Saturday, December 30, 2017

Update on the arctic invasion for Sunday thru Wednesday...

A strong, arctic cold front will enter the region on Sunday, causing an extended period of cold air temperatures and bitterly cold Wind Chill values across the local region. Some spotty very light precipitation is also possible from Sunday into pre-dawn Monday.

...Wind Chill Impacts...

Present indications suggest that Wind Chill values will average the teens to the lower 20s for an extended time, from near 2pm on Sunday through about 11am on Wednesday. Within this broad time period, minimum Wind Chill values may approach 10 degrees mainly during the pre-dawn hours on Tuesday morning.

If you must be outside for extended time periods during the above mentioned time period, precautions should be taken to prevent frost bite and/or increased fatigue due to the colder temperatures. We recommend wearing loose fitting clothing in multiple layers, as well as a heavy coat, gloves, scarf and a hat that covers the ears. For maximum protection, a ski mask or other face covering should be used especially if you must be outdoors for greater than 15 minutes at a time during the 
above mentioned time period, and especially during the period of minimum Wind Chills noted above.

...Temperature Impacts...

In addition to the concern due to bitterly cold Wind Chills, actual air temperatures will also become quite cold during the same time period. Below are the forecast minimum and maximum air temperatures forecast for Sunday-Wednesday (on average for the local area):
Day: Low/High
Sunday: 31/47 (falling daytime temperatures)
Monday: 26/33
Tuesday: 23/34
Wednesday: 21/45

As you can see, actual air temperatures will average near to below the freezing mark for a nearly a 48 hour period covering much of Monday and Tuesday. Minimum air temperatures will approach 20 degrees early on Wednesday morning.

Precautions should be taken to prevent freezing and/or bursting of pipes, particularly in older and/or poorly insulated structures during the above mentioned time period. To mitigate the risk of frozen pipes, we recommend allowing the cold water drip from the faucet served by exposed pipes. Running water through the pipe - even at a trickle - helps prevent pipes from freezing. It is also a good idea to keep the thermostat set to the same temperature both during the day and at night to avoid fluctuations in the air temperature surrounding the exposed pipes.

...Precipitation Impacts...

Patchy light drizzle and/or spotty very light rain is likely to develop at times mainly on Sunday midday into Sunday afternoon and evening. Some of the precipitation may mix with or change to spotty light freezing drizzle late on Sunday evening (mainly after 8-9pm) as temperatures approach the freezing point. Patchy light freezing drizzle is then possible into Sunday night as well as the pre-dawn hours of Monday morning as temperatures continue to fall.

At this time any frozen precipitation is expected to be very light in intensity, sporadic in nature and will likely be somewhat spotty in coverage. Therefore, at this time we do not expect significant local impacts from any frozen precipitation late on Sunday evening or Sunday night/pre-dawn Monday. We will continue monitoring trends for this period and issue any updates if conditions warrant.

Please note that wintry/frozen precipitation will be more common at times to the West of the local area - over the Hill Country - on Sunday evening/Sunday night, as well as possibly further South of the local area (including the San Antonio area) on Monday morning. More issues with icing especially of bridges, overpasses and other untreated/elevated surfaces may develop in these areas at times during the aforementioned time periods. 

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