Expires:No;;596575 FXUS63 KMQT 201739 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 1239 PM EST Tue Nov 20 2018 .SHORT TERM...(Today and tonight) Issued at 457 AM EST TUE NOV 20 2018 WV imagery and RAP analysis indicated an amplified pattern with a ridge over western North America and a broad mid/upper level trough from Hudson Bay and northern Quebec through the Great Lakes and ern CONUS. The next upstream shortwave trough was located over nrn Manitoba. At the surface, diminishing nrly flow prevailed across Lake Superior as a weak ridge builds into the area ahead of low pressure over sw Manitoba. Lake induced troughing has focused the more prominent remaining LES bands into Alger county. With weak acyc nw flow into the western Upper Michigan, mainly just flurries were observed. Today, The strongest forcing (700-300 mb qvector conv and isentropic lift) associated with the Manitoba shrtwv will remain north of Upper Michigan. However, some light snow is still expected over the west half with accumulations of a half inch or less, mainly this afternoon. As a trough trailing from the low shifts through the northwest late today into this evening, low level conv as winds veer sharply nw, a brief period of heavier snow will be possible with a quick inch or two. With the entrenched cold airmass, even with breezy sw winds, highs will only climb into the low to mid 20s. Tonight, After the trough moves through the rest of Upper Michigan, winds becoming nnw to n with 850 mb temps to around -20C will support at least moderate multiple wind parallel LES through the north half of Upper Michigan. Additional snow accumulations of 1 to 3 inches will be common with the higher snowfall rates over the west in the evening and into north central Upper Michigan overnight. With the DGZ coincident with the convective layer, fluffy LES with high SLR values are expected. Although inversion heights to 6k ft would only favor moderate LES, land breeze convergence overnight and potential for Lake Nipigon conditioning should bring the higher snowfall potential to areas between Marquette and Munising with some local amounts in the 3 to 5 inch range. .LONG TERM...(Wednesday through Monday) Issued at 408 AM EST TUE NOV 20 2018 Models suggest that the amplified pattern with a mid/upper level ridge off the West Coast and trough from Hudson Bay into the Great Lakes will become slowly progressive with the ridge building into the Plains by the middle of the week. As troughing develops over the western CONUS and into the southern Plains ridging will extend into the Great Lakes by late week. As a result, the colder air over the region through Wednesday will also give way to warming as the cold recedes to eastern Canada and northern New England. Beginning Wed, Winds veering from nw to n early in the morning will push preconditioned Lake Nipigon les band from western Alger into Marquette County likely clipping Keweenaw County as well. With the DGZ favorably positioned within the convective layer could see several inches of fluffy snow accumulation which may push snow totals near advisory levels at some locations. Increasingly anticyclonic low-level flow as Arctic high pres builds over northern Ontario on Wed will cause LES to diminish steadily through the afternoon hours. It will end over the far w as winds veer easterly there during the aftn. It will be a very cold day for late Nov with 850mb temps of -17C to -22C from w to e across the fcst area at midday. Highs will only range from the low/mid teens northwest and north central over high terrain to the lower 20s south central. Record low max temp of 15F here at NWS Marquette could certainly fall. As the high shifts e Wed night and winds continue to veer, will probably see some flurries/-shsn into south central Upper MI Wed night into Thu morning under shallow se flow across Lake MI. Elsewhere, it will be a very cold night if skies can clear anywhere for a few hours. However, it appears there will be little/no gap between the loss of lake stratocu and arrival of high/mid clouds under developing waa regime. Eastern fcst area would likely have best opportunity for temps to plummet toward zero. Thanksgiving Day...waa will strengthen thru the day. Despite decent isentropic ascent, sharply anticyclonic mid-level flow should keep pcpn from being a concern. Under breezy conditions, temps will rebound into the mid 20s to lower 30s. Plenty of clouds and mixing from winds will result in very little fall in temps Thu night. Shortwave trough will move across the Mississippi Valley late Fri evening and reach the western Great Lakes early Sat. While models continue to show differences in the structure/timing of trough, there is good agreement for pcpn to occur at some point Fri night/Sat. Ignoring the faster outlier GFS solution which has pcpn arriving Fri aftn, expect pcpn to arrive Fri evening and continue into Sat. Looks like column may cool sufficiently for at least a mix of rain/snow with the potential for a change to all snow. Doesn't look like a headline event, but if pcpn ends up as mainly snow, the wet snow will make for sloppy travel at times. Models and ensembles indicate there should see a break in pcpn for most areas on Sun as weak ridging moves across the region. 00z models still show next shortwave lifting across the mid-MS Valley and spinning up an Ohio Valley/Great Lakes low pres system Sun night/Mon. Operational models and ensembles exhibit plenty of uncertainty on the track and strength of this low and its potential impacts on the Upper Great Lakes for Mon-Tue. The 00Z GFS shows a deeper developing sfc low tracking farther nw into Lower Mi with a greater potential for perhaps a longer lake enhanced snow event into Upper Mi on its backside. Meanwhile, the farther se tracking 00Z ECMWF sfc low looks closer to EPS and GEFS ensemble means, which would probably result in minimal impacts from lake-enhanced snow for our area. This will certainly bear watching to see how the model runs trend with this developing system over the next several days. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1238 PM EST TUE NOV 20 2018 Mainly MVFR conditions are expected at KIWD/KCMX/KSAW thru this fcst period. A period of -sn this aftn, producing ocnl IFR vis especially at KIWD/KCMX, will give way to lake effect shsn tonight thru Wed morning in the wake of a passing arctic cold front. A brief period of shsn/+shsn with IFR or even LIFR vis may occur at KCMX as the front passes early this evening. As is typical for lake effect shsn, conditions tonight/Wed will be variable, fluctuating btwn MVFR and IFR at times. A heavier band of shsn will likely impact KSAW Wed morning, leading to prevailing IFR conditions and potentially brief LIFR. Gusty nw winds behind the arctic front will gust to around 25kt at KCMX tonight. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 457 AM EST TUE NOV 20 2018 Winds will become southwesterly and increase back to about 25 knots this afternoon ahead of an approaching surface trough. Behind that trough, winds will veer to northwesterly and then northerly for tonight and Wednesday morning but remain at about 25 knots over the western lake and 30 to 35 knots over the eastern lake. A few widely scattered gale-force gusts are possible over eastern Superior early with the trough passage this evening and toward Wednesday morning. With the stronger winds and very cold air, freezing spray will develop and may become heavier over the northern lake. Winds across the lake weaken below 20 knots Wednesday afternoon. Winds stay light through Thursday morning as a high pressure ridge drops south out of Canada across the lake. As the high departs to the southeast Thursday afternoon, winds become southerly and increase back to 25 to 30 knots for Thursday night into Friday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Voss AVIATION...Rolfson MARINE...JLB