Scientific Forecaster Discussion

000 fxus63 kgrb 192325 afdgrb Area forecast discussion National Weather Service Green Bay WI 625 PM CDT Fri Apr 19 2019 Updated aviation portion for 00z taf issuance Short term...tonight and Saturday issued at 247 PM CDT Fri Apr 19 2019 The latest analysis and satellite/radar imagery show surface high pressure stretching from the Central Plains, across far western Wisconsin, to Lake Superior early this afternoon. Skies are clear across northern Wisconsin, positioned between a large cloud shield to the east, and a band of mid cloud over the eastern Dakotas. Winds gusted into the middle to upper 20s earlier in the morning, but have since generally fallen below 20 kts early this afternoon. Will be able to cancel the Small Craft Advisory with the afternoon nearshore issuance. Forecast concerns generally revolve around temps and low relative humidities. Tonight...the surface ridge axis will shift directly across the region tonight. The jet stream and mid-level warm advection will push in some thin clouds into north-central WI late tonight, but should not have much of an impact on temps. Winds, however, may keep temps up over eastern WI compared to further west where winds will become calm. Lows ranging from the mid 20s near the u.P. Border to the mid 30s near Lake Michigan. Saturday...the surface ridge axis will slide to eastern WI. Will see more in the way of cirrus overhead, but the airmass will remain very dry in the mid and lower levels. South winds on the backside of the high will bring in warmer temps compared to today's readings. With light winds, highs will mostly reach into the middle 60s away from Lake Michigan. Long term...Saturday night through Friday issued at 247 PM CDT Fri Apr 19 2019 Models are trending slower and wetter for the system late in the weekend and early next week, but differences on amounts, timing and extent of the rainfall still exist, leading to plenty of uncertainty. See Hydro section for more info on the flood threat. Think the rain ahead of the low through Monday afternoon will be on the lighter side, then as better forcing and moisture arrives, heavier rain is possible Monday night and into Tuesday (if you believe the gfs). Models are showing some 1+ inch totals, focusing the heaviest rain over the northwest portion of the area, so definitely something to monitor. European model (ecmwf) and Canadian are still more progressive and get most of the rain out of the area by 12z Tuesday. Thunder threat look pretty low through Sunday with only a little elevated cape to work with. Better thunder chances arrive on Sunday night into Monday as elevated instability increases. Severe weather is not expected at this time as a healthy inversion below 900mb should keep the storms elevated. But if the warm sector gets a little farther north than forecast, a few surface- based storms will be possible. As for temps, models are really not on the same Page. On Sunday, the GFS has the southern half of the area in the warm sector, with 40s north and approaching 70 south of the front. The Canadian is a little farther north, and the European model (ecmwf) the farthest north near the Michigan border. On Monday, the GFS brings a back door cold front across the area, holding temps in the 40s all day Monday, aided by winds coming off the still very Cold Lake Michigan. The Canadian keep the southern half of the area in the warm sector with temps in the 60s to near 70. European model (ecmwf) is closer to the Canadian, dropping temps through the day. Will continue to keep the warmest temps across central WI on Sunday with cooler readings on Monday. Plenty of uncertainty remains on where the front will end up, along with how much precip/clouds will be around to influence temps. Once the system exits to our east, dry of weather is expected on Wednesday and Wednesday night, then another cold front and low pressure system will swing across the Great Lakes Thursday. && Aviation...for 00z taf issuance issued at 625 PM CDT Fri Apr 19 2019 VFR conditions are expected through this taf period under mostly clear skies. High pressure will keep mainly light and variable winds in place through the day Saturday. && Fire weather... issued at 247 PM CDT Fri Apr 19 2019 Relative humidities will drop to near critical values west of the Fox Valley this afternoon and across much of the area on Saturday afternoon. Gusty north winds will subside tonight with the approach of high pressure and then remain light on Saturday. Temps will be several degrees warmer on Saturday afternoon. && Hydrology... issued at 247 PM CDT Fri Apr 19 2019 Minor to moderate flooding continues on many area rivers, with Embarrass in major flood stage. Look for the the Wisconsin river basin to slowly fall through the weekend. Levels on the Wolf and Menominee will slowly rise through the weekend and into next week. With all the ongoing flooding issues, any rain late in the weekend and into next week will at least prolong the flooding issues across the area. Additional/new flood concerns could arise, especially if we get totals over 1 inch. && Grb watches/warnings/advisories... none. && $$

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