618 FXUS63 KMPX 170355 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1055 PM CDT Wed Apr 16 2025 .KEY MESSAGES... - Elevated fire weather conditions this afternoon due to low relative humidity and breezy winds. The two areas of most concern are southwestern MN and east-central MN to northern WI. - Strong to severe thunderstorms are possible beginning Thursday afternoon through early Friday. Large hail is the primary threat. - An active pattern persists through the middle of next week, with a larger system possible Sunday into Monday. && .DISCUSSION... Issued at 244 PM CDT Wed Apr 16 2025 The immediate concern this afternoon remains elevated to near- critical fire weather conditions for portions of southwestern Minnesota as well as east-central Minnesota to northern Wisconsin. Surface observations show temperatures in the low to mid 60s with winds out of the southeast at 15-20 gusting to 30mph in southwestern Minnesota and weaker winds with temperatures in the 50s elsewhere. The window for near-critical fire weather conditions has remained quite small with the peak over the next 3 hours before conditions begin to improve as we slowly lose daylight, resulting in weaker mixing and therefore slower winds and cooling temperatures. GOES 19 satellite imagery shows a band of thicker clouds along and north of I-94 moving eastwards with thinner clouds along the Minnesota River which will further point towards southwestern Minnesota being at greatest risk for fire weather conditions. Skies will remain partly cloudy tonight as our next chance for showers and thunderstorms arrives on Thursday as a surge of low to mid level warm air advection will produce spotty showers as early as mid morning, ahead of the primary forcing which will arrive as a low level jet strengthens later in the evening coinciding with the arrival of a mid level shortwave. Longer range CAM guidance that has resolved the entire event shows a swath of early convection moving from southwest Minnesota towards the Twin Cities metro and into northern Wisconsin ahead of a secondary round that looks to be stronger during the evening and overnight. Going through the suite of forecast soundings from both the global and CAM guidance, our CAPE profile is deep but not wide such that our peak updraft intensity will end up on the lower end of the spectrum despite 1500-2000 J/KG such that we will have an upper limit to just how strong storms will end up. Other key factors include weak to mediocre shear at best, strongest during the evening as the low level jet and mid level shortwave combine to produce a triple-point feature over southern Minnesota and northern Iowa. Lapse rates look to remain on the high end such that large hail will remain the primary risk with severe thunderstorms, with strong winds being a secondary weaker threat. LCLs should range from 3-4kft such that tornadoes are not favored at this time, especially given the poor low level shear compared to the better environment in the mid levels. All things put together, our best chance for severe weather will likely be elevated hail producing storms during the evening favoring southern Minnesota and northern Iowa progressing eastwards as the low level jet migrates towards lower Lake Michigan overnight into early Friday. There should be enough forcing north of the better environment to produce scattered to widespread showers such that most of the region will see at least some amount of rain from the event with lower amounts in west-central Minnesota. WPC QPF shows a peak QPF from the convective bands in the 1.5-2 inch range compared to 3-4 inches in the HREF LPMM QPF, however the HREF solution is likely too hot and would rely on multiple rounds of convection moving over the same area. As we move beyond and into the weekend, showers will end early on Friday with mostly cloudy skies lingering throughout the day as we do not see enough subsidence to erode the cloud cover until Saturday. Quick moving high pressure will result in mostly clear skies and cooler temperatures on Saturday before clouds return gradually Sunday ahead of our next system. The suite of global guidance all show a system moving through the region late Sunday into Monday with a large degree of variance in solutions among ensemble members. The deterministic GEM/ECMWF both show a well developed surface low and upper level trough swinging across the region from south-western Iowa to southeast Minnesota, which would place our area on the northwest cooler side and result in widespread rain showers but little to no chance for severe weather. The 12z GFS shows a much farther east trajectory and weaker surface based system such that we would end up almost completely dry for the same time period. GEFS/EPS/CFS guidance all show varying degrees within the ensembles, with generally 50-60% of membership showing meaningful precipitation falling at MSP and the rest favoring a drier solution. The most likely area to see precipitation will be southeastern Minnesota and western Wisconsin with lower chances to the northwest farther away from the system. One question is also if we manage to squeeze flurries or light snow out of the far northwestern edge as some members do have a few tenths of accumulation in the Alexandria area, however this is a low probability solution as less than 5% of members show anything but rain within the greater ensembles. Suffice to say, the Sunday to Monday system is by no means a high confidence forecast and will be something to monitor closely as we head towards the weekend, with the hope being ensemble guidance comes into better agreement with more membership showing either a dry or wet solution. The active pattern continues into the middle of next week as persistent 20 to 40 percent chance for showers persists through the end of the period with zonal flow aloft and potential for weak shortwaves as well as no strong surface systems. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1038 PM CDT Wed Apr 16 2025 All TAF sites to start out with VFR conditions and breezy SE winds. Winds will remain elevated through the overnight hours, from the SE with sustained speeds 10-15kts with gusts around 20kts. Strong nocturnal jetting ahead of an approaching low pressure system will produce southerly winds 40-45kts at the 2 kft level for much of the overnight hours, which is indicated fairly well in model guidance. Thus, have maintained LLWS mention at all sites. High clouds will prevail from mid-to-late morning then decks in the 020-030 level will move in fairly quickly early afternoon, developing into ceilings mid-to-late afternoon. Ceilings are likely to develop in the late afternoon hours, nearly in coincidence with SHRA/TSRA developing across the Upper Midwest. TSRA is more likely to impact central- southern MN into western WI, thus have left TSRA out of the AXN TAF but have its mention at all other sites. Rain is then expected for all sites during the evening hours with ceilings dropping to MVFR range and potentially IFR range. PROB30 is generally the best that can be put forth for TSRA thru 00z, though TSRA is looking more likely from 00z onward, especially for sites in eastern MN into western WI. KMSP...VFR to start with breezy SE winds with fairly high- confidence LLWS through the morning push. Mid-level ceilings are expected by midday, with rain showers just prior to the afternoon push. TSRA developing in the late afternoon hours may drift near/over MSP, or at least be close enough to impact departure/arrival paths. Higher confidence in TSRA after 00z, hence the prevailing mention there. TSRA window looks to be fairly short, with rainfall and ceilings down to IFR levels from mid-evening onward. Breezy SE winds will continue throughout the day, diminishing Thursday evening. /OUTLOOK FOR KMSP/ FRI...MVFR/-SHRA early, then VFR. Wind NW 10-15 kts. SAT...VFR. Wind NW 10-15 kts. SUN...Chc MVFR/-SHRA. Wind E 10-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...TDH AVIATION...JPC