698 FXUS61 KBTV 091920 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 320 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 NIGHT/... 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 /THURSDAY THROUGH THURSDAY NIGHT/... As of 319 PM EDT Tuesday...The warmer weather of Wednesday will be an afterthought come Thursday as a cold front and highly amplified mid-latitude trough come sweeping through the region. However, another day of temperatures in the 60s to near 70 degrees will be expected on Thursday prior to the passage of the cold front with 850 mb temperatures sitting at 13 to 15 degrees Celsius. Rainfall will be pretty showery around sunrise on Thursday with the northern periphery of the upper level ridge barely holding on ahead of the highly amplified trough. With the help of a strong mid-level and upper level jet, the cold front and frontal trough will quickly push into the North Country several hours after sunrise with rainfall quickly overspreading the region. Models continue to be quite optimistic with rainfall, which is entirely plausible given great southwesterly fetch of Gulf Moisture (PWAT values approaching 2 inches). Rainfall amounts will vary between a a half inch across northern New York to around an inch across southern and eastern Vermont. Instability will be rather limited given the timing of the precipitation but with temps and dewpoints in the 60s with temperatures cooling aloft (steepening lapse rates), a rumble or two of thunder is not out of the question. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 319 PM EDT Tuesday...The aforementioned cold front will continue to push across the North Country Thursday heading into Friday morning with below normal temperatures expected in it's wake. The North Country will remain under the influence of the upper level trough which will advect a potent Canadian air mass which will usher in some of the coldest temperatures of the season to date. A reinforcing short of cold air will be seen on Saturday as the axis of the upper level trough pushes through the region. This should help Saturday be quite a bit colder than Friday as 850 mb temperatures drop to 0 to -5 degrees Celsius with the coldest values close to the international border. Friday night and Saturday night will see many locations drop into the 30s with some locations dropping into the mid to upper 20s. The Champlain Valley will once again be on the warm side with temperatures struggling to drop below 38 degrees Saturday night. While under the influence of the upper level trough, a series of shortwaves will track along the longwave pattern which will bring some rain and snow chances to the region. While it is hard to try and pin-point these showers, it won't be until Monday until the first chance for showers would be possible. By this time, temperatures aloft will have already begun to modify under the fall sun. However, it wouldn't be out of the question for parts of the North Country to see some termination dust on the higher peaks of the Adirondacks and Green Mountains with some of these showers. Any snow at higher elevations that does fall will melt given temperatures warmer aloft but another deep trough begins to set up across the central US on Wednesday. && .AVIATION /19Z 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...Clay LONG TERM...Clay AVIATION...JMG/Neiles CLIMATE...JMG