Issued: 10am on Friday, October 8th 2021
Technical Forecast Discussion
Short Term (Friday 10-8-2021 through Sunday 10-10-2021)
Short term period is starting out with a weak upper level low over northern Illinois and attempting to merge into the main jet stream further to the north. This mid-upper level low will still be responsible for generating showers and thunderstorm during afternoon hours on Friday, but chances are lower compared to previous day, otherwise continues warm and humid conditions persist in our area. Our area will remain under weak short-wave trough, given lower heights in our area, through rest of Friday into Saturday evening before it departs our area. Right behind this trough, we have another ridge axis building into central plains into our area starting Saturday evening and really establish itself by Sunday with 585dm building in. On surface level, we will still have some clouds generated on Saturday with isolated afternoon showers/storm during diurnal heating, otherwise continued warm and humidity under partly cloudy conditions. We will finally catch a break on Sunday with bright skies and precipitation as surface builds over Appalachians. One key thing to note is warm front lifting north of our area early Sunday which is in association with surface low over northern plains region, but with no forcing, no precipitation is expected. Temperatures during this period will be in the upper 70’s Friday-Saturday and then warming into low-mid 80’s Sunday with lows in upper 50’s to lower 60’s. Temperature anomalies during this period will run about 13°F-17°F above normal given warm and humid southerly flow.
Long Term (Monday 10-8-2021 through Thursday 10-11-2021)
Long term period resumes with upper level ridge over our area and leading to persistent southwesterly flow in our area for Monday, but we do have fast approaching short-wave trough moving closer to our area from central plains while it is weakening rapidly, nonetheless a weak cold front moves closer to our area by late Monday night and likely fizzles out right over our area. Chances of precipitation is virtually non-existent given the fact that this system losses its moisture, but we will see few clouds build in Monday evening into early Tuesday. The ridge axis does move east while our area being under far western end of it, but look for new upper level ridge to pop right over Great Lakes and Ohio Valley area on Tuesday and intensify by Wednesday while strong upper-level low system powers through central and northern plains region at the same time. ULL will eventually weaken out and lift toward northern Minnesota area by late Wednesday into Thursday which then impacts downstream ridge by pushing it further to the east and weakens it a little so ridge will start to move east of us by Thursday. Overall this pattern on surface translates to surface high building back over southern Appalachians region from Tuesday into first half of Thursday under warm southwesterly flow. By late Thursday, a weakening cold front will approach closer to our area, and this will lead to increasing clouds by evening hours and some precipitation chances overnight Thursday. Temperatures during this period are not expected change at all as we are expecting our highs to still range from upper 70’s to low 80’s while our lows only drop into mid-upper 50’s so our overall temperature anomalies will remain about 13°F-17°F above normal.
