Meteorological fall (began September 1st) is running warmer than average across the eastern half of the country. More specifically, Indianapolis is running 4.8° above average through the period.
The culprit? A persistent strong eastern ridge (the same ridge that trapped Florence across the Carolinas after she made landfall).
That said, things are changing in significant fashion and these changes will result in much colder conditions as we wrap up the month and open October.
We note the PNA (Pacific North America pattern) trending strongly positive during the period.
A positive PNA typically leads to an eastern trough- especially during the fall months into the spring. Something like this kind of upper level pattern usually results.
Sure enough, the models are going to this look.
At the surface, the eastern warmth is reversed in a significant fashion with well below average temperatures. In fact, temperatures will grow cold enough to support high ground snow in the Rockies and northern Great Lakes and the threat of an early frost into the upper Mid West and perhaps portions of the Ohio Valley during the period.
Ah, true pumpkin spice season is right around the corner. 😉
II. Gusty Thursday: After a cold, calm start to our Thursday, southerly winds will become gusty late in the afternoon. This is a result of an approaching cold front that will impact the region Friday.
III. Unseasonably Cold Weekend: A cold front will pass Friday afternoon and a band of showers will accompany the frontal passage. Winds will shift to the northwest late in the day and drive in a sharply colder close to the work week. Air will grow cold enough to potentially support snow to mix in with the rain as precipitation comes to an end. Additionally, upper level energy and the colder air mass this weekend (the air will have a bite to it) could support mixed rain and snow showers Sunday. – Novelty stuff only, but those first flakes are always special to see. Nonetheless, temperatures will run well below normal. In fact, highs will be closer to our average low temperature this weekend.
IV: Reinforcing Halloween Chill: We still stand firm on the idea of warm costumes being required this Halloween as chilly reinforcements blow into town Monday night. This will result in Halloween featuring a high in the mid to upper 40s with lows Tuesday night/ Wednesday morning dipping to around freezing (upper 20s in outlying areas away from the metro). Most of Trick-or-treat hours should feature temperatures in the upper 30s and lower 40s.
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