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FXUS65 KBOU 072009 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 209 PM MDT Tue May 7 2024

KEY MESSAGES

- Freeze warning for the Palmer Divide early Wednesday morning

- Continued snowfall with blustery conditions across the high terrain this evening.

- Cool and unsettled pattern Wednesday through Friday.

- Warming Saturday through Tuesday with more normal late day shower and storm chances

SHORT TERM /Through Wednesday/
Issued at 1201 PM MDT Tue May 7 2024 Remainder of Today and Tonight...Still windy and quite frankly we're over it! Elongated trough axis and perpendicular jet streak careening into the Continental Divide continues to create pockets of heavier snow combining with stronger winds will drop visibilities to a mile or less. As mentioned earlier, lapse rates are still very steep so we're looking at convective snow showers, so impacts will vary greatly within a small amount of real estate. The Winter Weather Advisory continues through 6 PM MDT for the high country.

Across the foothills and plains, winds, virga, virga driven winds, maybe a hundredth or two of rain (right along the foothills), otherwise no big sensible weather concerns...did we mention wind!?

We continue the Red Flag Warning across southern Lincoln County as numerous gusts 30-40 MPH are expected the remainder of the afternoon with relative humidity values hovering right around 15% at this time.

Overnight we really don't lose the winds, though we remove a majority of the stronger gusts outside of the high terrain. While the skies do clear and the airmass is rather dry, we should cool enough to get close to the freezing mark in a lot of places early Wednesday morning. The highest confidence we have in a harder freeze is across the Palmer Divide where we expect shelter temperatures to drop into the upper-20s. DESI viewer shows nearly a 100% chance of being below freezing in this area...chances drop off quickly outside of the Palmer to around 30% of being below freezing. The warmer overnight temperatures and the addition of the winds is the main reason why we canceled the Freeze Watch tonight.

Wednesday
Much the same, though a tad less wind
finally! 700mb low pulls further to the east-southeast so winds should back more towards the northwest throughout the day. Lapse rates aren't as steep as today but a little bit of heating during the afternoon we could see some pop-up showers, 20% chance, across the northern plains counties.

LONG TERM /Wednesday night through Tuesday/
Issued at 200 PM MDT Tue May 7 2024

A more tranquil (and less windy!!) pattern will dominate our weather through early next week. There will still be a few showers or isolated thunderstorms around in typical spring fashion, but no big storms are in the works.

For Wednesday night into Thursday, the elongating upper level trough will sink slowly southward into Colorado and the Great Basin. Moisture will increase, leading to scattered but mostly light showers. It's quite a chilly system with 700 mb temperatures near -6C along the Front Range by early Thursday morning, perhaps leading to a little rain/snow mix all the way down to Denver's elevation, if we see precipitation Thursday morning. Then daytime heating would lift any snow levels closer to 7000 feet by the afternoon hours. That said, any accumulation in the higher elevations will still be light given weak dynamics and orographics. We may be hard pressed to push far into the 50s for highs considering the additional moisture and cooler airmass overhead.

For Thursday night, most showers are expected to come to an end as the best lift settles into the Great Basin, leaving a weak col but somewhat drier air over our forecast area. If it clears out sufficiently we could be looking at frost/freeze conditions again.
For Friday, enough instability would still exist though to keep a few convective afternoon and evening showers in the forecast, mainly over the higher terrain. Some drying should allow for more solar insolation, pushing highs into the 60s.

For Saturday through Monday, there is still uncertainty and no clear solutions for the forecast in this period. Ensembles are coming into a little better agreement, but it all depends on how far north the low kicks to the east, and the timing of said feature. For now, there's not much confidence in any one particular solution, as there's a relatively even split between lifting the upper low back up across Colorado at some point next weekend, or keeping it sufficiently to our south for mostly dry weather and warmer temperatures. There's still no clear solution at this point, so we'll go with the consensus model blends showing the warmer temperatures but also a chance of showers/isolated storms most days. This pattern would not favor any threats of significant weather or strong thunderstorms.

AVIATION /18Z TAFS through 18Z Wednesday/
Issued at 1156 AM MDT Tue May 7 2024

Today...VFR. Complicated wind forecast with predominant WSW surface flow. Issues come with any enhanced showery/virga activity that push the winds more directly west, especially for KDEN, for an hour or two this afternoon. Winds should begin to decrease by late afternoon and back slightly WNW. Medium confidence overall.

Tonight - Wednesday...VFR. Winds still on the decrease with a predominant WNW flow and some continued gustiness. Thinking gusts top out around 25 knots for our terminals. Medium confidence.

FIRE WEATHER
Issued at 1201 PM MDT Tue May 7 2024

Critical fire conditions will be in place into the early evening across southeastern Elbert and southern Lincoln counties due to very windy conditions and low humidity. Across the rest of the plains there will be elevated fire conditions.

BOU WATCHES/WARNINGS/ADVISORIES
Winter Weather Advisory until 6 PM MDT this evening for COZ031- 033-034.

Freeze Watch from midnight MDT tonight through Wednesday morning for COZ038>040-042>049.

Freeze Warning from midnight tonight to 8 AM MDT Wednesday for COZ041.

Red Flag Warning until 7 PM MDT this evening for COZ247.

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