November Winter Update
1. Long stretches of winter weather, cold and snow, are not for the short term from the northern Plains to the East, but perhaps for later December or January. However, there will be brief periods of winter weather in the near term like the blizzard later this week in the northern Plains, a possible storm for the Northeast Nov. 21-22 followed by cold shot and maybe again late month. Also, we still feel the winter season can extend into early spring, similar to 2013/14 winter and spring season. (Moderate to high confidence)
2. It will be colder this winter compared to last year, but not extremely cold overall. (High confidence)
3. For the Southeast, it will be a mild December and February, but chillier January. This is similar to the 1984/85 winter season. In addition, the fall was quite dry across the interior Southeast, and I do not see much drought relief for this region through the winter. Some analogs have very narrow band of above-normal rainfall which could be the path of developing storms along cold fronts, but we lean less rather than more. (Moderate to high confidence)
4. ENSO signal can be weak and not a dominating factor. Therefore, a weak La Nina to neutral winter season may not completely dictate the winter. Increasingly positive PDO, low sea ice, Siberian snowpack and the EPO going negative mid and late winter are other signals to impact this winter. Warmth from the tropics, still impacts of our super El Nino last year, can move to the northern latitudes and influence the pattern as well. (Moderate confidence)
5. The first half of the winter will have mainly a fast-moving northern branch of the jet stream carrying storms west to east. We expect frequent fronts, up-and-down temperatures and some snow spread from the Rockies to the Great Lakes and parts of the interior Northeast. (High confidence)
6. By January, the pattern can be more amplified. The pattern slows with two possible scenarios. One, fronts can move quickly to the coast with low pressure intensification along the mid-Atlantic or New England coast. The second can be waves developing along these fronts from the south moving up the East coast that can lead to rain or snow for big cities but more likely snow inland. (Moderate confidence)
7. Lake-effect snow slower to develop compared to our September update. Lake-effect can be heavy in late December and January. (Low to moderate confidence)
8. We still believe that December will not be as mild as record warm December of 2015. However, it does look warmer than our September update for the Plains and Midwest. (Moderate confidence)
9. The Southwest looks dry and warm overall. (Moderate to high confidence)
10. Arctic shots of cold will take aim at the northern Plains and Midwest, especially mid- and late winter. This results in a colder overall winter for the Plains and Midwest. However, due to the delay of strong shots for December, we are emphasizing mid- and late winter. The actual departures were brought up in the northern Plains and Midwest as a result of the change. (Low to moderate confidence)
11. Above-normal snowfall is expected around the Great Lakes, interior Northeast and eastern slope of the northern Rockies. (Moderate confidence)
1. Our first risk, which was a risk we had back in September, is temperature departures are too cold across the northern Plains and Midwest. The lack of snowpack, strong Pacific jet pushing mild air across Canada and the missed chance by the negative AO to send early cold into North America are all reasons for the change we made in December. It could be warmer! But if the western jet cuts off and the PDO strengthens on the positive side, it can turn quickly cold leaning big negative departures.
2. January could be a wild month if the northeast Pacific pattern shapes the way we think. We are very high on snow for the northern east slope of the Rockies and the interior Northeast. There can be multiple storms during January for the East.
3. The pattern for much of the Southeast looks dry. This fall has been very dry and drought conditions have worsened. I do not see any significant change through the winter which could mean bigger problems this spring to the growing season. Some analogs are wetter. There could be a small corridor that has some rain.
4. There is a outside chance that the winter just stays mild for most of the season. We have seen that cold air wants to hold on the other side of the globe across Asia and Europe this fall. If this continues, then this scenario can occur for North America. We are betting on stronger MJO and stronger positive PDO impacts to shake up and change the pattern.
1. At first it look like this winter would start early with snow for the Northeast, Great Lakes and Midwest. Yes, there can be some events in the shorter term, but it looks like most of the snow that falls this winter is during the second half and even into early spring. We made changes throughout the forecast relating to this idea.
2. December temperatures were take up by a few degrees in the northern Plains, southern Plains and Midwest. This can be seen later in the post.
3. Other changes were made to December precipitation, January temperatures and snowfall.
For the three-month maps, we have the new update followed by the comparison of the previous and new forecast. You can see the changes that were made on this update. Temperatures were impacted especially by changes in December and January for the northern Plains. Drought in the interior Southeast can extend through the winter.
The three-month forecast can have two parts. We now lean milder in the early part of winter for the northern Plains and Midwest. Also, the southern Plains and interior Northeast can be milder than earlier thinking. Midwinter, the pattern looks more amplified where fronts and storms can be stronger and temperatures can be more extreme. February is a risky call at this point. A shift in the storm track toward the Ohio and Tennessee valleys could mean more snow for the Midwest, Great Lakes and parts of the Ohio Valley, milder air in the East and colder air over the northern Rockies and northern Plains. However, we feel the winter will not let up. Similarities from 2013/2014 season may show up with a extended period of winter weather into the spring which may have impacts on retail and businesses with a late transition.
Below is a comparison of last winter (December through February) to this projected winter, temperature and precipitation. It was a mild winter for many with a super El Nino. We do not expect a very mild winter season. In addition, we expect drier conditions in the South and Southeast this winter, especially the Southeast which would be a big change from last year and where they need the rain after the dry late summer and fall. There were a couple of changes made on the change maps from September. The change in the northern Plains and Midwest will not be as great due to a change in December temperatures.
This is our snowfall forecast which includes the period from October through April. Right now, it still looks like it could snow right through April across many areas of the country. However, some areas can start out slow like the northern mid-Atlantic to the East Coast cities where we made a few adjustments on the map. We favor a lack of blocking this winter, but the Pacific pattern could have more influence downstream. We will see a frequent amount of storms coming down out of western Canada heading to the east from late November into December. However, a lack of solid cold air could result in more rain than snow from these systems. However, from January through March, the pattern can become more amplified, more cold in place and can result in bigger snow events. As the water temperature anomalies rebound off the Northwest coast and south of Alaska, upper-level highs may develop more often over Alaska and lead to a change in the pattern. Take a look at the two maps below.
Taking into account analog years, models and the pattern we described just above, this is a look at snowfall predictions for the coming season for a few selected cities. The first graphic is a listed of popular analog years and snow for those seasons. The second graphic shows the average of all those analogs, the top-four analogs, our forecast and the month where more snow fell on average for the analog years and cities. The yellow column is not a forecast. The top-four years were adjusted. Take notice that we did not go with high totals from Philadelphia on southward despite what the top-four analogs show. Rain may be a spoiler to big systems in January and February south of New York City near the 95 corridor.
Looked at the analogs closely again and finding variation in the month-to-month forecast. The analogs look too cool in December which affects the overall three-month period. The drought areas are not factored enough in this analog forecast. I think they are too cool for the Southeast and not warm enough in the Southwest. However, it looks like we will be using more energy compared to last year for the nation. Years used were 2005/06, 1995/96, 1983/84, 1984/85, 2013/14, 2011/12 and 1959/60.
1. Fast-moving northern branch of the jet will carry storms quickly west to east. (Moderate to high confidence)
2. Lack of snowpack, cold air escaping more toward the other side of the pole and a strong pacific jet sending mild air into the Plains and Canada are all factors for raising temperatures and easing on the extent of cold shots in the northern Plains and Midwest in December. (Moderate confidence)
3. Most northern branch systems will not be all-snow events but may mix or even mostly rain. However, later in December, these events can kick up more lake-effect snowfall. Snowpack will increase more in the central and northern Rockies, Northwest Cascades and northern areas of the Northeast. (Moderate confidence)
4. Mild conditions expected for the Southeast as an upper high may strengthen at times. 1984 brought a very mild December to the Southeast. Southeast ridge can hold back any long-duration cold for the Southeast and Northeast in December. In addition, drought conditions will hold across interior Southeast and central Gulf Coast states. This can favor and counteract higher-than-normal departures. Dryness can lead to cooler nights, but pleasantly mild afternoons. (Moderate to high confidence)
5. La Nina tends to favor stronger, moist systems in the north compared to the south. Even though officially ENSO will wind up neutral this winter, we favor drier conditions in the Southwest and Southeast, La Nina characteristics for early winter. (Moderate confidence)
6. Upper high will build at times in the Southwest- it looks to be warm and dry which can lead to a fast west to east onshore flow Northwest coast, downsloping and warming interior Northwest. Track of systems could bring heavier events from far northern California into western Oregon and Washington. (Moderate confidence)
The graphic above is the snow extent in Eurasia. There have been studies done that show the rising snowpack during October in Eurasia has a moderate to strong correlation for colder and snowier winters in eastern North America. The rising snowpack in Eurasia during October was excellent. This supports our ideas of more snow and more cold this year in parts of North America later into the winter. But in the meantime, sustained cold and persistent snow has been on the other side of the globe and not expected until midwinter.
I am keeping previous forecast for comparison. We made some big changes in December based on the bullet points mentioned above.
1. We have two-thirds of the nation forecast at near- to below-normal temperatures. Snowcover entering the month will determine the coverage and level of cold for January. The pattern will be more amplified in January compared to December with a building upper high toward Alaska. (Moderate confidence)
2. Lake effect can really crank this month and result in above-normal snowfall around the Great Lakes. (Low to moderate confidence)
3. Mainly northern branch lows will cut through the Midwest to the East with an occasional storm coming up from the south developing off these fronts. Warm waters Atlantic and Pacific and other tele-connections favor big storms again! Remember last January’s crippling storm late in the month for the mid-Atlantic. (Moderate confidence)
4. Upper high holds in the Southwest. This presses the northern jet stream and storm track into western Canada much of the time. It can be dry and quite mild in the Southwest including most of California. This is a big difference from last January where northern California had heavy rain and snow. (Most of region 8 drier, but northern 8 still at risk) (Moderate confidence)
5. We are playing down the damaging freeze for the Southeast this January. However, we believe that there can be cold shots that bring down temperatures resulting in frost, even a freeze. The chances are low that it will be damaging. Florida citrus is dealing with non weather-related problems currently. We are just concerned that any minor damage from weather will only enhance the situation. (Low to moderate confidence)
6. It will be dry much of the time through the southern Plains and extending at times into the Southeast. Cold shots can reach far to the south behind stronger systems. (Low to moderate confidence)
1. We are leaning a different way this February. There is a high risk in February on what the upper pattern will turn out. I feel the numbers will be extreme but we had to go more conservative at this point. (Low confidence)
2. Southwest and Southeast should be mild with below-normal precipitation. (Moderate to high confidence)
3. Upper high can build over the Southeast or East Coast. This can lead to warmer air and drier conditions east of the Appalachians. This also can force the storm track back through the Midwest and Ohio Valley where we have above-normal precipitation and above-normal snowfall. (Low confidence because everything can shift farther east)
4. Core of cold may aim more toward the northern High Plains and Upper Midwest. Based on some analogs and models, we have made the Northwest drier than earlier thinking. (Low to moderate confidence)
5. Ice events are a higher possibility across the interior Northeast southwest down the Appalachians into the eastern Ohio Valley. (Low confidence)
6. Severe weather is possible along the central and eastern Gulf coast, at times lifting up toward the Carolinas. (Low to moderate confidence)
