Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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
733 FXUS63 KARX 050808 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 308 AM CDT Wed Jun 5 2024 .KEY MESSAGES... - Scattered showers and thunderstorms develop this afternoon with a threat for hail and gusty winds from stronger storms. - Windy conditions expected later today and again Thursday, especially west of the Mississippi River. Advisory issued for parts of the area today, and may be needed again on Thursday. - Cooler than normal temperatures expected over the weekend. && .UPDATE... Issued at 307 AM CDT Wed Jun 5 2024 After further discussion with other forecast offices, some concern about how to best handle convective induced wind threat later today, along with increasing gradient wind setup overall. Late decision was to include a corridor of Wind Advisories with that possibility. Admittedly not a clear cut situation but this will give people at least some advance notice that wind gusts could be strong at times later in the day. && .DISCUSSION... Issued at 200 AM CDT Wed Jun 5 2024 Busy past 48 hours with convection fueled by relatively high precipitable water values for early June but that is mainly east of the area now as mid level trough and associated cold front push through. Drier airmass will certainly diminish the heavy rain threat but the overall threat for convection seemingly has not ended for the week. TODAY - Afternoon convection threat Upper low across southern Canada and strong mid level wind max rotating around trough base will strengthen troughing next 36 hours across western Great Lakes. With height falls, cooler air aloft, and June sun angle, model soundings suggest steep lapse develop with enough moisture for scattered afternoon and evening thunderstorms, even with a relatively shallow instability /CAPE/ layer. Warm cloud layer last couple days will be replaced with cooler air aloft raising hail chances in stronger storms, but perhaps greater risk will be wind gusts given such strong flow in the mid levels. Any stronger storm could tap into that wind level and mix it down to produce locally higher storm gusts. Marginal Risk /Level 1 of 5/ from Storm Prediction Center seems appropriate given setup. Gradient winds are also expected to increase this afternoon, especially across western areas, as trough amplifies. Highest probabilities for peak gusts at or above 40 mph via 05.00z HREF remain from Rochester MN to Mason City IA and points west. Not anticipating need for wind related headlines quite yet, but Thursday could be another story. THURSDAY - Higher winds / possible Wind Advisories As Canadian trough amplifies even more on Thursday and drops into Great Lakes, broad ridge builds across western CONUS. This process spreads belt of stronger mid level winds across northern Midwest into the Great Lakes. Seeing a bit more variability on how strong wind gusts might get in the ensemble data so not a slam dunk yet that headlines will be needed. But not out of the question to see some peak wind gusts in the 35 to 45 mph range during peak mixing of the afternoon. UPCOMING WEEKEND - Cooler than normal with diurnal shower chances Large trough evolution across southern Canada and Great Lakes will likely keep temperatures cooler this weekend along with more unsettled weather. Details hard to pull out that far in advance but diurnal shower activity a possibility. Luckily this pattern limits the threat for severe weather, always a good thing given we are approaching our climatological peak for storms. NEXT WEEK - Evolution of large western ridge and possible warm up Will certainly be watching evolution of larger upper ridge across western CONUS and developing heat wave. Some medium range guidance has been suggesting this will evolve east towards latter half of next week which could bring us back into a warmer and drier regime. Even some of the ECMWF ensemble guidance has been hinting at this perhaps peaking in the June 18-22 time frame. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1103 PM CDT Tue Jun 4 2024 A shortwave trough will move east of the area late tonight. As this occurs, the rain and isolated storms will gradually come to an end from the west. The rain will end at KRST around 05.06z and at KLSE around 05.08z. Subsidence in the wake of this trough will produce some clearing for late tonight and Wednesday morning and then another shortwave trough will move through the area during the afternoon. With steep low level lapse rates, there will be likely some scattered showers and storms. With strong winds just off the surface, there are concerns that these showers and storm could bring these strong winds to the surface. Definitely something to watch. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...Wind Advisory from 2 PM this afternoon to 7 PM CDT this evening for MNZ086-087-094-095. IA...Wind Advisory from 2 PM this afternoon to 7 PM CDT this evening for IAZ008-009-018-019. && $$ UPDATE...Shea DISCUSSION...Shea AVIATION...Boyne