Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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068 FXUS63 KARX 101931 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 231 PM CDT Fri May 10 2024 .KEY MESSAGES... - There will be showers and scattered storms this afternoon and evening. These will produce gusty winds. The strongest storms might produce isolated damaging winds. - Good viewing conditions are expected for the auroras tonight. - Additional showers and storms expected from Mothers Day into Monday evening. Severe weather is not anticipated at this time. && .DISCUSSION... Issued at 231 PM CDT Fri May 10 2024 This Afternoon and Evening - Showers and Scattered Storms A 500 mb shortwave will move southeast through the Upper Mississippi River Valley. 10.12z HREF probabilities of greater 40 dBZ and greater than 50 J/kg MUCAPE ranged from to 30 to 50% west of the Mississippi River and 50 to 90% across central and western Wisconsin. The highest probabilities are between 5 PM and 10 PM. Soundings continue to show an inverted V sounding in the sub- cloud layer. In addition, there will be rather steep 650-900 mb lapse rates (8-10 C/km), so we are looking at gusty winds from these storms. The HREF 4-hour maximum 10 meter AGL winds were mainly below 40 knots. The latest SPC Day 1 Outlook keeps central and western Wisconsin, and southeast Minnesota in a Marginal Risk (risk 1 out of 5) of severe weather. This makes sense since a few of the stronger low-top storms might produce isolated wind damage. Overnight - Good viewing conditions expected for the auroras tonight The first of 7 Earth-directed coronal mass ejections arrived shortly before noon. The solar wind has climbed to nearly 700 km/sec and the density is over 27 protons/cm3. The interplanetary magnetic field is currently south. The planetary K-index (Kp) has already increased to 7. The Space Weather Prediction Center (SWPC) continues to forecast that the Kp is expected to climb over 8 overnight. These values are favorable for our area to see auroras. 10.12z models are in fairly good agreement that skies will be mainly clear overnight. Temperatures would range from the upper 30s to mid- 40s. Northwest winds will be generally less than 10 knots. This will slightly lower the wind chills. They are expected to range from the mid-30s to lower 40s. Saturday - Mostly sunny and dry Saturday continues to show that high pressure will build across the region. 850 mb temperatures will be 1 to 3C cooler, so high temperatures are expected to range from the mid-60s to around 70. Soundings continue to support slightly lower surface dew points, so used the NBM 10th percentile to lower them some. This would lower afternoon relative humidities into the 20s and 30s. The northwest winds will be in the 10 to 20 mph range with wind gusts of 20 to 30 mph. Mothers Day through Monday Evening - Additional showers and storms expected A Canadian cold front will move into the area during the afternoon and evening of Mothers Day and linger over the area into Monday evening. This front will be the focus for some showers and storms. Like the past couple of days, the 0-6 km shear remains 25 knots or less, so severe chances look rather low. High temperatures will range from the mid-70s to lower 80s on Mothers Day and range from the mid-60s to lower 70s on Monday. Tuesday Night through Thursday - Much uncertainty The 500 mb pattern becomes much more uncertain. Some models are showing phasing between the northern and southern streams. Others are showing little phasing between these two streams. There is even some which have shortwave ridging over the area. As a result, just stayed with the NBM for both temperatures and precipitation. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1245 PM CDT Fri May 10 2024 A cold front will sweep through the area with increasing clouds, showers and a few thunderstorms. Forecast soundings show deepening mid-level moisture, however instability looks somewhat limited. Increase clouds through the afternoon fl070-100. The showers seem most likely to be near or at the TAF sites between 22-00Z. Due to low confidence in the thunderstorms did not mention at this time. Winds from the southwest with veer to the west and northwest with a period of strong gusts 25 to 35kts through 01 or 02Z. Winds diminish to less than 10kts with clearing skies after that. Northwest flow continues for Saturday morning and increase 10 to 20kts. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Boyne AVIATION...Zapotocny