The main focus for this portion of the forecast period is on late Friday night through Saturday when a significant frontal system is expected to plow through the Lower Mississippi Valley. Warmth and moisture will gradually increase ahead of the arrival of this system with the “warm sector” possessing enough instability to bring at least embedded thunderstorms amongst the widespread and locally heavy rain showers. Raw moisture levels being transported north from the Gulf of Mexico are not overly impressive, but the baroclinic potency of the system coming in will make up for that and ensure some rainfall totals up to a few inches in a couple spots (particularly in the Delta of Mississippi due to potentially longer residence time of high moisture transport owing to specific details of upper trough transition to negative-tilt status). We will be watching closely for the potential for flooding impact with this event. At this time there is still a decent chance the coming rainfall will not be enough to cause true flash flooding issues or greatly exacerbate rather high levels of locals creeks and rivers.
The other, perhaps bigger, worry with this system is the potential for at least isolated severe storms. As of now, the concern for this is mainly centered over the southeast half to third of the forecast area (especially The Pine Belt), where temperatures in advance of an expected squall line of showers and storms will probably manage to get to the upper 60s with dewpoint values peaking in the vicinity of the lower 60s. Usually the latter combination does not yield much instability, but in this case the temperatures well aloft will be colder than usual in the typical thunderstorm set-up in the region, thus aiding in destabilization. The surface low should deepen quickly late Friday night into early Saturday and then pass from southwest to northeast on the northwest fringes of our region. This orientation will support high levels of low to mid layer wind shear, which of course is a critical ingredient needed to yield severe thunderstorms in the cool season. The other big ingredient is the mentioned instability. The Storm Prediction Center is not yet carrying any categories of severe storm risk in our region, mainly owing to uncertainty on whether more than marginal instability will manifest. Given model trends today, the potential is increasing at least a MARGINAL risk may be issued for mentioned portions of Southern Mississippi with the next package. I will keep everyone updated on the latest from the SPC.
The final main risk with this system will be Saturday night into early Sunday when the core of the upper low tracks near (or just north) of the northern extremities of our region. Cold air will be dumping in quickly from west to east Saturday evening in the wake of the passing cold front and model consensus is good that a stripe of wintry precipitation will occur along and north of the upper low center, in association with the best deformation aloft. The consensus is decent that all of this wintry precip (at least of any real significance) will be north/northwest of Mississippi. However, the latest operational ECMWF model run did trend a little farther south and suggests the Mississippi Delta locales may have some issues. But, alas, this latter operational model run remains an outlier in suggesting more than insignificant flurries in the northern portion of Mississippi and I’m holding off on mentioning winter concerns in my forecast at this time, although I will for sure be monitoring the situation closely.
In the wake of the big system anticipate a brief bout of rather frigid air Sunday into Sunday night, before gradually moderating back up as we head through the first half of next work week. At this time the temperatures on Sunday do not look chilly enough to consider a hard freeze warning. However, if a stripe of heavy snow occurs to our northwest then the air mass coming in for Sunday could trend colder and this is something we will be watching out for. Otherwise, expect another big disturbance coming at Mississippi from the west by the middle of next week. Models have been trending warmer for this system and this increases confidence we will not be dealing with winter weather with this system. However, the warming trend is starting to introduce worries of heavier rain and maybe some storms. Of course, I will be here monitoring the trends.
PINE BELT EXTENDED WEATHER FORECAST
