After a week of cooler-than-normal temperatures in the Stateline, a sudden, but brief, warmup is in store just in time for Halloween.
On Friday, the 23rd, temperatures reached 70° in Rockford before a cold front moved in and brought high temperatures below daily averages for the next week. Of those seven days on the cooler side of normal, only one of them reached 50’s while the other six were stuck in the 30’s and 40’s. This cold stretch of weather included the coldest October 26th on record when the high in Rockford reached only 37° surpassing the previous record of 38° set back in 1942. However, a brief pattern change should pull temperatures above normal for Halloween, though it won’t last through the weekend.
A large system of high pressure contributed to a clear and dry Friday to kick off Halloween weekend but temperatures were stuck in the 40’s for most of the day with Rockford having only reached 46° for a high. A cool breeze out of the north and northwest kept conditions on the cooler side despite the sunshine. Meanwhile, a strong low pressure system has been stirring in southwest Canada and will propagate eastward through the weekend. As this storm moves closer to the Stateline and the high pressure system moves off to our east, winds will shift to southerly for Saturday. Sitting in between the two strong systems, a strong pressure gradient will form over the Stateline causing a swift increase in wind speeds. With sustained winds out of the south upwards of 25 mph and gusts as high as 35 mph, strong warm air advection will take place over the Stateline creating notably warmer conditions for Saturday. A similar situation is taking place in the northern Plains as of Friday evening where strong winds have not only spawned high wind watches and wind advisories but had also warmed much of the area into the upper 60’s and even lower 70’s Friday afternoon. Though the Stateline won’t get quite that warm, temperatures are forecast to climb into the middle to upper 50’s.
As the low pressure system continues to trek across far southern Canada, its cold front will move over the Stateline late Saturday evening causing a sudden shift in wind direction from southwesterly to northwesterly which will immediately begin advecting cold air into the Stateline. The now northerly winds will remain strong for Sunday as the pressure gradient tightens in between the low pressure center and a rapidly strengthening system of high pressure which will be moving into the central Plains for the latter half of the weekend. Gusts could reach 40-45 mph at times. This means conditions will cool down for Sunday just as quickly as they will have warmed up on Saturday. Highs on Sunday are forecast to stay in the lower 40’s with some areas likely not escaping the 30’s. Temperatures should recover fairly quickly, however, with 50’s likely returning by Monday and the latter half of next week reaching the 60’s.