steering winds become more west to southwest across the Upper Midwest and Great Lakes, while low level winds turn to the southwest. These conditions will allow highly desirable warmer air to move into the region early in the week. 925H temps may get as warm as 15 to 20C, which would result in daytime temps rising into the middle 60s to middle 70s, but remaining cooler by the lake, especially Tue. ECMWF and GFS trending toward upstream trof transitioning to split flow across the eastern half of the CONUS with cutoff low remaining in the southwest CONUS. More progressive trof in increasing zonal flow will move through the through the northern CONUS on Tuesday/Wednesday. The resulting northern stream low pressure system and cold front is trending toward moving through Wisconsin in the Tuesday and Tue night period. Low level moisture will be increasing ahead of the front, with dewpoints rising into the 50s. GFS soundings show a considerable Capping inversion across southern WI Tuesday afternoon, but elevated CIN does weaken to less than 50 j/kg that evening. While considerable uncertainty exists on timing and amount of low level moisture and instability, will be adding thunder threat to grids Monday into Tuesday night. Cooler, more stable conditions look to return on Wednesday. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Dense Fog Advisory until 10 AM CDT Thursday for LMZ080-779. && $$ Update...Boxell Tonight/Thursday and Aviation/Marine...Boxell Thursday Night through Wednesday...99

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