Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, 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
134 FXUS65 KGJT 220935 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 335 AM MDT Sun Sep 22 2024 .KEY MESSAGES... - Showers linger over western Colorado this morning with the northwest San Juan Mountains favored. Light snow at pass level could lead to slick conditions. - Showers and embedded thunderstorms pick up again this afternoon, mainly over the mountains, as daytime warming results in instability. - Unsettled conditions remain in place through Monday, with afternoon thunderstorms possible, mainly over higher terrain, before drier conditions move in Tuesday through the end of the week. - Temperatures rebound to near normal Monday and Tuesday followed by a warming trend during the latter part of the week as high pressure builds over the region. && .SHORT TERM /THROUGH MONDAY/... Issued at 335 AM MDT Sun Sep 22 2024 A vorticity lobe moving through the southwest quadrant of the closed low pressure system centered over the central Colorado mountains was responsible for a broad area of stratiform precipitation encompassing much of Mesa, Montrose, San Miguel and Ouray counties early this morning. Models indicated the low begins to fill after sunrise shifting slightly east of the Continental Divide by noon. Lapse rates ease as the cold pool aloft shifts off to the east and the vort-lobe passes to the south of forecast area. However, northwesterlies on the back side of the low working on saturated air at lower levels is likely to keep some scattered showers going over the northwest San Juan Mountains, and to a lesser extent, the central Colorado ranges. Lapse rates steepen with daytime warming so the higher terrain will see isolated to scattered showers and thunderstorms redevelop in the afternoon with more numerous storms over the San Juans. As has been advertised over the past several days, highs will be cooler than normal, though perhaps not as cool as earlier thought. Drying begins tonight as flow continues out of the northwest. Skies will be clearing leading to good radiational cooling which, in turn, is likely to aid the formation of fog in the higher valleys. On Monday, a low amplitude mid-level short wave trough moves southeastward over the forecast at peak heating. Models suggest enough moisture remains to fuel isolated showers and/or thunderstorms over the higher terrain. Increased sunshine combined with weak warm air advection is expected to bring temperatures to near normal levels to start the week. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 335 AM MDT Sun Sep 22 2024 The remainder of a trough of low pressure moves eastward Monday night as an amplified center of high pressure takes over much of the West Tuesday. With the polar jet pushed north of the high and ample dry air in place, weather conditions should remain dry, warm, and quiet this coming week. Winds under the high should remain rather calm too. A few afternoon terrain based gusts can be expected each day, but gradient winds should stay light. Temperatures under the high will surge well into the 80`s for our low valleys and 70`s for most of our mountain towns this week, making it feel much more summer-like than the fall conditions this weekend. Model agreement begins to diverge dramatically mid week though. A series of PACNW waves along the polar jet chip away at the blocking ridge beginning Wednesday. A potential tropical cyclone comes into the picture in the Gulf of Mexico too. Models are struggling mightily to resolve the downstream impacts of this tropical storm. For now, the flattening ridge hangs over the Rockies into the weekend with the polar jet still parked along the Canadian Border. Afternoon highs will feel a bit warm for late September, averaging 10 degrees over climatology. Morning lows will remain pleasant this week thanks to lower dewpoints hanging on. Hopefully the cool overnight conditions will balance out the warm afternoon highs this week as we wait patiently for the arrival of the next round of fall weather here on the West Slope. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 1039 PM MDT Sat Sep 21 2024 Some low ceilings and light rain will continue around the region through midnight and begin to taper off before daybreak. Ceilings will gradually improve to VFR conditions as the low lifts out of the region. The backside of this storm will likely form a few afternoon showers along the Continental Divide Sunday. Confidence is low in specific locales, but VCSH can be expected at KEGE, KASE, KTEX and KGUC. Light winds and VFR conditions will prevail elsewhere in the CWA throughout the afternoon. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...NL LONG TERM...LTB AVIATION...TGJT