Raleigh Weather Discussion
We will see the showers and cloud cover hang around the area today before we should see clearing and a substantial warm-up for Saturday through Monday. As I mentioned yesterday, we will likely be in the mid to upper 70s this weekend into Monday which would put us around 25-30 degrees above normal for this time of year. The all-time high temperature for January is 80 set on 1/30/02. We will flirt with record highs for the day I think this weekend, but I am not sure we will hit 80.
The balmy, may-like weather will last through Monday, but an approaching storm system will bring the chance of rain it appears by late Monday and a rainy and cooler weather pattern beginning by Tuesday. I think on Tuesday rain will be around all day with falling temperatures through the day into the 50s and 40s by late in the day for now ending this spring-like pattern.
A much cooler week appears on tap next week with some questions surrounding the possible weather on Friday. For the 4th run in a row, the operational ECMWF shows a cut-off low in the southern plains heading east, weakening, but having enough oomph to produce a round of precipitation in the southeast on Friday. On the northern edge of this the model has 850mb temperatures below zero, although surface temperatures taken literally are above freezing, but literally the 00z run of the model puts out 2-4 inches of snow across the NC piedmont. The trick part is this. The northern branch of the jet stream is going to flex it’s muscles late next week and next weekend, with a super cold and deep trough over southern and southeastern Canada. This can be a good thing for winter lovers in the south as it will suppress any impulse to the south allowing more cold air to be involved. However, if it is too strong and the timing of the impulse is not right, the northern branch will crush this southern impulse and it will dry out and be nothing. The GFS is showing that scenario. The ECMWF maintains the system long enough before weakening it to bring some snow to the area next Friday. A couple of the 6z GFS Ensemble members threaten some light wintry precip next Saturday, while the operational Canadian model shows nothing although the ensemble mean does show some precip. The Euro Ensemble mean does show some light precip Friday/Saturday indicating some of the ensemble members do have an event.
The bottom line is that there is still support for a possible wintry event next Friday or Saturday, although as I have been saying all week, it is hardly a convincing case yet. Keep it in mind though. Whether the precip pans out or not, it does look like temperatures will be below normal late next week and into the weekend. Some scenarios are colder than what I have forecast, especially the 00z Euro which has lows in the teens next weekend.
National Extended Weather Discussion/Thoughts
The presence of blocking and the polar vortex in southern and southeast Canada is certainly a cold signal for at least the northern tier of the US if not the central/eastern US. It appears that the eastern US trough will amplify around 1/21 to 1/22 with a significant cold shot for the East, although how significant is still up for debate. This is supported by the continued progression of the current MJO wave, which is in phase 5, a warm phase for the east in January, but should progress into colder phases 7,8, 1, 2 and in the next 10 days to 2 weeks. The composites you can see here:
http://raleighwx.americanwx.com/MJO.html
In fact the modeled weather pattern by the end of the 6-10 day period and beginning of the 11-15 day period is very close to MJO phase 7/8 composites for January.
The models want to break down the ridging in the Gulf of Alaska and western Canada around 1/24 to 1/25 which does fit with MJO phase 1 for January, but it is possible they are doing this a little too quickly. IF they are correct, we will likely see a moderating US, although the Lakes/East will likely remain cooler than normal.
With the lack of strong ENSO forcing (neutral ENSO), assuming the MJO wave does hold together, I would expect it could be the main predictive factor for the weather pattern for the next few weeks. It would likely argue for a cold pattern for the Lakes/Midwest/East from around 1/17 through probably 1/26 or so, but for trough to return to the Gulf of Alaska/western Canada by 1/26 or so and a moderating trend and possibly warm-up in the East for the end of January. This is of course speculation.
The CFS/ECMWF weeklies look to maintain the cooler looking pattern through the rest of January and into February. So that has to be considered as well.
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