Issued: 6pm on Sunday, October 31st 2021
Technical Forecast Discussion
Short Term (Sunday 10-31-2021 through Tuesday 11-2-2021)
We still starting out our short term period with a large trough impacting much of eastern U.S. states which brought us 1″-2″ of rainfall late last week. The storm associated with this trough has significantly weakened and has been pulling away from our area so look for clouds to decrease slightly. Reason for only slight decrease in clouds is due to another storm located over northeastern Ontario, which has a trailing cold front extending all the way down into eastern Illinois and western Indiana, and keeping clouds in our area on Sunday. This weak cold front will be moisture starved so we will not see much in the way of any precipitation, but look for our temperatures to cool down slightly behind this front by Monday. I also expect to see lot more sunshine for us during daytime hours on Monday as short-lived high pressure moves closer to our area before clouds increase again by late evening hours. Looking at upper level pattern, our wind flow has become more zonal temporarily out ahead of another trough which will start to dip into our area by Monday evening. We have a weak mid-level disturbance which will move by us during Monday night into Tuesday morning which will lead to isolated rain showers in our area during this period, but given we have a weak moisture return, coverage will not be widespread nor it would amount to much. As we head into Tuesday, trough will continue to settle in to our area with slight CAA happening through out the day. This won’t mean continued cooling temperatures wise throughout the day time hours, but our temperatures will only see minor rise with notably cooler conditions on Tuesday compared to previous day. Things are still expected to remain on cloudier side on Tuesday. Our temperatures on Sunday will be in right around 60°F for highs which will drop to mid 50’s Monday and upper 40’s by Tuesday with our lows remaining in upper 30’s Sunday and Monday night and drop down into upper 20’s Tuesday night and bring our area with first widespread freeze threat. Overall temperature anomalies for the first time in a while will end up below normal in order of 4°F-6°F range.
Long Term (Wednesday 11-3-2021 through Saturday 11-6-2021)
Our weather pattern starts to become difficult to figure out as models significantly diverge from this point onwards as we kick start into long range forecast. Models still largely agree that we will continue to have presence of trough over our area which will keep below normal conditions in place for us and it will be beautiful fall day with as high pressure sets shop and allow for plenty of sunshine during daytime on Wednesday. Most of the disparity in models is from Wednesday night into Friday afternoon so I will break down this part of the discussion in 2 scenario and mention about upper level pattern and expected surface level impacts for our area.
Scenario #1: Few models indicate that a short-wave will be embedded within main trough over Wisconsin/Minnesota area which is able to dig and swing down through Illinois/Indiana/Ohio like a pendulum motion. Time frame on the models is from Wednesday evening into Thursday evening when the short-wave is oriented in positive tilt and located over eastern Indiana and western Ohio by this point. With this trough configuration, we have WSW flow out ahead of it in our area, and we have moisture streaming northward towards our area with precipitation developing. The main caveat is the placement of the short-wave. If the short-wave ends up little bit further to the west and/or takes more of a neutral tilt from current projections, our area could end up seeing lot more precipitation. If the trough remains in positive tilt and is bit further to east from current modeling, we will have virtually have little to no precipitation and storm misses to our east. Any precipitation risk in this scenario will take place from Thursday evening into Friday. Light snow showers mixing in with rain showers is a strong possibility Thursday night as temperatures are expected right near freezing mark especially if more precipitation scenario comes for fruition. Please do note that accumulating snow is highly unlikely regardless of what happens due to marginal temperatures. Any precipitation should likely moves out of our area by Friday afternoon with drying conditions.
Scenario #2: There are also other sets of models which simply show that there will be no short-wave embedded within this main positively tilted trough and it would simply swing by our area through the day on Thursday and end up over northeastern states rather quickly by Friday morning. Because the trough is not slowing down in this scenario and allow for moisture to stream northward like scenario #1, we will virtually have no precipitation because of this and will only see clouds and brief sprinkles pass by our area. Another thing to note is that there is southern branch of energy even in this scenario, but because the trough simply swings by, this branch gets suppressed and most of the precipitation remains in southeastern U.S.
Given the complicated scenarios, I am going to take a blended approach to both solutions. Look for look for clouds to increase through the day on Thursday out ahead of the trough with isolated rain showers chances developing by Thursday night which quickly moves out by early Friday morning morning. Weather conditions remains on cloudy side through rest of the day on Friday with the storm moving to our east. For Saturday, our main trough departs to our east which will allow our temperatures to recover slightly as we are still under northerly flow and there no true riding overhead. Our temperatures during this period mid-upper 40’s Wednesday through Friday and warm up to lower 50’s for highs while our lows hold in upper 20’s to lower 30’s. Our overall temperature departure will continue to remain rather significantly below normal by 8°F-12°F for first time this fall season.