textproduct: Burlington

WHAT HAS CHANGED

As of 255 PM EDT Saturday...

No significant changes made with this forecast package.

KEY MESSAGES

As of 255 PM EDT Saturday...

1. Showers and embedded rumbles expected Sunday and again on Tuesday, but the probability of highly impactful or significant weather is less than 5% at this time.

2. A period of showery weather is expected mid to late week, with a emphasis on Wednesday night into Thursday.

DISCUSSION

As of 255 PM EDT Saturday...

KEY MESSAGE 1: Water vapor imagery shows deep dry layer associated with high pres both aloft and at the sfc wl cont to shift east of our cwa tonight, as llvl waa develops on increasing south/southwest flow. The combination of warm and moisture advection, along with a weak embedded disturbance over the northern Great Lakes and associated pocket of mid lvl moisture wl approach our International Border area overnight with a 30-40% probability of showers. Upstream radar does indicate some scattered activity angling toward our northern zones tonight. In addition, 925mb to 850mb south to southwest winds increase 30 to 40 knots overnight, which combined with some mid lvl clouds wl limit fog development, maybe some patchy fog in the CT River Valley. Temps with better mixing and some mid lvl clouds hold in the upper 40s NEK to lower 60s parts of the CPV.

Sunday-Sunday night fcst focus wl be timing and areal coverage of showers with a rumble of thunder. Latest trends continue to support highest 60-75% pops acrs the northern Dacks into northern/central mtns of VT on Sunday with 15 to 30% over southern areas. HREF indicates 60 to 80% prob of QPF >0.10" near the International Border, while only 10-30% prob over central-southern VT on Sunday. HREF suggested 40-60% of QPF >0.25 northern sections and <15% over southern areas, highlighting the north to south precip gradient expected and the associated pop configuration. The RRFS mean QPF is btwn 0.10" to 0.25" north to <0.05" south. Little has changed in the overall synoptic setup with embedded 700-500mb vorticity in the fast confluent flow aloft riding along a sfc cold frnt dropping southward, while best instability and deeper moisture is displaced to our south. As flow becomes northerly behind the boundary with lingering 200-400 J/kg of CAPE and moisture thru 700mb, feel a period of favorable conditions for upslope rain showers are likely btwn 00z-04z Monday. Have used the upslope climo tool to highlight this potential in the grids, which could include the eastern CPV associated with developing blocked flow. After midnight sounding data indicates a sharpening and lowering subsidence inversion with moisture trapped below 900mb, supporting areas of low stratus clouds and fog, especially in favorable upslope regions/mtns with more fog possible in the deeper valleys. Could be widespread based on latest trends. Highs Manley in the 70s again on Sunday with lows upper 40s to upper 50s by Monday morning. By Monday, a very dry airmass is overhead with PW values <0.50, but lingering low clouds/fog could prevail thru 10 AM based on sounding data. Once the clouds burn off a beautiful day withe plenty of sunshine and comfortable temps are expected.

Monday night and Tuesday...Pattern begins to shift again as strong mid/upper lvl ridge tries to expand northeast toward our cwa, while closed cyclonic circulation remains anchored over eastern Canada. This produces a fast confluent flow aloft with a sharpening southwest to northeast temps/moisture gradient over the Mid Atlantic/NE CONUS. As short wave energy aloft rides along this strengthening llvl boundary an area of moderate rain with embedded heavier thunderstorms is likely. However, placement of this activity and associated axis of heaviest precip has a very low predictability at this time, given large spread in guidance. Latest guidance shows best instability progs along and south of a Watertown to Albany line, which would be a favorable track for cluster of showers with embedded thunderstorms. NBM shows 60-70% prob of QPF>0.25" south of a MSS to BTV to LEB with just 20 to 35% over the NEK. The 25th percentile is 0.10", while the 75th is 1.0" with mean values btwn 0.25 to 0.75" mostly south of MSS to BTV to LEB line on Tuesday. For now have gone with NBM with highest pops acrs our southern cwa and less over the NEK of VT. Highs stay near seasonable levels.

KEY MESSAGE 2: During the middle and end of the week, an upper level trough will gradually shunt a ridge over the Midwest and Mid- Atlantic to the south, preventing any heat from building into the region. The last of a couple ridge runner type features will move through Wednesday night into Thursday, likely bringing an area of heavy rain with convective enhancement from elevated instability. The warm sector will not be fully established over the area so limited surface instability should limit the threat for severe weather. However, increasing PWATs and good dynamics will cause an axis of heavy rain to develop, though its exact placement is uncertain. The flood threat looks low at this point but will continue to be watched. For any flash flooding to occur, the band on Wednesday night into Thursday would likely have to occur in the exact location as the heavier bands in the beginning of the week for a chance. NBM probabilities of 2+ inches of rain are up to around 20 percent for southern Vermont, the part of the region that has the highest probability of seeing the heaviest rain. Surface high pressure gradually builds into the region for late week and next weekend, and it is potentially shaping up to be another winner of a weekend.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00Z Monday...VFR conditions will prevail through almost the entire next 24 hours. The exception will be tomorrow morning when some scattered showers should move through MSS, potentially dropping the visibility to MVFR for a brief period of time. However, thunder is not expected. Southerly winds will prevail this evening, generally between 5-10 KT. Winds become more westerly tonight and could gust up to 20 KT at MSS. LLWS will develop at most terminals this evening and will continue for most of the night, but it should end by 14Z. Isolated to scattered showers with a couple embedded thunderstorms will move through tomorrow afternoon along the international border, which could cause brief visibility reductions to MVFR/IFR and erratic winds.

Outlook...

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

MARINE

As of 255 PM EDT Saturday...

Have issued Lake Wind Advisory for tonight, based on increasing south to southwest winds 15 to 25 knots, especially the broad/open waters around midnight tonight. Given the warm water temps helping to increase mixing heights, feel as low level jet of 20 to 25 knots develops with channeled southerly flow, a few gusts up to 25 knots will be likely overnight on Lake Champlain. Wave will build 1 to 3 feet overnight into Sunday morning.

BTV WATCHES/WARNINGS/ADVISORIES

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