It was a super snowfall for Super Bowl Sunday weekend! Snowfall totals over a foot were
common from Des Moines east to Chicago. The featured snowfall analysis has most of the
state over seven inches. The initial snowfall had low liquid to snowfall ratios, which
made moving the snow a back-aching adventure. The tail end of the snowfall event
happened at colder temperatures and combined with strong winds, made for blowing and
drifting snow. Very cold air has settled into Iowa this Monday morning with even light winds
creating dangerous wind chills.
The initial rainfall and subsequent liquid equivalent snowfall produced significant totals of
precipitation for this time of the year. For Des Moines, the daily total on Jan 31st was
greater than the total for all other days for that month. The featured chart presents the
frequency of a given month having at least one half of its precipitation total fall in one day.
November easily wins the competition with over half of the years meeting this criterion.
While nowhere near the intensity of our past weekend snow producing system, a winter
storm system did clip Northeastern Iowa with an inch or two of new snowfall. The featured
map attempts to report only snowfall totals from that storm and not the current one that is
dumping snow this morning over Southern Iowa. The map tomorrow will contain totals from
the current snow producing system. For those of you that do not like the snow, much
warmer weather is in the forecast with a big snow melt upcoming.
Our most recent snow producing winter storm brought 3 to 6 inches over much of southern
Iowa yesterday morning. This snowfall was a much lighter (higher snow to liquid ratios)
snow than what fell over this past weekend. The forecast continues to point to a warm up
into the weekend that should help melt some of our recent gifts from Old Man Winter.
Morning low temperatures on Thursday were some of the coldest so far this season with
the Ames Airport hitting -22F. The featured chart presents one minute interval temperature
data for a few Iowa ASOS sites. It is interesting to note the fluctuations occurring and
differences between neighboring sites. The sites report in whole degree Fahrenheit, so
that explains some of the jitter in the plot. On mornings like this, low micro-climate affects
are strong as small pockets of cold or warmer air pass by the sensor. Once the sun takes
a hold, the differences are lessened by 10 AM as the lower atmosphere mixes out small
scale differences.
High temperatures on Saturday warmed to record levels over the High Plains, but places to
the east had plenty of snow cover present which limited the amount of warming that could
occur. The featured chart compares the morning snow depth reports to the afternoon high
temperatures from the NWS Cooperative Network. The chart plots observations for Iowa
and surrounding states. While this weekend's warm weather put a dent in the snow cover,
there is still plenty of it left and more cold air expected this week to keep it around.
Less than three weeks remain to the Meteorological Winter Season (1 Dec - 28 Feb). The
featured chart presents hourly temperatures from the Ames Airport weather sensor for this
period along with the daily high and low temperature climatology. We have had stretches
of warm and cold weather so far this season. The lack of snow cover for much of the
season is a big reason why we had warm periods. The near term forecast has us returning
to a cold stretch.
While light freezing rain over northern Iowa on Tuesday created some travel issues, the
rest of the state enjoyed another winter day this season without much travel concern on
Iowa's primary roads. The featured map displays the frequency that a given road segment
was in a non-normal (non-dry) state so far this year. The percentages shown on this map
are generally less than 30%.
Temperatures will struggle today to reach the upper teens as a brisk reminder of the winter
season arrives in Iowa. The featured chart looks at the hourly frequency of having a sub
freezing temperature partitioned by week of the year. For mid February, having a sub
freezing temperature is very common for the night time hours, but the afternoon hours are
slightly less than 50%. The chart would indicate that we have at least one month of time to
go before this type of weather becomes uncommon. You can generate this chart on the
website for other sites and temperature thresholds of your choice.
The featured map displays the percentage of winter seasons that fail to reach 50 degrees
for at least one day that season. There is nothing special about the number 50 for this
metric. The map depicts a large contrast over our region with southern locations at or near
zero percent (meaning they always see at least one day per winter over 50) and places
over Minnesota approaching one hundred percent (every winter is below 50). The climate
district averages are plotted, which raises the bar a bit for the threshold to be breached by
a number of local weather stations and not just one. It is interesting to note that the
gradient is not a flat north to south one, but tilts as you approach the high plains. The
proximity to the mountains helps those locations warm quickly as down slope wind events
drive rapid warm ups.
The featured table shows the hourly temperature reports from the Des Moines Airport for
Valentines Day. The temperature fell the entire day after starting out at 36 degrees at
midnight and dropped to 6 by the end of the day. The chart displays the most recent
Valentines Day with as cold an hourly temperature. For hours after 10 AM, you have to go
back to 2007 for temperature as cold as this year.
On Saturday, the hourly temperature at the Des Moines Airport was unchanged or got
colder with each successive hour. This is a somewhat rare occurrence with the last such
day like it back on 27 November 2011. The featured map provides an analysis of station
frequency of having such an occurrence since 1973. Setting aside some local climate
effects, the map shows the general pattern of having the highest counts over northern US.
For this type of event to occur, the cold air advection must be very robust to overwhelm any
bit of warming that may happen during the day with sunshine present.
The NWS has a Wind Chill Advisory issued for today as another round of very cold air
arrives in the state today. The featured chart displays computed wind chill values for Ames
along with periods with either a wind chill advisory or wind chill warning active. These alerts
are not always issued when temperatures get very cold along with very light winds as what
happened a few weeks back. High temperatures today will struggle with some locations not
exceeding the single digits.
Even with plenty of sunshine on Wednesday, temperatures struggled well below freezing.
There is currently plenty of cold air at the surface and above our heads as shown by the
featured chart of 850 hPa temperatures for the Omaha sounding site. We've had two
periods of near record warmth at this level followed by our current period at near record
cold. This level is just a few thousand feet above our heads and represents air that is
potentially mixed down during the say as the sun mixes the lower atmosphere.
The nation's recent weather pattern has been persistent with warm air in the western US
and cold air in the eastern US. The featured map displays the current streak of days
above or below climatology for daily high temperature. Some locations in the far east and
west are at some rather gaudy numbers at the moment. Iowa is currently siding with the
eastern US with recent temperatures well below average. The near term forecast looks to
persist this current pattern, so these totals should continue to grow!
The featured map presents the minimum temperature reports from airport weather stations
in the state so far this winter. This analysis suggests the entire state has seen sub zero
temperatures, but local micro climates make a big difference with how cold a location can
get. For example, Des Moines Airport has only dropped to -10 while Ankeny has reached
-18 and Ames -22.
The featured chart displays daily snow depth reports for the Ames COOP site since 1964.
Even with below freezing temperatures, our current snow pack has been slowly
disappearing. Sun shine and dry air are able to eat away at the snow even with air
temperatures below freezing. The chart nicely shows the winters with the most persistent
snow cover, like 2000-2011 and 1977-1979. You can generate this chart online for other
sites in the region.
With winter storm warnings in effect for today and another round of very cold air set to
arrive after the snowfall, it is difficult to imagine that spring time is almost here. The
featured map looks at the end date of the coldest 91 day period based on daily climatology
from NCDC. If you divide the year up into 4 equal length seasons (~91 days) and then
compute the coldest stretch of 91 days, you could consider this to be winter. So once this
stretch ends, you are then in springtime! This analysis shows that Iowa is only a few days
from starting spring, but this year will be a bit different as a cold February and warm
December will cause the coldest 91 day period this year to shift well into March.
Our most recent snow producing winter storm brought 4-7 inches over much of eastern
Iowa on Wednesday. Totals dropped off significantly to the west with southwestern Iowa
missing out completely. The entire state is experiencing the cold air arriving behind this
storm system and below freezing temperatures are expected into the first week of March.
A daily record low temperature for Waterloo has been set this morning, so it is good timing
to look at the yearly frequency of setting a new high and low record temperature. The
featured chart presents this metric by computing the number of new records set each year
from the beginning of the period of record. The black line represents a sort of theoretical
expected frequency based on the number of years that have passed. During the beginning
of the record, there are much fewer years of history so it is a bit 'easier' to set records.
Years that exceed this expectation are colored differently. For recent years, the warm
weather of 2012 certainly stands out as an anomaly.