November is off to a chilly start and longer range data suggests the chill grows more significant as we venture through the second half of the month. Officially, IND is running more than 1° below normal through the 12th.
Despite an active weather week ahead, the open to the new work week will be rather uneventful. Weak high pressure will keep us dry today and Tuesday. Fog and low clouds should give way to an increasingly bright sky by this afternoon (still more clouds than sun today) and partly cloudy skies Tuesday.
Our next weather feature approaches Wednesday in the form of a cold front. This will return showers to the area midweek. Rainfall amounts Wednesday should generally fall in the 0.25″ to 0.50″ range.
A stronger storm will impact the region as we close out the work week. Strengthening low pressure will track into the Great Lakes and drag a trailing cold front through our region Friday evening. A briefly milder southwesterly air flow will push temperatures close to 60° Friday afternoon/ evening before the sharply colder push of air blows into town for the weekend. The transition may include strong to severe thunderstorms Friday PM, and the Storm Prediction Center (SPC) has outlined a large portion of the region under a severe risk Friday. It’ll be important to stay tuned to future updates. Even outside of potentially damaging thunderstorm gusts, non-t-storm winds will gust over 40 MPH Friday.
Once the cold front sweeps through the region, a sharply colder air mass will plunge into the Ohio Valley for the weekend. Overnight data has trended even colder and would suggest falling Saturday temperatures (most of the day will be spent in the 30s) and highs only in the lower to middle 30s Sunday.
Speaking of cold, Thanksgiving week is looking unseasonably cold, and there’s also the potential of early-season snow (far too early for specifics).
Such a pattern illustrated above, per the European ensemble (image 1) and the GFS ensemble (image 2), would help drill a tongue of unseasonably cold air through the northern Plains, into the Mid West, and across the East.
We’ve been discussing early snow cover across Canada and the northern tier for weeks and how models would have to “correct” colder as they realize the air masses traveling over the snowpack won’t be able to modify as they normally would without that snowpack. The differences between this November and last are startling and show how the early snowpack is beginning to “feedback” on itself leading to early-season cold air.
2017 snowpack and temperatures anomalies through the first week of November:
Given the overall look to the pattern downstream, I anticipate the cold will continue to “press” and eventually overwhelm the pattern east as we progress through the second half of the month.