Thursday, October 22, 2015

Rain to "turn up" on Friday night

Public weather briefing

After a clear, dry day today, clouds will move in overnight and persist throughout Friday, followed by steady rainfall starting in the evening and continuing through till Saturday late morning. Sunday will see a return to clear, sunny and mild conditions. Into next week temperatures will remain around the 60 mark before a drop in temperature on Wednesday, along with high chances of rainfall.


Tonight. Partly cloudy. Low around 42.

Friday. Cloudy and moderate winds during the day, followed by persistent rainfall beginning in the afternoon, providing around a quarter of an inch by the end of the day. Winds will be moderate, with strong gusts. High around 56.

Friday night. Continued rainfall. Temperatures will increase overnight, around 60.

Saturday. Rainfall set to continue until late morning, with cloudy skies later on. Highs around 60, lows in the low 40s.

Sunday. Abundant sunshine. Highs in the low 60s and lows in the low 40s.

Outlook for Monday through Wednesday. Monday and Tuesday will be partly cloudy, with outbreaks of sunshine and highs in the upper 50s and lows in the mid 40s. By Wednesday temperatures drop, with highs in the low 50s. Showers are likely throughout the day.  [CONFIDENCE: MEDIUM]

Forecast Discussion

High pressure to the north-east will continue to bring quiet weather over night tonight. A low pressure system moving up from the central plains towards the Midwest will cause differential warm air advection over us into Friday morning.  Tightening of the pressure gradient will allow for gusty southeast winds in the afternoon.  By the evening we are located downstream of a short-wave trough and in the left jet exit region of a small jet streak, both of which will act to strengthen the low pressure and provide increased upward vertical motion due to upper level divergence over Wisconsin, bringing steady rainfall, which will last into the night. Q-vector convergence over Madison on Saturday morning suggests continued strong upward vertical motion, forcing precipitation to persist. This rainfall should end around midday and by the evening, high pressure will be overhead, which will remain through Sunday night and into Monday. Tuesday and Wednesday will see precipitation chances high again, as a deep mid level trough along with a surface low moves across the region. Wednesday onwards is likely to see differential cold air advection, as a result of deep low pressure systems off the west coast of the US moving east, resulting in much cooler temperatures.

Rich Johnson

1 comment:

  1. Overall this is a very nice forecast with excellent analysis. Temperatures were and are accurate in the forecast with periods of forecasted precipitation also fairly accurate. Timing of the precipitation events was a bit off: for instance, rain showers ended in the early morning on Saturday. Also, you forecasted that rain will fall over the region on Tuesday and Wednesday as a result of a low pressure system moves through, but you don't mention where it came from. It seems that the remnants of Hurricane Patricia will act in concert with a pressure minimum originating from the U.S. Northwest to bring the precipitation you mentioned by Tuesday afternoon. However, you did an excellent job on the diagnosis of pertinent dynamic phenomena that are affecting our forecast region.


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