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LONG TERM /FRIDAY THROUGH TUESDAY/......Once in a Generation Winter Storm to Slam the Region Heading intoand THROUGH the Christmas Weekend...Old Man Winter will unleash the full fury of winter upon our regionduring this period...as an extremely amplified longwave pattern willspawn one of the most intense storm systems in decades to impact theMid West and Great Lakes region. This system will likely end upsetting low pressure records once it passes north of the border andwill have the potential to generate at LEAST storm force winds overthe Lower Great lakes.As if the very real threat for damaging winds of 60-70 mph were notenough...there will also be the risk for a prolonged...paralyzingheavy lake effect snow event. The very strong to damaging winds,blowing and drifting snow with localized blizzard conditionspreceded by a rapid flash freeze all coming right before theChristmas holiday weekend resulted in a *long duration* winter stormwatch being issued for western NY. A Winter Storm Watch has also nowbeen issued for Jefferson and Lewis county from midday Fridaythrough Monday. While heavy lake effect snows have already occurredthis winter season...this will be the first event with multipleimpacts from such intense winds. Winter storm watches are already ineffect for parts of western New York with the high component wrappedinto the same product.An extremely amplified longwave pattern during this period willspawn one of the most intense storm systems in decades to impact theMid West and Great Lakes region. This system will likely end upsetting low pressure records once it passes north of the border andwill have the potential to generate storm force winds over the LowerGreat lakes.Explosive cyclogenesis will take place over the mid western statesinto southern Ontario on Friday...as an anomalously strong 150kt H25jet will pass through the base of a very deep longwave trough. Thiswill support rapid deepening of a corresponding sfc low that willtrack southern Ontario by late Friday. The `bombing` low will deepenfrom roughly 990mb in the vcnty of Lake Erie/Lower Michigan lateThursday night...to 982mb over southernmost Ontario Friday morningto about 968mb near the Ontario-Quebec border by Friday evening...easily meeting the definition of bombogenesis (24mb/24hrs). Suchdeepening is relatively rare in the LOWER Great lakes...but morecommon across the UPPER Great Lakes and certainly with Nor`eastersalong the coast. Some of the parameters of this intense storm areclimatologically `off the charts`...such as MSLP and strength ofboth the low level and upper level jets. One could certainlydescribe this storm system as a once in a generation type of event.Subtle differences remain...but there remains general modelagreement in the overall large scale scenario...which addsconfidence.The rapidly intensifying low is forecast to pass just to our west onFriday. Winds will ramp up in the cold air advection and during whenmax pressure rise/fall couplet crosses. This is about as good as itgets in terms of maximizing winds/gusts to the sfc. Several guidancepackages are now advertising wind gusts over the IAG Frontier tonear 60 mph late in the day as another intense 70kt LLJ enters theregion. This is NOT when the strongest winds are expected though.That is yet to come.In regards to pcpn on Friday...the strong winds will open the doorfor MUCH colder air to pour across our forecast area. This willresult in a RAPID change over of the rain to snow with deepfrontogenetic forcing leading to a burst of moderately heavy snowthat will yield accumulations of several inches expected by lateafternoon. Temperatures that will start the day in the low to mid40s in most areas will PLUMMET into the single digits across theSrn Tier by the end of the day...while readings will range from theteens across the remainder of wrn NY to the lower 30s east of LakeOntario. This dramatic plunge in temperatures will likely result ina flash freeze of the snow/water/slush.As the extremely deep storm system further deepens in place over theOntario-Quebec border Friday night...a strong secondary coldfront/sfc trough will plow across our forecast area. This will beaccompanied by the second 70kt low level jet that...being found inthe cold sector...should largely mix to the sfc at times. The threatfor high winds at the sfc will be greatest in the typical corridorfrom Lake Erie and the IAG Frontier to Rochester and then to theThousand Island region. Increased winds some in these corridors.Power outages will be a concern as will be blowing snow and driftingsnow.The widespread synoptic snow during the first half of Friday nightshould then taper off as the deepest forcing exits and limiteddrying arrives in the mid levels. Meanwhile...a 230-240 flow of -20cH85 air will promote an area of lake snow to become establishedBuffalo northward...across IAG and the Northtowns. The snow...whether it be synoptic or lake induced in nature...will be blownaround by +50 mph winds so significant blowing and drifting can beanticipated along with near zero visibility and at least localizedblizzard conditions. As is typically the case...the very strongsouthwest flow will also shove a great deal of water up to theBuffalo end of Lk Erie...so lakeshore flooding will be apossibility. More specifics on that in the lakeshore floodingdiscussion.A very tight sfc pressure gradient will remain in place across ourforecast area on the day before Christmas...so while the windsshould diminish as bit by way of a weaker LLJ especially later inthe day, they will still be strong enough to possibly cause issuesand certainly to support continued blowing snow. Models have trendeda bit quicker with veering of winds, to more of 240-250 flow so thatmore of the Buffalo Metro would be impacted by lake snows Saturdayinto Saturday night with the visibility remaining near zero at timeswithin the band. It will be quite cold with Saturdays highs rangingfrom the single digits over the Srn Tier to the teens and low 20selsewhere resulting wind chills falling to as low as 10 to 20degrees below zero.Christmas Day promises to remain cold with highs only in the teensto low 20s and winds to 30 mph generating wind chills of 10 below tojust a few degrees abv zero. Meanwhile...a 240-250 flow will keepthe lake snow machine in full gear for sites near and just south ofthe Buffalo and Watertown areas. No big change to forecast thinking.While the very cold weather will persist into Monday...sfc basedridging should help to at least lessen the potential for additionalsignificant lake snows later Monday into Tuesday. Possible thatconditions moderate more significantly by middle of next week, butnot surprisingly, not a clear signal yet.