textproduct: Burlington

WHAT HAS CHANGED

As of 239 PM EDT Monday...

No substantial changes were made.

KEY MESSAGES

As of 239 PM EDT Monday...

1. Scattered showers, with steadier rain primarily in southern and eastern Vermont, will persist through this evening as a Nor'easter departs to the northeast. A slow clearing trend will occur tomorrow with dry weather returning.

2. High pressure will keep our region dry over the next few days along with a warming trend and variable cloudiness. Localized breezy conditions will develop on Thursday.

3. Several rounds of showers possible late week and this weekend.

DISCUSSION

As of 239 PM EDT Monday...

KEY MESSAGE 1: A very well defined low pressure center spinning northeastward continues to be evident on satellite imagery and will approach Cape Cod this evening. The system's upper level low is displaced well to the northwest over southern New England, and most of the rain is located on its northwestern flank with observed rainfall rates near 0.1"/hour. As the upper low tracks farther north early this evening, bands of light to moderate rain will slide that way such that steadier rain should move across all of central and eastern Vermont before exiting to our east tonight. Additional rainfall in this swath is likely to be in the range of 0.1" to 0.5", which will lead to storm totals localized in southern Windsor County approaching 2", but with most of the region in the 0.25" to 1" range.

As rain comes to an end, there will still be a lot of low level moisture and only modest drying aloft from the north-northwest overnight. Hence, expect early morning low clouds with the 925-850 millibar layer remaining saturated, and perhaps localized fog almost areawide with perhaps exceptions in the lee of some of the higher peaks such as near Schroon Lake, NY. As the day progresses, cyclonic flow will linger and help maintain a thin layer of shallow clouds such that mountains remain obscured, slowly improving from west to east as top-down drying occurs. Only as the weakening upper level low departs into southern Maine or Gulf of Maine, much of western portions of northern New York will trend sunny while clearing remains limited to late in the day in much of Vermont. The cloud cover will lead to only a small variation in temperature from sunrise to sunset again as in recent days. Areas that see a longer period of sunshine such as in the St. Lawrence Valley should be several degrees warmer, where highs will approach 70 degrees.

KEY MESSAGE 2: The main forecasting challenge mid-week will be related to low clouds and fog, particularly Wednesday morning. The air mass looks a little too warm to be dealing with frost potential, with above normal 850 millibar temperatures near 50 degrees requiring an extremely strong subsidence. We will have seasonably moist air still in place following the early week rain and humid conditions, and boundary layer winds will be quite light as deep layer ridging moves overhead. This is a near-ideal setup for temperatures to drop well below crossover values. And as a result, widespread patchy and dense valley fog is likely, especially given how long our nights are this time of year.

Aside from some higher altitude clouds, a tranquil period Wednesday into Thursday is expected as temperatures verge on unseasonably warm. Based on the latest blend of models, high temperatures in the lower elevations across Vermont and the Champlain Valley on Thursday will likely be in the 75 to 80 range. This would put the daily record high at Montpelier in some jeopardy (about a 20% chance of at least tying the current record from 2002). One other notable aspect on Thursday will be modest southerly/southwesterly channeled flow. Have boosted winds on Lake Champlain, with soundings showing favorable conditions especially in the morning hours when sustained winds could be above 20 knots. Likewise, have increased wind gusts in the wide valleys with potential for 30+ mph values. An approaching cold front and the increased flow out in front of this system later in the day points to seasonably stronger winds in the St. Lawrence Valley, approaching 40 MPH in a reasonable higher end scenario. Given climatology, sustained winds look marginally strong in this area but gusts will not be impactful.

KEY MESSAGE 3: A weak cold front looks poised to bring scattered showers to the region late Friday afternoon and Friday night. The lack of thermal gradient on the back side of the cold front will limit overall vertical ascent which will likely bring just a round of light rain to the region. High pressure will build into the region Saturday morning with clearing skies expected through the day with light winds. Another round of rainfall looks possible on Sunday as a low pressure system moves off the Virginia coastline and up the east coast. This system will be significantly more transient that this past Nor'easter which makes the window of rainfall much smaller. There remains a lot of uncertainty regarding the track of this low pressure system but the trends have been further south and east. Some correction in low track is expected over the next few days but Sunday could be on the wet side if the low tracks further inland over the weekend. Thereafter, high pressure will build back into the region for early next week with seasonally cool temperatures expected.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday...Widespread MVFR to localized IFR ceilings continue this afternoon as a Nor'Easter remains off the east coast. We should see a gradual decrease in ceiling height by 21Z as flow becomes more northerly with a sharper decrease in ceilings after 00Z. The idea is that most places drop to 200 to 600 ft overnight with only gradual improvement back to MVFR conditions expected by 16Z on Tuesday. Winds will remain light out of the north during this timeframe. Scattered showers this afternoon may bring a brief reduction in visibility but no significant obscurations are anticipated at this time.

Outlook...

Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. NO SIG WX. Thursday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Friday: Mainly VFR, with areas MVFR possible. Chance SHRA. Friday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Saturday: VFR. NO SIG WX.

BTV WATCHES/WARNINGS/ADVISORIES

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