Area Forecast Discussion

WHAT HAS CHANGED

As of 837 AM EDT Sunday...

A quick morning update has been issued to better capture the current weather and precipitation across the region based on surface observations and webcams. Temperatures across northern New York have cooled even quicker than initially forecast, leading to a quicker transition to snowfall in several locations. Precipitation will continue this morning into the afternoon.

KEY MESSAGES

As of 230 AM EDT Sunday...

1. Gusty winds this morning, then widespread rain will change to snow or rain and snow mix this afternoon. Minor snow accumulations and slushy, slippery travel is possible throughout the day today.

2. Unseasonably cold conditions Sunday night into Monday night will be accompanied by a chance of snow showers, especially Monday morning. Any standing water could freeze and become black ice early Monday morning. Cold weather will continue into Tuesday.

3. Temperatures are favored to warm back to seasonal averages through the week with some potential for showers late next week.

DISCUSSION

As of 230 AM EDT Sunday...

KEY MESSAGE 1: A large, highly amplified longwave trough is supporting a large area of precipitation along a slowing cold front that is crossing the forecast area this morning. Temperatures have fallen 15- 25 degrees since this time yesterday in several locations, and we anticipate temperatures will continue to fall this morning and into the afternoon, reaching the 30s (highs of the day have likely already occurred this morning), well below seasonal averages. The upper level jet configuration, with jet streaks to our north and south by midday today, will be favorable for widespread precipitation behind the surface front. Confidence of precipitation is high today, though confidence of precipitation TYPE is a bit more challenging based on the wide spread of modeled temperatures throughout the day today across northern New York and Vermont. Highest confidence of snow exists at higher elevations, which should see a quick changeover to snow from west (the Adirondacks early morning) to east (Greens later in the morning). Probability of greater than a tenth of an inch of snow accumulation increases sharply in the Adirondacks around 8 AM, then in the Greens around 11 AM. Confidence of this same amount in the St. Lawrence Valley this morning is around 30-40%, similar in the Champlain Valley around midday where wet bulb and dynamic cooling may influence temperatures. Confidence is a little higher in the Stone Valley (Rutland area) and east of the Green Mountains where colder air is likely to collect. About 85-95% chance of higher than a tenth of an inch in areas east of the Greens like Newport, the Northeast Kingdom, and Montpelier/Barre area this afternoon, then 50- 60% chance in Rutland in the afternoon-evening hours. The Connecticut River Valley typically holds onto milder temperatures, so probabilities there are closer to 10-30% this evening. Overall, snow accumulations are not expected to be extremely impactful or noteworthy, with perhaps 4-7 inches at the highest elevations and a dusting to a couple tenths of an inch in valleys. The ground is starting quite warm, and the sun in April is stronger than it was just a month ago, so any snow at lower elevations may not stick or may melt shortly after accumulating. It'll be difficult to get a sense of how much snow actually fell in many spots. The main impacts would be some slushy, slick travel while snow is actively falling, and this should be a narrow window of time for most areas where people live and drive. Extra caution should be used, though, if traveling through mountain passes or in high elevation areas. Snow may take springtime drivers off guard, particularly since most cars have removed snow tires at this point in the season. Precipitation is expected to taper off tonight as drier air flows in.

KEY MESSAGE 2: Cold air will continue to flow into northern New York and Vermont Sunday evening and Sunday night, with 850mb temperatures as low as 12-14 C. By early Monday morning, surface temperatures are expected to be in the 20s and lower 30s, well below seasonal averages, which could result in areas of black ice from any lingering standing water. Another cold front will swing through the region as well, bringing the potential of some snow showers back up to around 30-50% Monday morning then decrease throughout the afternoon. There will be some instability, lingering low level moisture, and convergence along this front to support at least some shower activity. Atmosphere will still be fairly dry Monday, so additional accumulations likely stay minimal. Highs Monday will likely struggle to reach into the 30s and lower 40s, quite chilly for this time of year. The coldest night will be Monday night, when high pressure noses in from the mid- Atlantic and optimal radiational cooling conditions arrive. Lows are forecast in the mid teens to mid 20s under clearing skies. Tuesday we'll likely have a slight recovery in temperatures as light south to southwest flow increases again and sunshine dominates at least the morning hours. Highs could reach into the 40s and lower 50s but remain below typical temperatures for late April. A backdoor cold front could bring some additional chances of precipitation Tuesday night, 15-35% chance.

KEY MESSAGE 3: Long wave ridging is expected to displace troughing through next week, shunting the polar front jet and main storm track northeastward into eastern Canada. This pattern favors slowly warming temperatures despite a continued northwest flow pattern. Highs are projected to warm from low/mid 50s midweek into the 60s heading into the weekend while lows correspondingly warm from the 30s into the 40s. A weak shortwave may provide some light shower chances into extreme northeast Vermont Wednesday night from a transient clipper system, but by and large most of mid to late next week looks to dry. Models begin to diverge late Friday into the weekend as the evolution of a large scale upper low over the Canadian Maritimes develops. A back door cold front may lead to some shower chances late Friday into Saturday, but shower chances become uncertain for the remainder of the weekend. The GFS ensembles denote stronger upper level flow which will kick the system into the Atlantic, allowing for a connection of a southern stream of energy with energy from an upper low in central Canada, resulting in a double barrel like pattern. The Euro ensembles, however, show a more blocked flow pattern with the Canadian Maritime system poised to remain stationary this weekend, limiting any moisture advection into our region, with potentially a drier end to the weekend. The evolution of this northern Atlantic upper low will set the stage for our weather pattern this weekend and next week.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Widespread light rain and drizzle is on the leading edge of a cold front currently washed out over northern New York. Reinforcing energy will push the cold front eastward this morning with increasing moisture and sharply falling temperatures. Cold air will lead to a mix of rain and snow during the mid to late morning into this afternoon. Rain changing to snow will begin at SLK first, with this snow becoming heavy at times at the onset, and lightening by early this afternoon. Confidence has increased in precipitation changing to at least a rain snow mix with potentially some prevailing snow at PBG/BTV between the late morning and mid afternoon. Widespread IFR visibilities 1-2SM are expected between 14-21Z for all Vermont sites at SLK with potentially brief 1/2-3/4SM visibilities as the main boundary slides through each terminal with any heavier rain/snow. Ceilings will also continue to lower to 500-900 ft agl this morning and early afternoon, before improving back to MVFR by mid afternoon. Precipitation will begin to taper off between 21-23Z with improving conditions to VFR. Snow showers this evening may be possible across the region but will be isolated in nature with minimal impacts before drying by tonight with west winds.

Outlook...

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

BTV WATCHES / WARNINGS / ADVISORIES

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