Expires:No;;944297 FXUS63 KMQT 172231 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 631 PM EDT Tue Sep 17 2019 .SHORT TERM...(This evening through Wednesday) Issued at 346 PM EDT TUE SEP 17 2019 A relatively high amplitude mid-level ridge stretches north to south from Hudson Bay to the Mid-South region this afternoon, with a shortwave trough currently located near the Arrowhead of Minnesota riding up the western periphery of the ridge. This produced showers and thunderstorms throughout today, but the stable air of the lake has kept the thunder to the west thus far. A brief sprinkle near Ironwood or across the northern Keweenaw through this evening are possible, otherwise the thick cirrus shield has kept temperatures a few degrees cooler over the west. Highs have been generally in the 70's except some lower 80s where downsloping southerlies have helped raise temps and some 60s where low clouds and flow off Lake Michigan have hindered a diurnal warm-up. Tonight, a somewhat drier low-to-mid-level airmass will move into Upper Michigan as a strong SWerly LLJ kicks in. If any fog were to redevelop tonight, it would likely be over the east, advecting in from Lake MI. But low stratus seems more likely to dominate these areas. Another shortwave will push SW to NE across MN late tonight into tomorrow in association with low pressure centered over Lake Manitoba. This will increase the pressure gradient over Upper Michigan leading to a breezy daytime with gusts of 15-25 mph, locally to 30 mph over the west and north, though there are significant differences in gust potential between models. The GFS is indicating a much weaker inversion than the NAM and thus stronger gusts, and the forecast has been nudged a little in that direction. But looking at upstream soundings from today, the GFS forecast inversion seems a little unrealistic so, as usual, reality will likely be somewhere in between. In terms of precipitation, it looks like overnight showers and storms will fall apart before reaching the UP, with only a slight chance for a shower to hold together into Ironwood in the late morning or early afternoon. POPs slowly increase through the late afternoon over the western third of the area, and a rumble of thunder or two will be possible. Temps during the day will be similar to today, with low 70s near Lake MI, and mid 70s to low 80s elsewhere. .LONG TERM...(Wednesday night through Tuesday) Issued at 255 PM EDT TUE SEP 17 2019 The main story from the middle of the week into the weekend is the continued well above normal temperatures and humid conditions. Upper- level ridging which builds across the western Great Lakes today will shift slightly east on Wed and then remain fairly stationary across the Great Lakes through the end of the work week. A couple of shortwaves and associated sfc low pressure systems ejecting out of the western CONUS trough into the western/northern Plains and then into central Canada will favor a southerly flow of very warm, moist air into the western Great Lakes region, tapping into moisture all the way from the Gulf of Mexico. The first shortwave lifting from the northern Plains into central Canada will push a weak frontal boundary into Upper Mi Wed night into Thu, which will tend to stall out over or near the area through Fri. The stalled out frontal boundary will result in chances for showers/storms Wed night into Fri, along with continued warm and humid conditions. A stronger shortwave and associated cold front is expected to move through the area late Sat into Sun, likely bringing a better chance for widespread showers/t-storms before drier, cooler and much less humid air moves in behind the front Sunday night into Monday. Wed night, weak frontal boundary just west of the cwa finally gets propelled into Upper Mi Wed night as a shortwave and associated sfc low over southern Manitoba late Wed lifts to James Bay by 12Z Thu. Ahead of the cold front late Wednesday into Wednesday night, 1000- 1500 j/kg of instability and 20 to 25 knots of deep layer shear may allow for a few stronger, pulse thunderstorms to develop. Given the unidirectional flow along the frontal boundary, and PWATs running 1.5+, heavy rain especially over areas that may see training showers/storms could become a possible flooding concern. However, with the front weakening as it moves overhead and shortwave dynamics lifting well north of the area, shower coverage may ultimately end up being more scattered which would limit potential flood concerns. Thursday into Friday, models indicate the above mentioned cold front will continue to weaken overhead and essentially stalls out and transitions into a stationary front Thu into Fri, but then pushes back northward into Canada on Friday night as prevailing s-sw flow strengthens on backside of mid-upper ridge axis. Lingering moisture and humid conditions along the stalled out frontal boundary Thu-Fri will lead to enough instability for periodic isolated to scattered showers/t-storms through the period. Nothing severe is expected as shear will be weak through the period. Best chance of pcpn may end up being Thu afternoon into Thu night when many models indicate the passage of a weak shortwave across the area which could aid formation of convection along the frontal boundary. Fri night into early Sat, with the stationary frontal boundary expected to lift north of the area Fri night with the strengthening prevailing s-sw flow off the sfc, expect a period of quieter weather Fri night into Sat morning before the next shortwave pushes a stronger cold front across the area bringing increasing chances of showers/t-storms late Sat into early Sun. Sat-Sun, the movement of the longwave trough toward the Upper Great Lakes will funnel an additional round of strong WAA and moisture transport across the region late Fri night into Sat. Operational models differ on timing/advancement of long wave trough and its associated cold front into the Upper Great Lakes this weekend. The 12Z GFS and 12Z ECMWF are certainly faster than the 12Z Canadian with the advancement of the cold front, bringing the front into western Upper Mi late Sat and then across the rest of Upper Michigan through 12Z Sun. Meanwhile, the slower 12Z Canadian and the previous 00Z ECMWF run really don't have the front advancing across area until late Sat night into Sunday which generally agrees better with the GEFS ensemble members and means. If models trend toward this slower solution, showers/t-storms may not end up impacting the U.P. until Sat night into Sun time frame. Again, with PWATs around 1.5 inches ahead of and along the cold front expect the potential of brief heavy rain with any of the t-storms. Behind the system, CAA wrapping around behind the system as it pulls off to the north should finally bring us some relief from the muggy and very warm conditions later Sun into Monday and return us to more fall-like weather. Models and ensemble forecasts generally support another day of dry weather on Tue as WAA from the west allows the airmass to slowly moderate. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 630 PM EDT TUE SEP 17 2019 VFR conditions are expected at CMX and IWD through the forecast period. SAW though will again see upslope fog from Lake Michigan which will take the visibility down to IFR this evening through Wed morning before VFR conditions there return. LLWS will set up overnight at all three sites. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 346 PM EDT TUE SEP 17 2019 As low pres lifts into Manitoba tonight and to Hudson Bay Wednesday night, southerly winds will continue to gradually increase across Lake Superior, especially over the e half. Gusts of 15-25kt tonight will increase to 25-30kt on Wed over the east half. Winds will generally be lighter over western Lake Superior. Over far western Lake Superior, ne winds may persist thru tonight. Since the cold front associated with the low pres will dissipate as it crosses Lake Superior Wed night/Thu, winds will fall back to under 15kt on Thu. Winds should be under 15kt on Fri, then increase again Sat as the next cold front approaches. May see gusts to 20-30kt again on Sat. Occasional fog will remain possible until the frontal passage. Most likely locations for fog occurrence will be over approximately the eastern quarter of the lake as well as locations near the MN Arrowhead. . && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...KCW LONG TERM...Voss AVIATION...07 MARINE...KCW