wxgeek's weather-Summer to hang on a bit longer-Update 9/4

Update Wed Sept 4

Dominant upper level High currently centered over east central CO today, so another day with near record temps across eastern CO. Plume of monsoon moisture currently located across the lower Colorado River basin into UT and CO. Some dry air depicted on water vapor satellite imagery is creeping northward into southern CO, so precip chances lower south of US 50 today. In general, today will be much like yesterday, isolated afternoon and evening storms forming over the mountains and foothills and drifting slowly northeastward. Storm motion today from the southwest at 5-10 mph, so any storms that form have the potential for brief heavy rain due to slow movement. Storm yesterday that formed near Black Mountain dropped 1.15 inches of rain on Conifer Mountain is less than an hour. Not bad to receive 75% of our average monthly precip (1.53 inches) in 1 hour. Storms may drift into the Urban Corridor and adjacent plains late this afternoon and evening.

Upper High is expected to remain over eastern CO through Thursday, then drift slowly east into western KS this weekend and farther east into the TN valley early next week as an upper level trough moves across the northern Rockies. Upper ridge then re-builds over the Great Basin late next week and will remain over the Inter-Mountain West into the following week. As the upper High moves east, better monsoon flow is expected across CO later this week into the weekend as monsoon moisture still present across northern Mexico and the Desert Southwest. This implies afternoon and evening showers and thunderstorms will prevail across CO through the coming weekend. Majority of activity will be from the foothills west, but activity likely to spread onto the Urban Corridor and adjacent plains as well. Some storms may contain heavy rainfall as they will be fairly slow moving.

Cold front associated with the upper trough is expected to move into eastern CO late Monday, bringing cooler temps and additional low level moisture which will increase precip chances especially from the foothills east late Monday into Tuesday. Warmer temps and more isolated storms will follow later next week as upper ridge re-builds to the west of CO, putting CO under drier northwest flow aloft. Not really any big changes being advertised by long range models into late September at this point. Appears the monsoon could last a bit longer than usual this year, which is good news for fire danger.

For reference, the average snowfall on Conifer Mountain in September is 3.8 inches over the past 21 seasons. It has snowed in September in 12 of the past 21 seasons, so a 57% probability of seeing snow in September on Conifer Mountain, although the past 3 seasons have been without snow. Currently is not looking likely for snow this September, but that could of course change.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Upper level ridge currently centered over south central CO and is expected to remain anchored over CO for the remainder of the week. North American Monsoon is still going with average daily dew point temps in Tucson around 60 deg F (54 deg F is required for Monsoon). Hence, weather across CO this week will be warm to hot, with isolated afternoon and evening showers and thunderstorms mostly from the foothills west. Some storms may drift east onto the Urban Corridor and plains as flow aloft is expected to be westerly most of the week. Precip amounts not expected to be very heavy, although storms will be fairly slow moving at 5-15 mph. Temps near record levels will be with us each day this week, some slight cooling this weekend but temps still a good 5-10 degrees above seasonal norms.

Upper level ridge is forecast to move slowly east during the week into eastern CO by Friday, then drift farther east into KS and MO by early next week. As the upper ridge moves farther east, better monsoon flow will return so precip chances will increase this weekend and early next week. In addition, an upper level trough will move through the northern Rockies early next week which will drag a weak cold front into northeast CO, which will also add low level moisture and increase precip chances over eastern CO early next week and bring temps closer to seasonal norms.

Upper level ridge is then forecast to re-build over UT late next week before another upper level trough moves across the northern Rockies the following weekend. In general, CO will see temps well above seasonal averages for the first half of September, with near normal to slightly below normal precip. Long range models beginning to show a gradual transition to a more Fall like upper level pattern by the middle of September with stronger upper level winds moving farther south, and more vigorous upper level troughs beginning to move into the Pacific Northwest and across the U.S./Canadian border region. We may begin to see more normal temps and some stronger cold fronts by the middle to end of September, all pretty normal. Currently do not see any early season cold snaps or snowfall for CO in the extended forecast, but this time of year, forecast models can change their tune quickly.

_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".