U.S. Temperature Outlook
Similar to the past two winters, our primary variables point to another warm outcome for the 2017-18 season. The warmth will be especially pervasive across the southern and eastern regions of the U.S. Below is a summary of the variables that we analyzed this Fall:
- Trend: The trend of warmer winters over the past few decades puts this variable solidly in the warm direction
- La Niña: With a La Niña event present this winter, there are equal odds of a cold/warm season
- Quasi-Biennial Oscillation (QBO): With a negative QBO, the odds are also equal of a cold/warm winter
- Combination of La Niña and a negative QBO: Slight colder bias
- Polar Vortex (PV): Warm early/more variable late
- Snow: Neutral
- Tropical Forcing: Warm east/cooler west
- Sea Surface Temperatures (SSTs): Warm
With more weight placed on the evolution of the Polar Vortex this Fall, combined with tropical forcing, sea surface temperature (SST) patterns, and snow cover, we forecast enhanced temperature variability and more cold air intrusions into the U.S., relative to the past two winters. We expect this season to be biased toward the warm side, but results are unlikely to be as extreme as the past two “mega-warm” winters. The map below indicates the spatial distribution of the temperature forecast for the December through February period:
The regions with an increased risk of longer cold durations this winter are the Pacific Northwest, Northern Rockies, Northern Plains and adjacent areas in Southwest Canada. The eastern and southern U.S. have the highest probabilities for warmer-than-normal temperatures. As for timing, the first part of the winter (prior to January 1) is the most likely period for widespread warmth, especially in the southern and eastern sections of the nation. If there will be a multi-week period of widespread colder-than-normal weather in the lower 48, the most likely time will be in January and/or February. This will be dependent upon a PV breakdown and a strat warming event occurring, which we feel is likely, and more importantly, the impact of this event on the flowage of Arctic air into the Mid-latitudes–whether the U.S., Europe, or Asia receives the most significant impact from this event remains to be seen.
U.S. Precipitation Outlook
Areas of enhanced or suppressed risk of precipitation are largely based on the upper-level jet stream patterns that set up during the season. Due to the nature of precipitation, there is more uncertainty in the variables that drive the location of “atmospheric rivers” that inevitably produce wet/stormy areas versus dry/inactive areas. Our research has led us to conclude that, mainly driven by the La Niña event, we forecast the northern U.S. to be the wettest area (basis normal), while the southern U.S. will most likely be on the dry side. We anticipate an enhanced storm track/jet stream in the northern U.S. and a suppressed storm track in the southern U.S.
Winter storms will likely develop more frequently from the far western Great Lakes to the Pacific Northwest–this includes adjacent areas of Canada. Storm development and storm frequency are less likely compared to normal across the southern U.S. and along the East Coast. We also believe the total number of Nor’easters this season will be less than normal (less than climatology).
Continue reading for sector-specific highlights. For the full report with in-depth analysis of the variables that drive this forecast, please contact us.
In terms of potential impacts to logistics and supply chains this winter, we are forecasting the northern U.S. to be the wettest area (basis normal), while the southern U.S. tends to be on the dry side. In other words, we anticipate an enhanced storm track in the northern U.S. and less frequent storm systems across the southern U.S. The risk for longer delays and disruptions to shipping and transportation look to be along routes and interstates from the Northern Rockies to the Great Lakes. This includes key east-west interstates such as I-80, I-90, I-84 (PNW), and I-94, as well as northern portions of north-south interstates such as I-25 and I-35. This is also similar to the risk areas of last winter.
Additionally, the expected variable temperature pattern enhances the risk of temperature extremes on both sides of the spectrum. Shipping of temperature sensitive products will likely require various windows of equipment protection. Protection from freeze will likely be more enhanced across the Northern Rockies and Northern Plains through the winter. For the central and eastern U.S., this risk will increase mid-to-late winter, although the specifics will come down to the timing of the Polar Vortex (PV) becoming unstable.
Based on our forecast, there is an increased risk of livestock stress via precipitation and cold temperatures this winter across the Central and Northern Plains, Northern Rockies, and southwest Canada. This includes the key feedlot areas in northern CO, NE, and IA. There is a reduced risk of long-term stress in the key Southern Plains feedlot areas–southern KS, OK, and TX.
With a more variable temperature pattern expected across the middle of the country, there is an increased risk of more extreme frost/freeze cycles in the winter wheat belts of the central U.S. The precise extent, depth, and location of snow cover will be critical for protection from winterkill damage; this is an unknown right now. At this time, it appears the timing of potentially more extreme cold and heightened winterkill threats will be mid-or-late winter. This is true in the U.S., but also in the other major winter crop belts around the Northern Hemisphere–Europe, Black Sea, and China.
As a result of our temperature outlook, we are initially calling for national gas-weighted heating degree days to total ~3,639 with a 75% probability of HDDs registering between 3,400 and 3,850. This centerline seasonal forecast is below the 5, 10, and 30-year normals but over 350 HDDs higher than last year. Our December-February HDD centerline forecast is 2,529 HDDs which is between the 10/30-year and 5-year normals.
An extremely cold or warm winter is unlikely at this time due to expectations of more temperature variability this season. In other words, we are currently not seeing similarities in the driving forces of the pattern as the past two warm winters or the colder winters of 2013-14 and 2014-15. Below is our current HDD forecast breakdown by month:
- November: 525 HDDs, compares to the 10/30yr normals of 541/555 and 441 in 2016
- December: 820 HDDs, compares to the 10/30yr normals of 835/852 and 856 in 2016
- January: 924 HDDs, compares to the 10/30yr normals of 946/931 and 824 in 2017
- February: 785 HDDs, compares to the 10/30yr normals of 785/780 and 583 in 2017
- March: 585 HDDs, compares to the 10/30yr normals of 599/620 and 589 in 2017
Hence, we expect a warmer/slower start to the heating season during November and December due to the Polar Vortex evolution and expectations for lack of long-term anomalous cold in the central/eastern U.S. demand centers. January and February are the months with a higher risk of above normal national heating demand and more anomalous, possibly multi-week cold in the central/eastern U.S. due to higher probabilities of the PV weakening/stratospheric warming event. If these temperature expectations verify, expect heightened variability and to adapt to quick temperature regime changes.
Snowfall/precipitation totals will most likely be higher than normal across the Northern Rockies and Northern Plains, possibly into the Great Lakes. Overall, this is shaping up to be another good snow/hydro year across the Northern Rockies and the Pacific Northwest.
Contact us to connect with our meteorologists and receive an in-depth assessment of how your business could be impacted by the variable conditions this winter.