In typical May fashion, a rather unsettled week lies ahead with chances of rain and thick clouds expected nearly every day. Temperatures start out chilly on Monday but will moderate back closer to normal the rest of the week despite continued wet weather.
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This week’s highlights include:
- A chilly, gloomy, and somewhat rainy day is in-store for Monday with several weak systems passing through
- While slightly warmer, the pattern remains unsettled much of the week with chances for rain Wednesday through Saturday
- Unfortunately, drought-stricken southern Colorado will get the short end of the stick
A gloomy Monday with rain showers
We start the week on an active note! Two shortwave disturbances are riding across Colorado in the northwest flow on Monday while a chilly airmass and upslope reside at the surface. The GFS 500 mb map for mid-day Monday is shown below outlining the set-up. The first and stronger wave will move through during the morning into afternoon. A second, weaker wave will progress through the area later this evening into tonight.
Combined these two systems will bring lots of cloud cover and produce good chances for rain throughout the day.
GOES-East shows thick clouds blanketing Colorado Monday morning
The initial wave this morning will support lowering cloud bases thanks to upslope at the surface rotating around a Denver Cyclone, especially from Boulder to Fort Collins where the upslope is the most pronounced. The counter-clockwise flow across the Metro area this morning is shown below. The degree to which this low-level circulation holds today will determine how cold and gloomy we remain through the day. We suspect it will be quite a bit colder than the upper 50’s models are indicating today around Boulder with low clouds never letting go.
By early afternoon, convective showers and a few storms will move from the higher terrain eastward across the more stable and chilly Denver Metro area. Not everyone will see rain, but most of us should. Rain showers will be possible through the afternoon and evening into a portion of the overnight with the secondary wave slow to follow. Overall, it will be a cool and gloomy day with highs in middle 40’s to lower 50’s.
HRRR model-simulated radar for Monday at 3PM (left) and 6PM (right). A chance of showers and a few storms will exist through out the day.
As rain comes to the end overnight Monday night, low clouds and fog are expected to develop across much of the area lingering into Tuesday morning.
Warmer but remaining unsettled through the week
From Tuesday onward, we shift into a warmer but still unsettled pattern as weak large-scale troughing takes hold across the northern Rockies. While there will likely be several embedded pulses of energy moving across Colorado during the week, the exact timings, tracks, and intensities are difficult to predict at this time. The most likely scenario is at least slight chances for diurnal showers and storms across the Front Range, with chances increasing anytime an impulse coincides more closely with peak daytime heating.
West southwest flow and weak trough will linger across Colorado through the week. Expect near normal temperatures, lots of clouds, and almost daily chances for rain.
While Tuesday looks dry for the immediate area, rain chances come back Wednesday and especially Thursday and Friday with late-day thunderstorms becoming the new norm. Clouds will be widespread this week as well due to the unsettled nature of the pattern and elevated moisture in the middle and upper-atmosphere. Expect generally mostly cloudy skies much of the week with only short breaks of sunshine here and there.
Ensemble guidance, which by the way is a great tool to use while the outlook for our weather is a bit muddied later this week, shows the best chances for rain will be today, Thursday and Friday. More than 1/2″ of liquid is indicated by the end of the week in Boulder and Denver.
More broadly, much of Colorado will see the beneficial rains, most notably the eastern Plains towards Nebraska and Kansas where better chances for thunderstorms will exist much of the week.
Unfortunately the areas that need the rain the most won’t see as much. A large portion of southern Colorado has been “upgraded” to Severe or Extreme Drought classifications within the last few weeks. The most recent graphic from the U.S. Drought Monitor is shown below. While things remain in good shape across the Front Range, the same can’t be said for the southern half of our state.
We shouldn’t throw in the white towel yet. There is still several weeks of typically unsettled weather left for the state before things normally begin to dry up in early June.
Forecast Specifics:
Monday: Overcast, gloomy and cool with isolated rain showers becoming more widespread by afternoon. Some thunder is also possible. Showers will linger into the late evening with low clouds and fog developing after midnight. Highs in the lower 50’s on the Plains and middle 40’s in the Foothills.
Tuesday: Low clouds and patchy fog in the morning, then mostly cloudy and dry with highs in the upper 60’s to near 70 degrees across the Plains with middle 50’s in the Foothills.
Wednesday: Partly to mostly cloudy and warmer with a slight chance of late-day showers. Highs in the lower to middle 70’s on the Plains and lower 60’s in the Foothills.
Thursday: Mostly cloudy with a chance of thunderstorms in the afternoon and evening. Highs cooler in the upper 60’s to lower 70’s on the Plains with upper 50’s in the Foothills.
Friday: Partly to mostly cloudy and unsettled with a chance of late-day thunderstorms. Highs near 70 on the Plains and in the upper 50’s in the Foothills.
The Weekend: After more of the same unsettled weather on Saturday, a weak ridge is shown to develop by Sunday which should dry things out considerably with warmer temperatures as well. Confidence is low for this ridge, however.
High Country: Daytime instability and lift from a series of shortwaves this week will lead to almost daily chances of showers and storms developing across the High Country (and even some accumulating snow on Monday). Most days won’t be a wash out, but afternoon and evening showers will be the norm. Check SummitCAST for daily updated forecasts for more than 120 mountain hiking destinations across Colorado.
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