Monday, Sep. 5 & Tuesday, Sep. 6 Outlook
Unsettled weather forecast for swath extending from western Gulf to New England; we're paying closest attention to cold front sinking through NYC on Monday
Welcome to any new readers! And as a reminder to long-ish time readers, we’re testing a new format for these outlooks. To both old and new—we’re grateful you’re here.
If you have questions about the content of this outlook, the answers might be in this post (we keep adding to it). Otherwise, let us know if something doesn’t make sense (we welcome feedback of all kinds!).
Monday, September 5
We elected to cover Monday-Tuesday this week (rather than Sunday-Monday as usual) to reflect return travel from the long weekend. To that end, our Holt-Winters model forecasts that TSA will screen 2.102 million travelers, but doesn’t see the demand stimulation from Labor Day. Thursday finished in the 85th percentile of our prediction interval (which would convey 2.23 million screened on Monday), though a bit confusingly, Friday finished in the 17th percentile (suggesting 1.99 million).
While Monday might start dry in the NYC area, a cold front sliding south from New England will produce widespread rain1 and isolated thunderstorms. Abundant moisture and the slow-moving nature of the frontal boundary introduces the potential for training showers and storms; the Weather Prediction Center has placed the region at a slight risk for excessive rainfall. For the moment, American is by themselves in having published a travel waiver (covers NYC and BOS), though we wouldn't be surprised to see at least United join them.
Meanwhile, cold, unstable air aloft2 moving out of the Great Lakes will produce numerous showers and thunderstorms from the Ohio Valley to southern Appalachians.
Tuesday, September 6
We forecast TSA will screen 1.843 million travelers (± 0.5σ, or a prediction interval of about 38%, is 1.78-1.91 million travelers).
Showers linger around NYC on Tuesday as the front is slow to clear the area. As the boundary drops into the Washington area, low pressure is forecast to develop along the front: widespread showers are likely (and perhaps a rumble of thunder).
I.e. an upper-level low.
While it links to a Google Sheet, it’s an Excel file and relies on the XLOOKUP function, which does not exist in Sheets. You can download the file and open in Excel, which should resolve the #NAME? error; if any readers don’t have Excel, let us know and we can work on a solution.