Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
709 FXUS65 KBOU 070340 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 940 PM MDT Sat Jul 6 2024 .KEY MESSAGES... - Cooler temperatures and scattered storms are possible early Sunday morning until late afternoon across the region. - Lower thunderstorm chances and warmer next week. && .UPDATE... Issued at 933 PM MDT Sat Jul 6 2024 Light convection is still around at this hour with plenty of outflow boundaries. Tonight`s cold front is right around Cheyenne currently and is moving around 25 knots southward. For this evening`s grid update, altered pops down a bit and did some wind repairs. Some of the models show a decent Stratus deck to develop overnight into Sunday morning. That could affect tomarrow`s, later in the day, instability. && .SHORT TERM /Through Sunday/... Issued at 200 PM MDT Sat Jul 6 2024 It`s rather dry across the plains today, while the bulk of the moisture remains confined to the mid levels and to our east into Kansas. There`s plenty of shallow cumulus development evident on satellite over the high country, but instability today will be meager outside of the far northern/northeast plains. Ongoing and organized convection across Kansas and Nebraska should promote some decent moist easterly outflow late afternoon, with dewpoints progged to rise into the mid to upper 50`s for our northeast plains. This should translate into a fairly late window for convective activity today. Suspect most if not all storms this evening would remain sub-severe, and it`s possible that activity could be tapered a fair bit if we cool down enough to result in a weak low-level cap. Perhaps the better opportunity for convection would arrive with the approaching cold front near or just after midnight, providing some additional lift. This front will bring enhanced low-level moisture, and some low stratus, to most areas east of the foothills. Although a few light showers can`t be ruled out during the morning, believe moisture will be a little too shallow to support anything too meaningful. It`ll certainly be considerably cooler, with highs dropping below normal into the lower to mid 70`s across our lower elevations. The cooling will be more subdued in the high country, but increased afternoon cloud cover will still provide for some moderation in temperatures. It`s across our higher elevations, which will be largely free of morning cloud cover, where conditions will be much more favorable for initiation of afternoon convection near midday, especially in Larimer County. Some CAMs depict robust thunderstorm development over the urban corridor instead, but this seems at odds with the pattern considering the likelihood of relatively widespread and persistent cloud cover early on under a largely weak upslope regime. Thus, likely (60%+) PoPs look reasonable for much of our Front Range mountains and foothills for Sunday afternoon, with lower potential (30-50%) for the Denver metro, mainly from convection rolling off the higher terrain. We could see some late day enhancement across the plains where instability will be slightly more favorable, but all in all, the threat for any severe weather should remain on the low side. && .LONG TERM /Sunday night through Saturday/... Issued at 200 PM MDT Sat Jul 6 2024 An upper level ridge approaches Colorado starting Sunday night. Lingering storms and showers are possible for South Park, Palmer Divide, and adjacent plains through midnight. Winds shift to southwest flow especially for the foothills to the lower elevations. Not many changes to PoPs during Monday to Wednesday. It seems each afternoon, drier air will limit thunderstorm development mainly for the foothills, Park county, and parts of the Palmer Divide. During the afternoon hours Monday through Wednesday, the combination of daytime heating, weak instabilities of MLCAPE 200-500 J/kg, and DCAPE values approaching 1000 J/kg will likely lead to sub-severe storms producing strong winds. PWATs vary between 0.50-0.80 inches during this period thus it is possible storms could produce brief heavy rainfall. Status quo in the long-term outlook towards the end of next week. Thursday, the upper level ridge becomes stationary over Colorado. This will likely lead to increasing surface temperatures and light winds across the region. Although winds do not meet fire weather criteria, widespread low relative humidities are expected across the foothills to plains through next weekend. By Friday, there is excellent agreement amongst ensembles that lower elevations rebound back to the upper 90s with a few spots possibly reaching the lower 100s. Additionally, 500mb heights display the upper ridge persisting through next weekend limiting thunderstorm development mainly for the Front Range foothills. && .AVIATION /06Z TAFS through 06Z Monday/... Issued at 935 PM MDT Sat Jul 6 2024 A number of convective outflow wind surges have pushed across DIA this evening. Real data suggests the cold front could be getting into DIA around 06Z. Some models are showing lower ceilings behind the cold front in the upslope flow. Will go with SCT-BKN 020-030 for now, but they may be lower. Those ceiling should dissipate before 18Z on Sunday. As stated above, not sure how the Stratus will eventually affect Sunday`s instability. Went with "VCSH" and VCTS" for now for Sunday afternoon and evening. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.......RJK SHORT TERM...Rodriguez LONG TERM....AD AVIATION.....RJK