textproduct: Burlington

WHAT HAS CHANGED

As of 221 PM EDT Sunday...

Confidence continues to grow for critical fire weather conditions Tuesday.

KEY MESSAGES

As of 221 PM EDT Sunday...

1. Dry weather continues for the first half of the week with critical fire weather conditions possible Tuesday due to gusty winds and low relative humidities.

2. A soaking rain, starting Wednesday night but primarily on Thursday, will be followed by an unsettled and cool weather pattern Friday through the weekend.

DISCUSSION

As of 221 PM EDT Sunday...

KEY MESSAGE 1: Surface 1021 mb high pressure is sitting over New England this afternoon, and atmospheric pressure is expected to increase over the next few days as an omega block remains in place. Upper level ridging over the Ohio Valley and Great Lakes will shift overhead tomorrow, resulting in light and variable winds at the surface both this afternoon and tomorrow. Other than some drifting high clouds, sunshine is also abundant this afternoon as a result, which should last into the midweek. This will allow temperatures to rise a little higher each day, with highs today in the lower to mid 60s this afternoon becoming the upper 60s and lower 70s both tomorrow and Tuesday. A very dry layer will persist above the boundary layer and efficient mixing could cause dew points to be slightly lower than forecast on any given day. Therefore relative humidity values will be around 20-35% each afternoon through Tuesday with recoveries overnight to around 60-90%, depending on how well we radiate out temperatures each night. Anticipated lows are in the upper 20s to upper 40s through Monday night. Winds will increase notably on Tuesday, with southerly gusts between 20 to 35 mph possible, especially on mountaintops and in the Champlain Valley. The winds, combined with the low relative humidity, are causing critical fire weather conditions to become increasingly likely. By Tuesday night, we expect the strong southerly flow to make for a cloudier, milder night with lows in the 40s and lower 50s. There could even be an isolated shower or two (probability 20-40%) in northwestern New York on Tuesday night as a shortwave and associated moisture crosses the region. The potential for a wetting rain Tuesday night is about 10-30% in northern New York with highest chance in the St. Lawrence Valley. More information about the potential for rain mid to late week will be found in Key Message Two.

KEY MESSAGE 2: Trends towards a mainly dry period, and a final warm day for the week, continues for Wednesday. By evening, as a compact wave of low pressure spreads widespread rain northeastward from Ohio moving into the eastern Great Lakes, chances for precipitation will increase in our region. Ensemble agreement on timing being primarily overnight/early Thursday is noted by 6 hourly PoPs near 80% from 2 AM to 8 AM Thursday. This southern stream system, fed in part by the Gulf waters/subtropical air, will tend to peter out as a secondary low forms over the Mid-Atlantic region. This secondary low will maintain a steady rain in Vermont for much of Thursday. While there will be a feed of Atlantic moisture as precipitation begins to become more consolidated in New England Thursday morning, the large scale setup looks more favorable for eastern New England than Vermont in terms of heavier rainfall potential. That being said, the most recent run of the ECMWF Extreme Forecast Index shows a similar signal for both Vermont and New Hampshire for a noteworthy rainfall that comes up shy of extreme (values above 0.7 and below 0.8); this was a notable increase from 24 hours ago, so it bears watching. The pressure falls to our south/east will also minimize any potential wind hazards with this system. While there will not be an upstream block to stall out the low pressure area as it passes to our east, its deformation/commahead and northward track favors rain chances lingering into Thursday night and Friday. Given the extended dry period we have had and the resulting low streamflows and river/lake levels, no hydrological impacts are expected with basin average rainfall somewhere in the 0.5" to 1.5" per ensemble (NAEFS, GEFS) 25- 75% percentiles. Greatest potential for those heavier amounts are in central/eastern Vermont; lowest potential is over the Champlain and St. Lawrence Valleys in New York.

As low pressure pulls northward into Maine, an upper level gyre will reinforce a longwave trough over southern Canada/northeastern CONUS, pulling in cooler air during this period. Blustery conditions will occur with northwesterly or westerly flow through the period and steep lapse rates, especially with any sunshine. Below normal temperatures will occur, although nothing extreme is noted relative to climatology. The coldest 925 millibar temperatures in the ensemble mean are indicated as low as the 10th percentile in the climatology Saturday morning with only a little moderation during the weekend, especially Sunday afternoon. Relative to normal the coolest weather will tend to be in southern/western portions of northern New York. High temperatures each day will trend slightly warmer, but even so valley highs in the mid 50s would still be about 10 degrees below normal.

As shortwave troughs circulate around, enhanced shower chances could occur over the weekend, which would potentially result in some mountain snow. At this time it looks like the orientation of the gyre will keep steadiest precipitation focused either to our east or to our north. As a proxy to mountain snow shower potential, the probabilities of 850 millibar temperatures falling below freezing will increase from west to east during the period. Per the AIGEFS, Thursday evening chances surge above 80% in the Adirondacks through the overnight hours, and surging from near 50% to 80% Friday morning in the Green Mountains. Friday night into the rest of the weekend 850 millibar temperatures will certainly be below freezing.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Through 00Z Tuesday...High confidence of VFR at all taf sites for the next 24 hour hours as surface high pres prevails. The probability of any mist/fog toward sunrise at MSS on Monday morning, similar to this morning is very low, given the dry airmass in place. North to northeast winds 4 to 8 knots this evening will become terrain driven under 5 knots by 03z and continue through Monday.

Outlook...

Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA. Wednesday Night: Mainly VFR, with local MVFR possible. Likely SHRA. Thursday: Mainly MVFR, with areas IFR possible. Likely SHRA. Thursday Night: Mainly MVFR, with areas IFR possible. Chance SHRA. Friday: Mainly MVFR, with areas VFR possible. Chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.