Area Forecast Discussion
Issued by NWS La Crosse, WI

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000 FXUS63 KARX 252053 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 353 PM CDT Sun Oct 25 2020 .SHORT TERM...
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(This evening through Monday) Issued at 330 PM CDT Sun Oct 25 2020 ...Very Cold with Near Record or Record Cold Monday and Tuesday... Forecast concerns in the short term will be light snow accumulations ending and record snow and cold temperatures. Record snowfalls for RST and LSE are weak for today (10/25)...only 0.4" at RST set in 1981 and LSE a trace for eight other years. At 18Z, we had tied those records. Here at ARX, we measured 0.1" through 18Z. See temperature records below. The MPX sounding was had high relative humidity through 500mb and it was mostly -8 deg C to -16 deg C. The 300mb winds did show a coupled jet and combined with lift,the approaching 500mb trough and frontogenesis, we had a band of snow. This band was also coincident with the 850mb front where temperatures were warmer than -9 deg C and light east or northeast winds to the south and colder than -9 deg C temperatures with northeast to northwest wind north of the front. IR satellite, radar, and observations at noon showed a band of light to moderate snow locally from Blue Earth to Rochester toward Chimney Rock. This band extended well to the southwest across Nebraska to Colorado. There were reports of some sleet mixed in and the snow was just pushing into La Crosse. By 3pm...the light snow had overspread much of the forecast area, but was lightest in northeast Iowa and for Clark County. The back edge of the widespread returns from snow was over southwest Minnesota KFRM. The next band is spreading northeast from western Nebraska and will have to metwatch this. Tonight...The forcing will continue, however the 850mb front will shift southward into Illinois by 12Z and we loose. The RAP had a good handle on the 700-500mb frontogenesis this morning and has another round of frontogenesis this evening. The CAMs in general are not as robust with snow this evening with less than an inch of additional accumulation, but should watch for this as we still have some upper level support in the area and are saturated in the dendritic growth zone tonight and will want to keep an eye as the next ripple lifts northeast. Expect the band of light snow to shift southeast of the forecast area by 12Z. The clouds will hang on tonight and this should help low temperatures remain in the 20s. A mix of clouds and sun is on tap for Monday, but it should be cold and may be close to a record . Some lingering moisture could generate some clouds and instability snow showers. The instability showers are showing up across North Dakota and northern Minnesota, so these could develop Monday. .LONG TERM...(Monday night through Sunday) Issued at 330 PM CDT Sun Oct 25 2020 The extended period is generally dry across the forecast area with moderating temperatures. A broad area of surface high pressure will extend from the Rockies toward the Great Lakes. Meanwhile, the closed 500mb low is forecast to be over AZ/NM. Forecast soundings and timesections hint that there may be some middle clouds that could hinder low temperatures. For now, we do have a record low forecast at RST and a near record low at LSE. Through the work week, a milder westerly flow is forecast to develop Wednesday. A weak cold front slips south Wednesday night and Thursday, however southwest surface flow returns Friday. A ridge of high pressure builds in for Saturday with near normal highs in the 50s. This breaks down for Sunday.
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&& .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 1219 PM CDT Sun Oct 25 2020 Light snow will continue at KRST/KLSE into this evening before tapering off. We`re expecting total accumulations of around 1.5 inches at KRST and around 1/2 inch at KLSE. Plan on IFR vsby in the snow this afternoon, improving this evening. Will then have to contend with some MVFR cloud though after the snow comes to an end though. Look like we`ll see VFR conditions Sunday morning then...after 07z at KRST and after 12z at KLSE. Look fro northerly winds through the period aob 10kt. && .CLIMATE...
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Issued at 330 PM CDT Sun Oct 25 2020 Record Low Maximum La Crosse is forecast to have a high in the upper 30s Monday. Their record of 34 degrees for 10/26 was set in 1887. RST has a high of 32 forecast, but their record low max is 22 set in 1887. Tuesday, the record low maximum is 29 set in 1925 for La Crosse and the forecast is 40. For RST, the record is 33 set in 1967 and 1933 and the forecast is 34. Record Low Tuesday Morning At La Crosse, the record low of 17 was set in 1976 and the forecast is 20. At Rochester, the record low of 13 was set in 1936 and the forecast is 14.
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&& .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...DAS CLIMATE...Zapotocny

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