Another System Today

Wednesday, November 17th 2010, 5:03 am
By: News On 6

Good morning!  Yesterday afternoon we added a slight chance of showers for today's forecast across the Tulsa metro and slightly higher chances across northern Ok.  This is due to a stout upper level short wave that is moving rapidly in our direction and data this morning also suggest we should keep the slight pop in the forecast.  We discussed this feature yesterday, and while most of the energy will remain to our northeast, this mornings observational and model data suggest some precip may spill into the region.  Some precipitation seems likely along the OK and Kansas state line. 

Another issue will be the gusty north winds and the cold air advection that will follow.  Advection is a fancy $2 dollar word for horizontal movement of air.  Basically the cold air will move behind the boundary and will lead to a blustery afternoon and evening.  The clouds will clear out Thursday morning allowing the temperatures to drop into the freezing category again across the northern third of the state.  I think the magnitude of this air mass will be and we've made a minor adjustment to the highs for Thursday.  You'll need to take the big coat this afternoon and keep it for Thursday. We should be able to reach the upper 50s and lower 60s this afternoon before seeing temperatures drop into the lower 50s by 5pm.

The south wind will kick in Friday through the weekend allowing for a relative warm up with afternoon highs in the 60s and lower 70s.  The fire danger will be elevated due to the dry and windy conditions. 

Next week will be interesting to say the least. Upper level ridging center near the Aleutian Island chain and a polar vortex near Hudson Bay Canada will result in a favored pattern for a chunk of true arctic air to move southward.  We usually don't see this type of set up in late November, but the pattern would support some cold air moving southward.  The upper air flow over the western and central part of the nation will be from the northwest and this flow will be conducive to bring some colder air into the plains next week.  These air masses expected to arrive across the plains next week,  if truly arctic in nature, will be shallow.  The depth of the cold air is "thin" and is usually not modeled well by any computer data.  The EURO historically will have the best shot at this air mass but we're still too far out from the time and space domain to offer anything but a general overview of what may happen early next week.  This boundary could be nearing southern or central Kansas Monday with the leading edge moving into northern Ok Tuesday.  The really cold air may be more to the north, possibly in central Nebraska to points northwest.  Another upper level system will slide across the northern high plains Wednesday and effectively allow another surge of cold air to move southward Wednesday and Thursday. I would think this second surge of cold air would be the coldest air of the autumnal season to date. 

Next weeks expected air mass intrusion is not anticipated to be a major arctic outbreak compared to January standards, but this type of scenario has been studied in the past by researchers from Texas A&M and was presented in publication from by Marshall J. McFarland in 1976. 

The "McFarland Signature" was developed to help forecast deep intrusions of arctic air into the Rio Grande of Texas which can lead to devastating agricultural effects.   These types of major arctic blasts are almost always exclusively occurring in late December and January and associated with near record surface high pressure readings. Again, Our expected intrusion of colder air next week is not expected to be considered a major arctic outbreak, but should result in very cold air by Thanksgiving.  Things can and do change, so check back often for updates regarding the forecast and the Holiday weather trend.