Today’s video:
PDF report (click link to the right to open in HD): 12-10-19 Long-range analysis
Key Points:
- A few weak waves to track in the Midwest this week with some light snow chances.
- Data hints that the system next week could bring snow chances to someone in the Midwest/Ohio/TN Valley. This is possible given brief period of a –AO.
- The North Pacific continues to favor warmer risks for the week 2 period especially in the Eastern US.
- A poleward shift of the jet is favored in week 2 which favors more mild Pacific air into the Eastern US.
- The North Pacific pattern has to change up to see a consistent colder pattern flip in the East US. The BSR suggests this happens at the end of the month.
- Signals for more of a –AO/-NAO to begin 2020 will help with a source of colder air.
- Sub-tropical jet will be main storm driver in week 2 with weaker Northern stream leading to wet risks south/east and drier risks in the Central US.
Weeks 1/2 temperature outlooks:
Week 1:
- The arctic blast data was advertising last week trended weaker and shorter leading to less notable cold in week 1.
- However, we still have the risk of some colder air behind a storm system late this weekend.
- Overall this pattern closely resembles the North Pacific Correlation.
Week 2:
- While we are nowhere near as warm as last year, we do anticipate a warmer pattern in this period.
- The MJO has continued to move despite model forecasts and the strong road-block on the equator. Phase 3 is a warmer risk.
- +EPO (trough near Alaska) signals from a strong, poleward Pacific jet also favors East US warmer risks.
- The North Pacific Pattern correlation suggests southeast warmth which we considered heavily. This tool has done very well as of late.
- Given the sub-tropical jet being the primary storm driver and a –AO – there is a cooler risk in the TN Valley/SE pending how much cool air storm systems can pull in. East Coast storm induced warmer risk.
Weeks 1/2 precipitation outlooks:
Week 1:
- Northern stream produces some light wintry events in the Northern Plains and Upper-Midwest this week but no major systems.
- Next system to really keep an eye on will be late this weekend into early next week. Big volatility on the data but –AO would hint at a snow threat for someone.
- Risk would be for wetter in the southern OH Valley if system can trend further north.
Week 2:
- A strong Pacific jet will flood moisture on the West Coast, however, the stronger jet in week 2 looks to be the sub-tropical jet for the CONUS.
- This will lead to numerous storm systems in the TN/Lower OH Valley.
- With a –AO state possible at times, snow chances are not off the table.
- Given the weaker northern jet and central US ridge, we are favoring a drier pattern for the Central Plains.
Weeks 3/4 updated outlooks:
Discussion:
- Today’s week ¾ forecast update undergoes some warmer changes for the time being. Confidence in this period is VERY low. We’ve discussed internally how analogs do not seem to be working at all right now and it’s most certainly likely related to the change in climate since 2000. The biggest culprit right now is the north pacific pattern with the +EPO, while we’re seeing encouraging signals with the AO/NAO the Pacific needs to flip back with its –EPO in order to cash in on the cold brewing in the higher latitudes. We’re essentially in a holding pattern right now and what happens between now and 12-25 will determine how winter goes. If the EPO and polar vortex do not go in the way we think they will winter will likely struggle to see any kind of durable cold. IF the EPO/SPV/AO/NAO does what we think they can do this morning we still largely believe the last week of DEC and all of JAN can feature durable, sustained cold. As I said above we’re in a holding pattern right now and need to watch how things evolve next 2 weeks. Keep in mind model data much beyond day 8/9 is nearly useless for the time being.
Updated mid/late December pattern drivers:
Updated Winter pattern drivers:
