Well, I hope this Christmas has found everyone
well as we worship Jesus Christ, the Son of God, for his first advent and look
forward to his second coming.
Previous Forecast Review:
The last forecast I issued was for Christmas Eve.
It was actually kind of an interesting day. The high was 50ºF which I am pretty happy about. The lowest temperature recorded in the three day history for KTKI Christmas Eve morning was only 40ºF. But my low forecast was “saved” by the very rapid drop in temperature that night. It actually reached 32ºF just before the clock struck 12:00 AM Christmas Day (which is a temperature bust for those who wanted to save their precious and tender vegetation). Wind speeds have been very tricky. The max winds for Christmas Eve were basically in the 20kt range with higher gusts. I’ve posted the sounding from the Fort Worth WFO showing the significantly mixed boundary layer at 6:00 AM. The mixing process clearly would have to have been wind driven and not thermally driven. (As the day progressed and thermal processes became more important the boundary layer did get deeper). This well mixed layer at the surface is what allowed for some of the faster winds aloft to be transported down to the surface and busted my wind forecast. Oh well…
The last forecast I issued was for Christmas Eve.
It was actually kind of an interesting day. The high was 50ºF which I am pretty happy about. The lowest temperature recorded in the three day history for KTKI Christmas Eve morning was only 40ºF. But my low forecast was “saved” by the very rapid drop in temperature that night. It actually reached 32ºF just before the clock struck 12:00 AM Christmas Day (which is a temperature bust for those who wanted to save their precious and tender vegetation). Wind speeds have been very tricky. The max winds for Christmas Eve were basically in the 20kt range with higher gusts. I’ve posted the sounding from the Fort Worth WFO showing the significantly mixed boundary layer at 6:00 AM. The mixing process clearly would have to have been wind driven and not thermally driven. (As the day progressed and thermal processes became more important the boundary layer did get deeper). This well mixed layer at the surface is what allowed for some of the faster winds aloft to be transported down to the surface and busted my wind forecast. Oh well…
Back to the forecast at hand…
Forecast (12:00 AM to 11:59 PM):
High: 56ºF
Low: 35ºF Peak Wind: 23kts
Precipitation: 0.12”
Forecast Discussion:
I’ve made the assumption that the cold front will not reach KTKI before
midnight tonight (seems highly likely given its very slow progress through
central Oklahoma tonight) and therefore the high will simply be whatever the
temperature happens to be at midnight. For that the skies will likely remain
cloudy (though the western edge of the cloud cover almost reached KTKI) and
winds may increase out of the south-southeast as the front approaches. These
factors should prevent the temperature from dropping significantly and thus a
mid-upper 50’s seems about right. Noted that both 12z GFS and 12z NAM MOS
(model statistical output) had 56ºF at midnight.
Tomorrow
will be a day of steady falling temperatures, strong post frontal winds, cloudy
skies, and possible precipitation. The low temperature for the 27th
will occur at 11:59 PM as continued cold air advection occurs. One of the
trickiest parts of the forecast will be whether clouds and precipitation clear out in
time to allow temperatures to plummet prior to midnight on the 28th.
Winds will be lighter after dark tomorrow evening, but will still be decent and
keep the low level air mixed to some extent. The GFS and NAM keep clouds over
the area and do not clear them out till just after the period ends. Thus, I
decided to lean towards another above freezing low. If clouds clear out just
one hour sooner this will bust.
Precipitation is very tricky. As one might expect with such a warm and moist pre-frontal environment upstream from an upper level vorticity maxima, isentropic assent and positive DVA will aid in destabilizing the atmosphere and could allow for showers to develop along the front. The Fort Worth WFO has gone with a 40% chance for tonight into tomorrow morning with the GFS and NAM printing out about .1” of precipitation near McKinney. In addition, assent caused by positive DVA could yield a second batch of showers as the upper-level trough axis approaches. The NAM does not indicate this second precipitation event having much of an impact on precipitation amounts, but the GFS does (though the amount is very small).
Precipitation is very tricky. As one might expect with such a warm and moist pre-frontal environment upstream from an upper level vorticity maxima, isentropic assent and positive DVA will aid in destabilizing the atmosphere and could allow for showers to develop along the front. The Fort Worth WFO has gone with a 40% chance for tonight into tomorrow morning with the GFS and NAM printing out about .1” of precipitation near McKinney. In addition, assent caused by positive DVA could yield a second batch of showers as the upper-level trough axis approaches. The NAM does not indicate this second precipitation event having much of an impact on precipitation amounts, but the GFS does (though the amount is very small).
Just a quick note, the RAP has significantly more precipitation and thus went ahead and increased the expected amount. I am not going to wait around for the 00z runs to put this out there so here it goes!
