Expect a quick burst of snow overnight that should just replace the inch we got Friday. There is decent ensemble consensus for another quick burst of snow Tuesday/Wednesday ahead of the last truly cold air mass (at least for right now). This one also looks like another 1-2 inch type storm although it’s too far out to determine exact storm track. Aside from the snow chances, the big question meteorologically is what will happen to the pattern next? Will we remain in the icebox for the rest of the month or will things warm up?
Here’s what we know…
1) As the trough axis swings across the eastern U.S. Tuesday/Wednesday, the polar vortex (PV) will retreat northward due to the shift in momentum. Note the difference in the location of the PV from Sunday to Wednesday. This will keep the coldest of the arctic air north of KY and allow temperatures to rise back into the 30s for Wed/Thurs.
2) There is strong model consensus that a shortwave will crash into the western ridge late in the week, which is supported by the decrease in the PNA. This will lead to a split flow pattern by next weekend which means both the polar and sub-tropical jets will be active.
3) Split flow patterns in February are often associated with the potential for winter storms in the eastern half of the country. The dominance and shearing power of the PV and a lack of a blocking ridge upstream (negative NAO) over the past few weeks has effectively kept any big storms from forming along the East coast. However, split flow patterns provide the access to the moisture (sub-tropical jet) and cold air (polar jet) necessary for major winter storm formation. Timing will be the key, as shortwaves from each jet will need to phase together to develop a big storm. The lack of a major upstream blocking ridge (I don’t see much support for negative NAO) won’t necessarily prevent the phasing of the jet streams, but it sure won’t make it easy. One thing in our favor is that we are still in a weakening El Nino, so once the PV pulls northward this week, I expect to see the sub-tropical jet become more active.
The Bottom Line:
It’s just speculation, but I feel that the evidence available suggests that the Feb 10-24 period should feature temperatures a bit colder than normal for the mid-south. If the split flow does persist, I think the probability of at least one major winter storm in the eastern U.S. is fairly high. Regardless, this pattern should be much stormier than what we’ve seen the past two weeks under the dominance of the polar vortex.