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
559 FXUS65 KBOU 191702 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1102 AM MDT Thu Sep 19 2024 .KEY MESSAGES... - Dry and warm through Friday with elevated fire weather conditions. - Storm system will impact the area this weekend. 70-80% chance of precipitation, but considerable uncertainty regarding how much. There is a chance of significant rainfall, and several inches of mountain snow depending on track/evolution. - Turning much cooler by late Saturday and Sunday. Below normal temperatures early next week, then likely (60% chance) back to drier and warmer weather toward the middle of next week. && .UPDATE... Issued at 1101 AM MDT Thu Sep 19 2024 Satellite pictures indicated a few clouds over the mountains at this time. Normal diurnal wind patterns were indicated over the plains. Temperatures were already in the lower and mid 70s F over the plains with mid and upper 50s in the mountains. Not to much to change with the grids, just some minor temperature and wind alterations this update. && .SHORT TERM /Through Tonight/... Issued at 353 AM MDT Thu Sep 19 2024 Southwest flow aloft continues today as an upper level low dives south along the California coast. Ridging in the southwest flow aloft will lead to weaker flow and less wind today. The airmass remains dry with mostly sunny skies. The dry conditions will elevate fire weather conditions this afternoon. Winds will be a little weaker than yesterday. The mountains and higher foothills may see southwest gusts of 25-30 mph. Temperatures will be similar to what we saw yesterday with highs in the lower to mid 80s over northeast Colorado. For tonight, dry conditions continue with only some high clouds lifting north across the area. Mild overnight lows are expected with upper 40s to mid 50s over northeast Colorado. && .LONG TERM /Friday through Wednesday/... Issued at 353 AM MDT Thu Sep 19 2024 The last day of above normal temperatures and dry conditions ends Friday. Cross sections display strong southwest flow and weak mid- level moisture leading to a few high clouds along the eastern plains. With mostly sunny skies, afternoon temperatures will reach the mid to upper 80s along the plains. Additionally, higher elevations are expected to reach the low 60s to mid 70s. The combination of dry conditions and increasing low level southwest winds could lead to near critical fire weather conditions mainly for the Palmer Divide and adjacent plains. Winds remain borderline with gusts up to 20-22 mph. As the incoming trough approaches northeastern Colorado, winds shift northwest overnight into Saturday morning. Recent models runs have introduced a southerly track which has delayed incoming precipitation. There is good agreement between the ECMWF, GFS, and Canadian where the center of the upper level low reaches the Four Corners starting late Saturday afternoon. There were concerns on previous runs with convective development occurring along the higher elevations before the bulk of the system arrives to northeastern Colorado which could lead to a greater flash flood threat for recent burn areas. This outcome has lowered due to rain becoming more stratiform and this should ease the flash flood threat over the burn areas. In terms of QPF, GFS ensemble members have a greater spread from 0.2-3.50 inches versus the ECMWF ensembles therefore there is still large uncertainties in precipitation amounts. With significant differences, decided to lean towards a blend NBM and ECMWF of 0.60-2.20 inches total precipitation for the plains and Palmer Divide. Areas such as northern Weld, Logan, Sedgwick and Phillips may receive higher totals depending on flattening ridge south of our region. Additionally, decided to increase PoPs both late Saturday through early Sunday to reflect higher confidence in timing of rainfall for the plains and snow for areas above 11-12k feet. Snowfall totals between 3-6 inches could occur and those traveling to areas such as Berthoud Pass should prepare for slick roads through late Sunday morning. Next week, models aren`t in agreement with the next trough entering northeastern Colorado. Thus decided to lean on NBM PoPs of isolated chances of showers across the region both Monday and Tuesday afternoon. Temperatures remain below normal during this period. && .AVIATION /18Z TAFS through 18Z Friday/... Issued at 1058 AM MDT Thu Sep 19 2024 Models keep the east and southeasterly winds going at DIA through the afternoon hours. Speeds should stay below 15 knots. Drainage winds should kick in around 04Z this evening. There will be no ceiling issues. && .FIRE WEATHER /Friday through Wednesday/... Issued at 353 AM MDT Thu Sep 19 2024 Near critical fire weather conditions are possible along the Palmer Divide and Lincoln county Friday afternoon. Relative humidities drop to the lower teens. Southwesterly winds could produce wind gusts up to 20 mph with occasional gusts up to 25 mph. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE..........RJK SHORT TERM......Meier LONG TERM.......AD AVIATION........RJK FIRE WEATHER....AD