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
051 FXUS63 KARX 251009 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 509 AM CDT Tue Jun 25 2024 .KEY MESSAGES... - Storm Chances Depart Early This Morning, Primary Area Of Storms Today Remain Along & South Of Local Forecast Area In Iowa With A Thin Line of Storms Possible Locally - Storm Chances Return Friday & Into The Weekend. Near 1" Of Rain Possible. && .DISCUSSION... Issued at 237 AM CDT Tue Jun 25 2024 Storms Early This Morning: Have been monitoring ongoing storms through the early morning hours from west to east. The associated low was mostly following a warm front zonally draped from southern Minnesota through central Wisconsin. Sufficient forcing remained farther north in northern Minnesota and north-central Wisconsin as the warmer elevated air lacked a profound opposing boundary locally with a cap of CIN. Storm Chances Today: As the responsible surface low exits to the east early this morning, the nose of increased low level theta e lingers across much of the Upper Mississippi River Valley into northern Wisconsin. The highest confidence storm scenario for today is along and south of our southern periphery where a pressure saddle sets up a zonal shrinking/stretching axis across Iowa. The narrow axis limits exact confidence of initial storm formation, potentially grazing our far southern counties in northeast Iowa and far southwest Wisconsin. Local confidence remains low as forecast soundings keep a stronger, albeit limited cap of CIN in our southern spots. There will be exorbitant instability, 4500+ J/kg, within the warm, moist airmass along our southern periphery. Therefore, storms that do pop will quickly turn into towering cumulus. Given initial forcing along a narrow axis, storms expected to remain quasi-stationary at first, further firing along the southerly advecting cold pool. Some models do suggest another scenario with a quick perturbation lifting storms from northwest to east-central Iowa around the same time, even less involved with the local area. Regardless, this perturbation will eventually pick up much of the storm activity and progress everything east-southeast late in the evening into the overnight. During this time, a secondary small, limited strength line of storms expected to initiate farther north, zonally across the forecast area. A narrow dry punch of air associated with the main cold/dry frontal boundary would be the responsible forcing mechanism. Instability expected to remain meager, while there is some adequate shear to persist some small storms. Lightning appears to be the primary hazard at this time. Storm & Rain Chances Friday & Into The Weekend: Storm chances return Friday morning on the cusp of a low pressure system lifting to the northeast through the Central Plains. A well- phased closed area of lower heights remains well to the northwest, limiting initial confidence in storm/precipitation extent. An upper level ridge also remains parked over the Upper Mississippi River Valley during this time, preventing the initial farther east push. Eventually, more zonal flow builds in, allowing the synoptic trough that joins its main flow advect storm chances locally into the weekend. Current long term global ensemble confidence suggests 0.5" to 1" primarily along our southern counties in northeast Iowa and southwest Wisconsin. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1227 AM CDT Tue Jun 25 2024 Main taf concerns is thunder potential at both RST/LSE taf sites early in the taf period. Cold front will track across the area overnight. Latest trends have convection developing and remaining focused over western/northern Wisconsin. This would place and movement of convection to be mainly north of the taf sites. At this time...have removed convection from the RST taf site and have kept a vicinity thunder at LSE for a small chance convection could develop south into southwest Wisconsin. After 08z Tuesday...cold front/convection pushes east of taf sites and VFR conditions are expected to prevail at both RST/LSE taf sites. && .HYDROLOGY... Issued at 501 AM CDT Tue Jun 25 2024 Recent heavy rainfall has resulted in river flooding along many area rivers and streams in northeast Iowa, southeast Minnesota, and western into central Wisconsin. Ongoing flooding concerns will last into next week for the largest rivers such as the Mississippi. Minimal impacts are expected from shower and storm chances this afternoon and evening, primarily remaining south of Interstate 90. Drier days are on tap through Thursday, assisting the downward trend in river levels seen primarily in tributaries and smaller rivers. Rain and storm chances return early Friday morning. Soils will remain well saturated by this time, therefore precipitation amounts will be important to keep an eye on as forecast hour nears. Continue to reference the latest flood statements for additional updates and details. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...DTJ HYDROLOGY...JAR