Sunrise 6:15 AM   Sunset 7:43 PM Moonrise 1:46 PM   Moonset 3:49 AM

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FXUS65 KBOU 172107 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 307 PM MDT Wed Apr 17 2024

KEY MESSAGES

- Breezy with a cold front and possible showers in the evening.

- Cooler, breezy and unsettled through Saturday with precipitation off and on. The best chances will be tonight into Thursday morning and again Friday afternoon into Saturday.

- Drier and warmer early next week.

SHORT TERM /Through Thursday/
Issued at 256 PM MDT Wed Apr 17 2024

Area radars are showing light rain showers over the northern border of the CWA at this time. There are a few snow showers over the higher peaks of the mountains north of I-70 as well. There are northerly surface winds over southern Wyoming and some portion of western Nebraska, which could be the advertised incoming cold front or outflow associated with the showers. Most of the models don't show that cold front to get into the northern border CWA until 00Z or even later this evening.

Models continue to show fairly strong westerly jet level flow overnight and Thursday. The QG Omega fields have weak upward vertical velocity over the CWA overnight into Thursday morning.
There is also decent upslope flow over the plains and foothills tonight into early Thursday afternoon. However, moisture progs continue to show pretty shallow moisture with this system. There is a bit of CAPE around the northern half of the CWA early this evening. There is also a tad progged over the southwestern CWA Thursday afternoon. The QPF fields show limited measurable precipitation for CWA overnight and Thursday as well. Will go with "scattered" showers for the plains overnight and even lower pops on Thursday. There could be a bit of snow mixed in over the plains late this evening and overnight, but accumulations are not expected. Will go with "likely" pops over the mountains and foothills east of the divide overnight. Mostly snow is expected but accumulations will be on the light side. Significant precipitation is not expected with this system tonight or on Thursday.

For temperatures, readings should cool down significantly behind this evening's cold front, with the plains dropping into the lower to mid 30s for lows overnight. Thursday's highs look to be 20 to 30 F cooler than today's highs.

LONG TERM /Thursday night through Wednesday/
Issued at 229 PM MDT Wed Apr 17 2024

Thursday night into Friday morning, a strong northwesterly flow aloft will be over the forecast area. light rain/snow showers primarily along the northern border and over the northeast plains will linger as the under the left exit region of an upper level jet max moving into the Midwest. Friday afternoon into Saturday, another period of light to moderate precipitation will move across the region. The next surge of northeasterly upslope will develop along the Front Range starting around 00z Saturday, continue overnight, then weaken and taper off Saturday morning.
Spatial cross-sections suggest the best chance of snow west of the Continental Divide will occur Friday afternoon/evening, then the focus will shift to the east slopes of the Front Range and northeast plains Friday night into Saturday morning. Overall the upslope is strongest Friday evening and confined from the surface to 700 mb. The mid and upper level QG ascent will be weak through midday, before weak subsidence moves across from the west. Based off the 0-1km MLCAPE, the GFS20 suggests 300-500 j/kg of instability especially in the mountains for Friday and Saturday afternoons. Can't rule it out for areas in and near the foothills and Palmer Divide but those areas may be fighting better low level stability. There will be a higher probability of showers vs thunderstorms (10-20%).

A drier northwesterly flow will be over CO by Sunday with a warming trends. There will be enough moisture around to support a slight chance of afternoon/early evening showers/thunderstorms. The ridge axis will stay to the west of CO with a persistent northwest flow aloft through Tuesday, then the ridge shifts over CO on Wednesday.
High temperatures by Sunday will warm to around 70, Sunday through Tuesday, then back to near 80 by Wednesday.

AVIATION /18Z TAFS through 18Z Thursday/
Issued at 1200 PM MDT Wed Apr 17 2024

Southeasterly winds should prevail at DIA much of the afternoon.
The various models, including the high resolution models, bring a decent cold front with northwesterly upslope winds behind it around 02Z this evening. Will go with ceilings in the BKN- OVC015-030 range after 04Z. Significant precipitation is not expected with this upslope event and visibilities could get down to 4SM -SHRA BR.

BOU WATCHES/WARNINGS/ADVISORIES
None.

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