Wednesday, September 17, 2014

A cool Thursday expected with warm and humid conditions arriving for the first half of the weekend.

Public weather briefing

Following an absolutely brilliant Wednesday, the passage of a "backdoor" cold front ushers in cloudier and cooler conditions for Thursday. Skies are expected to clear out overnight on Thursday, setting up a rather seasonable Friday with clear skies and temperatures around 70. The passage of a warm front on Friday night brings a chance of scattered thunderstorms towards dawn and may damper some of the early morning tailgates, as rather warm and humid conditions move in for Badger Gameday. The passage of a cold front brings a renewed chance of thunderstorms Saturday afternoon and evening before more crisp, autumnal weather returns for the second half of the weekend and early next week.


Tonight. Clear with increasing clouds towards morning. Light winds. Lows in the upper-40's.

Thursday. Partly sunny. Light ENE winds 5-10 mph. Highs around 65.

Thursday night. Clearing overnight. Light southerly winds. Lows around 50.

Friday. Sunny and warmer with a chance of scattered thunderstorms after midnight. Southerly winds around 10mph. Highs in the low-70's. Lows around 60.

Saturday. Mostly sunny and more humid with a chance of scattered thunderstorms. Breezy. Highs in the upper 70's.

Outlook for Sunday through Tuesday. Clearing Sunday morning with mostly sunny skies Sunday afternoon through Tuesday. Highs in the mid-to-upper 60's and lows in the 40's. [CONFIDENCE: MEDIUM]

Forecast Discussion

Subsidence accompanying a Canadian anticyclone settles in over the area early this evening, bringing light winds to southern Wisconsin. The approach of a backdoor cold front appears to be associated with subtle ascent over southern Wisconsin, promoting increasing clouds towards morning and a cooler Thursday, though no precipitation given the relatively dry air mass in place. A forecast challenge surrounds how far this "backdoor" cold front is expected to move inland and the degree of cloud cover expected. Less cloud coverage and a less progressive front may encourage warmer temperatures than currently forecast.

Strong warm-air advection from the southwest, as the Canadian anticyclone shifts eastward, ushers in warmer temperatures on Friday. Maximized areas of warm-air advection during the overnight hours on Friday, encouraged at the nose of a strong low-level jet, may support the development of a few scattered thunderstorms towards morning. Conditions will be more humid and warmer on Saturday in advance of a strong cold frontal boundary that will move through the area on Saturday evening. Deformation along the frontal boundary suggests a region of low-level frontogenesis and the development of precipitation along the length of the boundary Saturday afternoon and evening across the state. Lifted indices appear to be favorable for convection to occur. Following the passage of the front, another Canadian anticyclone settles into the area from the north, ushering the return of more autumnal weather.

Andrew C. Winters

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