Guessing the Weather

Sunday 1-07 EDIT: See new post Guessing the Weather, Part 2 (many of the links are changing with the mid-range forecasts)

Now that we're starting to taper for the Houston Marathon, probably the biggest remaining factor on marathon performance next Sunday is the weather. Computer modeling has improved long range weather forecasting, but any forecast past four or five days still isn't much more than a wild ass guess. Regardless, I still enjoy tracking the forecast. Here's what the 8-16 day Global Forecast System model shows for Houston:

8-16 Day GFS

The model shows a cold front coming through on Saturday. The low for Sunday morning is predicted in the 40s and the model shows nearly no daytime heating. The model shows a North wind at 10-12 mph and precipitation accumulation up to two tenths of an inch. One thing is certain: the forecast will change between now and Sunday the 14th.
Edit on 12-31: The model now shows Thursday through Saturday as cold, with things warming up on Sunday! Sunday now has a predicted low in the mid-50s with a high near 70 and a Southeast wind building up above 10mph. With all of this variation, at least we do know there's not much certainty in this forecast.
Edit on 1-1: The model now shows Thursday through Sunday and beyond as unseasonably warm! Sunday now has a predicted low in the mid-60s with a high near 70 and mild South winds. I hope this forecast changes soon.
Edit on 1-2: Still warm and humid for Sunday the 14th. ouch
Edit on 1-3: Still shows a low in the 60s for Sunday. I'm ready for a change in this forecast.
Edit on 1-5: The model still shows Sunday as warm and humid, but now shows a strong cold front coming in Sunday evening.
Edit on 1-6: The model now shows that strong cold front coming in SATURDAY NIGHT. The GFS Meteogram is in Universal Time, so Houston is 6 hours behind the chart. The model now shows Sunday morning in the 50s and cooling off through the day. Morning wind is North near 20. Don't find yourself alone on Post Oak.

Accuweather predicts freezing rain Saturday night. Ha.
Edit on 12-31: Accuweather has already changed Saturday night's forecast from a low of 30 to a low of 49.
Edit on 1-1: Accuweather hasn't changed Saturday night's forecast, still a low of 49, but raining and a Sunday high of 73.
Edit on 1-2: Accuweather has a low of 52 now and a high of 73.
Edit on 1-3: no change in the Accuweather forecast.
Edit on 1-5: Accuweather has rolled over to the 6-10 day forecast. It still shows 52 as Sunday's morning low, but now has a high of 56 rainy and windy with a morning low on Monday at 28.
Edit on 1-6: Accuweather has also picked up on an earlier cold front arrival. Their low is now 40 with a high of 49 on Sunday.

Edit on 1-5: The Weather Channel has Marathon Sunday in the 6-10 day forecast. It shows a Sunday low of 52 with a high of 70 and scattered showers. Note: Over the years I've noticed that The Weather Channel's long range forecast heavily biases seasonal averages. Their long range forecast rarely predicts extreme temperatures.
Edit on 1-6: The Weather Channel shows a Saturday night low of 59 and a Sunday high of 70.