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
146 FXUS65 KBOU 152325 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 525 PM MDT Sat Jun 15 2024 .KEY MESSAGES... - Warmer, drier, and breezy on Sunday with Heat Advisories across the southeast Denver metro. - Critical fire weather conditions on Sunday, likely continuing on Monday. - Snowmelt producing minor impacts from high streams. Gradually diminishing flows next week. - Cooler for Tuesday and Wednesday && .SHORT TERM /Through Sunday/... Issued at 228 PM MDT Sat Jun 15 2024 Gusty showers will linger into the early evening hours today. One of these high-based showers produced a microburst almost directly over KAPA earlier in the afternoon with a gust to 44kt... and while that`s likely on the higher end of the gust potential, it wouldn`t be surprising to a few additional gusts of 40-50 mph. Showers will quickly diminish near sunset. Tomorrow`s forecast is surprisingly challenging. Southwesterly flow aloft will gradually strengthen through the day, advecting a hotter/drier airmass into the region. Model cross sections show very little moisture through the column, and skies should be mostly sunny through the day. Meanwhile, temperatures should also increase to about 18-20C, which is roughly 2-4C warmer than today. This would all be pretty straightforward, if not for a push of cooler/more moist airmass associated with a weak front/outflow from a storm system tracking across the northern Rockies/Great Plains this evening. Guidance is in good agreement that this shallow boundary will reach the northeastern edge of our forecast area by Sunday morning, but models remain largely inconsistent on how that boundary moves during the afternoon hours. This is further complicated by the potential for a lee surface trough/Denver cyclone to form during the day as well. On the hotter/drier side of this boundary, high temperatures should reach the mid to upper 90s. Experimental Heat Risk values are borderline for issuing advisories, but given the lack of cloud cover and the (relatively) early season... have opted for a Heat Advisory for Denver and southeast into the Palmer Divide and Lincoln county. There will also be an increased fire danger on the dry side of this boundary and across the high country (see the Fire section below). && .LONG TERM /Sunday night through Saturday/... Issued at 228 PM MDT Sat Jun 15 2024 The extended forecast period will begin with a persistent southwesterly flow aloft as upper level troughing develops over the western CONUS. After another 90+ degree day across the plains on Monday, things will cool down for Tuesday and Wednesday with a cold frontal passage before the heat ramps back up for the end of the week. Monday is forecast to be warm and dry ahead of the aforementioned cold front. Forecast soundings indicate a dry boundary layer with DALR and a lacking moisture profile. With only 13% of ensemble members showing a roughly 15% chance of precipitation, will keep isolated PoPs in the forecast for locations over the eastern portion of the CWA. With relative humidities and wind gusts crossing into critical fire weather criteria, highlights will likely be needed Monday afternoon. See the fire weather discussion below for more details. Southwesterly flow aloft will continue Tuesday and Wednesday, however, the passing cold front will help usher in some moisture and cooler air from the north. Max temps will drop to a few degrees below normal, and roughly 10-15 degrees cooler than what was felt on Monday. A few showers and isolated storms are possible in the afternoon over the mountains and the Palmer Divide, but from a deterministic standpoint, agreement with regards to moisture and precipitation is lacking past this point. Ensembles show a 30% chance of overnight storms and showers across the plains on Tuesday night, east of DIA, with thunderstorms more likely over the farthest east locations. Southerly surface flow looks probable to provide ample moisture support from the Gulf to allow for afternoon storms to develop for the remainder of the week. Surface dewpoints look to steadily increase beginning Wednesday, and may reach the upper 50s to mid 60s across portions of the plains by Friday. Temperatures will climb back up into the 80s and 90s beginning Thursday, and ensembles show mean CAPE values climbing to 1000+ J/kg both Thursday and Friday across portions of the plains, mainly east of DIA. && .AVIATION /00Z TAFS through 00Z Sunday/... Issued at 523 PM MDT Sat Jun 15 2024 VFR through the TAF period. Slight chance (20%) remains for a very brief high-based shower in the vicinity of KDEN over the next ~2 hours. Main impacts would be from variable/gusty outflow winds with little precipitation expected, with highest potential being for NW outflow winds in the next couple of hours from ongoing convection due north of the Denver area. Expecting a transition to southerly drainage flow this evening. Low confidence in the wind forecast tomorrow as a weak frontal push, a Denver cyclone, or a well mixed southwest flow are all possible by midday Sunday. For now have opted to keep a fairly light northeast in at DEN. && .FIRE WEATHER... Issued at 228 PM MDT Sat Jun 15 2024 A much drier airmass is expected to advect into the high country and portions of the Palmer Divide/plains tomorrow. HREF ensemble mean relative humidity falls to 10-15% across the high valleys and across the Palmer Divide/plains south of I-70 by the early afternoon. Winds are marginal but would likely support a window of near Red Flag criteria gusts for several hours on Sunday afternoon. However, a shallow cold front is also expected to sink south into the plains Sunday with substantially more surface moisture north of the boundary. Some uncertainty with the position of that boundary and about overall fuel conditions, but enough confidence to go ahead with a Red Flag Warning where confidence is a little higher. Multiple days of 90+ degree temperatures and fuels at critical status will lead to widespread elevated and critical fire weather conditions across the forecast area on Monday afternoon. Critical fire weather conditions are likely for Zones 212-216 and Zones 238-247 and Zone 249. Highlights will be issued in the coming shifts. && .HYDROLOGY... Issued at 228 PM MDT Sat Jun 15 2024 Elevated flows continue in the mountain streams, with Flood Advisories remaining in effect for the streams above Granby and Grand Lake. Remain alert of the dangers of water that is running high and cold. Flows are expected to gradually decrease next week as the peak snowmelt is passing by. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from noon to 6 PM MDT Sunday for COZ213-214-241- 245>247. Heat Advisory from noon to 7 PM MDT Sunday for COZ040-041- 045>047. && $$ SHORT TERM...Hiris LONG TERM...Bonner AVIATION...Rodriguez FIRE WEATHER...Bonner/Hiris HYDROLOGY...Hiris