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
429 FXUS63 KARX 070847 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 347 AM CDT Sun Jul 7 2024 .KEY MESSAGES... - Off and on showers and storm chances through the middle of the week. Minimal threat for organized severe weather is expected at this time. - Temperatures remaining slightly below average through the middle of the week before trending warmer possibly by Friday and next weekend. - The Mississippi River is near crest from Brownsville, MN to Guttenberg, IA with locations north noting falling river stages. Mississippi River locations are expected to observe falling river stages from southwest WI/northeast IA on north this week. && .DISCUSSION... Issued at 347 AM CDT Sun Jul 7 2024 Today - Tonight: Scattered Showers and Storms The overall synoptic setup on GOES-16 water vapor imagery shows a closed upper-level low pivoting across the Dakotas into NE Minnesota with mid-level Q-vector convergence helping to maintain an area of showers and storms across eastern Minnesota and western Wisconsin. To our south, a subtle shortwave can be noted instigating an area of more substantial rainfall and storms where the nose of 850mb moisture transport is focused. As a result, could expect some more meaningful rainfall across portions of northeast Iowa and southwestern Wisconsin this morning with the 07.00z HREF painting modest probabilities (40-60% chance) for 0.25" or more in this area. As we continue through the morning and afternoon, expecting both these features to generally progress northeast as the overall broader upper- low begins to become negatively tilted. Eventually, the aforementioned Q-vector convergence shifts northeastward into portions of north-central and central Wisconsin into the afternoon and evening. Consequently, the recent runs of the CAMs have been trying to resolve some scattered showers and storms across this area. Some MLCAPE (1500-2000 J/kg) is present in the 07.05 RAP oriented in an axis from SE Minnesota into north-central Wisconsin. With some effective bulk shear of around 30 kts to work with across north-central Wisconsin and some hodograph curvature, could not rule out a strong to severe storm with some small hail and gusty winds. However, mid-level lapse rates struggling to push 6 C/km would make it fairly challenging for severe criteria hail. Monday - Wednesday: Additional Chances For Showers and Storms Heading into the upcoming work week, seasonably cooler temperatures persist with intermittent showers and storm are expected as a synoptic trough situated over the region. Likely with the cyclonic flow in place many of these scattered showers and storms will be diurnal in nature. Consequently, will keep chance (20-50%) mention for precipitation chances through Tuesday. Overall guidance favors light rainfall amounts during this period as the 07.00z EC ensemble struggles to paint much in the way of probabilities (0-30% chance) for over 0.1" for any given round of showers and storms. Of course if storms are slow moving or repeat, amounts may be locally higher. As we head into Tuesday night and Wednesday, deterministic guidance (07.00z GFS/EC/NAM) tries to push some precipitation into southern Wisconsin overnight Tuesday and early Wednesday morning with the extratropical low from what is left of Tropical Storm Beryl that would be placed somewhere in the vicinity of IL/IN/MO area. Hard to really say where the low will be situated as there remains very large spread in various members during this time. The GEFS family appears to be the most aggressive with any amounts as it paints some lower probabilities (10-30% chance) for 0.5" or greater of QPF on Wednesday. Currently, would trend to be lighter amounts similar in southwestern Wisconsin with guidance keeping the vast majority of the precipitation shield to our south/east with only wrap around cyclonic showers as it passes well to our east during the day Wednesday. Thursday - Saturday: Trending Warmer and Perhaps Drier Heading into late week, guidance suggests a building ridge to the west will help increase heights into late week which should aid in increasing subsidence and start a warming trend. This is shown in the 07.00z grand ensemble (GEFS/EC ensemble/Canadian ensemble) with the inter-quartile range for highs temperatures at La Crosse reaching between 86 to 90 with a median of 88 degrees, slightly above average for this time of year. Guidance tries to trend for drier conditions for Friday and the weekend, however will have to watch for any subtle shortwaves that try to sneak their way in. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1001 PM CDT Sat Jul 6 2024 Probability for showers and perhaps a bit of thunder continues to trend lower at RSE/LSE overnight. Have therefore removed the SHRA mention at LSE and continued to refrain from thunder mentions. Moving ahead to Sunday afternoon, continue to see a good signal in guidance for MVFR cumulus development and have therefore placed this into the TAFs for a few hours at each site. A shower or thunderstorm may develop out of this cumulus, but probability remains too low for a mention with this update. && .HYDROLOGY... Issued at 347 AM CDT Sun Jul 7 2024 The Mississippi River is noting falling river levels from north of Brownsville, MN with Lake City, MN falling below flood stage. Locations near crest from Brownsville, MN on south to Guttenberg, IA. River stages are expected to fall into this week from northeast Iowa and southwestern Wisconsin on northward along the Mississippi River. Generally lighter rainfall amounts of up to around 0.5" from now through Tuesday are expected, with locally higher amounts possible with any storms that pass over. May have to watch the remnants of Tropical Storm Beryl for more substantial rainfall across southwestern WI/northeast IA for Tuesday night and Wednesday. However, the probabilities for heavier rainfall with this system remains low as guidance keeps much of the heavier rainfall farther south and east of the local area. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Naylor AVIATION...Ferguson HYDROLOGY...Naylor