Experimental Forecast for 12-23-2014

I thought that it would be fun to try to do daily forecasts during Winter Break so that I could keep up with all that I was supposed to have learned this past semester. 

So, to begin…

Location will be Collin County Regional Airport (KTKI) because of the ASOS weather observation station located there.

Forecast (12:00 AM to 11:59 PM):
High: 53ºF       Low: 42ºF       Peak Wind: 15kts        Precipitation: 0.53”

Discussion:

Nearly stationary long wave trough situated over the Central United States should amplify over the next 24 hours and bring strong enough assent over North Central Texas for some precipitation. This will be due to cyclonic vorticity advection (CVA) into the base of the trough axis and cold air advection in the low levels across the high plains in the Surface to 700 mb layer (noted to be strongest at 850 mb). Clouds have already overspread North Texas as of 6:00 PM in association with the vorticity maxima over Colorado and the left exit region of a jet streak aloft.

Weak cold air advection at the surface will be ongoing at the start of the forecast period with winds out of the northwest. However, clouds and precipitation should keep the low from dipping into the upper 30’s early tomorrow morning. The high will be considerably lower tomorrow than it was today given the weak cold air advection and cloudy skies.

The tricky part of the forecast period will be the low temperature that could occur by midnight Christmas Eve. That is dependent on when the sky clears and how much cold air advection is still taking place (and mixing of the boundary layer due to wind). For now think that the temperature will not drop below 42ºF before the period ends.

Went with a little over a half inch of precipitation given the very crude estimations from the GFS and NAM. It would appear that the main cause of the precipitation is a maximum in differential vorticity advection (DVA) in the 700 mb – 500 mb layer that progresses across North Texas. Both models have an enhanced swath of over a half inch (though the 18z runs have backed off of this slightly) running from southwest to northeast across the region surrounding the DFW area. Not sure what kind of mesoscale feature would be associated with this other than the center of positive DVA. The rain should move out of the area by noon as the area of strongest DVA exits the region.