Saturday, October 25, 2008

Coldest of the Fall

The title to this blog might become a trend within the remaining days of this Fall season, but our nighttime low temps are always interesting to track this time of year as we slowly transition into winter. This morning we had a low temp of 39, and we haven't had a temperature in the 30s since April 16. So the front that moved through this past Thursday certainly delivered us the low temperature this morning.

On to the forecast:
My thoughts going into our forecast hinge on one factor: another cold front. Yes, we have another cold front already brewing in the Northern Plains. This front will bring us more of a true "Canadian" air mass into the lower MS River Valley, but we will be warming tomorrow ahead of the front.
Right now we have a 1020mb high over the ARLaMiss (just to our west), but this high will quietly move a little south by mid-day tomorrow and bring in a slight push of moisture from the west. The increase in moisture and 850 temps to 12°C will allow us to see temps in the upper 70s across South Mississippi. Although things will continue to change as we move through the day tomorrow. Our biggest change will be ramming down the whole Eastern Corridor of the nation. We, however, will be located in the NVA (negative vorticity advection) zone of the cold front. This really means we will find ourselves on the "left side" of the trough where the convergence and lift are not available for rainfall activity (or even cumulus clouds). Also dewpoint temps will really crash into the upper 20s on Monday Night. Another interesting note should be made about the 1035mb High settling in over the Southern Plains by Tuesday.

So what do I see from this? The front will move through late Sunday night and into early Monday morning, which allows monday afternoons temps to struggle getting into the mid-60s. Most of Miss. will see lower 60s and upper 50s. Basically, our air will be nearly "bone" dry Monday night allowing excellent longwave radiational cooling. Right now I have a forecast low of 36 but you wouldn't have to pull my arm to hard to drop in the lower 30s. Now I must also realize that several folks in our state will potentially see their first frost of the year during this episode.

After Monday things will still be mild. Tuesday looks to be very similar to Monday's forecast, but things will slowly become more "mild" by the middle of the week. Wednesday highs will be the upper 60s before the late-week highs jumping into the lower 70s for Thursday/Friday.

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