Sunrise 5:31 AM   Sunset 8:24 PM Moonrise 1:56 AM   Moonset 3:21 PM

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FXUS65 KBOU 021754 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 1154 AM MDT Sun Jun 2 2024

KEY MESSAGES

- A couple severe storms over the northeast corner of the state late this afternoon.

- Summer heat through most of this week, with a few 90 degree readings over the plains. Breezy but a little cooler Tuesday.

- Chance of showers and storms for Monday night

- Return to more normal temperatures and a chance of storms towards next weekend

UPDATE
Issued at 1017 AM MDT Sun Jun 2 2024

Scattered thunderstorms are still on track to form over far northern Colorado and southern Wyoming by mid afternoon. A cold front/outflow boundary races south across northeast Colorado during the late afternoon hours. Current temperature are generally in the upper 60s to lower 70s over northeast Colorado. Lowered high temperatures a couple degree for today due to the cold front/outflow boundary shutting off heating a little early and a somewhat cool start to the day. Airmass moistens some behind the front, leading to an increase in instability. Isolated showers and thunderstorms will be possible behind the northerly push later today. The severe threat over the far northeast plains is still on track.

SHORT TERM /Through tonight/
Issued at 339 AM MDT Sun Jun 2 2024

A few thunderstorms have passed through the northern portion of the forecast area overnight associated with a passing shortwave. These will continue to move eastward and are expected to be out of the area in the next few hours. This morning will bring mostly clear skies before noon when clouds will begin to develop over the high terrain and move east across the plains. The main concern for today is the enhanced threat for severe weather across the northeastern counties of the forecast area. As a dryline shifts east toward KS and NE through the afternoon, the majority of the CWA should remain on the west side with the exception of Logan, Sedgwick, and Phillips Counties. Hi Res guidance are in good agreement that storms will likely initiate along the dryline this afternoon and then propagate eastward into a very unstable airmass east of CO. With MUCAPE values looking to reach upwards of 2000 J/kg, 0-6 km bulk shear values of 40 - 55 kts, and a high probability of rotating updrafts per the HRRR ensemble, the SPC has placed Sedgwick and Phillips Counties within their enhanced category for today with the possibility for scattered supercells to develop that could bring damaging winds, very large hail, and a few tornadoes this afternoon. The threat is likely to remain through around 3Z before it shifts eastward out of the CWA

Farther west, the low levels are much drier and forecast soundings depict an inverted-v type environment. With high DCAPE values up to 1400 J/kg portrayed in some model guidance, the main threat will be strong gusty outflows.

Today will be a warm day as temperatures are forecast to reach the high 80s with a few locations reaching the 90 degree mark, which would make this the warmest day of the year thus far.

LONG TERM /Monday through Saturday/
Issued at 339 AM MDT Sun Jun 2 2024

Summer heat will be the main theme for most of the upcoming week.
That said, there are still a couple weather disturbances to deal with, and some cooling noted by the end of the week.

Monday will feature very warm temperatures with highs pushing 90F across the I-25 Corridor and plains. There will be a little more of an inversion to start the day behind tonight's outflow/frontal push, but that should all but erode Monday afternoon with westerly flow aloft and sufficient daytime heating and mixing.
Despite the drier low levels, we'll likely see high based virga or showers attempt to develop in/near the mountains late in the afternoon as the next weather disturbance pushes toward the area late in the day.

There is a change in the forecast for Monday night as a strong upper level speed max moves across the spine of the Northern Rockies. That puts northeast Colorado in the left exit region of this unseasonably strong speed max (150 kts over Idaho). Thus, despite the relatively dry airmass, we would expect at least scattered shower and isolated thunderstorm development in the evening, that could last through much of tomorrow night. This is a new change in the forecast. The threat of any severe weather should be limited by the lack of any appreciable MLCAPE. However, couldn't totally rule out a stronger storm over the far northeast corner overnight depending on return of low level moisture.

Given the stronger Northern Rockies shortwave, there is now more agreement that Tuesday will be a little cooler but windier.

Then, ridging quickly pops back for Wednesday, in what will likely be the hottest day of the year so far. We think 90F+ is likely (>70% chance) over almost all of the plains including Denver.
Thursday could still be hot depending on strength of potential backdoor cold fronts associated with deep upper low dropping into the Great Lakes Region Thursday.

By Friday and next weekend there is more agreement in the cooling trends in the latest ensemble data. Despite some ridging aloft, that could lead to more moisture and a higher chance of showers and storms developing at some point toward next weekend. Most of the uncertainty revolves around when this will happen, so we've generally accepted the model averages here.

AVIATION /18Z TAFS through 18Z Monday/
Issued at 1154 AM MDT Sun Jun 2 2024

Generally light northerly winds are expected at DEN through 19-20Z. A good amount of uncertainty if gusty west-northwest winds will form after 20Z ahead of a strong northerly wind shift. At APA, gusty west-southwest winds have formed, but are expected to stay south of DEN. The cold front/outflow boundary races south across the Denver area 22-23Z bringing gusty north winds to 35 knots. Behind it, isolated showers are expected to form with a slight chance (~10%) for a thunderstorm. Brief light/moderate rain and gusty winds will be possible with activity.
North/northeast winds linger into 00-03Z window and then turn clockwise and settle a southerly direction around 06Z.

For Monday, light winds prevail through 18-20Z. A round of high- based showers and thunderstorms are expected after 20Z. Gusty outflow winds will be common and are expected to produce wind shifts at the Denver airports.

HYDROLOGY
Issued at 315 AM MDT Sun Jun 2 2024

Alpine snowmelt will increase runoff the next several days.
Hydrologic forecasts from the River Forecast Centers show a few streams getting to action stage toward Monday or Tuesday, which means flows will be high and fast but flooding threat limited.
Please use caution and respect these fast moving and cold flows in the high country.

BOU WATCHES/WARNINGS/ADVISORIES
None.

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