Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000 FXUS65 KBOU 270218 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 818 PM MDT Mon Jun 26 2017 .UPDATE...
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Issued at 812 PM MDT Mon Jun 26 2017 Widely sct storms will continue over Park county and across srn Lincoln county the next few hours. Outflow bndry has moved into the Denver area fm the east however visbile imagery shows very little cumulus developing along it. Thus doesn`t look like this feature will produce any tstms.
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&& .SHORT TERM...(This evening through Tuesday) Issued at 305 PM MDT Mon Jun 26 2017 Low level moisture is mixing out about as expected this afternoon. Dew points are down into the 30s near the Front Range, with 40s from Sterling to Akron. There is still more moisture further east, though temperatures are also a little cooler. Still a slight chance of getting some storms in southern Lincoln county and possibly from Holyoke to the southeast corner of Washington county. Also a possibility of some mountain storms but in a much drier environment this should be quite weak/isolated if there is any. Low level moisture returns on southeasterly flow overnight. A chance of some low clouds or fog south of Limon, but probably too well mixed for any substantial fog. Warmer and drier air aloft will move over this low level moisture on Tuesday. This will provide a capping inversion, and more dry air to mix out the moisture over the western two-thirds of our area. Once again there will be less mixing over the eastern border areas, and there could be enough moisture for strong to severe storms, though the odds get better further east. Forecast temperatures look reasonable. There may be enough high cloud cover to hold back highs on Tuesday a little bit, in which case our mid 90s highs across most of the plains may be a couple degrees too warm. .LONG TERM...(Tuesday night through Monday) Issued at 305 PM MDT Mon Jun 26 2017 On Wednesday zonal flow will be over Colorado. A ~996mb surface low pressure area moving east across the Central Plains will pull a weak cold front south across our area early morning Wednesday. Temperatures will be a little cooler behind the front, with high temperatures 7-10 degrees cooler across the Plains. The mountains will also get a slight break from the heat with 700 mb temps cooling 2-3 degC compared to Tuesday, resulting in high temps generally 4-7 degrees cooler. Despite FROPA the winds return west at all levels during the daylight hours and rapidly scour out available moisture. PWATs will be in the 0.25 to 0.40" range, and our area should remain dry. With the dry conditions and gusty winds in the 20 mph range and above, despite cooler temps, fire weather will still be a concern across the valleys of Summit and Grand counties, much like Tuesday. Given a red flag warning for Tuesday will hold off on highlights for Wednesday but conditions for fire growth will continue to be favorable. On Thursday a broad trough over MT/ND shifts east, putting Colorado in northwest flow which will continue into Saturday. The low levels remain very dry on Thursday and rain chances are very low mountains and Plains. The exception could be the far eastern Plains where surface dewpoints after mixing should be in the mid 40s, supporting marginal instability. Thunderstorm chances are similarly low but non-zero for the Plains and High Country on Friday afternoon as low-level moisture starts to increase behind another weak cold frontal passage, with easterly low-level flow and PWATs increasing to near 0.5" across the I-25 urban corridor. Temperatures will be right at seasonal normals Thursday with highs mid 80s across the Plains and upper 60s to upper 70s in the mountains, but 3-5 degrees cooler on Friday with the frontal passage and a glancing blow of cooler 700 mb temps across far northern Colorado. This weekend the models differ on thunderstorm chances based on the mid and upper level flow patterns. The GFS indicates a weak short wave trough moving within the mean northwest flow Saturday afternoon, which initiates robust convection over the high country and moves it over the Plains. The ECMWF builds a ridge over Colorado with scattered convection confined to the southern half. Either solution favors a warming trend with seasonal high temperatures in the mid 80s both days across the Plains, Sunday warmer than Saturday. In terms of thunderstorm chances, given model differences, low PoPs are prudent from the Continental Divide east to Kansas Saturday afternoon. If the GFS is right CAPE/Shear combinations Saturday and Sunday afternoons are favorable for organized and strong convection. Low-level moisture return with the GFS looks too optimistic so have not bought into the GFS solution for this weekend...yet. On Monday models generally agree a weak ridge approached Colorado from the west with dry conditions and near normal temperatures. && .AVIATION...
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(For the 00Z TAFS through 00Z Tuesday evening) Issued at 812 PM MDT Mon Jun 26 2017 Ely flow has developed behind an outflow bndry but winds should become more sely by 10 pm and then sly by 06z. Winds will become more ssw by 09z.
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&& .FIRE WEATHER... Issued at 305 PM MDT Mon Jun 26 2017 Warm temperatures, low humidities, and winds gusting to 30 mph will create Red Flag conditions in the mountain valleys on Tuesday afternoon. There may also be some isolated dry lightning over the mountains. It will also be breezy with low humidities in and near the east slopes of the mountains, where the fuels are not as dry. On Wednesday conditions will be similar to Tuesday across the valleys of Grand and Summit Counties. Slightly cooler temps and less wind relative to Tuesday, but the combination of low RH and wind around 20 mph with higher gusts will keep the risk of rapid fire growth elevated. Given the Red Flag warning Tuesday afternoon and slight better conditions expected Wednesday afternoon, will hold off on a watch or warning. && .BOU WATCHES/WARNINGS/ADVISORIES...
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Red Flag Warning from noon to 9 PM MDT Tuesday for COZ211-213- 214.
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&& $$ UPDATE...RPK SHORT TERM...Gimmestad LONG TERM...Schlatter AVIATION...RPK FIRE WEATHER...Gimmestad/Schlatter

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