Sunrise 5:50 AM   Sunset 8:01 PM Moonrise 5:57 AM   Moonset 9:14 PM

  Print   HELP   Reset   Save   Recall  New

FXUS65 KBOU 090130 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 730 PM MDT Wed May 8 2024

KEY MESSAGES

- Continued light snowfall in the mountains with some blowing snow over the higher passes

- Cool and unsettled weather Thursday through Friday, with accumulating snow in the Front Range mountains, higher foothills, and Park County

- Gradual warming this weekend into early next week, but still somewhat unsettled with scattered showers and storms most days

UPDATE
Issued at 730 PM MDT Wed May 8 2024

Water vapor satellite imagery showing a low spinning over the Great Basin and a second low tracking southwest across the Black Hills. These two come together over the Great Basin Thursday.
Radar shows a good amount of showers over Wyoming. Models indicate most of this activity stays north of Colorado, though wouldn't be surprise to see a few over far northern Colorado as well. Airmass over the area is still dry with a temperature/dew point of 20-30F, so it will take a while to moisten up. This will happen behind a cold front that pushes south through the area Thursday morning. Northeast low level flow behind the front will produce low clouds and areas of rain. Best chance for rain/snow and heaviest rain/snow will be over the upslope favored areas, mainly west of I-25 and also over the Palmer Divide. This will be a chilly system with the snow level falling to 6000-7000 feet. For the update, delayed the increase in PoPs until Thursday morning, after 12Z. Also removed/decreased the mention of thunder across the Front Range where stratus is expected to stabilize the airmass on Thursday.

SHORT TERM /Through Thursday/
Issued at 245 PM MDT Wed May 8 2024

The latest radar scans currently show rain showers over the Northern Rockies of Montana and Wyoming this afternoon associated with an elongated upper level low. This low will shift southwestward into Colorado and Utah overnight funneling moisture into the forecast area.

For this afternoon and tonight, SPC mesoscale analysis shows mid level lapse rates have increased enough this afternoon creating enough instability to bring a slight chance of thunderstorms to areas mainly west of I-25 while rain showers are possible across the plains. Precipitation will develop along the northern state border and spread south as a cold front passes from north to south later on tonight bringing a chance for snow showers to develop in the mountains and foothills. Temperatures will be a few degrees below normal across the plains and foothills, and 10 to 15 degrees below the norm for the higher elevations.

By tomorrow morning, snow levels will drop to between 6000'-7000'as the elongated low splits into two and upslope flow develops across the Front Range mountains. Max temperatures will be well below normal as widespread 50s will be seen across the plains, 40s for the foothills, and 30s and 40s for the mountains. See the long term forecast below for specifics on snow amounts.

LONG TERM /Thursday night through Wednesday/
Issued at 143 PM MDT Wed May 8 2024

The models have trended wetter with the elongating trough dropping across our area, and the impacts of this could last through Thursday night and even into early Friday morning. There is persistent QG lift through this period, but the bulk of it will stay to our south. That said, there is more of an upslope component now advertised to last through Thursday night as the elongated trough redevelops into a slightly deeper closed low in the Great Basin. Thus, with all those ingredients we increased PoPs and QPF/Snow forecasts for locations in/near the Front Range through tomorrow night. Regarding snow levels, we think most of the accumulating snow should stay above 7,000 feet per latest forecast soundings, but we did have to nudge snow levels down down to account for the upslope component and potential enhanced precipitation rates and latent heat of melting. Thus, we would not be surprised to see some accumulation down to ~6,500 feet should the more significant precipitation/upslope develop. We could certainly need Advisories for the Park/Summit County areas, and possibly into portions of the foothills in updates to follow.
Current potential shows upward of 6-12" possible for Park County and east facing slopes above 7,000 feet.

By later Friday and Friday night, we'll turn to neutral forcing or weak subsidence. Precipitation coverage will be on the decrease, although there is still some weak upslope and potential for shower redevelopment with sufficient daytime heating. There's not a lot of heating, however, with high temperatures likely struggling to reach 60, and most likely holding in the 50s closer to the foothills.

For the weekend, there seems to be more ensemble agreement that weak troughiness will remain over the forecast area. This will lead to only gradual warming, but a continuation of scattered showers and a few thunderstorms each day. Instability is limited, so there is little if any threat of severe.

We finally expect a return to above normal temperatures by early next week. That's when we begin to transition to more of a zonal flow with downslope aiding the warmup. It is springtime, however, so we'll continue to see a chance of showers and storms most days.
The severe storm threat will remain limited due to a lack of instability. It's not impossible, however, that we start to see a little stronger convection toward Tuesday or Wednesday if we can build enough low level moisture.

AVIATION /00Z TAFS through 00Z Thursday/
Issued at 545 PM MDT Wed May 8 2024

VFR to prevail through the rest of the evening and into the overnight hours. West to northwest winds to decrease after sunset (02Z). Wind direction becomes tricky to forecast and likely becomes variable.

Cold front pushes through the Denver area around 12Z bringing northeast winds and low clouds (1500-2500 feet) with it. Models still showing a somewhat large window (12-15Z) when the front could push through. Expect ceilings to slowly rise after 18Z, but remain under 6000 feet through Thursday. After 00Z Friday ceilings will slowly lower. Lowest clouds/visibility and best chance for rain showers are expected to be at BJC due to the northeast upslope flow.

BOU WATCHES/WARNINGS/ADVISORIES
None.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Denver/Boulder, CO,