339
FXUS61 KBTV 051926
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
326 PM EDT Fri Jul 5 2024

.SYNOPSIS...
Isolated showers and storms will continue tonight, and then
become more widespread Saturday morning. After brief drying,
some more showers and storms are likely to develop Saturday
afternoon, especially over Vermont. Drier days are forecast for
Sunday and Monday although remaining humid at the ground and
warm. Another round of showers and thunderstorms likely late
Tuesday into Wednesday along a cold front passage. Slightly
cooler and less humid air returns midweek.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 319 PM EDT Friday...BTV has managed to hit 90 for a second day
in a row now. A subtle upper trough and plenty of warm, moist air is
supporting some isolated convection across the region. Some dry mid-
level air impinging across the area is helping to limit extent, and
lack of deep layer shear is keeping everything garden variety
without much entrainment of that mid-level dry air. There won`t be
much change to the forecast tonight. There may be some fog due to
lowering surface pressures, light wind with high moisture, and some
rainfall. The primary fog areas will be the favored valleys and
wherever rain falls today. Lows ranging lower 60s in the Dacks and
Northeast Kingdom, and mid 60s to lower 70s across the rest of the
forecast area.

For tomorrow, rounds of showers and storms will be the theme. A
surface trough presently over Kentucky will lift northeast. With
accelerating southwesterly flow and even richer moisture, showers
and thunderstorms could occur even overnight. Then, a vigorous vort
max rounds a negatively tilted upper trough. Alongside the activity
from Kentucky, this appears to start secondary development of low
pressure. High resolution guidance is now depicting a healthy swath
of rain lifting into the region between 6 AM and Noon. Some rain
could be locally heavy as this is tied to the warm front with 1.75
to 2 inch PWATs. This will lift northeast, and then some relatively
drier air will filter in the region. The broader extent of rain will
likely suppress heating. So high temperatures have been lowered for
tomorrow, and are now mainly in the low to mid 80s, though some
upper 80s may still take place in the Connecticut River Valley. With
the high humidity still in place, there may still be some heat
indices in the lower 90s there tomorrow.

Showers and thunderstorms will fire later in the day, but mid-
level lapse rates will be poor, and there appears to be dry mid-
level air behind the morning activity. This may hamper updrafts
combined with the cooler surface temperatures now expected. With
shear in the 55-60 knot range at 0-6km, it appears likely to
destructively interfere with storms. Still, additional heavy
rain may take place in shower activity. Combined with the
morning activity about 0.33 to 0.75" is broadly expected, but a
swath up 1.50" is likely. The highest chance will be across
Bennington and Windham County where the HREF probabilities of
exceeding 1.50" in 24 hours to be about 30-50 percent, while it
is generally less than 30 percent in Rutland and Windsor County.
Given flash flood guidance in southern Vermont is relatively
high due to being somewhat dry as of late, it is possible that
the area can manage the rain. But we`ll keep an eye. Conditions
remain humid, and so temperatures will generally stay in the 60s
Saturday night with some isolated showers in the upper trough
still.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
As of 319 PM EDT Friday...As mid-level trough and strong mid-upper
jet depart to the northeast of the region on Sunday, expecting
gradual 700-500mb height rises with Sunday being the drier of the
two weekend days. Indicated just a 20 percent chance of an early
morning shower in n-central/nern VT with departing mid-level trough
axis, followed by mostly sunny and warm conditions areawide. Valley
highs will generally reach the 83-88F range. Little overall
change in dewpoints, with very humid conditions continuing
(dewpoints in the upper 60s). Weak high pressure builds in
Sunday night with a humid night expected. Should see some patchy
fog overnight with lows only dipping into the mid-60s, except
near 60F for the northern Adirondacks and far nern VT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 319 PM EDT Friday...Broad mid-upper level trough and cyclonic
flow returns to the Great Lakes and Ohio Valley for the mid-week
period next week, with a continued very warm, humid air mass with
S-SW low-level flow across NY and New England. Appears that
precipitable water values will remain above climo averages, with PW
values of 1.50-1.75" likely for Tuesday and Wednesday. This should
be our most favorable period of mid-level/large-scale forcing as a
shortwave trough progresses through the region from W-E per 12Z GFS
and ECMWF deterministic forecasts. Have indicated 60-70% PoPs late
Tuesday into early Wednesday areawide, with a chance for embedded
thunderstorms given low-moderate CAPE values. Mid-level lapse rates
aren`t very impressive at this early stage in the forecast, but sfc
temperatures near 90F and hot PBL conditions may be sufficient to
support a few stronger thunderstorms late Tuesday into Tuesday
evening, and we`ll need to continue to monitor that potential in the
coming days. Any thunderstorms would also have the potential to
bring brief heavy rainfall. Should see a slight cooling trend
Wed/Thu with highs in the low-mid 80s. Current trends indicate
lesser precipitation chances for the late Wednesday through Friday
time frame.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Through 18Z Saturday...Mainly VFR conditions are expected, but
short intervals of MVFR or IFR possible depending on isolated
shower development. The chance for a thunderstorm impacting a
TAF terminal appears low and have only mentioned VCSH for now.
The precipitation forecast is tricky, with several atmospheric
impulses maintaining the potential after sunset. Tried to
depict VCSH mainly where there is at least moderate confidence
in activity near a terminal. Winds are currently variable across
the region, and will become north to northeast at KPBG, KMSS,
and KBTV, while remaining light and variable elsewhere. Some fog
may develop overnight, which will depend on rainfall. For now,
have highlighted 4 or 5 SM at KEFK, KSLK, and KMPV. With clouds,
it will not be radiation fog, but mainly a function of surface
relative humidity and possible rain. A broader swath of rain
will lift northeast between about 08z and 15z. This will have
embedded heavy rain and thunder, but impacts to visibility are
generally not shown in TAFs for now. Ceilings will lower with
this batch of rain down to 1500-3000 ft agl. Some improvement
will take place as rain shifts east about 15 or 16z and 5 knot
winds become south to southeast, except likely east or northeast
winds at KPBG and KMSS.

Outlook...

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

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Haynes
SHORT TERM...Banacos
LONG TERM...Banacos
AVIATION...Haynes