weather.gov 
 
 
 
National Weather Service Burlington, VT Twitter Page National Weather Service Burlington, VT Facebook Page
Local forecast by
"City, St" or zip code
  
 Current Hazards
    
 Current Conditions
    
 Forecasts
    
 Model Data
    
 Climate
    
 Weather Safety
    
 Miscellaneous
    
 Contact Us


Summary
The January Thaw of 2008 occurred at nearly the identical time to the "pseudo"- January Thaw of 2007, but the conditions prior to each event were VERY different.

The Cold and Snowy start to the young 2007-08 Winter was a reversal of the 2006-07 Winter, when the first widespread winter storm across the North Country occurred on the Martin Luther King Jr. Holiday Observance (1/15/2007). Snowfall at the National Weather Service Office in South Burlington, Vermont was a meager 12.0 inches through January 5th, 2007, compared to 56.3 inches through January 5th, 2008.

The "pseudo"-January Thaw of 2007 occurred January 4-6th with maximum temperatures in the 50s and 60s across much of the North Country with 70s across southern New Hampshire, southern New England and New York. Actually, this was more of a continued, extended mild spell that started in December 2006 (which averaged 7.8 degrees above normal), rather than a defined "thaw", given there was no prolonged, preceding cold spell along with a lack of snow cover or river/lake ice to melt.

Meanwhile, the opposite occurred with The January Thaw of 2008 that occurred January 6-9th (which happened to occur on the same dates of the 10th Anniversary of the Devastating Ice Storm of 1998), with maximum temperatures in the 50s and 60s across the North Country. However, the preceding trend was opposite to the start of the winter of 2006-07, with the 4th snowiest December (2007) and the average December 2007 temperature near normal, but 7.8 degrees colder than in 2006.

Therefore, the apparent impact of the thaw was quite noticeable this year as snow cover across the region would diminish substantially or even disappear in spots during this warm spell.
Click to enlarge
Snow Depth Map ~ January 3rd, 2008
Click to enlarge
Snow Depth Map ~ January 10th, 2008
Click to enlarge
Ausable River HydrographIn addition, river ice that was non-existent in January 2007 was prevalent prior to this thaw. Thus, snowmelt would cause increased water run-off into area streams and rivers, which caused some abnormally high water flows and some localized ice jams.

This resulted in water levels to exceed their banks with some very minor flooding, specifically along the AuSable River in New York and the Missisquoi River in northern Vermont.
Click to enlarge
Missisquoi River Hydrograph
Click to enlarge
Otter Creek Hydrograph
Click to enlarge
Winooski River Hydrograph
Click to enlarge
Passumpsic River Hydrograph


Meteorological Background
Click to enlarge
Surface Features Time LapseAn arctic cold front moved across Vermont and northern New York on January 2nd, immediately following a New Year's Day snowfall that delivered 4 to 8 inches across the region. Arctic high pressure moved into the Mississippi and Tennessee River valleys with an elongated ridge axis across New York into Quebec by the morning of January 3rd with the ridge axis cresting across New England on the night of the 3rd. An arctic air mass, strong high pressure with clear skies, calm/light winds and fresh deep snow cover created ideal radiational cooling conditions for sub-zero temperatures during the early morning hours of the 3rd and 4th.
Click to enlarge
Mid and Upper Level Flow Pattern at 500mbBy the early morning hours of January 4th, the ridge axis had dampened and shifted southeast of the North Country allowing for a developing southwest "return" flow of milder air at the surface. Meanwhile at mid and upper layers of the atmosphere, the dominating ridge settled across the southeast United States, while a developing trough was entering the Pacific Northwest coast of the United States. This accounted for a very broad southwest flow to develop across the eastern United States including the North Country until the Pacific Northwest trough moves across the country and through the Northeast by January 9th.
Click to enlarge
Maximum Temperature Loop ~ January 3rd to 10th, 2008The influence of milder air moving into the region was apparent on the 4th and continued through the weekend into early next week.

Maximum temperatures rebounded from zero to 15 degrees above zero on the 3rd to mainly into the 20s on the 4th, 30s on the 5th, upper 30s to upper 40s on the 6th, mid 40s to mid 50s on the 7th, 50s to lower 60s on the 8th, and primarily in the 50s on the 9th as a surface cold front and mid atmospheric disturbance moved across the region.
Click to enlarge
Maximum Temperatures ~ January 8th, 2008
Click to enlarge
Maximum Temperatures ~ January 9th, 2008
Click to enlarge
Minimum Temperature Loop ~ January 3rd to 10th, 2008Meanwhile, minimum temperatures witnessed even greater changes with sub-zero temperatures throughout the North Country on the early morning of the 3rd and 4th, followed by teens and lower 20s across much of the region during the early morning of the 5th, primarily 20s on the 6th, 30s on the 7th, 30s and 40s on the 8th and 30s, 40s and lower 50s on the morning of January 9th.

On the 9th, an upper level trough and surface cold front moved across the region with scattered rain showers and cooler air that ended the main thaw.
Click to enlarge
Minimum Temperatures ~ January 4th, 2008
Click to enlarge
Minimum Temperatures ~ January 9th, 2008
A typical pattern/feature emerged with respect to minimum and maximum temperatures across the North Country, that being the coolest temperatures were east of the Green Mountains, especially the Connecticut River Valley with the mildest readings experienced in the Champlain and St. Lawrence River valleys. The coldest readings in the east are associated with a phenomenon called an inversion. Colder air is denser than the arriving milder air, thus the mild air flows above the cold air and ground, thus forming an inversion. This inversion acts as a lid trapping the cold air beneath from escaping and the mild flow from reaching the surface.

Larger, broader valleys such as the St. Lawrence and Champlain valleys that are parallel to the flow are more receptive to the influx of milder air, thus scouring out the cold dense air. Meanwhile, deeper, narrower and shorter valleys like the numerous smaller river valleys within the Green Mountains and the Connecticut River Valley retain the coldest air at the surface, forcing the milder air aloft, thus producing an inversion.

This phenomena often occurs with the approach of a storm system from the southwest moving into the North Country with precipitation falling as snow then quickly changing to rain across much of New York and the Champlain Valley of Vermont, while snow will change to rain aloft but the ground temperature remains below freezing thus the precipitation becomes freezing rain in the valleys of Vermont east of the Green Mountains. However, this inversion can occur on benign weather days preventing the mild air from reaching the deeper valleys thus witnessing tremendous temperature ranges within Vermont. For example, on the morning of the 9th, minimum temperatures were in the upper 40s to mid 50s across the Champlain Valley, while it was in the upper 20s to lower 30s in the Connecticut River Valley and further, it was milder in the lower 40s in higher elevation communities like Sutton, while it was near 30 in St. Johnsbury.

As mentioned above, tremendous snow melt occurred across much of the North Country including the higher elevations that were much milder above the inversion, yet the cooler regions of eastern Vermont witnessed the least snow melt.
Click to enlarge
High Resolution Visible Satellite Picture on January 3rd, 2008
Click to enlarge
High Resolution Visible Satellite Picture on January 12th, 2008

NWS Burlington Cooperative Observers Snow Depths ~ Thursday morning, January 3rd, 2008
NWS Burlington Cooperative Observers Snow Depths ~ Thursday morning, January 10th, 2008
The Ausable River at Ausable Forks in Essex county, New York showed minor rises due to snow melt from January 4th through 7th until an ice jam formed within the vicinity of the gage house on the morning of January 8th. This caused a sudden rise in water levels, but this ice jam was short-lived. After the initial decrease in water levels, proceeding the break-up of the ice jam, river levels continued to rise due to tremendous snow melt and subsequent run-off until cresting on the 10th, where a cold front passed across the area and the rapid snow melt ceased.
The Missisquoi River gage at East Berkshire, Vermont experienced a very similar pattern to that of the Ausable Forks gage in Essex county, New York. However, this river experienced an ice jam later in the snow melt process (January 9th), thus when the ice jam "broke-up", snow melt and additional run-off was diminishing.
A hydrograph for the Otter Creek at Center Rutland shows gradual rises in water levels through the 7th, followed by more significant rises from January 8th-10th due to maximum temperatures in the 50s and 60s with overnight minimums well above freezing (especially in the higher elevations).
A hydrograph for the Winooski River at Essex Junction shows gradual rises in water levels through the 7th, followed by more significant rises from January 8th-10th due to maximum temperatures in the 50s and 60s with overnight minimums well above freezing (especially in the higher elevations).
A hydrograph for the Passumpsic River at Passumpsic shows gradual rises in water levels through the 7th, followed by more significant rises from January 8th-10th due to maximum temperatures in the 50s and 60s with overnight minimums well above freezing (especially in the higher elevations).
High pressure across the Tennessee-Ohio River Valleys and eastern Great Lakes on the morning of January 3rd dampens and shifts southeast, allowing a return flow of mild air from the southwest into the Northeast. A warm front moves across the region on Friday the 4th, but the main source of milder air is ahead of a system that originates across the Rockies on the 7th, moves into the Mississippi River Valley on the 8th and then into the Great Lakes and across southeast Canada on the 9th.
Deep cold trough lies across the eastern half of the United States on the night of January 1st, on the heels of an exiting storm system off the New England coast. This trough exits the region on the 3rd with an initial westerly zonal flow and moderating temperatures into the northeast. Some weak ridging off the southeast United States along with a developing trough along the Pacific Northwest on the 5th/6th develops a southwest flow across the United States. On the 7th, the western trough moves east and the southeast ridge strengthens, thus a more pronounced southwest flow develops with much milder air advecting into the Northeast until the 9th, when the trough lifts northeast through the Great Lakes and southeast Canada.
Maximum temperature loop begining on the morning of January 3rd (thus the maximum temperature actually occurred on the 2nd). Arctic air was arriving on January 2nd after the New Yearís Day snowstorm had exited the region, temperatures in the single digits above zero were observed along the Canadian border with 20s in the southern Champlain and Connecticut River valleys. The arctic air was thoroughly entrenched across much of the North Country on the 3rd, but hints of milder things to come were moving into the St. Lawrence River Valley. Thereafter, a gradual moderating trend moved into the region for the 4th through 6th with the main thaw occurring on the 7th, 8th and eventually ending late on the 9th (last frame). Record maximum temperatures were observed for several sites on the 7th and 8th.
Maximum temperatures ending at 7 am EST Wednesday, January 9th (Tue. 1/8 Max T) shows widespread 50s to mid 60s across the region with some 40s in protected deep valleys across eastern Vermont. Normal maximum temperatures should be lower 20s to around 30 degrees across the North Country.
Maximum temperatures ending at 7 am EST Thursday, January 10th (Wed. 1/9 Max T) shows widespread 50s across the region with some 40s in protected deep valleys across eastern Vermont. Temperatures were just a few degrees cooler than Tuesday (1/8) due to cloud cover and rain showers as a cold front moved across the region during the day.
Minimum temperature loop begining on the morning of January 2nd as the arctic air was arriving after the New Yearís Day snowstorm had exited the region. Notice the near zero temperature readings in the St. Lawrence River Valley vs. the teens in the Connecticut River Valley. This was followed by widespread sub-zero temperatures on the morning of the 3rd and 4th, then a gradual moderating trend west of the Green Mountains on the 5th becoming widespread through the 9th with slightly cooler temperatures returning by the morning of the 10th (last frame).
Minimum temperatures ending at 7 am EST Friday, January 4th shows sub-zero temperatures across Vermont and northern New York for the second consecutive morning
Minimum temperatures ending at 7 am EST Wednesday, January 9th shows sub-freezing temperatures east of the Green Mountains on Vermont, due to a strong inversion and unfavorable winds in the narrow Connecticut River Valley. Meanwhile, minimum temperatures in the 40s to lower 50s across the western slopes of the Green Mountains of Vermont west across New York due to a more favorable south to southwest wind flow in the more broader south and southwest oriented Champlain and St. Lawrence Valleys.
A high resolution visible satellite picture shows the snow cover across the northeast United States after recent snowfalls on December 31st and January 1st.
A high resolution visible satellite picture shows the depleted snow cover across the northeast United States after the recent January Thaw. Snow cover is nearly non-existent along and south of the Massachusetts-Connecticut-Rhode Island state lines. Although more difficult to see, due to cloud cover across New York and entering Vermont, there are dark patches of ground surrounded by snow along the Vermont-New York border as well as along the Canadian-Vermont-New York borders west of the northern Green Mountains of Vermont. Note that snow cover, albeit much less reflective than the January 3rd image due to substantially diminished amounts, remains across the Adirondacks of New York, as well as northern New England along and east of Vermontís Green Mountains.


National Weather Service
Burlington
1200 Airport Drive
S. Burlington VT 05403
(802)862-2475

Webmaster: Webmaster
Page last modified: January 31, 2008
About Us
Disclaimer
Credits
Career Opportunities
Glossary
Privacy Policy