Central PA Winter 25/26 Discussion and Obs

[Blizzard of 93]

0z GFS keeps hope alive for tomorrow evening with up to 2 inches for the LSV this run.

[TheDreamTraveler]

Does anyone know why we've been having so many air quality alerts recently? I don't remember getting so many so often the past few months. Not a fan honestly.

[Jns2183]

So Sam Lilo did a ridiculous million winter simulation to try to quantify what Boston experienced that fabled 30 day stretch in 2015 when 90+ inches fell in 30 days. Reaching a conclusion it was a 1:26000 year event. I did similar for Harrisburg based upon 125 years data and 30,000 simulation years.

Based on the analysis of the simulation data (max30_histogram_bins_0p25.csv) and the historical seasonal maxima calculated from the Harrisburg records, the Gamma Distribution remains the best-fitting mathematical model.
1. The Model: Gamma Distribution
The Gamma distribution is ideal for modeling physical quantities that are always positive and exhibit a "heavy tail" (skewed towards high values), such as extreme snowfall events.
Variables Defined:
* x: The 30-day snowfall amount (in inches).
* \alpha (Shape): Determines the fundamental shape and peak of the curve.
* loc (Location): The shift/offset from zero.
* \theta (Scale): Controls the "spread" or horizontal stretch of the distribution.
* \Gamma(\alpha): The Gamma function (an extension of factorials for non-integers).
Equation with Derived Coefficients:
Using the simulation data for the fit:
* * * 2. Goodness of Fit
We used the Kolmogorov-Smirnov (KS) test to evaluate how well the model describes the data. A lower KS statistic (closer to 0) indicates a better fit.
| Dataset | KS Statistic | P-Value | Interpretation |
|---|---|---|---|
| Simulation Data | 0.0155 | 1.05 \times 10^{-6} | Excellent Fit. The model follows the simulation counts almost perfectly across the entire range of values. |
| Historical Observations | 0.1438 | 0.0097 | Moderate Fit. The model generalizes the history but over-predicts low-snow years and under-predicts the mid-range "typical" snowiest months. |
3. Analysis
* Simulation vs. Model: The Gamma curve is a near-perfect approximation of the simulation data. It successfully captures the rapid rise in probability between 0 and 10 inches and the long, thin tail extending past 60 inches.
* Historical Gap: As shown in the right-hand graph, the historical observations are more "clumped" than the model predicts. In reality, Harrisburg has a very strong peak of seasonal maxima between 15 and 25 inches. The model (derived from simulation) peaks slightly earlier (around 10 inches).
* Extreme Tails: The simulation model is much "bolder" than the historical record. It suggests a non-zero probability of 30-day periods exceeding 80 inches, whereas the historical record (spanning ~126 years) has never surpassed ~51 inches.
* Conclusion: The equation is a highly reliable model for the theoretical distribution of 30-day snowfall. However, if used to predict a typical winter in Harrisburg, it will slightly underestimate the "average" peak snow month while significantly overestimating the potential for unprecedented "megastorms."


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[Ruin]

14 minutes ago, TheDreamTraveler said:

Does anyone know why we've been having so many air quality alerts recently? I don't remember getting so many so often the past few months. Not a fan honestly.

yeah I even had them when its windy its total bs 

[Yardstickgozinya]

35 minutes ago, TheDreamTraveler said:

Does anyone know why we've been having so many air quality alerts recently? I don't remember getting so many so often the past few months. Not a fan honestly.

 Apparently it's from particulate and other pollutants  getting trapped under a persistent inversion facilitated by the extremely cold air we had as of late according to the NWS. 

[Yardstickgozinya]

2 hours ago, Ruin said:

yeah I even had them when its windy its total bs 

It's not fog brother. Wind can often be what's transporting pollution and particulate to you. It's all relative to where the pollution, particulate, pollen radiation, etc, source region,and you are located.  It also appears to me that there is an excess amount of particulate in the air for this time of year. What you're seeing in the pictures below is not moisture or mist. I'm outside every night with a headlamp. My eyes are well, trained to tell the difference between solid particles and water droples. It's not the larger particles that actually cause the respiratory issues, It's the smaller particles making the picture look grainy, and the ones you can't see, that are responsible for the  majority of respiratory and analergy issues.. Cpa is also subject to what are known as oreographic pollen and or pollution showers later in the day and night as the atmosphere cools ,due to our eastern proximitie to the Appalachian mountains .  Cpa can dbe a rough place for people with allergies and health problems due to air quality ,especially when the atmosphere starts to cool after those hot and warm days in the spring and fall, when the pollen and mold counts are elevated.

[Ruin]

1 hour ago, Yardstickgozinya said:

It's not fog brother. Wind can often be what's transporting pollution and particulate to you. It's all relative to where the pollution, particulate, pollen radiation, etc, source region,and you are located.  It also appears to me that there is an excess amount of particulate in the air for this time of year. What you're seeing in the pictures below is not moisture or mist. I'm outside every night with a headlamp. My eyes are well, trained to tell the difference between solid particles and water droples. It's not the larger particles that actually cause the respiratory issues, It's the smaller particles making the picture look grainy, and the ones you can't see, that are responsible for the  majority of respiratory and analergy issues.. Cpa is also subject to what are known as oreographic pollen and or pollution showers later in the day and night as the atmosphere cools ,due to our eastern proximitie to the Appalachian mountains .  Cpa can dbe a rough place for people with allergies and health problems due to air quality ,especially when the atmosphere starts to cool after those hot and warm days in the spring and fall, when the pollen and mold counts are elevated.

I never seen a bad air quaility alert in windy weather why? cause it blows stigmatic air 2 I rarely ever see it in cold weather why? the particles have a way harder time in lower humidity to bond and cause smog and or other pollution you often see in muggy very humid conditions int he summer. Myself besides from getting sick this winter I had no problems breathing at all.  

[Yardstickgozinya]

@Ruin it's one thing if you're just simply saying you've never seen it. It's another one if you're trying to say it doesn't happen. .  Every single spring and fall  we have no shortage of air quality alerts on  windy days, it's not a rare thing by any means.  Air quality alerts in the winter is a little more rare but it's not unheard of either.

 Air quality alerts are frequently issued during windy conditions. While wind often disperses pollution, it can also transport smoke from distant wildfires or stir up dust, sand, and ash, causing AQI levels to spike into dangerous orange, red, or purple zones. High winds can transport pollutants across large distances, worsening air quality far from the source. 

  Pollution and particulate matter (PM) generally travel, persist, and accumulate more in cold, dry air. Cold air is denser and sits closer to the ground, trapping pollutants, while low humidity prevents moisture from washing particles out of the atmosphere. Thermal inversions often occur, acting as a lid that keeps pollutants trapped. 

 Humidity can help hold down pollen particles, but the overall effect on allergy symptoms is complex and often negative. While moisture can weigh down pollen grains and stop them from traveling far, high humidity often leads to increased mold and dust mite populations, which can exacerbate allergies. 

https://en.wikipedia.org/wiki/Dunning–Kruger_effect

 

[Mount Joy Snowman]

Low of 28.  Looks like the lower level warmth will win out with the column too slow to cool to the surface.  Perhaps a slushy half inch on the tail end.  Then we finally lose our pack this week.  MDT and LNS both topped out at 48 yesterday.  Onward.

[mahantango#1]

[Yardstickgozinya]

3 minutes ago, Mount Joy Snowman said:

Low of 28.  Looks like the lower level warmth will win out with the column too slow to cool to the surface.  Perhaps a slushy half inch on the tail end.  Then we finally lose our pack this week.  MDT and LNS both topped out at 48 yesterday.  Onward.

  I'm easy to please. If I can get in a couple mile walk under some mood flakes, it gets chalked up as a win in my book. Yesterday was the first day that my pack took a hard hit. I lost more snow yesterday than all the other days combined since the storm. 

[ChescoWx]

Our 13th winter event of the season arrives tonight followed by milder but wet weather most of this upcoming week. We should see rain overspreading the area from SW to NE across the area between 3pm and 5pm. The rain should mix with and change to snow especially over the higher ground of NW Chester and SE Berks Counties. Those higher spots over 600ft ASL could see up to a couple inches of slushy snow on non-paved surfaces. Lower spots should have a tougher time seeing much snow accumulation but either way roads should remain wet. Temperatures tomorrow today and tomorrow will be close to normal near 40 degrees. Except for tonight and Monday night we should see overnight lows remain above freezing till next weekend. We will also see rain on Wednesday and again on Thursday night through Friday. Some areas may finally get rid of this snow cover that has been on the ground for more than a month.

 

[Itstrainingtime]

1 hour ago, Mount Joy Snowman said:

Low of 28.  Looks like the lower level warmth will win out with the column too slow to cool to the surface.  Perhaps a slushy half inch on the tail end.  Then we finally lose our pack this week.  MDT and LNS both topped out at 48 yesterday.  Onward.

Yes, that's been my fear. Last couple of days I thought the writing was on the wall.

[Blizzard of 93]

It’s all about precip rates. If we would get good precip, it would snow. Marginal situations require good rates to overcome & snow.

[Blizzard of 93]

The “better” runs early yesterday had the LSV getting .4 to .5 of precip that produced 3 to 4 inches of snow on the snow maps. 
Now, in that same time period, the models are closer to .2 of precip, so that’s only producing around 1 inch or snow or less in recent runs.