Raleigh Weather Discussion
We are going to see some impressive late January warmth the next two days as warm air surges in ahead of a cold front across the central US. Temperatures will likely be near 70 today for most locations and tomorrow will likely see widespread reading s in the mid to perhaps upper 70s! I think the Triangle will probably be in the 74-78 range. The all-time January record high is 80.
Also we will have to worry about some severe weather tomorrow afternoon and evening. High-resolution models, including my company’s in-house 4km model, show a squall line moving across the state tomorrow afternoon and evening. This squall line will likely be low topped thunderstorms with not much in the way of thunder or lightning, but with brief very heavy rain and strong winds. Gust potential values are in the 50-60mph range with this line and that will probably mix down with some of the thunderstorms. Some isolated tornadoes cannot be ruled out, as the wind field aloft will be strong, but strong straight-line winds will be the primary worry as the line moves across. I think the line will reach the Raleigh area probably between 8-10pm tomorrow.
Cooler temps will move in behind this front with temperatures back to near or slightly below normal levels. It looks like we will see several upper level impulses move through the area over the next week or so. The first one Friday night will likely have no precip associated with it outside of the mountains, while another stronger impulse is likely to move through Saturday night and Sunday morning with a round of some light rain. It is possible, that there could be some light snow mixed in some areas, but for now that chance is too low for me to put in the forecast. Just keep it in mind.
Another upper disturbance could move through Tuesday with a chance for some light rain. Warmth will be building across the central US late in the forecast period and will probably start to move in by late next week.
National Weather Discussion/Forecast
It looks like much of the nation will see a mild period in the 11-15 day period which would take us into mid-February. The models are showing the polar vortex weakening in North America with two distinct polar vortices over the Bering Sea and over Europe. The models do build ridging in the Gulf of Alaska and western Canada (-EPO/+PNA) which are cold signals, but the vortex in the Bering Sea means a +WPO and while there are some higher than normal heights in the polar regions, we do not see an optimal setup for a –NAO or any appreciated blocking signatures outside of a possible developing –EPO block.
This means that much of the country will be prone to mild temperatures, with a persistent trough in the Southwest US. Now, it is possible that the models could change in time with this weakness over the Southwest and progress it out. If that were to happen we would see more than likely a full-latitude trough over the central/eastern US with the ridging building in the Gulf of Alaska. However, if this Southwest US trough is correct, it will serve to pump up a ridge over the Southeast, which would keep most of the US warmer than normal.
The GFS/GGEM Ensembles in time do want to progress towards a trough over Hudson Bay/eastern Canada, but this would probably not come for a couple of weeks.
Last night’s ECMWF weeklies were not exactly cold looking. Today’s CFS weeklies have warmed up for week 3 but are cold for week 4.
In general, I do not see evidence for widespread cold for the first half of February in the modeling for sure. As I mentioned earlier that could change if the models handle the Southwest US system differently. Perhaps we will see colder trends by mid-month. We shall see. Winter is entering its final stages and we are starting to run out of time.