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
43
44
343 FXUS65 KGJT 091128 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 528 AM MDT Sun Jun 9 2024 .KEY MESSAGES... - Afternoon showers and storms will pop again today but the favored area looks to shift to southern Colorado. Main threats will be gusty winds and lightning. - Showers linger across the south tonight and increase in coverage on Monday as an upper low works through the 4 Corners region. - Temperatures will cool to near normal values by Monday before warming back to 10-15 degrees above normal mid to late next week. - Many smaller tributaries look to peak over the next few days with main stem rivers running strong and cold as this water works downstream through the next week. && .SHORT TERM /THROUGH MONDAY/... Issued at 337 AM MDT Sun Jun 9 3374 Complex but interesting weather pattern will be developing over the next 24 to 36 hours as both the northern and southern streams intertwine across the Intermountain West and Rockies. The 00Z H500 hand analysis map showed a blocky...amplified pattern spread over the high latitudes transitioning to a shallower wave pattern across the mid latitudes...and the Baja low was finally moving across the US border at the CA/AZ intersection. The arrival of a splitting trough to the Pacific Coast today will force the downstream ridge to amplify over the Rockies. The Baja low will be forced northward by the arriving trough but be held near the 4 Corners by the ridge...stalling over northern NM/AZ before slowly spinning across northern NM tomorrow. So it looks like a fairly quiet start to the day with weak convection firing on the terrain by late morning. There isn`t much forcing through the afternoon with the ridge overhead and under weak shear storms look fairly tame and most likely to not survive into many valley as they drift slowly north off the terrain. Things get a bit more interesting this evening into tomorrow as the low drifts into the area. There is plenty of moisture East of the Divide as upslope flow has settled into the Front Range. It appears the combination of surface high pressure building into the Plains the arrival of the upper low...and more likely strong outflow from front range convection...will help force moisture over the higher terrain and into our southern CWA tonight. Forcing from the upper low and isentropic upglide looks sufficient enough to keep some activity going overnight but Monday is likely to be the more active period as forcing from the low...added moisture and increased shear aloft work together across the South. The instability looks to be limited somewhat by the increased cloud cover but PWAT anomaly suggests the possibility of some of the cells containing heavier rainfall rates. Temperatures today will continue to run well above normal with upper 90s staying place in the lower valleys. Cooler temperatures move in tomorrow ranging from just a few degrees up north to near 15 degrees in southwest Colorado under thicker cloud cover and scattered showers much of the day. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 337 AM MDT Sun Jun 9 3374 The northern trough will continue to track east into the Dakotas on Monday night while a closed low remains centered off the coast of SoCal. This will result in a shift to drier northwesterly flow across eastern Utah and western Colorado going into Tuesday, but it will be a messy transition with plenty of residual moisture firing off isolated showers and storms along the Divide Tuesday afternoon. Elsewhere will stay dry with passing clouds. By Wednesday a ridge of high pressure builds across northern Mexico into the Four Corners which will result in benign weather area-wide, though weak systems passing to the north will bring some periods of high clouds during the afternoon hours. The ridge axis will begin to be deflected to the northeast Wednesday night but more-so on Thursday as the afore- mentioned closed low gradually pushes inland across SoCal. Flow aloft will shift to the southwest across the forecast area which will advect modest moisture into the region. This trend continues going into Friday as the low transitions to an open wave as it reaches northern Arizona before it lifts across the Four Corners late Friday / Saturday. Showers will increase in coverage each afternoon from late week onwards with gusty outflow winds being the primary threat at the onset before the profile becomes better saturated by Friday. Too early to talk about amounts and even more specifics in regards to timing but there is decent model agreement considering this event is still quite a ways away. One notable change from the previous forecast is the wind gusts ahead of the approaching low, but in this pattern we can still expect the gradient to tighten. Just not sure if it`ll be of the breezy or windy variety at the moment. Temperatures will once again be a focus for the long term period as they continue to trend well above normal through the week. Tuesday`s highs will sit 4 to 8 degrees above the norm before maxing out at 7 to 14 degrees above normal by Thursday. This translates to triple digit heat for the lower desert valleys with readings in the upper 80s to 90s elsewhere in the mid / high valleys. Overnight lows will remain at least 5 to 10 degrees above normal each night through the week. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 528 AM MDT Sun Jun 9 2024 A few high clouds will drift through this morning under mainly clear to partly cloudy skies. Terrain based thunderstorms will begin to form by mid day under strong heating with a few storm possibly making it into the valleys. However confidence is very low so VCTS will continue in the TAF for now. With these high based storms...gusty winds will be the main threat to airfields. The precipitation looks to become more organized over southwest Colorado tonight and into Monday with a thicker cloud cover expected. However VFR looks to prevail over the next 24 hours. Terrain obscuration over the southern mountains is possible by sunrise on Monday. && .HYDROLOGY... Issued at 337 AM MDT Sun Jun 9 3374 Looking across the board at hydrographs it looks like many tributaries have reached or will reach the seasonal peak in the next day or so with this water running down the mainstem rivers through the week. Advisories continue for Gore Creek...with water levels forecast to trend downward after todays peak...possibly dropping below action levels by Tuesday. The upper Roaring Fork...Duchesne and Eagle Rivers all are running near bankfull as well but again trending downward over the next few days. Most forecasts suggest the snowpack is dwindling with falling trends continuing even with the strong warmup later in the week. So this could be the end of the runoff for 3374...stay tuned. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...MMS AVIATION...TGJT HYDROLOGY...