Troy Kimmel Weather

Forecasting Austin and South Central Texas Weather Since 1984

troyk

TK’s Weather Discussion….

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Updated 845am CT Wednesday / 22 January 2014

…. A Strong Cold Front By Early Tomorrow ….
…. Wintry Precipitation Possibility Tomorrow Night into Early Friday ….
…. Sunshine Returns with a Slow Warming Trend for the Weekend ….

On this Wednesday morning…. a cold front is moving south southeastward from Iowa and northern Kansas and northeast Wyoming. A low pressure area is developing over west Texas.  High pressure is centered.. to our east.. over Mississippi and western Tennessee. As a result of this surface weather pattern, our surface winds are south southwesterly across our area.

In the upper levels of the atmosphere… a counterclockwise rotating upper level low pressure covers eastern Canada and the eastern two thirds of the USA. An upper level low pressure disturbance is rotating eastward as part of the broad low pressure area over the central and eastern USA and is located off the coast of southern California. As a result of this upper air wind pattern, the upper level winds over south central Texas and the Austin metro area about 18,000 feet above the ground are west northwesterly at 35 to 40 mph.

As surface high pressure continues to move east of the area.. a dry and warmer southwesterly surface wind flow will prevail today. As winds pick, please note the high fire danger given the dry conditions.

By after midnight tonight, the stronger cold front.. from the north.. will arrive about the same time that we see the influence of the upper air disturbance to our west.. and the subtropical jet stream and its associated mid and high level moisture.. overrun the colder air. As upper air disturbances move overhead and create atmospheric lift, we’ll see a better chance of light precipitation beginning by midday tomorrow through tomorrow night with much colder temperatures. As temperatures fall below freezing tomorrow night, there is a chance we could see rain change to light sleet and snow with the precipitation continuing into the early morning hours Friday. Some very light accumulations are possible.

As the upper level disturbances depart the area, a more stable and warmer weather pattern will develop.. with abundant sunshine.. over the upcoming weekend.

Another strong cold front will arrive about daybreak Monday with temperatures turning colder again.

Regarding my forecast, my local forecast confidence: My confidence in my forecast is very high through tomorrow.. then falls to low to medium for tomorrow night and Friday morning (some question on precipitation types – freezing or frozen – as well as amounts/accumulations). My forecast confidence rises back to high to very high for Saturday and Sunday into early next week.

Have a good Wednesday…
Meteorologist Troy Kimmel

Contact me:
[email protected]
http://www.facebook.com/troykimmel

TK’s Special Weather Briefing…

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Austin / Travis County and South Central Texas Special Weather Briefing
Prepared by Incident Meteorologist Troy Kimmel (www.troykimmelweather.com)
550pm CT – Tuesday / 21 January 2014

.. Possible Winter Precipitation with the Possibility of  Some Snow Accumulations Thursday Night …

.. Synoptic / Forecast Discussion …
By late tomorrow into tomorrow night, a southward moving cold front.. the leading edge of much
colder arctic air.. will advance southward across our area. As this colder air continues to advance
southward over the area, a series of west-to-east moving upper air disturbances  will move overhead..
riding up and over the much colder surface air.. beginning Thursday morning and continuing into
Thursday night and into the early morning hours Friday.

The latest computer and manual forecast guidance suggests that “overrunning” light precipitation will
develop over our local area during the mid and late morning hours Thursday and continue through Thursday
afternoon and Thursday night before ending with the departure of the upper air disturbances by the
early morning hours Friday morning. The key to this forecast and the forecast precipitation type will
be surface and upper air temperature profiles and actually how cold the atmosphere becomes Thursday
into Friday.

The latest guidance now suggests that surface temperatures locally will fall and hold in the 30s to near 40 for
much of the day Thursday before falling below freezing around sunset Thursday evening and then into the mid and
upper 20s for the overnight hours Thursday night into Friday morning. Temperatures will only rise into
the 30s for highs Friday because of lingering cloud cover. With the slow rise in temperatures Friday, it may
be late morning into midday hours before we get above freezing.

Earlier guidance had suggested that precipitation would be mostly in liquid form.. freezing rain.. but the
latest guidance has now gone for a more substantial deeper layer of subfreezing air and therefore, much
more favorable for frozen precipitation.. i.e., ice pellets/sleet and snow. Given this and the fact that we
could see liquid equivalent precipitation amounts of up to one to two tenths of an inch (0.10-0.20″), it now
seems possible that some areas of south central Texas and the adjacent Texas Hill Country could see
up to 1/2 to 1 inch of snow/sleet accumulations especially in the Thursday night time period when surface
air temperatures are well below freezing. This could cause hazardous driving conditions locally in the
Thursday night into midday Friday time period.

Please note.. as I mention every time we encounter this type of winter weather episode.. the difficulty in
forecasting winter precipitation types at 30 degrees north latitude (the Austin area).  A relatively thin
warmer than expected layer of temperatures aloft could easily cause this to be more of a freezing rain
event (ice).. just as a layer of much drier air aloft than expected can reduce the amount of precipitation
that reaches the surface.

Please consider this update as a “heads up” regarding the potential for a Thursday into Friday morning
winter weather event. I will continue to monitor this situation carefully and will issue another update
tomorrow (Wednesday). As usual, please continue to be weather aware  and listen for later statements.

tk

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If you have a smart phone (iPhone, Android), I strongly recommend the use of the MyWarn App.. which operates in the background of your phone to let you know when there’s a general “heads up” risk of severe thunderstorms and/or tornadoes (day 1 and day 2 outlooks from the NWS/Storm Prediction Center in Norman, OK). As the risk becomes more immediate and tornado and severe thunderstorm watches from the NWS/Storm Prediction Center and flash flood watches from the NWS/Austin-San Antonio become necessary, you’ll be notified. Finally, when the weather becomes an imminent and urgent threat to life and to property and tornado, severe thunderstorm and flash flood warnings are issued from the NWS/Austin-San Antonio, you’ll be the first to know through this app whether you’re at your home or on the road in the USA. The GPS location feature of your phone tells the app where you are and you’re notified immediately whether you’re in Austin or Chicago.  All the details can be found here.