289 FXUS63 KDLH 092059 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 359 PM CDT Wed Oct 9 2019 .SHORT TERM...(This evening through Thursday night) Issued at 359 PM CDT Wed Oct 9 2019 A potent fall system remains on track to affect the Northland starting tonight and continuing into the extended period. After a warm day, temperatures will start a downward trend that will be accelerated by a cold front that will start pushing through Thursday night. A positively-tilted upper level trough stretched from the Northern Rockies to the Intermountain West this afternoon. Low pressure was observed at the surface over the eastern Dakotas with a cold front extending back into the High Plains of eastern Wyoming to another area of low pressure. As the trough digs through the Rockies tonight, surface cyclogenesis will take place in eastern Colorado with the low moving into central Kansas overnight. Southerly flow ahead of the system will persist over the Northland overnight with showers spreading in to mainly our Minnesota zones as the night progresses. A few rumbles of embedded thunder will be possible from central into north-central Minnesota this evening as CAPE values creep into the 200-500 J/kg range, however, no strong or severe storms are expected with relatively unidirectional shear preventing storm organization. This axis of instability lifts north of the region after midnight. Winds will not completely diminish overnight, and, along with cloud cover, this will keep lows on the warmer side, only dropping into the 40s and lower 50s. The upper trough will slowly work into the High Plains as the day progresses Thursday and then into the Central Plains overnight as a strong upper low deepens and moves northeastward. The surface low will move from central Kansas Thursday morning to near north- central Minnesota by daybreak Friday. This will bring a cold front through the Northland Thursday night into Friday morning. Showers and embedded thunderstorms will remain possible through the day Thursday across much of the Northland with better chances arriving during the afternoon and into the overnight ahead of the cold front. No strong or severe storms are expected during the period and temperatures are expected to keep P-type as all liquid through the end of the period. Highs Thursday will reach into the 60s across northwest Wisconsin with 50s for northeastern Minnesota. Temperatures will be slow to cool Thursday night into Friday morning with 24-hour lows expected to occur later on Friday. By daybreak Friday, temperatures will range from the upper 30s and lower 40s in the Brainerd Lakes area to the middle 50s in the Minnesota Arrowhead and northern Wisconsin. .LONG TERM...(Friday through Wednesday) Issued at 359 PM CDT Wed Oct 9 2019 The main focus for the extended continues to be on a potent upper- level system that will bring some accumulating snow to the region this weekend, along with temperatures well below seasonal average. A nearly vertically-stacked mid- to upper-level system will strengthen over the Northland. Associated surface low pressure will deepen, with strong cold air advection building behind the low. The upper-level low is progged to remain cut-off, which will allow it to linger over the region through the upcoming weekend. This large- scale forcing with this system looks quite impressive, but the bulk of the forcing will remain just to the northwest of our forecast area. However, pretty impressive 500 mb height falls will occur over our region, on the order of 20 to 25 decameters. Precipitation types during the day Friday look to remain as rain as the colder air remains to our west. Then, this colder air will filter in Friday night, characterized by 925 mb temperatures between 0 to -5 degrees C. This will allow snow to mix in with the rain, and eventually transition to mostly snow into early Saturday morning. Southerly flow ahead of the surface low, coupled with the colder air building into the region, should support some lake effect snowfall along the higher elevations of the North Shore through the day Saturday, with 850-surface delta-T values around 15 to 17 degrees C - supportive of the lake enhancement. The precipitation types will be highly dependent on the time of the day, with mostly rain expected during the day Saturday, transitioning back to snow overnight. This appears to be the theme through Sunday night as well. Some uncertainty does remain on this scenario given a hint of a dry slot possible over our region Friday night into Saturday, which would tamper down snow amounts. Moreover, the snowfall rates appear to be fairly minimal, given the lack of strong isentropic ascent within the dendritic growth zone to overcome warmer surface temperatures. The latest forecast snowfall amounts are generally between 1 to 3 inches, so no heavy accumulations are expected at this time. Highs on Friday will likely be in the morning hours before the colder air pours into the region, with highs in the lower 40s southwest to the middle 50s northwest. Highs on Saturday and Sunday will then be in the middle to upper 30s. Monday through Wednesday continues to show the upper-level low churning over the region, keeping chances of a rain/snow mix over the region. Temperatures will warm only slightly, with highs in the lower to middle 40s. Some drier air will return on Wednesday as high pressure builds into the region. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1241 PM CDT Wed Oct 9 2019 Gusty southerly winds will continue into the evening hours today, with VFR conditions expected as dry air remains in place. However, there will be a transition to cloudier skies overnight, some chances of rain showers, and the potential for low-level wind shear overnight as winds aloft will remain fairly strong, while winds near the surface will slowly diminish. The high-resolution models seem to be in decent agreement with the timing of rain showers overnight as a mid-level disturbance lifts northward ahead of an area of low pressure, so tried to refine the timing of these showers. There will be a slow transition to MVFR and IFR ceilings Thursday morning as the area of low pressure strengthens. && .MARINE... Issued at 359 PM CDT Wed Oct 9 2019 Low pressure continues to move eastward into western Minnesota this afternoon, which will keep the region in south to southeasterly flow across western Lake Superior. Some breezy conditions have developed over portions of the South Shore this afternoon, mainly near the Chequamegon Bay and Saxon Harbor areas. Wind gusts have exceeded 25 knots at times, so have issued a Small Craft Advisory, in effect from now through the evening hours. Winds are expected to diminish overnight tonight below Small Craft Advisory criteria, but will remain from the east to southeast through Thursday. This persistent east flow will lead to building waves Thursday night into Friday, particularly along the North Shore, as the area of low pressure strengthens over the region. Waves of 3 to 6 feet will be possible during this time frame, mainly from Silver Bay northeast towards Grand Portage. These conditions will be hazardous to smaller vessels. && .PRELIMINARY POINT TEMPS/POPS... DLH 50 58 46 52 / 20 80 90 70 INL 50 59 47 52 / 70 90 100 80 BRD 52 58 41 42 / 60 90 100 50 HYR 50 64 49 54 / 10 60 90 80 ASX 50 66 50 60 / 10 40 90 80 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ SHORT TERM...BJH LONG TERM...JTS AVIATION...JTS MARINE...JTS