Issued: 2pm on Wednesday, October 20th 2021
Technical Forecast Discussion
Short Term (Wednesday 10-20-2021 through Friday 10-22-2021)
Our short term period is starting out on a high note with clear skies and chilly weather as true fall like pattern finally settles in for our area after significantly warm start to our fall season. Clear skies in our area is courtesy of surface high located over Appalachians region, but look for some increase in cloud coverage as we move into later parts of Wednesday with sharp rise in temperatures through the afternoon hours. This will happen due to southwesterly flow behind the high pressure pumping in milder airmass from the south. Our 500mb pattern is featuring a ridge over most of Ohio Valley region currently with main axis over Illinois which will then gradually move eastward and out of our area by Thursday morning out ahead of short-wave trough located over northern Illinois. Continued southwesterly flow out ahead of the front will lead to increasing humidity levels and cloud coverage which in turn will cause our temperatures to not cool nearly as much as it has over past 3-4 mornings. We currently have a surface low over eastern Nebraska which will move eastward over Lake Michigan area by Thursday morning which is associated with the short-wave trough. There is cold front which will be extending down through central sections of Indiana into western Kentucky with rain showers developing for eastern Indiana and western Ohio. As we move into late afternoon hours, cold front will swing through our area, and any precipitation will move out by evening hours. Please do note that moisture return is not great with this storm so I am not anticipating higher quantity of precipitation. One interesting thing which has caught my eyes is the fact that this short-wave trough will take a neutral tilt when located over our area and then take a negative tilt into western Pennsylvania. Given dew-points in upper 50’s with minor forcing, we will have some instability in order of 200-500 J/Kg, we may see a minor wind threat and SPC has issued a marginal risk of severe weather for far eastern Ohio and Western Pennsylvania for this. Please note that this does not include any parts of our region, but still something to keep an eye on as this is very close to our area, even then not much would be expected anyways. Cloud coverage will start to decrease a little by Thursday night as the short-wave weakens out before they increase once again out ahead of another cold front moves by midday Friday. We may see some isolated showers with this before we start to dry out once again by late Friday night. Behind this second front, we will have upper level trough quickly building over most of Ohio Valley region and intensifying, this will help to keep chilly weather around for our area. Looking at the temperatures, highs will be in lower 70’s for Wednesday and Thursday and then cool down to around lower 60’s for Friday with morning lows dropping from lower 50’s Wednesday night to mid-upper 40’s Thursday and Friday night. Overall temperature anomalies are going to be 4°F-7°F above normal for this time period.
Long Term (Saturday 10-23-2021 through Tuesday 10-26-2021)
Long term forecast period begins with a trough remaining over our region, but as we move into later parts of the days, this trough will gradually move into most of Mid-Atlantic and Northeastern states by late Saturday night. The daytime Saturday is shaping up to be a clear day with chilly conditions as high pressure is expected to settle in overhead. Our weather starts to become much more interesting starting Sunday as the upper level pattern may not be the best way to represent what is expected. This is one of the few time when we focus more on surface to 850mb features to gage a better idea. As of Sunday morning, most models show that we have developing surface cyclone over central Plains with warm air extending eastward over Ozarks and southwestern portions of Ohio Valley. We also have high pressure near Hudson bay funneling in colder air mass for far eastern Ohio Valley along with most of Mid-Atlantic and Northeastern area at this same time. As the low moves northward, we will have WAA related rainfall breaking our for most of Ohio Valley region, which does include our area, starting late Sunday morning and continuing through the day. As we move forward in time, the high pressure continues to slide southeastward into and get stuck over eastern Ontario while surface low moves into Iowa by Monday morning. From this time onward, there is very high uncertainties as to how things will play out as there is rather significant disagreements amongst the models, but the general theme is rain chances hangs in our area through the day Monday and continue into early parts of Tuesday before things start to clear out a bit. Our area might see decent amount of rainfall in order of 0.50″-1.00″, if not more, but we are still few days away to know for sure. Another thing to note is that our temperatures will indeed rise Monday and Tuesday as the warm front will likely go north of our area no matter the exact position of surface low given our expected upper level pattern. Going back to upper-level pattern for Sunday-Monday, we have weak rising heights in our area with stronger area over northern Ontario region, but there is a weakness noted in western Ohio Valley region as of Monday morning. Modeling of upper level trough feature is different depending on what runs we look, hence the differences with placement of surface low as mentioned above, but the overall theme is this “weakness area” will move to our east. One thing which models do agree on is about significant height rises over the central sections of the country which will try to move into our area at the very end of our forecasting period. Our temperatures during this time period will see gradual rise during this period as we start out Saturday with highs down in lower 60’s, rising to mid 60’s Sunday, and then rising into upper 60’s to lower 70’s Monday and Tuesday. Expected lows will be cold in upper 30’s Saturday night which then rises to upper 40’s for Sunday and Monday night before dropping down again into lower 40’s Tuesday night. Temperature anomalies during this period will be 1°F-3°F above normal for the long term period.