Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000 FXUS65 KBOU 222158 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 358 PM MDT Fri Mar 22 2024 .KEY MESSAGES...
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- A weather system will affect the area Sunday through Monday morning. This system may bring heavier snowfall to portions of the mountains, southern foothills and Palmer Divide Sunday night. However, confidence in exact details remain low at this time. - Snow shower activity will continue in the mountains Tuesday and Wednesday with mainly dry conditions over the plains.
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&& .SHORT TERM...
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(This evening through Saturday) Issued at 300 PM MDT Fri Mar 22 2024 Current satellite imagery shows clear skies and sunshine continue across the forecast area this afternoon. Temperatures have made it to the mid 50s and should continue to climb with additional radiational heating. Enough Pacific moisture will move into the high country tonight to allow for some scattered late night snow showers. Accumulations will be minor. Strong winds will develop over the highest elevations early Saturday morning with gusts reaching 45kts. 35kt gusts are possible across parts of the plains east of DIA throughout the day. West/southwesterly flow will help temperatures reach the mid to upper 60s across the foothills and plains Saturday, which will bring max temperatures to roughly 10 degrees above normal. Saturday will also see increasing chances for rain showers to develop throughout the afternoon. Forecast soundings are unstable but show dry low levels, therefore anything that may form will likely become virga and have trouble reaching the ground. .LONG TERM...(Saturday night through Friday) Issued at 350 PM MDT Fri Mar 22 2024 A jet stream will move eastward into Colorado Saturday night with our forecast area being under a diffluent, left exit region of the jet. This will provide lift and with some weak instability across the northeast plains, there will be showers and thunderstorms that will continue through the evening into the overnight hours. These will mainly be to the north and east of DIA. Despite this lift, there will not be much mid to low level moisture in the mountains so light snowfall is expected to fall from the occasional snow showers. On Sunday, a shortwave trough will move from Arizona towards southeast Colorado. Meanwhile, there will be strong lee cyclogenesis over southeast Colorado. With limited moisture in the morning, there will be mostly dry conditions before noon. By the afternoon, a cold front will move southward out of Wyoming. This will bring additional moisture behind it initially and will shift winds out of the north with strong gusts up to 50 mph by Sunday evening. A combination of factors including, moisture behind the trough, lift from the cold front, and instability due to steep mid level lapse rates, will create showers and thunderstorms across the plains. The most likely area of thunderstorm initiation will be along the Palmer Divide and eastward to southern Washington County. Some models are showing most unstable CAPE upwards of 1,000 j/kg in Washington County and storms that form there will likely have hail associated with them. This hail should stay below severe limits but it is possible a storm or two produce 1 inch hail. By Sunday night, the entire system will strengthen as the shortwave trough deepens over the CO/NE and CO/KS borders. The 700 mb trough will deepen as well and this will help to create strong northerly winds across all of the plains. Convective showers will begin to turn into more stratiform precipitation as the evening progresses. The aforementioned cold front will decrease temperatures below freezing across the plains as rain switches to snow. The timing of this precipitation type switch will determine how much snow the plains receive. If the front comes through quicker, snow may begin closer to sunset. However, if the cold front is slow, the transition to snow may not occur until late in the evening. Given the northerly flow, the Palmer Ridge will receive the heaviest snow amounts. Ensembles would suggest values in the 4-10 inch range there. The west suburbs of Denver will receive more snowfall than the east suburbs with generally 2-8 inches expected. Areas from DIA northward towards Greeley and Fort Collins may not see much snowfall at all from this system. The Front Range mountains and foothills are expected to pick up moderate amounts of snow as the precipitation type issue is less of a concern there. There was consideration for highlights for these areas but since the worst impacts will not be until Sunday afternoon, it was decided that we will hold off. The area that may have the most uncertainty of all is the far northeast corner of Colorado. Depending on where the storm tracks, it could rapidly develop in far western Nebraska or Kansas. If this were to be the case, significant snowfall amounts could fall on the northwest side with areas like Holyoke and Julesburg receiving double digit snowfall totals. However, the more likely scenario is that the storm intensifies farther to the east leaving eastern Colorado much drier. Due to this uncertainty, the 90th percentile snow grids were increase substantially over the far northeast corner of Colorado. Very cold air aloft will continue to be overhead on Tuesday and Wednesday. While there are no intense shortwave troughs to provide lift, there will be enough instability in the mountains and foothills for afternoon snow showers to form. Some of these snow showers may drift onto the plains but little, if any, accumulation is expected. Conditions will be much warmer Thursday and Friday as ridging will build in aloft. The mountains will likely get another shot of snow on Friday and into the weekend as Pacific moisture along with strong westerly flow will arrive.
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&& .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1147 AM MDT Fri Mar 22 2024 VFR through the TAF period. Wind directions will be typical south/southwesterly drainage overnight. There is some uncertainty on whether a cyclone develops in the morning, but winds will likely become more westerly by Saturday afternoon. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Bonner LONG TERM...Danielson AVIATION...Bonner

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