My last blog showed images of the changes the models were showing, which would potentially, finally set up a Winter type pattern for the US, with the Polar Vortex(strong arctic low pressure) finally moving from Alaska(where it’s been stationed all Winter) to NE Canada, near Hudson Bay. This is a typical location during northern hemispheric Winter. The models show a strong PNA(top of roller coaster in the western US) with a ridge and cold air sliding down into the US and a change to wintertime conditions. However, one thing that was missing, was a negative NAO, which would help block the flow from quickly stretching out into the Atlantic. Due to this lack of a block, the flow became too progressive or quick moving, and this caused what was a sharp high pressure ridge to flatten and stretch to the east, allowing the flow to almost take on a zonal(west to east) flow. Until we get somewhat of a -NAO blocking signature into place, I don’t think we’ll see the cold and wintry conditions lock in for the southern and eastern US.
However, with a sharp ridge properly positioned in the western US and the polar vortex located in NE Canada, and sliding to the south, the polar vortex could function to keep the ridge in proper position and suppress southern energy and eventually pull the southern energy to the N/NW, keeping the ridge from flattening too much and causing a potential strong amplification or phasing of the northern and southern air streams toward the end of this week into next weekend.
With this in mind, we turn to the current model output for this upcoming week and weekend. Currently, the GFS, Nogaps, DGEX and Canadian computer models are showing the potential for a storm to develop in the Gulf of Mexico and move up the Atlantic coastline. There is a possibility for a phasing of a northern steam system with a piece of energy in the southern stream, which would potentially make this a very dynamic system, which could strengthen quickly, as it moves from the Gulf to the SE Georgia coast, and bring significant snowfall to the south and up the east coast. Other possibilities are that the southern energy will move more quickly than the northern energy, which may allow for snow on the northern fringes of the system, but a weaker system, or the northern energy moving more quickly than the southern energy, causing the system to move north into the SE US and up the Appalachians, giving the southern US heavy rain, followed by a possible changeover to snow. At this point, all possibilities are equally likely. The GFS, DGEX, Nogaps, and Canadian models are all showing the possibility of a phasing system, or at least a decent snowmaker from the southern Appalachians region up the east coast. I am attaching images.
After this, it appears blocking may finally set up and provide a much, much colder last half of February. One thing to note is that the Polar Vortex split and movement to NE Canada was a result of a stratospheric warming event, which has now caused extensive cold into Europe. Similar patterns, such as took place in 1985, allowed record cold into the US not long after a similar outbreak in Europe. The potential is there for record breaking cold after 2/15. I’ll keep you updated.
GFS model at 7pm this upcoming Saturday, showing the Gulf of Mexico Low pressure areas developing and moving off of the Georgia coast by 1am on Sunday. Note the high pressure ridge(green) in the western US and the flow coming south and then bending back to the northwest, around the polar vortex(low up in NE Canada at top of purple area). Another image shows the blue freezing line at 5000ft altitude, and associated snowfall north of that line.