Weather Outlook Through The End of September
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Author:  wxgeek [ Sep 16, 2019 1:15 pm ]
Post subject:  Weather Outlook Through The End of September

Partly to mostly cloudy day today as moisture moves up from the south ahead of a deep early season upper trough moving onto the West Coast. Temps will remain above average today, but not as hot as the weekend, and winds will remain relatively light today. Best precip chances will be across southwest CO with a slight chance for a stray afternoon or evening shower or thunderstorm locally, but any precip would be on the light side. Gusty outflow winds and dry lightning will be a concern for fire weather this afternoon and evening.

As upper level trough moves into the Great Basin on Tuesday, southwest flow aloft will increase over CO and create gusty southwest winds of 15-40 mph across much of western CO including foothill areas. Precip on Tuesday will be mostly confined to areas east of the Divide, with a slight chance for a brief shower or storm locally, but any precip would be light. Main concern Tuesday will be strong southwest winds for firefighting efforts. Temps will remain slightly above average.

Wednesday will see lighter winds as upper trough moves to our east while another potent upper trough moves onto the West Coast, but southerly winds of 10-20 mph will still be possible in foothill areas, so still not ideal for firefighting efforts. Temps on Wednesday will be near average and there will be a chance for afternoon and evening showers and thunderstorms, but any precip would remain under 0.10 inches.

Upper trough will move into the Great Basin on Thursday, and to our north on Friday. This will create windy conditions for most areas of CO each day, with southwest winds of 20-40 mph on Thursday, and westerly winds of 20-45 mph on Friday. Temps will be above average Thursday and near average Friday. Little if any precip expected statewide each day, so very high fire danger days and tough conditions for existing firefighting efforts.

For the weekend, exiting upper trough to our north will keep a brisk westerly flow aloft over CO Saturday, then upper ridge builds over the state on Sunday. Slight chance for afternoon and evening storms on Saturday, then dry statewide on Sunday. Saturday will see more gusty southwest winds with temps near average, then lighter winds and temps slightly below average on Sunday.

For next week, upper trough moves over CO on Monday which will keep temps near average, but little if any precip expected. The rest of the week a very large upper level ridge moves into the Great Basin and this will keep CO dry and warm with little if any precip statewide through next weekend. This will create high fire danger as ground fuels continue to dry out.

Author:  wxgeek [ Sep 18, 2019 10:45 am ]
Post subject:  Re: Weather Outlook Through The End of September

Another warm and mostly dry day on tap for most of the state today as temps will remain above average. Winds will from the southwest at 10-20 mph today, and there will be a slight chance for afternoon showers and isolated thunderstorms from the mountains to the Urban Corridor. Any precip would remain light and should end by sunset.

On Thursday, temps warm an additional 5 degrees so well above average. Winds will be more southerly at 10-20 mph and precip chances will be very isolated. On Friday upper level trough that has brought snow to the Cascades and Sierras this week will move into the Great Basin and create gusty southwest winds across much of CO with speeds of 15-35 mph with temps remaining above average, so high fire danger. There will be isolated precip chances over the mountains with a slight chance for a brief shower in foothill areas, but little if any precip expected locally.

For the weekend, as upper trough moves to our north and east, a cold front will bring cooler temps to most of CO this weekend with temps near average Saturday, and 5-10 degrees below average Sunday. It will remain mostly dry each day with only a slight chance for an isolated shower each day.

For next week, models diverge on the handling of a upper level trough moving into the Great Basin on Monday. ECMWF keeps this system as a closed upper low over SoCal, while the GFS is more progressive and moves it to our south Tuesday into Wednesday. Big implications on precip, as ECMWF would keep CO dry next week, while GFS solution would bring ample precip to much of CO Monday through Wednesday. Currently I would lean towards the ECMWF model, but will keep a close eye as GFS solution would bring snow to areas above 9000-10,000 ft next week. ECMWF keeps temps above average all week, while GFS would have much cooler temps.

The tropics remain very active with 3 named storm in the Atlantic Basin and two in the Eastern Pacific. Imelda bringing very heavy rain to southeast TX, and Humberto will pass close to Bermuda, but no other immediate threats to populated areas.

Author:  wxgeek [ Sep 20, 2019 8:33 am ]
Post subject:  Re: Weather Outlook Through The End of September

Windy day across the state today as upper trough moves to our north. Southwest winds of 20-45 mph will be possible in the mountains and foothills today, which will create dangerous fire weather conditions. Temps will remain above average today, and precip will be limited to areas north of I-70 and mostly east of I-25. The upper trough will bring up to a foot of snow to areas of the northern Rockies today above 7000 ft, so an early start to winter farther north.

A cold front will drop south over CO tonight which will create calmer winds and cooler temps for the weekend. Winds become northeasterly on Saturday and temps will be below average by 5-10 degrees for most areas, so much more Fall like feel. Latest models suggest a chance for showers and thunderstorms will develop across much of eastern CO Saturday afternoon through about midnight from the Divide east with up to 0.10 inches possible in foothill areas.

Sunday will be mostly dry statewide and temps will be near average, so a nice early Fall kind of day.

For next week, GFS has come into agreement with the ECMWF on the pattern for next week. They bring a upper level trough into the Great Basin on Monday, then develop a cut-off upper low over western AZ Tuesday into Wednesday and eject it to our south on Thursday. The end result for CO will be dry conditions Monday through Wednesday with temps slightly above average each day. By late next week a very deep upper trough will move along the West Coast and carve out a long wave upper trough position along the West Coast. This will bring a decent chance for precip to CO west of I-25 Thursday afternoon with showers and thunderstorms possible as temps dip below average.

As upper trough digs along the CA coast next weekend, CO will remain mostly dry Friday through Sunday with temps above average. Gusty southerly winds will increase over CO next weekend creating elevated fire danger.

Author:  wxgeek [ Sep 22, 2019 2:51 pm ]
Post subject:  Re: Weather Outlook Through The End of September

Beautiful early Fall day across the state today with temps slightly below average after a cool start. No precip expected statewide.

For the week ahead, upper level trough will dig along the West Coast and become a cut-off upper low in AZ Tuesday into Wednesday. This will leave CO dry with temps above average Monday through Wednesday.

By late Thursday, the upper low begins to eject to the northeast across CO. Precip is not expected to enter the state until Thursday afternoon and should be limited to southwest CO. Ahead of this system, southwest winds will increase Thursday and cause temps to rise well above average east of the Divide. Thursday night into Friday morning precip will move east of the mountains into foothill areas and the Urban Corridor and continue during the day on Friday as precip spreads east into the plains. Snow level could lower to near 10,000 ft on Friday bringing the mountains our first good snow of the season. Precip should move east of I-25 by Friday evening. Temps will be well below average on Friday.

For the weekend, deep upper trough will carve out across the Inter-Mountain West. This will bring a chance of precip to much of CO, especially west of I-25 both Saturday and Sunday as temps remain well below average. Snow level Saturday will be 10,000-11,000 ft and lower to 9,000-10,000 ft on Sunday.

Models swing upper trough into CO early next week which would bring precip to western CO Monday that would move into eastern CO on Tuesday and lower snow level down to 7000 ft and bring the chance of our first snow to foothill areas, but that is still a long ways off and lots could change.

Author:  wxgeek [ Sep 24, 2019 3:13 pm ]
Post subject:  Re: Weather Outlook Through The End of September

Sunny, warm and dry day across the state today with temps above average. A weak cold front will swing down over eastern CO tonight which will cool temps closer to average on Wednesday. No precip expected statewide on Wednesday.

On Thursday westerly winds will increase across the state and that will cause temps to rise well above average for most areas. The only precip Thursday will be across southwest CO. On Friday, the closed upper low that has been hanging out over AZ all week will finally kick out across CO. This will create better precip chances for most areas of the state with showers and isolated thunderstorms possible, but precip amounts are expected to remain light, generally under 0.10 inches for most areas which will not do a lot to alleviate fire concerns. Temps will remain near average on Friday. Snow level should remain above 12,000 ft on Friday.

For the weekend, a deep upper trough will move into the Pacific Northwest which will leave CO under a mostly dry southwest flow aloft. There will be a chance for isolated afternoon showers and thunderstorms each day, with best chances west of the Divide. There will also be gusty southwest winds of 15-35 mph each day that will create high fire danger.

For next week, models have some differences. Early in the week, ECMWF keeps upper trough over Oregon, while the GFS moves it east into the Rockies by Tuesday. Both models keep most of CO dry Monday and Tuesday with temps near average Monday then well below average Tuesday. On Wednesday, GFS brings upper trough across CO while ECMWF keeps the upper trough well to our north. GFS would bring some mountain snow to the northern mountains with snow level near 8000 ft, while the ECMWF keeps CO dry. Temps will be below average Wednesday, and much cooler if the GFS solution is correct.

For the latter part of next week, upper ridge is forecast to build over CO which will keep precip out, and warm temps above average Thursday into Saturday. Chance for some precip across western CO on Sunday.

Author:  wxgeek [ Sep 26, 2019 2:28 pm ]
Post subject:  Re: Weather Outlook Through The End of September

Warm and windy day across most of CO today. Temps are 10-15 deg above average and will approach record values in some areas. Westerly winds of 15-35 mph combined with very low RH values will create very high fire danger for areas west of I-25 today. Gusty westerly winds may persist overnight in mountain and foothill areas.

On Friday, cut-off upper low over AZ will be picked up by upper trough moving to our north. First, a weak cold front will drop south over CO Friday morning which will cool temps back near seasonal norms. Second, there will be enough moisture to create showers over western CO Friday morning that will move east into eastern CO Friday afternoon and evening that will linger into Saturday morning. Snow level looks to remain above 12,000 ft, but some light snow may dust higher peaks in the mountains.

For the weekend, deep upper low will move into the Pacific Northwest that will bring rain and snow to much of the northern Rockies and Pacific Northwest. In Colorado, we will simply see increased southwest flow aloft that will create breezy to windy conditions for much of the state that will keep fire danger very high. Sunday foothill areas could see winds of 35-50 mph from the southwest, along with RH values below 15%, so critical fire weather conditions that will likely prompt Red Flag Warnings. For precip, only a slight chance for isolated showers Saturday over the mountains. On Sunday, showers will be possible west of Vail Pass in the afternoon and evening. Temps for the weekend will be near average Saturday, and 5-10 deg above average Sunday.

For next week, large upper trough will move east into the Northern Rockies Monday into Tuesday. In Colorado, Monday will see more dry conditions with temps near average and breezy southwest winds. On Tuesday, a cold front will bring cooler temps below average and a slight chance for a few afternoon showers along the Urban Corridor and foothills. On Wednesday upper trough passes to our north as CO remains mostly dry and temps will remain well below average.

Late next week yet another upper trough moves into the Pacific Northwest leaving CO under southwest flow aloft. At the surface, mostly dry conditions expected with gusty southerly winds and temps near average.

For next weekend, ECMWF brings some precip and cooler temps, while the GFS keeps CO mild and dry.

Author:  wxgeek [ Sep 29, 2019 3:19 pm ]
Post subject:  Re: Weather Outlook Through The End of September

Very dangerous fire weather conditions today across most of CO. Southwest winds of 25-50 mph will persist across much of CO through this evening with RH values below 15%. Winds will lessen some overnight, but gusty southwest winds of 15-35 mph will persist into Monday morning for most foothill areas. Temps are well above average today statewide, with a few isolated showers across western CO west of Vail Pass.

For the week ahead, deep upper level low over the Pacific Northwest that has brought 1-2 feet of snow to the northern Rockies will slowly move east into the northern Rockies Monday into Tuesday. This will keep a strong southwest flow aloft over CO so strong southwest winds will persist on Monday with speeds of 20-45 mph, so another critical fire weather day. I plead with everyone to think twice about any activity that can create a spark, which includes recreational shooting. Please wait until better weather conditions allow you to safely conduct these activities. Temps on Monday will remain above average and RH values will be below 10% for many areas.

A cold front will move across eastern CO Monday night and bring much cooler temps to eastern CO on Tuesday. This may also usher in low clouds and fog into foothill areas Tuesday morning along with some drizzle. Tuesday afternoon and evening there will be a slight chance for isolated showers and thunderstorms from I-25 into foothill areas. Low clouds will persist across much of eastern CO Tuesday night into Wednesday morning creating more fog in foothill areas along with light drizzle. Clouds may linger into early afternoon hours for much of eastern CO. Temps Wednesday will be well below average statewide.

On Thursday, upper level ridge builds over the Rockies and will provide dry conditions statewide along with temps returning to near average. On Friday, upper level trough will pass to our north and create some gusty westerly winds, but dry conditions statewide. Temps will rise above average due to katabatic warming.

For the weekend, another upper level trough will pass to our north and bring a cold front that will lower temps below average on Saturday, but dry conditions will persist. On Sunday, temps will remain below average after a slight chance for some precip in the morning.

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