954 FXUS63 KARX 181006 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 406 AM CST Sun Feb 18 2024 .KEY MESSAGES... - Warmer Today, Gradual Warming, Continuing Into Midweek With Anomalous Temperatures Peaking In The 50s For Some on Wednesday - Little To No Precipitation Potential Midweek Within More Moist, Warm && .DISCUSSION... Issued at 347 AM CST Sun Feb 18 2024 Warm, Quiet Weather Week On Tap: Other than the return of well above normal temperatures for the first half of the week, quite quiet conditions expected through next Saturday. The backside of the broad trough that extends into the northeastern CONUS will linger across the Upper Mississippi River Valley today, keeping low level temperatures relatively stable. Although, given the warmer overnight temperatures and continual clear skies, highs in the 30s are expected, a few degrees warmer than Saturday. Warming Into The 40-50s Midweek: The WAA regime resumes tonight as an upper level area of lower heights traverses the Northern Plains towards the Mid Mississippi River Valley furthering the appendage of increased low level theta e northeast. The low weakens as it shifts south and west of the Upper Mississippi River Valley as upper level heights build. As a result, the 40 degree isotherm traverses the forecast area through Tuesday. Heights continue to build across the Northern Plains through midweek furthering return flow farther northeast as the 50 degree isotherm and 40 degree isodrosotherm reach the Upper Mississippi River Valley. Global ensemble confidence (GEFS/EPS 18.00Z) has remained very high (80- 100%) over the last 2-3 runs for the 50 degree isotherm bifurcating the forecast area on Wednesday This temperature and moisture nears 1.5 standardized anomalies above model climatology (NAEFS/ENS). Extreme Forecast Index shift of tails has 60-90% of members with potentially record breaking daytime highs for much of the work week. As for record break overnight high minima, only 60-70% of members potentially break records Thursday and Friday. The skew in 90th percentile remains insignificant with shift of tails values remaining at or below zero. Have continued with National Blend temperatures in the 50s for most as they line up well with highest ongoing confidence. Cooling Latter Half Of The Week: An upper-mid level trough simply sags southeast to the Lower Mississippi River Valley before undergoing any form of phasing or deepening, pulling the upper level cold tongue across the Upper Mississippi River Valley with it. EPS continues the warmer solution over the GEFS with daily maximum and minimum temperatures above freezing, 60% confidence, while GEFS has 100% confidence for overnight lows below freezing. Double the spread for 6-hour temperatures in the GEFS over the EPS for 25th to 75th percentile (IQR). Precipitation Potential Midweek: As for moisture, both the EPS and GEFS exhibit moderate confidence (40-70%) for 0.5" of Precipitable Water bifurcating the forecast area initially Tuesday. Although, associated dProg/dt has been quite variable, rising/falling in the EPS whilst consistently decreasing in the GEFS over the last few runs. Location (i.e., northern extent) of the higher moisture will be more impactful Wednesday as there's 100% ensemble confidence for a mid-upper level wave sagging southeast from Manitoba. Any upper and mid level forcing has been on the decline locally in mean ensemble dProg/dt: a weakening upper level jet streak and weakening mid level vorticity. Resultant precipitation confidence has been on the decline, now 0% in southeast Minnesota to 40% into central Wisconsin for at least 0.01" of QPF in 24 hours. The spatial extent for 100% confidence has shifted northwest over the last couple of runs, reaching the westward knob of Illinois along the Mississippi River. Reminiscent of the split flow around the forecast area during Summer 2023 keeping precipitation chances to the north and south. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 932 PM CST Sat Feb 17 2024 VFR conditions will continue to prevail through the TAF period with mainly clear skies and westerly winds slowly diminishing overnight, shifting northwest on Sunday. Winds will subside quickly on Sunday evening under high pressure. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...JM