February 28, 2001
Easy forecast short range, tough forecast long range. That is the theme for today's discussion. Nothing in life is easy, but relatively speaking, the forecast through early weekend is clearer in regards to predicting apparent weather than what may transpire as we approach the start of the first full week of March. Again, this discussion will be relatively brief due to time constraints and model differences with the medium/long range forecast. In a nutshell, partly cloudy and seasonably cool through early weekend with the 'potential' for a major winter storm early next week.
Wednesday will be partly cloudy with nothing more than an early morning flurry or snow shower. Highs around 40. Thursday will also be partly cloudy with similar high temps across the region. A touch cooler Friday under partly cloudy skies as a weak trough presses through in response the the Polar Vortex (PV) taking up residence in Southeast Canada. Saturday will be mostly sunny with highs in the upper 30s to near 40.
Depending on which piece of guidance you buy into (I don't purchase guidance myself, but choose to borrow ideas from it), clouds may start to overspread the region on Sunday. Majority of differences occur with a) the speed of the upper low ejecting out of the Southwest (yes, fairly confident the entire piece ejects out in tact) and b) what happens with the PV over Southeast Canada. Models seemed to have generally slowed a touch with the timing of the ejecting SW upper low. On the other hand, guidance is now hinting that as the PV begins to shift East, another piece of energy gets 'left behind' (actually looks more like a shortwave actually gets thrown West from the main PV) and dives South to attempt a phase between jets. This is crucial . . . if the PV shifts east without sending or retrograding a shortwave back to the West and then digs it into the H5 trough, the 'potential' storm would likely head out to sea off the SE coast (NC/SC area). If the PV does indeed redevelop West and a piece of energy digs into the rear quadrant of the trough, the low has a better chance of heading farther North. Finally, if the latter scenario comes to fruition, and the digging shortwave 'phases' with energy from the former Southwest upper low, much of the East will be in for a crippling snowstorm, the likes of which many haven't seen since 1996.
As for the surface, an area of low pressure should develop in the Western Gulf sometime during the day of Friday as discussed yesterday. Meanwhile, a decent area of high pressure looks to be centered in the Plains. The low (or lows as the system may transfer it's energy a few times in response to blocking) will skirt the Gulf Coast. As the low continues it's advance, it should begin to take a jog to the North around Alabama. At that time, the area of low pressure should redevelop on the Southeast Coast around South Carolina. This is where the upper air pattern comes into play to determine the eventual track. At that point, we either have a) the low heading NE and out to sea (can't see that happening based on the tilt of the upper level and H3 troughs respectively), b)the low moving NNE towards Hatteras and then NE or even ENE, or c) a full latitude phase with a major coastal storm for the majority of the East Coast.
With scenario 'a', we get spared, unless you call partly to mostly cloudy skies a disaster. While scenario 'b' sounds unimpressive at face value, one must look at QPF maps to see that there will be a sharp cutoff from very heavy precip to virtually nothing. Scenario 'b' could still give our area measurable snow, but likely not a storm of historical proportions. Scenario 'c' would be an all out snow storm for much of the East Coast, although one could argue that coastal areas remain rain (likely this time of year) and sleet mixes with snow here at times.
So much for being brief! What do I think at this time? Well, as I stated, based on current guidance and ensemble solutions, the out to sea off the SE coast scenario seems unlikely at this time. Not to say it can't happen, but the pattern is not such that would allow for that to happen. Scenario 'c'(the monster storm scenario) seems a bit far fetched. It would take quite a push of energy to redevelop the PV West towards the Great Lakes meanwhile digging a shortwave in the rear quadrant and phasing with the upper low. Again, not to say it can't happen as some models suggest, but the odds of that happening aren't great. Am leaning towards the middle of the road scenario. My thinking is that this is more a Mid Atlantic event at this time as opposed to an entire East Coast event. Even with this possibility, we could still be on the Northern fringe of the precip shield as the storm hits Hatteras, North Carolina. As stated above, the cutoff between heavy and no precip will be tight. It wont take much to bring the heavier amounts of moisture into our region. A few words of caution on this. 1) This potential system is still 5-6 days away and things often change quite a bit in that time frame (although it is nice to see guidance at least picking up on the storm). 2) Many systems this winter which were forecast to remain South of out area wound up tracking a bit farther North. Take Feb 22nd for example. We were expecting 2-4" of snow here, the low moved North a tad, and we ended up with 7". So, in short, we have lots of time to nail this thing down.
Once again to reiterate, a quiet 4 days coming up with the 'potential' for quite a storm affecting parts of the East early next week. Haven't changed my thinking that the system is well-developed and stacked at all levels (means that low pressure is aligned vertically at all levels). This storm will be loaded with deep Gulf moisture and areas which fall under the heavy precip as snow will likely get hammered with a paralyzing March snowstorm. Should be an interesting next couple of days as models play flip-flop and finally converge on a solution (my guess is around Friday morning we start to see the foundations for a somewhat 'solid' forecast. We shall see. Take care!
