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Displaying AFOS PIL: AFDARX Product Timestamp: 2019-03-06 17:38 UTC
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030 FXUS63 KARX 061738 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1138 AM CST Wed Mar 6 2019 .SHORT TERM...(Today through through Friday) Issued at 200 AM CST Wed Mar 6 2019 Models remain in good agreement with taking an upper level shortwave trough from the west coast this morning...eastward across the central/northern plains and then across ia/il late tonight/thu. QG convergence somewhat weak and confined above 700 mb locally with some potential aid from weak 300 mb jet streak. Some frontogenetic support on the northern side of the shortwave, with models continuing to point to a thin band on the 600 mb sfc - generally a favorable location to find snow bands. Models continue to paint some light qpf across southern portions of the forecast area mostly thu aft/evening keeping the main snow accum farther south into central IA. Will continue chancy pops for parts of northeast IA/southwest WI, with minor accums (1" or less) possible. Might eventually need likely for the light snow potential. .LONG TERM...(Saturday through Tuesday) Issued at 200 AM CST Wed Mar 6 2019 Weekend storm shows no wavering (as of yet) with consistent signals in the EC and GFS to drive an upper level shortwave out of the desert southwest, closing off a low as it shifts northeast across the great lakes by 12z Sun. Upper level jet support, hefty low level thermodynamics and deep/relatively strong QG convergence all there for lift. Moisture won't be a problem with nose of 850 mb moisture transport punching into WI with PWS upwards of 1" and NAEFS anomalies at +1. Broad swath of pcpn looks to move in toward 12z Sat in the west, quickly spreading east through the day and continuing Sat night. Models suggest the bulk of the accumulations would move north of I-90 by 12z Sun as the storm system lifts into southeast Canada. The bigger questions are not "will there be precipitation" (there will), but WHAT falls, WHERE and how MUCH? The GFS and EC have different answers to those questions... 1) GFS: strong, more wound up resulting in a more northwest track - takes its sfc low across the heart of the forecast area at 06z Sun. Northwest-southeast running x-sections shows a deep above 0 layer through much of the forecast area at 00z Sun, slowly eroding west to east and cooling by 12z Sun. This solution suggests rain for the bulk of the area at the outset, with a gradual transition to wintry mix/snow by Sun morning. Much of what falls would come as rain and flooding/ice jam concerns would be heightened, although a good portion would soak into the existing snow pack. Some snow accums would still be likely, but more for the far west/north as the storm exits, and on the order of a few inches. 2) EC: 00z run remains weaker and thus takes a more eastward track with the storm, shifting its sfc low over southern WI at 06z Sun. Previous 12z run was farther east (southeast WI) which resulted in less warm air locally. This 00z run's slight shift west makes warm low level air more of a factor - ala the GFS. 12z solution favored snow to wintry mix as the main ptype, this 00z leans more toward the GFS with a mix of everything. Highest snow accums still to the west and north. Confidence isn't high one way or the other with only a small shift having a big impact. Will continue to ride the model blends for now and keep pcpn types as rain and/or snow. Will continue to refine these details as we move closer to the weekend. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1137 AM CST Wed Mar 6 2019 Main taf concerns through the period is potential for flurries and possible MVFR conditions at LSE taf site with VFR conditions expected at RST through the taf period. Weak surface front will move across the area this afternoon and evening. The 06.12z deterministic models suggest stratocumulus clouds and the possibility of flurries in association with the surface front/shortwave trough mainly along and east of the Mississippi River. Ceiling heights are expected to lower into MVFR this afternoon into early evening...however the deeper moisture will be east of the LSE taf site. Brief period of MVFR could occur at the LSE taf site this afternoon/evening. After 01z Thursday...VFR conditions are expected to prevail at both RST/LSE taf sites. Wind direction will shift to the west to northwest late this afternoon and wind speeds will remain around 10 knots to less than 10 knots through the taf period. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Rieck LONG TERM....Rieck AVIATION...DTJ