Category Archives: Long Range Discussion

First Frost Of The Season Comes Right On Schedule…

The average date for the first frost and freeze in Indianapolis takes place on October 11th and 14th, respectively.  Right on cue, the first frost of the season will take place for most central Indiana neighborhoods over the weekend.  If you happen to miss out on the frosty conditions this week, reinforcing chilly air will descend on the region early next week.

We forecast (3) of the upcoming (7) nights to fall into the 30s.  This is, obviously, a significant change from the extended summer like conditions we’ve been dealing with as of late.  One primary driver behind the significantly cooler pattern has to do with the change in the PNA.  The shift towards a positive PNA will result in the cooler air remaining in place with more staying power than the fleeting cool shots of a few weeks ago.

A series of cold fronts will sweep through the Ohio Valley over the upcoming couple of weeks and each will likely feature progressively cooler conditions.

With the positive PNA in place, it’s no surprise to see the mean trough setting up shop over the eastern portion of the country.

At the surface, we see the cool pattern taking hold into not only the short-term, but the 10-15 day range, as well.

No Comments Autumn, First Freeze, First frost, Forecast Discussion, Forecast Models, Harvest'18, Long Range Discussion, PNA, Summer, Unseasonably Cool Weather, Unseasonably Warm

Looking At The Week Ahead: Significant Changes To A MUCH Cooler Pattern Loom…

We’re opening the new week with the same old unseasonably warm and muggy weather pattern that was with us the majority of last week, but significant changes loom during the week ahead.  Ultimately, summer will be laid to rest (finally) and a legitimate, “stick and hold” fall pattern will take hold.  The transition will feature a “game changer” of a midweek cold front that will take us from an August to a November feel in as little as 24 hours.  Here are some highlights between now and then:

I. A strong ridge will continue to promote an unseasonably warm and muggy feel by early-October standards. Scattered “splash and dash” storms are possible through the early portion of the week, but organized significant rain isn’t anticipated.

II. TD 14 will strengthen into Tropical Storm Michael later today and eventually a hurricane before making landfall along the Florida panhandle during the middle of the week.  The remnant moisture of Michael will then race northeast and impact the flood-ravaged Carolinas during the latter stages of the work week.

III. As Michael’s remnant moisture tracks northeast into the Carolinas, a strong cold front will sweep through the Mid West and Ohio Valley.  Better chances of organized showers and thunderstorms will arrive ahead of the front Wednesday.  Once the front passes, a dramatic wind shift to the northwest will push a MUCH cooler and drier air mass into the region.

IV. We note the PNA (Pacific North America pattern) is flipping to a positive state and that will drive a more sustained period of colder air during the medium and longer range period- or mid and late October.

The air will grow cold enough to support the potential of frost during the 5-10 day period on at least a couple of nights.  Additionally, reinforcing chilly air may ignite the lake effect to our north and northeast during Week 2…  “Times, they are a changing!”

No Comments Autumn, First frost, Forecast Discussion, Forecast Models, Harvest'18, Lake Effect Snow, Long Range Discussion, Rain, snow, Summer, T-storms, Tropics, Unseasonably Cool Weather, Unseasonably Warm, Weather Rambles

Heavy Storms For Some Tonight And Looking Ahead…

A warm front is draped across the state this evening.  At the same time, surface low pressure is spinning across north-central MO with a trailing cold front entering IL.  This evening, a warm and moist airmass continues to advect into central Indiana.

As we type this update, widely scattered thunderstorms are impacting areas from Lafayette to the northeast side of Indianapolis.  A more organized complex of thunderstorms is firing to our southwest- from south-central IL to southeastern MO and into AR.  This is ahead of the cold front.

Looking at forecast radar products, the majority of data brings a couple rounds of showers and thunderstorms through central parts of the state around 9p to 10p, continuing into the overnight and predawn hours.

9p forecast radar
11p forecast radar
2a forecast radar
5a forecast radar

With high precipitable water values in place (approaching 2″ through tonight), locally heavy rain is likely with thunderstorms through the night.  We expect widespread additional rainfall tonight of 0.50″ to 1″ with locally heavier amounts.  A few embedded strong to severe storms are also possible tonight with the primary concern being damaging straight line winds and large hail, but an isolated quick spin-up tornado can’t be ruled out.  We suggest ensuring your weather radio is set with the ‘alert mode’ on tonight.

As we flip the page, a few scattered showers will remain in our forecast Tuesday PM before a much cooler and drier air mass invades Tuesday evening- continuing into Friday morning.  Several central Indiana neighborhoods will dip into the 40s Thursday and Friday mornings.

2a forecast temperatures Thursday.

Enjoy the cooler air while you’ve got it, as a developing heat wave will engulf much of the region as we close the month and open September.  Needless to say, despite the unofficial end to summer just around the corner, there’s still plenty of summer left in the tank.  This is the type pattern that can produce an extended stretch of lows around 70° and highs around 90°.

No Comments Forecast Discussion, Forecast Models, Heavy Rain, Labor Day Weekend, Long Range Discussion, Rain, Severe Weather, Summer, T-storms, Unseasonably Cool Weather, Unseasonably Warm