NWS Billings - 2012 Weather Summary


Uploaded by NWSBillingsMT on 03.01.2013

Transcript:
Hello everyone. This is a 2012 weather summary brought to you by the National Weather Service
in Billings. 2012 will go down in history as a record-setting warm and dry year, with
escalating drought conditions and a long and difficult wildfire season. On the following
slides we will take a closer look at the warm and dry conditions, and summarize some of
the more significant events that occurred during the course of the year.
Here are final precipitation and temperature statistics for Billings, Miles City and Sheridan.
With total precipitation of 7.13 inches and an average temp of 51.1 degrees, it was the
driest and warmest year on record for the city of Billings, where records go back to
1934. For Miles City, it was the warmest and 2nd driest year on record, 2nd to only the
extremely dry 1988 (the year of the Yellowstone fires). For Sheridan, thanks to a few upslope
precipitation events on the east side of the Big Horn Mountains, it was only the 4th driest
and 5th warmest year on record. Interestingly, for both Billings and Miles City, 2012 is
the only year to rank in the top 5 for both temps and precipitation. 2012 was an extremely
warm and dry year for not only our region, but a large portion of the country.
Now let’s take a look at how the year broke down by month at Billings. The top chart shows
temperature departures from normal for each month. As you can see, nine of the 12 months
were warmer than normal, and March was particularly warm, finishing over 9 degrees above normal.
The month of March actually made the difference between a very warm year and a record-setting
year for us. We have had warmer summers in the past (the June through August period of
2012 was 4th warmest, behind the historically hot summers of 1936, 1961 and 1988), but combined
with the very warm spring we experienced, the overall year was our warmest since records
began in 1934. In terms of precipitation, all but two months were below normal. Notice
the very high precipitation deficits in April, June, July and September. The April through
June period is typically our wettest time of year, with an average precipitation of
almost six inches. Our wet season was absent in 2012, which led directly to escalating
drought conditions and an early onset of the wildfire season.
So why was it so warm and dry in 2012? Well, there isn’t one reason for this, and many
factors contributed to the warmth and dryness of 2012. The 2011-2012 winter was a dry one,
particularly in the northern plains of eastern Montana and the Dakotas, where snow cover
was significantly absent much of the time. The lack of snow in the plains and an early
mountain snow melt was followed by a dry spring, all of which resulted in very low soil moisture
and an extremely poor green up across the region. Soil moisture and evapotranspiration
help to keep temperatures down and precipitation chances up, so the extreme dryness made matters
worse, i.e. dry feeds dry. Overall, by May, it was becoming increasingly apparent that
we would have a hot and dry summer. By late June in a normal year our precipitation becomes
dependent on thunderstorm activity, which is generally spotty and short-lived. Thus,
in 2012, having experienced a dry winter, spring and early summer, there was little
chance of making up the precipitation deficits that had already occurred.
Now let’s take a look at a few of the more significant weather events to occur during
2012. Probably the most significant winter event of the 2011-12 winter occurred in mid
January, when an arctic air mass combined with Pacific moisture to bring heavy snowfall
and very cold temperatures to much of the region. The heaviest snowfall fell in a band
between Billings and Miles City, with the Hysham area receiving the most snowfall at
about 20 inches. The city of Billings received about 10 inches. In addition, below zero temperatures
were widespread. The snow and cold did not stay for long though. The onset of drier downslope
winds, or chinook winds, resulted in warmer temperatures and melting snow cover shortly
after this event. March of 2012 was a record warm month across
the region, and the statistics for this month were truly remarkable. Several daily record
high temperatures were established during the month, with many 70 degree days observed.
Miles City actually experienced 12 days with a high temp of at least 70 degrees, and only
a hundredth of an inch of precipitation fell at the site. The final day of the month was
the warmest, with a whopping 80 degrees observed at Billings, Sheridan and Miles City. This
tied the record for earliest occurrence of 80 degrees at Billings and Sheridan. Remember
from two slides ago, the extremely dry ground contributed to the very warm temperatures,
and this fact actually made temperature predictions difficult for our forecasters. What a month
it was! One of the few significant precipitation events
of the year occurred over Memorial Day weekend. As you can see from this map, much of the
area received between a half inch and two inches of precipitation over a period of a
few days. Embedded within this fairly wet period of weather was a late season snow event.
Amazingly, 3.5 inches of snow fell at the Billings airport on the night of May 25th,
establishing daily snowfall records on the 25th and 26th. This was also the latest measurable
snow to occur at Billings since 1975. Record cold temperatures also occurred on these days.
Heavy snow fell over the north slopes of the Beartooth Absaroka Mountains, and as a result,
Beartooth Pass did not open as scheduled over Memorial Day weekend. Unfortunately, this
precipitation event was not enough to offset the extreme dryness we were experiencing overall.
An epic hot, dry and windy day occurred on June 26th. High temperatures on this day were
in the 100s everywhere from Billings east, including a new all-time record high temp
of 111 degrees at Miles City. This record at Miles City broke the previous record of
110 degrees which had occurred five times previously. In addition to the heat, wind
gusts of 30 to 50 mph were widespread with single digit humidity. The fire season began
early this year, and several wildfires spread rapidly on this day, including the Dahl Fire
near Roundup and the Ash Creek Fire near Ashland. One significant impact of the hot and dry
year was a long and difficult wildfire season, not only in our region but across much of
the western states. Wildfire season in our area, which typically peaks from late July
into September, began in June and lasted into early October this year. The National Weather
Service provides Incident Meteorologists, or IMETs, who travel to the more significant
wildfires and provide onsite weather support for the team battling that fire. One of the
IMETs in the Billings forecast office was dispatched six times to eight fires, and was
away from the office for a total of 54 days. Because of the long hot and dry summer, the
National Weather Service in Billings also issued many Red Flag Warnings over the course
of the season, in order to alert fire weather personnel of the adverse weather conditions
that make rapid fire growth more likely. The onset of precipitation and cooler temperatures
in October finally brought an end to our wildfire season.
Drought conditions were not evident early in the year, but as warm and dry conditions
persisted, drought intensified rapidly. By late summer, as you can see from the map here,
much of the state was in moderate to severe drought, with some areas experiencing extreme
drought. The drought had both agricultural and hydrologic impacts. This made lives very
difficult for ranchers and farmers, and anyone whose livelihood depends on water and agriculture.
Though the onset of cooler temperatures and precipitation in the fall began to lessen
these impacts, drought conditions remain across the region as we move into 2013. Precipitation
so far in the 2013 water year, which began October 1st, has been above normal over the
west slopes of the Beartooth Mountains, but is below normal over the plains and eastern
slopes of the mountains. Hopefully, the mountains will receive a good snowfall this winter,
and near to above normal precipitation will occur across the region in the spring. There
is currently no clear signal to suggest either above, below, or near normal precipitation
for the late winter and spring months. The end of a particularly dry stretch of weather
occurred on October 3rd. Billings recorded no measurable precipitation from August 16th
through October 2nd, and this 48-day streak was the 3rd longest on record. The dry stretch
at Sheridan was even more significant. Sheridan went a whopping 53 days without measurable
rain, beginning August 11th, and this was a new record for the site. Furthermore, the
trace of precipitation that fell at Billings during September was a record low for the
month. Interestingly, the October 3rd precipitation event did include some wet snowfall. Measurable
snow fell at Billings on this day, meaning only 129 days elapsed since the last spring
snow event occurred on May 26th. This 129 day snow-less streak between last spring and
first fall snow events was the 5th shortest on record. Remarkable for how hot and dry
the summer was! Finally, a snow event on Christmas Eve guaranteed
a white Christmas across the region. And as you can see from the map here, much of the
northern half of the country experienced a white Christmas in 2012. The 3.4 inches of
snow that fell at Billings on the 24th was a record for the day, and the first measurable
snow on Christmas Eve since 1996. Looking ahead to the remainder of the winter,
the official forecast from the Climate Prediction Center calls for slightly increased chances
of below normal temperatures and above normal precipitation in our region for the January,
February and March period. These outlooks should be used with caution, as we typically
experience large temperature fluctuations and alternating wet and dry periods during
the course of our cool season. Overall, the climate signal is not strong in our area for
the remainder of the winter. This concludes our presentation. The latest
weather information from the National Weather Service can be found on our web site at weather.gov/billings.
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