Issued: 7pm on Wednesday, October 27th 2021
Technical Forecast Discussion
Short Term (Wednesday 10-27-2021 through Friday 10-29-2021)
Short term period is starting out with a fairly weak upper level ridge located over most of Ohio which extends northward into most of Ontario and Québec and becomes stronger while our old system has moved eastward into Western Atlantic Ocean. On surface, we do have some clouds over our area despite the surface high located over western Michigan because of weak WAA believe it or not. One of the rare instances where WAA is directed from east to west versus south to north or west to east direction. We also have another deeper trough located over southern Plains states. Clouds will thin out later Wednesday evening into early overnight hours of Thursday before they are on the increase towards early Thursday morning. The clouds will be on increase once again as the trough moves closer to our area and be located over southern Missouri and northern Arkansas area by Thursday morning and takes on a negative tilt. Expect surface storm to peak in intensity as it is the right exit region over south Missouri. Moisture from this storm will be pulled northward into our area as we will be under southeasterly flow so look for increasing rain showers risk during the late afternoon and early evening hours on Thursday with better chances during overnight hours. Modeling for upper level pattern becomes rather interesting for Thursday as we have another weak short-wave trough from northern Plains quickly dropping into the main trough located into southern U.S. which in turn deepens the main trough and we have “pin-wheel” effect with both troughs merging into one and swinging northward into central Appalachians region by Friday evening as of result. The translation of the pattern on surface, starting again on Thursday morning, after the initial surface low peaks in intensity in southern Missouri into central Kentucky while secondary surface low starts to develop just east of the Appalachians mountains by late Thursday night into early Friday morning period. What will happen is the energy transfer from the initial low to the new low and allow for relative quicker intensification. When the secondary storm will be on the northeast side of the main trough, this storm will also occlude and start to weaken. Rainfall totals by Friday night will approach 1 inch mark by then. Looking at our temperatures, It has remained in lower 50’s for high Wednesday, but Thursday and Friday will likely be the warmest days as our high temperature remain in low to mid 60’s. Morning lows will be in mid 40’s Wednesday night and warm up to lower 50’s for Thursday and Friday night. Overall temperature anomalies for highs will be right at normal but lows will be about 8°F-11°F above normal so we average out around 4°F-7°F above normal during short term period.
Long Term (Saturday 10-30-2021 through Tuesday 11-2-2021)
The surface low will continue to weaken out and occlude as sits over central Pennsylvania throughout the day on Saturday with rain showers still around for our area as the surface low swings too far to the northeast of the main upper level trough and loose support for intensification. Another reason for weakening of the surface storm is that overall trough is becoming weaker itself, but the main axis it is still situated over Mid-Atlantic region so the surface low continue to hang back in our area so chilly and damp conditions will continue for Saturday as well. When precipitation is all set and done by Saturday afternoon, we will likely have rainfall totals in 1.0″-1.5″ range with locally more possible. The trough will weaken more significantly on Sunday and our heights will start to rise once again for us, but the presence of overall troughing pattern will still hold for 2nd half of the weekend. Any notable surface high pressure will be fairly far away from us so while clouds decrease and allow more sunshine, it will still be partly cloudy for our area with daytime temperatures rising by few degrees. As we propagate into Monday, models depict that we would have a temporary weak above normal heights building right over our area on 500mb level, but we have another large area of trough sitting over northern plains of U.S. and up into much of central and eastern Canada waiting to push southward heading into Tuesday. We will see formation of surface high pressure right over our area and allow for further reduction in cloud coverage on daytime hours of Monday, but as we move into nighttime hours, clouds will increase out ahead of cold front approaching. This cold front is associated with the trough to our north, which finally quickly builds in our area through Tuesday, and will likely bring rain showers chances for us again from Monday night into Tuesday time period. Given that we are about 5-6 days or so away from this time frame, we are seeing some model disagreements on how the evolution of a “more organized” storm, and associated precipitation with it, will take place. Longer range models suggest that weather conditions will likely get cold enough for our area to see first widespread frost/freeze with overall sustained at or below normal temperatures. More details on longer range during the next update on Sunday. Our temperatures will still remain in upper 50’s for Saturday as well before we warm up into lower 60’s Sunday into Monday before we cool back into mid 50’s for Tuesday. Lows will trend cooler form mid 40’s Saturday night and dropping into lower 40’s Sunday night, and eventually down into mid-upper 30’s for Monday and Tuesday night. Our overall temperature departures during the long term forecast period will end up almost exactly where we should be with slightly positive nighttime departures while slightly negative departures for daytime hours.
