Raleigh Weather Discussion
We will continue in a cold pattern for the next several days with a couple of chance for some light wintry precipitation. The first chance will come late tonight and tomorrow morning. Some upper level energy will pass by to our north as a cold front re-enforces our cold air mass. There could be enough lift associated with this disturbance to produce a few isolated snow flurries late tonight and early tomorrow morning. There will likely not be enough moisture to even wet or dust the ground, but there could be a few flurries around, especially near the Va border and also in the NC mountains.
A more impactful event could occur during the day Friday and into Friday evening as an upper level disturbance digs into the TN Valley and moves across the lower mid-Atlantic/upper Southeast. It appears that this will likely be mostly in a freezing or frozen form across many areas, but the big question now is will enough precipitation fall to make this a big deal? Model forecast amounts have decreased some since yesterday, with at least for the RDU area the latest run of the GFS (6z) being the driest with total liquid QPF in the 0.05 to 0.1 inch range and of the operational models, the 6z NAM the wettest around 0.4 inches of total liquid QPF. If you remove those two, the rest of the guidance is in the 0.15 to 0.3 range for the RDU area. The guidance is also split some in how much of this is snow or a wintry mix. Right now it seems to me the best forecast is for a snow to wintry mix event for the RDU area Friday afternoon and evening. With the 3pm-11pm time the most likely time precipitation will fall. A cold air mass in place Friday will become a wedge of cold air trapped east of the mountains during the day Friday so temperatures may pop into the mid-30s Friday afternoon, but will quickly fall into the upper 20s to near 30 once the precipitation begins. Right now I would go with perhaps an inch of snow for the RDU area changing to sleet and perhaps some light freezing rain before ending. IF this is true, travel during the Friday rush hour and through Saturday morning will likely be treacherous. I plan to update this event and make a first call/forecast map this afternoon after the 12z guidance has come in. An early peak at the 12z Nam shows it is in line with the 6z run.
After this event, it will be cold Saturday and Sunday again before we start to warm up Monday and in more earnest as the week progresses. In fact the warm-up for mid next week looks impressive as we could be back into the upper 60s by Tuesday and Wednesday of next week with warm southwest flow ahead of a strong cold front. Rain will likely be around Wednesday and Thursday before we cool off some by Friday. Some guidance does suggest that a wave could form on the tail end of this front by Friday/Saturday of next week and we will have to watch that for wintry potential as cold air will move in behind the front.
National Extended Forecast/Discussion
The pattern looks to be a cold one for the eastern 1/3 to ½ of the US as we head into the 11-15 day period. The GFS and ECMWF Ensemble means agree on a ridge along the west coast and also over Greenland with a trough into the Great Lakes and eastern US. It looks like an extended period with below normal temperatures for those areas. This again agrees well with the MJO phase progression through phases 7, 8, and 1 into early to mid-February. If a new MJO wave were to fire into phases 2,3 by mid month we could see a warmer pattern for the 2nd half of February.
The latest run of the CFS weeklies has actually warmed a bit, the first time I have seen this in several weeks. SO that is worth monitoring. Also worth monitoring is how the models allow jet stream energy to undercut the ridge in the West late in the 11-15 day period which could portend the potential for a stormy period around 2/5 to 2/10 or so.