315 FXUS63 KGRB 080810 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 310 AM CDT Mon Jul 8 2019 Forecast discussion for routine morning forecast issuance .SHORT TERM...Today...Tonight...and Tuesday Issued at 310 AM CDT Mon Jul 8 2019 High pressure across the Great Lakes region will keep the area dry through Tuesday. The only issue to start will be the smoke layer aloft from fires across Canada, which is currently not visible during the nighttime hours. However area vsbys indicate the smoke layer is probably mixing down across portions of the area, particularly central and north-central Wisconsin. Model winds aloft indicate that northwest flow should keep this smoke layer overhead or nearby until later this morning or this afternoon when winds turn to a more southwesterly direction on the backside of the high across the region. Until this happens smoke could mix down to the ground at times, reducing visibilities to 3 or 5 miles at times with the smell of smoke possible. Some patchy fog may also reduce visibilities as well until later in the morning when it mixes out. METAR observations indicate the fog is not widespread or persistent as visibilities jump up and down from hour to hour. Daytime highs will generally range from 80 to 85 degrees. Overnight mostly clear skies will allow lows to fall into the 50s, however with winds turning southerly lows will be a bit warmer tonight, especially across north-central Wisconsin. Some patchy fog is again possible tonight, however it isn't expected to be widespread or a high impact. On Tuesday the forecast has trended drier with each run. Instability during the afternoon is basically non-existent given the sinking motion associated with the high along with a very dry low layer and warm air between 700 and 800 mb. Therefore rain is not expected Tuesday afternoon as the highs rise into the lower to middle 80s. .LONG TERM...Tuesday Night Through Sunday Issued at 310 AM CDT Mon Jul 8 2019 The main components responsible for much of the weather across the CONUS this week to be an upper-level high pressure anchored over the Four Corners region and a mid-level shortwave trough moving across the northern tier of states. This trough will bring northeast WI our next chance for showers/thunderstorms at mid-week (Tue night-Wed night). Mean flow to be west-northwest for late week into next weekend with a weaker mid-level trough/cold front due to arrive late Friday into Saturday. Temperatures are expected to be at or above normal early in the week, drop below normal mid-week with the trough and then climb above normal headed into next weekend. As the primary mid-level shortwave trough moves from the northern Plains into the Upper MS Valley Tuesday night, a push of WAA and hints of a subtle shortwave to move into WI. Even though better instability to be situated farther to the west, will still mention a slight chance of thunderstorms across the forecast area to accompany a band of showers. Any precipitation would mostly likely hold off until after midnight in the east as some drier air will need to be overcome. More clouds and the threat of showers will keep temperatures up overnight with readings only dropping into the 60-65 degree range. A cold front is forecast to precede the arrival of the shortwave trough into the western Great Lakes region on Wednesday and bring a good chance of showers/thunderstorms to the forecast area. The main question remains whether we are able to see any breaks in the clouds/precipitation to allow the atmosphere to destabilize and perhaps allow some storms to become strong or even severe. MUCAPES to reach 1.5 to 2.5K J/KG by early Wednesday afternoon with 0-6 km bulk shear of 35-45 knots which is more than enough to sustain updrafts. SPC does place eastern WI under a slight risk and central WI under a marginal risk for severe thunderstorms, so this situation will need to be watched closely over the next 48-60 hours. Large hail and damaging winds would be the main threats. Besides the strength of the storms, locally heavy rain is also possible as PW values rise into the 1.5-1.75 inch range. Max temperatures on Wednesday to be in the upper 70s to around 80 degrees near Lake MI, upper 70s to middle 80s inland. A lingering chance of showers/thunderstorms can be expected over northern and eastern WI into Wednesday evening before ending as a ridge of high pressure enters the Upper MS Valley and starts to advect drier air into WI. Look for skies to become partly cloudy with min temperatures to range from the lower to middle 50s north-central WI, to the lower 60s east-central WI. This ridge of high pressure is expected to gradually move east into the western Great Lakes on Thursday with cooler/less humid conditions to overspread the area. Under partly cloudy skies, look for max temperatures to reach the lower to middle 70s near Lake MI, middle to upper 70s elsewhere. After a quiet Thursday night with the surface ridge sliding through WI, attention turns to an approaching cold front/weak mid-level shortwave on Friday. Moisture availability may be an issue initially, so the bulk of the daylight hours may remain dry. May leave a small pop for north-central WI for Friday afternoon, otherwise anticipate a gradual increase in clouds. Max temperatures on Friday to be in the middle to upper 70s lakeside, upper 70s to lower 80s inland. As the cold front/shortwave combination move through the area Friday night, will need to carry chance pops. It is now beginning to look like Saturday may be able to dry out as the cold front is progged to not stall until it reaches north-central WI and a weak high pressure starts to move toward WI. This weak high pressure may be able to keep the rest of the upcoming weekend dry as well, although the ECMWF suggests clouds to be on the increase on Sunday as a push of warmer/more humid air takes aim at WI. For now, have opted for a dry forecast through the weekend. Temperatures for both Saturday and Sunday to be above normal with a noticeable increase in humidity levels. && .AVIATION...for 06Z TAF Issuance Issued at 1131 PM CDT Sun Jul 7 2019 Smoke originating from Canadian forest fires may mix down to the surface at times tonight, and reduce visibilities to 4-6SM. Earlier, satellite showed that the smoke was thickest over the northeast half of the forecast area, so would expect the most significant impacts to occur there. It is uncertain whether or not the smoke will continue to impact the region on Monday, or shift east of the forecast area. Temperature/dew point spreads are getting low across much of the forecast area, so have expanded patchy MVFR/IFR fog over the entire region overnight into early Monday morning. Otherwise, expect cumulus clouds to redevelop toward midday Monday. Light and variable winds will become south to southeast. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....Kurimski LONG TERM......Kallas AVIATION.......Kieckbusch