We will see a gradual warm-up the next few days as we may finally crack 40 today and should be well into the 40s tomorrow despite another cold start in the low 20s. A storm system will approach the area this weekend bringing milder temperatures and a chance for rain.
So far this has been through the first 8 days of the month, the 3rdcoldest start to December on record for Raleigh only behind the cold, snowy winters of 2002-03 and 1976-77. Last year as cold as it was, the lowest temperature at the RDU airport was only 15. Yesterday the airport had a low of 16. The storm system this weekend will likely bring a chance of rain by Saturday afternoon to the Raleigh area. There is a very small chance the rain could begin as sleet or mixed with sleet in the foothills and mountains but a quick changeover should occur. This storm will bomb out on Sunday and a line of moderate to heavy rain will likely move through Sunday followed by a sharp drop in temperatures Sunday evening. There is a chance the rain could end as a flurry Sunday night, although there would likely be no accumulation.
An air mass colder than the one we are dealing with now will move in Sunday night and stick around through much of next week. We will likely see lows in the teens for at least a couple of mornings and highs may not get above freezing on Monday and Tuesday for many areas.
The presence of a strong 500mb low near the Canadian Maritimes and a strong west-baxed –NAO block over Greenland is usually a good recipe for an east coast winter storm. However to have a real good chance it helps to have ridging in western North American to help send shortwaves diving towards the Gulf of Mexico. We do not have strong ridging in the west, and thus systems are moving west to east across the western and central US and are not getting a getting a chance to amplify. The GFS and ECMWF do show a light precipitation event on Thursday and the ECMWF shows this could be a wintry mix. However, the GFS is a little warmer and would probably be a cold rain. The GFS Ensembles and Canadian models are rather dry, so as of now I wouldn’t put too much stock in this yet. But I will keep an eye on it.
The very west based –NAO in the models support the development of a closed low over the Great Lakes. This is shown by the operational ECMWF model, the Canadian model, and many of the GFS/ECMWF ensemble members. This would likely result in another rain event by 12/18-12/19 but the continuation of a cold pattern. The models continue to show an extremely west based –NAO through at least Christmas and likely beyond. If this is true, then my winter forecast of a warm January is likely in jeopardy.