The Weather Wire
May 2010 Volume 17 Number 05
Avg High - 61.7
Avg Low - 33.9
Snow - 0.5"
Season Snow - 59.3"
Precipitation - 2.51"
Avg High - 70.5
Avg Low - 43.8
Avg Snow - 1.3"
Avg Precip - 2.32"
Watches and Warnings
There always seems to be some confusion when weather watches and warnings are issued. Not to mention what constitutes a severe thunderstorm. A review of summertime watches and warnings and their definitions may be helpful for future severe weather events.
In general a watch means conditions are favorable for that event, while a warning means that the event is already occurring or is imminent and action may need to be taken.
Definitions used with Summer Severe Events
Severe Thunderstorm Watch: Conditions are favorable for the formation of severe thunderstorms in AND NEAR the watch area. By definition, a severe thunderstorm has hail 1" inch or larger, and/or winds greater than or equal to 58mph. Note heavy rain is not a necessary component of a severe thunderstorm. Watch the sky and stay tuned to know when warnings are issued.
Severe Thunderstorm Warning: Issued when severe weather has been reported by spotters or indicated by radar. A severe thunderstorm warning indicates the storm has hail 1 inch or larger, and/or winds GE 58mph. Warnings indicate imminent danger to life and property to those in the path of the storm.
Tornado Watch: Conditions are favorable for the formation of tornadoes in AND NEAR the watch area. Implicit in this watch are the possibility of severe thunderstorms, as defined above. Remain alert for approaching storms. Know what counties are in the watch area by listening to NOAA Weather Radio or your local radio/television outlets.
Tornado Warning: A tornado has been sighted by spotters in the field, or indicated by NWS Doppler radar.
Flash Flood Watch: Issued when heavy rain may develop and result in flash flooding in or near the watch area.
Flash Flood Warning: Flash flooding in the warning area has developed or is imminent!
Urban and Small Stream Flood Advisory: Local flooding of small streams, streets, or low lying areas such as railroad underpasses is occurring or is imminent. Note: this is issued for lesser rainfall events than a flash flood, though danger to life and property still may exist.
Note: Watches tend to cover a large geographic area (many counties), and tend to be issued for moderately long time periods (3-6 hours). Warnings cover a much smaller area (portion of a county or portions of several counties) for a much shorter time period (30-60 minutes typical).
With the widespread precipitation of the last several months few areas of drought remain over Colorado, though some dry areas have developed in western Colorado.
The map below shows forecasted temperature deviances for May 2010. As can be seen, normal temperatures are expected for much of the state, though the southwestern areas of the state are expected to have above normal temperatures.
The map below shows forecasted precipitation deviances for May 2010. All of Colorado is expected to have above normal precipitation for the month..
Little in the way of drought remains in Colorado.
April of 2010 came in right around normal for temperatures with above normal precipitation and below normal snowfall with only 0.5" reported at DIA. For the month there was an average high of 61.7 degrees compared to 60.9 and an average low of 33.9 which was slightly below the normal of 34.2, this resulted in a monthly mean of 47.8 which is 0.2 degrees above normal. Precipitation for the month was 2.51" at DIA compared to 1.93" on a normal year resulting in 0.58" above normal precipitation even with the surplus of over half an inch for the year DIA is still below average. The snowfall of only 0.5" was well below the normal of 7.4" and now results in below normal snowfall through the end of April for DIA. This snowfall amount does not represent the rest of Denver very well at all as there are many Denver suburbs with 70-100" so far this winter season and that does not include the snow so far this month of May. The most significant rain/snow event occurred on the 23rd-24th with heavy snowfall in the foothills and over Douglas County where there were snowfall rates of 3-4" per hour occurred with snow totals of 10-20" or more. DIA reported most of the months precipitation during this time with 1.57" of rainfall and only a trace of snow.
Now that we are already into the second week of May it may be safe to assume that this month will be colder than normal with above normal snowfall for many locations. Up to this point temperatures are 7 degrees below normal but with warmer weather ahead this will change but temperatures will not be warm enough to get back to even. Monthly totals so far for DIA during the month of May stand at 1.05" of precipitation and 1.3" of snow. Average precipitation for May is 2.32"
and is Denver's wettest month of the year. There is still a ways to go if we are to have normal precipitation for the month but we should get there. The 1.3" of snow is on par with average and there may not be any more measurable snow for the lower elevations. Typically people say, "Wait till mothers day to plant outdoors." Well this year we have had to wait till after mothers day and another freeze or frost during the month cannot be ruled out so keep a close eye on temperatures and cover plants if necessary.
Sunrise/Sunset (Jan - June Denver area)
Sept 2009 to Apr 2010