ChescoWx

If not for Philly maybe the how much for my backyard question LOL!

Some of you may remember I used a program called WXSIM to build my own "in my backyard" forecast. Well with AI and my own detailed weather station climate history at this location since 2004. I have developed a new hyper local backyard forecast. Below is the high level background on how it was built. I will also track this AI forecast vs. my NWS Point and Click forecast to see how accurate or not it actually turns out to be. How the East Nantmeal Backyard Forecast Is Built A ten-day forecast for one hilltop in northern Chester County, trained on that hilltop’s own twenty-two year record — and measured against the National Weather Service’s own guidance on days it had never seen. 40.10968°N, 75.73363°W · 677.7 ft USGS 3DEP Davis Vantage Pro 2, fan-aspirated, in service since 2004 CoCoRaHS · NWS Skywarn CHPA-174 The short version Five weather models are pulled for this exact coordinate — the European ECMWF, NOAA’s GFS, the German DWD ICON, the Canadian GEM, and the National Weather Service’s own National Blend of Models. Each one is corrected using its own track record at this East Nantmeal site — how wrong it has been here, in this month, at this hour of the day, at this many days out. The corrected forecasts are then combined, weighted by how much each has earned. Finally the whole trace is nudged toward what the station is reading right now, by an amount that decays as the present stops mattering. Nothing in it is a physical simulation. It does not model soil moisture or cold-air drainage from first principles. It measures what those things have actually done to this thermometer, over years, and applies that. The site Everything rests on one sensor. A Davis Vantage Pro 2 with a solar fan-aspirated shield, five feet above ground over grass, in service since 2004. The anemometer is roof-mounted, and reads well below open exposure because hills rise in every direction. Corroboration: the station behaves like its elevation and is accurate A forecast trained on one sensor invites an obvious question — is that sensor telling a coherent story, or just producing numbers? One way to test it is to compare against a research-grade station nearby and ask whether the difference between them looks like physics. Avondale 2N is a U.S. Climate Reference Network site about nineteen miles south, at 409 ft — 268 ft below East Nantmeal. USCRN stations use triple-redundant sensors and are built for exactly this kind of reference use. The two records overlap for 7,139 days, from January 2007 to August 2026. East Nantmeal minus Avondale 2N, 7,139 overlapping days, 268.5 ft apart. The two stations track each other almost perfectly day to day — r = 0.996 on highs and 0.988 on lows across nearly twenty years. And the offset between them is exactly the shape elevation predicts: the higher site runs cooler by day and warmer by night, giving East Nantmeal the narrower diurnal range. Cool days come from elevation; mild nights come from cold air draining off a hilltop into the valleys instead of pooling on it. Expressed as a lapse rate, that is −5.08 °F per 1,000 ft on highs and +5.23 on lows. Earlier work in this archive, using an entirely different station pair — Phoenixville 1E, some 550 ft lower — and a different era, arrived at −5.23 and +4.85. Two independent comparisons landing within a few tenths of each other! I will post the latest forecast below. Let me know if any questions or suggestions. Thanks!

Some of you may remember I used a program called WXSIM to build my own "in my backyard" forecast. Well with AI and my own detailed weather station climate history at this location since 2004. I have developed a new hyper local backyard forecast. Below is the high level background on how it was built. I will also track this AI forecast vs. my NWS Point and Click forecast to see how accurate or not it actually turns out to be. How the East Nantmeal Backyard Forecast Is Built A ten-day forecast for one hilltop in northern Chester County, trained on that hilltop’s own twenty-two year record — and measured against the National Weather Service’s own guidance on days it had never seen. 40.10968°N, 75.73363°W · 677.7 ft USGS 3DEP Davis Vantage Pro 2, fan-aspirated, in service since 2004 CoCoRaHS · NWS Skywarn CHPA-174 The short version Five weather models are pulled for this exact coordinate — the European ECMWF, NOAA’s GFS, the German DWD ICON, the Canadian GEM, and the National Weather Service’s own National Blend of Models. Each one is corrected using its own track record at this East Nantmeal site — how wrong it has been here, in this month, at this hour of the day, at this many days out. The corrected forecasts are then combined, weighted by how much each has earned. Finally the whole trace is nudged toward what the station is reading right now, by an amount that decays as the present stops mattering. Nothing in it is a physical simulation. It does not model soil moisture or cold-air drainage from first principles. It measures what those things have actually done to this thermometer, over years, and applies that. The site Everything rests on one sensor. A Davis Vantage Pro 2 with a solar fan-aspirated shield, five feet above ground over grass, in service since 2004. The anemometer is roof-mounted, and reads well below open exposure because hills rise in every direction. Corroboration: the station behaves like its elevation and is accurate A forecast trained on one sensor invites an obvious question — is that sensor telling a coherent story, or just producing numbers? One way to test it is to compare against a research-grade station nearby and ask whether the difference between them looks like physics. Avondale 2N is a U.S. Climate Reference Network site about nineteen miles south, at 409 ft — 268 ft below East Nantmeal. USCRN stations use triple-redundant sensors and are built for exactly this kind of reference use. The two records overlap for 7,139 days, from January 2007 to August 2026. East Nantmeal minus Avondale 2N, 7,139 overlapping days, 268.5 ft apart. The two stations track each other almost perfectly day to day — r = 0.996 on highs and 0.988 on lows across nearly twenty years. And the offset between them is exactly the shape elevation predicts: the higher site runs cooler by day and warmer by night, giving East Nantmeal the narrower diurnal range. Cool days come from elevation; mild nights come from cold air draining off a hilltop into the valleys instead of pooling on it. Expressed as a lapse rate, that is −5.08 °F per 1,000 ft on highs and +5.23 on lows. Earlier work in this archive, using an entirely different station pair — Phoenixville 1E, some 550 ft lower — and a different era, arrived at −5.23 and +4.85. Two independent comparisons landing within a few tenths of each other! I will post the latest forecast below. Let me know if any questions or suggestions. Thanks!

A bit more humid today before a cold front crosses the area late tonight which could spark some showers but will then usher in some beautiful weather through at least mid-week with below normal highs in the mid to upper 70's and lows in the 50's.

A bit more humid today before a cold front crosses the area late tonight which could spark some showers but will then usher in some beautiful weather through at least mid-week with below normal highs in the mid to upper 70's and lows in the 50's.

Widespread cool 50's overnight with our usual chilly spot in Warwick Township down to 54.4. In most spots it was our chilliest morning since back on July 26th. Below normal temperatures look likely to continue through most of this week with highs mainly in the 70's and lows in the upper 50's to lower 60's. Some shower chances but no washouts around this weekend before we clear out to start the new work week.

Widespread cool 50's overnight with our usual chilly spot in Warwick Township down to 54.4. In most spots it was our chilliest morning since back on July 26th. Below normal temperatures look likely to continue through most of this week with highs mainly in the 70's and lows in the upper 50's to lower 60's. Some shower chances but no washouts around this weekend before we clear out to start the new work week.

We are under a flood watch thru 2am for between 1 to 2 inches of rain and maybe more for some spots that get under a thunderstorm. We will get cooler tomorrow and that will last through the next week with temperatures mainly in the upper 70's to near 80 degrees for high temperatures. We should see nighttime lows back into the 50's by early next week.

We are under a flood watch thru 2am for between 1 to 2 inches of rain and maybe more for some spots that get under a thunderstorm. We will get cooler tomorrow and that will last through the next week with temperatures mainly in the upper 70's to near 80 degrees for high temperatures. We should see nighttime lows back into the 50's by early next week.

Thanks! Mike, that is really the crux of the discussion and I think we've arrived at the same place. "The magnitude of the adjustment is inferred, but not well documented in the sense that it has been verified by field measurements" - that is precisely the claim I've been making, and I appreciate you putting it plainly rather than trying to make me prove it. And thank you for the two references. Parallel observation is the gold standard and I hadn't seen either paper. Vincent 2018 is the one I want most - 88 site pairs with five-year overlaps quantifying how much uncertainty homogenisation introduces against directly measured ground truth is exactly the number missing from this discussion. If the answer is small, that's a real argument for confidence in the method that isn't an appeal to benchmarks on synthetic networks. If it's large, that's worth knowing too. Either way it's measured rather than modelled.

Most spots dry out a bit today with sun returning we could see a couple showers toward evening especially across southeast parts of the area. A bit less humidity today and especially tomorrow before the chances of showers increase again by Thursday afternoon into the night. The weekend looks to continue shower chances as we continue to erode any drought concerns across the area.

Most spots dry out a bit today with sun returning we could see a couple showers toward evening especially across southeast parts of the area. A bit less humidity today and especially tomorrow before the chances of showers increase again by Thursday afternoon into the night. The weekend looks to continue shower chances as we continue to erode any drought concerns across the area.

A general 1" to 3" of rain fell across the area yesterday and overnight with 3.18" recorded at the Warwick DEOS. We could see some sun retrun this afternoon with a slight chance of a shower toward evening before we clear out and see a couple great weather days both tomorrow and Wednesday. Humidity should also be less through mid-week. Shower chances return later Thursday afternoon and through the start of the weekend.