187 FXUS61 KBTV 091750 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 150 PM EDT Tue Oct 9 2018 .SYNOPSIS... A frontal system will remain over or just north of the area through Wednesday night with generally mild weather and only a few scattered showers across northern counties. A strong cold front will cross the area on Thursday with a widespread wetting rainfall expected. Behind this front a seasonably cool airmass returns for the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 137 PM EDT Tuesday...Main change for 130 pm update was to increase pops to reflect current radar trends. No big changes otherwise. Prior discussion... A complex temperature and cloud forecast continues to unfold across our area over the next 36-42 hours as a warm front lifts northward through the area today, then settles back southward into far northern counties on Wednesday. A wide variety in temperatures already exists early this morning as the front has lifted into the Adirondacks and the Champlain Valley, while making only slow progress into the SLV and eastern VT. Case in point the 300 am observations showing KMSS still holding at 50F while just 30 nm to the southeast KPTD has risen into the lower 70s. Strong warm thermal advection riding atop this retreating cold pool continues to spark scattered showers and a few thunderstorms across northern NY into the Ottawa and St Lawernce Valleys and the idea of a few showers continuing across our northern NY zones today still looks reasonable per model blended QPF output. High temperatures will be quite tricky given a continued stable layer near 925 mb keeping ample moisture trapped beneath. By mid to late afternoon I feel enough boundary low level heating and mixing should allow most places to trend partly sunny, though admittedly my confidence is only modest across the Adirondacks and north central/northeast VT. As such I've kept the warmest readings in the Champlain/St Lawrence Valleys and southwestern VT where late afternoon values should top out in the 75 to 80 degree range. Elsewhere, lower to perhaps mid 70s look reasonable. That said my forecast confidence is only modest. If you believe the strict Hysplit back-trajectory output at 500m our source air today originates from the Mid Atlantic states yesterday where highs ranged from 83 to 88F. However, it looks as if we'll struggle to mix that deeply, thus my reasoning described above. While most maximum temperature records should be safe, a few spots, most notably KBTV and KMSS may come close. Please see climate section below for specific records. By tonight the warm front lifts bodily north of the area under broad south to southwesterly flow. Any chances of showers should be confined to the far north and points northward into southern ON/QE overnight in closer proximity to the front. Low temperatures to remain quite mild, generally holding in the 60s. On Wednesday the temperature/cloud forecast doesn't become any easier as guidance continues to indicate the front surging back south/southwestward into the far northern counties during the day with cloud/shower threat increasing along with falling temperatures. To capture these trends I used a blend of most recent NAM12, 4km WRF and GFS FV3 hourly temperature output. This would suggest high temperatures to continue mild across central/southern counties - 73 to 78F which should remain largely unaffected by the boundary. Further north, mid-day readings to top out in the upper 60s to lower 70s before readings fall sharply by later in the afternoon as the front passes and winds trend northerly. Indeed, if you believe the raw hi-res output, portions of the northern Champlain and St. Lawrence Valleys may fall back into the upper 50s to lower 60s by late afternoon. Time will tell. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 401 AM EDT Tuesday...Wednesday night into Thursday is a challenging forecast. The front that has been waffling around over the North Country will be in the process of dropping a backdoor cold front from the north Wednesday night into Thursday morning over the International Border into the northern Champlain Valley. As that happens, the rest of that same backdoor cold front will also be pressing in from the east to northeast. So there's going to be a bit of squeeze some where west of the Greens but east of Lake Champlain where temps will be a fair bit warmer than all other surrounding obs. I've trended hourly temps and max/min temps to try and capture the front but wasn't quite ready to go with the 8-10 deg F drop in an hour that the NAM12 is forecasting. By mid morning on Thursday southerly flow should pick up and usher in a warmer and moist airmass pushing PWATs into the 1.7-1.9" range which is well above normal for this time of year. As the main cold front associated with an upper level low centered just south of James Bay pushes into the North Country on Thursday afternoon expect periods of moderate rainfall. All totaled we'll be looking at on the order of 0.75-1.2 inches of widespread rainfall which will be very beneficial given much of the area is still in drought status. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 401 AM EDT Tuesday...Over the weekend the big "highlight" is that we'll be cooler on Friday into Saturday. The cooler temps should be cold enough that higher elevation locations should see a dusting of snow as an upper level trough brings a chance of showers/flurries depending on elevation both Saturday and Sunday. Saturday looks to be the coldest of the extended at 850mb temps stay below zero for the forecast area and our high temps might struggle to warm above 49 degrees. Saturday night currently looks like we'll see widespread temps around freezing with the colder hollows in the upper 20s. Any snow will quickly be melted at warmer air pushes in overnight Sunday as our next low pressure system starts to approach the region. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Through 18Z Wednesday...Ceilings will be gradually lifting to VFR at all terminals in the 18-00Z time frame. A few/scattered showers will be possible across the far north and to the lee of Lake Ontario where a slight threat of thunder also exists. Any storm could produce local turbulence and gusty winds in excess of 30 kts. Vermont terminals should remain storm-free. Winds mainly south to southwesterly in the 6 to 12 kt range with gusts to 15 kts this afternoon, though locally higher at KBTV with gusts to 25 kts expected. After 00Z confidence remains low in regard to cigs, with conflicting guidance showing values either holding VFR or lowering to MVFR/IFR. For now have kept broader valley terminals mainly VFR, though highlighted lower cigs at KRUT/KMPV/KSLK where progs are somewhat higher. Winds to generally remain south/southwesterly, though trend light to around 5 knots. Outlook... Wednesday Night: Mainly MVFR, with areas IFR possible. Chance SHRA. Thursday: Mainly MVFR, with areas IFR possible. Likely SHRA. Thursday Night: Mainly VFR, with local IFR possible. Chance SHRA. Friday: Mainly VFR, with areas MVFR possible. NO SIG WX. Friday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Saturday: Mainly VFR, with local MVFR possible. Slight chance SHRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight chance SHRA. && .CLIMATE... Here are record high temperatures for today, October 9. DateKBTV KMPV K1V4 KMSS KPBG KSLK 10-09 80|2011 78|2011 79|2011 81|1997 81|1970 84|1909 && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG/Neiles SHORT TERM...Deal LONG TERM...Deal AVIATION...JMG/Neiles CLIMATE...JMG