textproduct: Burlington

WHAT HAS CHANGED

As of 322 AM EDT Saturday...

Increased probability of precipitation and associated precipitation amounts over central and southern Vermont tonight into Sunday.

KEY MESSAGES

As of 322 AM EDT Saturday...

1. Several rounds of showers and embedded thunderstorms expected tonight through Sunday night across our forecast area with marginal risk for severe on Sunday.

2. Drier and cooler with patchy frost possible on Monday night, followed by warmer and more unsettled weather by mid to late this upcoming week.

DISCUSSION

As of 322 AM EDT Saturday...

KEY MESSAGE 1: Early morning GOES-19 Night Fog product is indicating areas of patchy dense valley fog in climo favored areas as temps have dropped into the mid 30s SLK to lower 50s in the CPV. Coolest night of the fall season acrs most of our cwa under 1020mb high pres centered over central NY attm. Sfc high pres wl shift off the New England Coast this morning with developing southerly flow at all lvls expected to develop by this aftn. GOES-19 mid lvl water vapor imagery shows potent s/w energy, deep moisture, and associated convection over the Ohio Valley which is progged to angle toward our cwa tonight into Sunday. Moisture advection wl increase quickly on deep south to southwest flow with pw values surging btwn 1.50 and 1.75 by 12z Sunday. In addition, CAM show developing elevated instability parameters under developing waa tonight acrs our central and southern cwa. 00z HREF mean qpf btwn 06z-12z shows 0.25 to 0.50" acrs central/southern VT, while only a few hundredths to 0.20" near the International Border. Based on this and a shift northward in both CAMS and global guidance, have increased qpf and pops, especially acrs central and southern VT zones and portions of the High Peaks tonight. Temps warm into the 70s today and only cool into the mid 50s to mid 60s tonight with developing clouds/winds and precip anticipated with some increase in humidity levels by 12z Sunday.

For Sunday, SPC has expanded the marginal risk for severe to the International Border, which wl be conditional on how much clearing/instability can develop ahead of approaching s/w and cold frnt. Deep layer shear is favorable with values in the 40 to 55 knots range, but instability is questionable based on how much sfc heating can occur. Thinking strong mid lvl wind field may shear convective updrafts and limit vertical growth, especially with sfc based CAPE values only in the 800 to 1200 J/kg range. If more sfc heating/instability can develop the potential for strong to severe thunderstorms would increase acrs our cwa on Sunday aftn/evening. Additional showers and embedded thunderstorms are expected btwn 00z- 09z Monday as potent northern s/w energy drops toward the SLV. Better instability is shifting into eastern New England, so potential for svr aft 00z is limited. Temps warm into the mid 70s to lower 80s on Sunday and cool back into the lower 40s to lower 50s by Monday morning. Based on cyclonic northwest flow and associated caa, expect clouds to linger, especially acrs the upslope areas of the northern Dacks and central/northern Greens on Monday morning, before high pres clears the skies by afternoon.

KEY MESSAGE 2: A progged 1026mb high pres builds directly overhead by 00z Tuesday with mostly clear skies and light winds anticipated overnight. This wl allow for temps to quickly fall back into the upper 20s SLK to mid/upper 40s CPV by 12z Tuesday with areas of patchy frost and fog likely. Our fast flow aloft prevails for Tues thru most of the upcoming week with increasing chances for precip on Tues evening and again for mid to late week. The system for late Tues is looking less and less impressive as dynamics are sheared apart in the fast westerly flow aloft and best moisture is falling apart as it encounters very dry air from departing high pres. Have trimmed back pops from likely to chc with this forecast package. Better moisture/dynamics arrive Thurs associated with pw values near 1.5" and some weak sfc based instability angling toward our cwa ahead of weak cold frnt. After below normal temps on Tues, values should warm back into the 70s to near 80F for Weds/Thurs, before slightly cooler air arrives by next Friday. Lows generally at or above normal after Tuesday due to the lack of strong sfc high pres.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Through 06Z Sunday...Aviation challenge is timing and areal coverage of fog and associated LIFR/VLIFR this morning. Latest GOES-19 fog product shows fog development near SLK and just starting in the Winooski River Valley near MPV. Highest probability (90-100%) of IFR or lower conditions is at SLK/MPV with likely (65-75%) at EFK and chance (30-40%) at BTV/MSS. Have used prevailing group at SLK/MPV/EFK for fog, tempo at MSS and just vcfg at RUT/BTV for now, as confidence is too low to mention IFR attm with light terrain driven winds under 5 knots. Winds become southerly at 5 to 10 knots with localized gusts 14 to 20 knots expected at BTV/PBG and MSS by 15/16z. Ceilings begin to lower toward MVFR conditions after 00z this evening ahead of our next system.

Outlook...

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

MARINE

As of 322 AM EDT Saturday...

A Lake Wind Advisory is in effect for this afternoon and tonight for developing south winds. Expect south winds 5 to 10 knots this morning to increase 15 to 25 knots by mid afternoon with localized gusts up to 30 knots possible near sunset. These gusty south winds will continue overnight into Sunday at 15 to 30 knots with a few higher gusts likely. Wave build 1 to 3 feet by this afternoon and increase 2 to 5 feet overnight.

BTV WATCHES/WARNINGS/ADVISORIES

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