827 FXUS63 KDLH 242359 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 559 PM CST Tue Dec 24 2019 .UPDATE... Issued at 559 PM CST Tue Dec 24 2019 Updated for the 00Z Aviation discussion. && .SHORT TERM...(This evening through Wednesday) Issued at 359 PM CST Tue Dec 24 2019 Low stratus and fog will reduce visibility to less than one- quarter mile for most areas tonight and early Christmas morning. There is a slight chance of drizzle and freezing drizzle tonight with a period of drier conditions Christmas morning. Light precipitation develops from south to north Christmas afternoon as a mix of drizzle, freezing drizzle, and snow. Low stratus and fog developed over the Northland today and will linger tonight and Christmas Day. Visibility will be less than one-quarter mile at times. Have issued a Dense Fog Advisory, which started at 3 PM for the Arrowhead and goes into effect at 9PM for the remainder of the Northland. A combination of orographic and weak isentropic forcing for ascent will keep a slight chance of drizzle/freezing drizzle in play tonight in the Arrowhead. The threat of precipitation is non-zero elsewhere, but generally below 10%. The lower levels will remain saturated southwesterly winds above keeping a stout thermal inversion in place Christmas Day. The weak forcing for ascent will translate eastward and out of the area early Christmas morning, which will bring an end to the light precipitation. Low clouds and fog will likely linger through the day. The warm air aloft will slowly saturate by late Christmas afternoon and isentropic lift will return. A wintry mix of drizzle, freezing drizzle, and light snow will develop from south to north during the afternoon hours. Snow and ice accumulation on roads may make for slippery travel. .LONG TERM...(Wednesday night through Tuesday) Issued at 359 PM CST Tue Dec 24 2019 A return to active weather. First system arrives late Wednesday as a warm front begins to enhance precipitation rates out of the thick stratus deck. There will likely be a transition zone where a wintry mix occurs with rain/drizzle will be more likely near Park Falls, while snow will be more likely at Intl Falls while the mix lies in between. QPF amounts are fairly light, but enough to cause issues. Presently expecting about a 1/4" of melted liquid equivalent, but that will translate to a few inches of snow near Intl Fals and up to a 0.20" of ice along the North Shore as this system deepens over the MN/WI area before the low crosses directly overhead of the Twin Ports. Decent dynamics being on the left exit of a strong upper level jet streak may allow this system to deepen further than current models show, so something to keep an eye on. This system is the precursor to a much larger system that is percolating for the weekend. There will be a brief break between systems on Friday into the early morning hours of Saturday, but then a large system moves into the region from the western Kansas/eastern Colorado. This has all the look and feel of a nice Colorado low which will likely blanket a good portion of the Northland with several inches of snow if the current predictions are on track. One thing to note is that this system has been steadily drifting to the northwest (originally bringing heavy snowfall to southeast Wisconsin), but has now drifted enough to the NW to impact the Northland and has been consistently impacting largely the same area for at least 4 consecutive runs. So confidence is increasing in an impactful storm for the Northland including the city of Duluth. Increased PoPs well above NBM output - though probably didn't go high enough. Still quite early to decipher amounts, but it looks like another storm that will warrant winter storm headlines. This could be particularly troublesome for those heading back from holiday travel. Start thinking now about your travel plans and keep an eye on this weekend system. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 559 PM CST Tue Dec 24 2019 LIFR/IFR conditions expected through much of the TAF period as copious low level moisture has converged upon the area to produce saturated atmosphere across the Northland. Expect some lowering of conditions in the next few hours, as the few sites that are still have VFR/MVFR visibilities deteriorate to IFR visibilities in fog. Condition to remain IFR/LIFR overnight tonight and into Tuesday morning until 15z, with some improvement in visibilities, though ceilings are expected to remain IFR/LIFR through the end of the TAF period. && .MARINE... Issued at 359 PM CST Tue Dec 24 2019 Winds will return tonight and increase into Wednesday as an area of low pressure approaches from the south. Sustained winds of 15 to 20 knots is expected for most areas with higher gusts. These stronger winds will continue into Wednesday evening before decreasing late. Waves will build on Wednesday, especially along the North Shore to the Twin Ports and along the Bayfield Peninsula. Small Craft Advisories will likely be needed there. Freezing drizzle is possible through the evening. && .PRELIMINARY POINT TEMPS/POPS... DLH 29 35 32 36 / 20 50 70 80 INL 21 32 28 34 / 20 40 80 90 BRD 29 35 30 35 / 10 50 70 60 HYR 29 38 33 39 / 10 40 50 60 ASX 29 37 33 39 / 10 40 60 70 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...Dense Fog Advisory from 9 PM this evening to 10 AM CST Wednesday for WIZ001>004-006>009. MN...Dense Fog Advisory until 10 AM CST Wednesday for MNZ012-019>021- 037. Dense Fog Advisory from 9 PM this evening to 10 AM CST Wednesday for MNZ010-011-018-025-026-033>036-038. LS...None. && $$ UPDATE...LE SHORT TERM...Huyck LONG TERM...Wolfe AVIATION...LE MARINE...Wolfe