Fall 2025 Medium/Long Range Discussion

[RCNYILWX]

I put together a long range pattern thoughts document for LOT staff a few days ago regarding the the impressive agreement in a cold and potentially active pattern with some staying power.

It'll be primarily -EPO driven at first but then with the stratospheric warming/SPV stretching event ongoing, that tends to translate with blocking also developing in the AO and NAO domains. If we can keep the PNA neutral to negative, could set up for a rare snowy December for a good chunk of the region.

For Chicago since 2010, the only Decembers that had both above normal snowfall and below normal temps are 2010, 2013, and 2016. Below normal temps but below normal snow occurred in 2017 and 2022. I know that Detroit had a very good December in 2017 from a much more favorable clipper track there.



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[DocATL]

Now we get to watch the models do their back and forth dance. GFS looks yuck with a stronger ridge, Canadian looks better.

[sbnwx85]

5 minutes ago, DocATL said:

GFS a big fail for next weekend into early the next week for Chi. Yuck.

The system Saturday is weaker and south. Then a cutter with rain which seems inevitable no matter what happens Saturday.

[cyclone77]

Looks like it'll take another day or two to work out the fine details with this lead wave.  Lots of moving parts.  The large scale pattern really does support a high-end storm evolving out of this immediately following the lead wave.  Hope we can sync things up properly to take advantage of it.

[sbnwx85]

I know @Chambanais pulling hard for the 00z Euro.

[A-L-E-K]

Weekend duster starting to dab out and extended losing the sauce, sad

[Baum]

1 hour ago, A-L-E-K said:

Weekend duster starting to dab out and extended losing the sauce, sad

Too soon. Let the hope and hype build for another 48-72 hours before you crush dreams.

[Baum]

Festive if anything, to open the holiday season. Maybe a whitening on the newly strung garland and lighting. Beats 62 and open golf courses in my world.

 

LATE FRIDAY NIGHT THROUGH SATURDAY, A POTENTIALLY PROLONGED   PERIOD OF WARM ADVECTION DRIVEN PRECIPITATION PAIRED WITH   SUFFICIENTLY COLD TEMPS ALOFT AND AT THE SURFACE MAY SET THE STAGE   FOR AN ACCUMULATING SNOW EVENT. WHILE THERE'S A LARGE SPECTRUM OF   PLAUSIBLE OUTCOMES AMONGST ENSEMBLE MEMBERS, THE MULTI-ENSEMBLE   PROBABILITY FOR 1"+ (10:1) SNOWFALL IN 24 HOURS CENTERED ON   SATURDAY-SATURDAY EVENING IS >=60% EVEN AT THIS EXTENDED LEAD   TIME. THE ECMWF/EPS DEPICTION HAS BEEN GENERALLY MORE ROBUST THAN   THE OTHER GUIDANCE SUITES, BUT ULTIMATELY IT'S MUCH TOO FAR OUT   FOR SPECIFICS, ASIDE FROM FEELING COMFORTABLE WITH ~60% POPS IN   THE GRIDDED FORECAST. OUR MAIN MESSAGE IS TO KEEP A CLOSE EYE ON   SUBSEQUENT FORECAST UPDATES AS THIS TIMEFRAME DRAWS CLOSER FOR THE   POTENTIAL FOR WINTER WEATHER IMPACTS TO POST-THANKSGIVING TRAVEL.    -LOT