939
FXUS61 KBTV 071431
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1031 AM EDT Sun Jul 7 2024

.SYNOPSIS...
Surface high pressure building east from the Great Lakes will provide
the North Country and Vermont with dry weather through Monday.
Humidity will be slightly more comfortable as well, while high
temperatures in the 80s to near 90 will persist. A weak frontal
boundary may provide some showers and thunderstorms on Tuesday, then
our attention turns to the potential for heavy rain Wednesday into
Thursday associated with the remnants of Hurricane Beryl.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 1030 AM EDT Sunday...No major changes with the morning
update. Minor adjustment were made to account for a localized
stratus deck in northern New York has yet to burn off. We are
also seeing the expected cumulus development occurring
throughout the CWA, but not expecting more than stray showers
with the mid-level cap.

Previous Discussion:
We`ve got a nice break from active
weather forecast for the next 36 hours as surface high pressure
builds east from the Great Lakes into the forecast area. Early
morning dense river valley fog will lift into some fair weather
cumulus today from midday through the afternoon, and while a
weak shortwave aloft lifts northeastward along the international
border this afternoon, soundings show a mid-level cap
persisting so not expecting much of anything. It`s not a non-
zero chance though that something very isolated could develop,
so have maintained some 5-10% PoPs along the northern tier
zones. Humidity will be slightly better today as well, despite
925mb temps around +21C supporting similar highs to yesterday in
the mid-80s to near 90. Afternoon dewpoints should fall into
the low 60s, compared to yesterdays low 70s, so we`ll knock down
the muggy meter just a little bit.

Afternoon clouds should dissipate to mainly clear skies again
tonight, setting the stage again for more dense river valley fog to
form. Lows will be slightly cooler than the previous night as well
with some mid 50s possible in the Adirondacks to low/mid 60s
elsewhere. Monday should be a beautiful start to the week with
abundant sunshine, dewpoints just a smidgen cooler in the upper 50s
to low 60s, and highs once again above normal in the mid-80s to
around 90.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 345 AM EDT Sunday...By Monday night, winds will shift to the
south as an upper level disturbance approaches from the Great Lake
with overnight lows generally in the 60s. Upper ridging starts to
break down on Tuesday as a positively tilted upper level trough
approaches from the Great Lakes. As such, shower and thunderstorm
chances do return on Tuesday. There remains plenty of timing
differences amongst the models on the timing of potential
convection. If they do come through at night, the threat for severe
weather will likely be greatly diminished. For now, have kept PoPs
at 40-50 percent chance category. Accordingly, WPC Day 3 Excessive
Rainfall Outlook (ERO) has stayed at the marginal risk category
(level 1 of 4) for now. The hydrologic situation does quite a bit
more concerning heading into Wednesday. More on that in the long
term discussion.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 345 AM EDT Sunday...A year ago, the North Country was dealing
with an unprecedented flood event on July 9-11. We are getting
increasingly concerned about a potentially significant hydrologic
episode right on the 1 year anniversary of last year`s flooding. To
be clear, there are important differences between July 2023 and July
2024. Last year`s flooding was not tropical in nature. But there are
also many similarities. According to the Northeast Regional Climate
Center data, much of our forecast area with the exception of Windsor
county saw 125-200 percent of normal monthly rainfall in June. And
July has been wet so far. Grounds are saturated and dry stretches
have been hard to come by. In coordination with the WPC and
neighboring offices, the Day 4 Excessive Rainfall Outlook (Wednesday
8 AM to Thursday 8 AM) was upgraded to Slight risk (level 2 of 4).
Bear in mind that Slight risk is 15-40 percent probability of
rainfall exceeding flash flood guidance within 25 miles of a point.
PWATs, which are already AOA 90th percentile, will be enhanced even
further past maximum of SPC sounding climatology due to the moisture
from Tropical Cyclone Beryl. PWATs of 2.3 to 2.5 inches are 3 to 4
standard deviations above normal. With slow-moving surface
boundaries and generally a lack of atmospheric forcing to push out
the tropical air mass, rounds of heavy rainfall and embedded
thunderstorms will greatly the risk of flash flooding given the
grounds are becoming saturated. The greatest sources of uncertainty
right now are the areal placement of the richest PWAT plumes and
timing of convection. It is certainly plausible that our region
escapes next week relatively unscathed. But it is important to be
prepared for the reasonable worst case scenario, which is for
scattered to numerous flash flooding if we do get repeated
rounds of heavy rainfall and storms to tap into the abnormally
moist atmosphere. Please stay up to date with the latest
forecast.

As we head into Friday and next weekend, a cold front should push
the richest PWAT plume (200+ percent of normal) into southern New
England and the mid Atlantic states which will allow for slightly
drier albeit still seasonably moist air mass to potentially give the
North Country a break from the rainfall. Some of the more
pessimistic guidance shows potential for the cold front to lift back
north as a warm front and bring the risk for more heavy rainfall
into the North Country next weekend. But that is a low probability
scenario at this time so generally went with a blend of guidance for
this portion of the forecast.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Through 12Z Monday...IFR fog at KMPV and unexpected IFR
ceilings at KMSS will both lift to VFR conditions within the
next 2 hours, where thereafter VFR will prevail at all sites
with just some FEW-SCT fair weather cumulus developing through
the day. Light and variable winds this morning will trend
southwesterly at 4-8kts from midday through the afternoon, with
the exception being at KPBG where the wind direction will be
more southeasterly due to the lake breeze. Skies trend back
towards SKC after 00-02Z, with another night of IFR fog likely
at KSLK, KMPV, and KEFK.

Outlook...

Monday: VFR. Patchy BR.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Chance SHRA, Chance TSRA.
Tuesday Night: VFR. Chance SHRA, Slight chance TSRA.
Wednesday: VFR. Chance SHRA, Slight chance TSRA.
Wednesday Night: Mainly MVFR, with local IFR possible. Chance
SHRA, Slight chance TSRA.
Thursday: MVFR/IFR conditions possible. Chance SHRA, Slight
chance TSRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Langbauer
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Lahiff