FXUS61 KBTV 181735
AREA FORECAST DISCUSSION
National Weather Service Burlington VT
135 PM EDT Thu Jul 18 2019
An active period of weather is expected across the North
Country beginning Friday through Saturday. Mainly dry weather
is expected today with temperatures warming into the mid to
upper 80s with comfortable humidity levels. Humidity increases
Thursday night with hot and humid conditions expected on Friday
and Saturday. Chances for thunderstorms exist both Friday and
Saturday. Any storms that do develop on Saturday have the
potential to be strong to severe. More seasonable weather
returns by early next week.
.NEAR TERM /THROUGH FRIDAY/...
As of 134 PM EDT Thursday...No changes needed with this update.
Previous Discussion...Thursday is still looking like a pleasant
day across the North Country with high pressure mostly in
control. Early morning fog will mix out by sunrise leaving
mostly sunny skies for much of the area. Residual moisture
across southern New England/NY will advect northward on return
southerly flow. This will increase cloud cover mainly across
Rutland/Windsor counties. Elsewhere skies will be mostly sunny
with passing high level clouds.
Overall chances for precipitation will be minimal with the best
chances across northern New York. CAM models are in good agreement
on area of showers developing due to surface convergence with the
lake breeze off Lake Ontario and southeasterly flow over the Tug
with storm(s) moving northeastward into southern St Lawrence and
Franklin counties late Thursday afternoon. With real lack of
forcing, and a well defined cap at 700-600mb, vertical development
of these storms should be limited. Any storms that do develop will
dissipate towards sunset with loss of daytime heating.
High pressure will slide eastward Thursday night as southerly flow
increases across the area. PWATs begin to increase during this time
frame which will keep nighttime temperature up. This will be the
first of several nights with low temperatures near 70 for the
Champlain/St Lawrence valley and mid/upper 60s elsewhere. With fast
zonal flow aloft, pieces of shortwave energy will move across the
area Thursday night/Friday. Models indicate decaying convection will
enter our western northern New York zones by Friday morning. This
residual precipitation and cloud cover may limit the initial extent
of daytime heating but expecting good recovery during the daytime
hours with temperatures still warming into the upper 80s to low 90s.
With dew points in the low 70s, heat indices will be in the upper
90s. The chance for an afternoon thunderstorms still looks possible
with plenty of CAPE (~1500-2000 J/kg) and moisture, however shear is
marginal and mid-level cap and dry air will limit both vertical and
areal extent of storms.
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 458 AM EDT Thursday...The main concerns for the end of the week
will be heat and humidity, followed by the chance for strong to
severe thunderstorms on Saturday.
Very warm and muggy conditions will persist through the short term
as we remain on the periphery of a heat ridge centered to the south
and east. 925mb temps of 24-27C indicate highs will at least
approach 90 across much of the North Country, with the wider valleys
likely topping out in the lower to mid 90s. This combined with
dewpoints in the 70s will make for dangerously hot conditions, with
heat index values around 100F. Heat advisories look likely, but at
this time only a few scattered locations are expected to exceed heat
warning criteria. Have therefore held off on any Excessive Heat
Watch. There won`t be a lot of relief Saturday night as we`ll have
another muggy night with lows in the upper 60s and lower 70s.
The other issue for Saturday will be the potential for convection.
This is less certain than the heat concerns, as model guidance is
showing significant differences in placement of precipitation. While
moisture and instability will be abundant (both the NAM and GFS have
CAPE values 2500+ J/kg), 18/00z NAM now has a surface frontal
boundary and upper jet located well to our north. The lack of this
lifting mechanism combined with a substantial cap has resulted in
the NAM producing absolutely no precipitation across the region
Saturday or Saturday night. Meanwhile, the 18/00z GFS has the weak
boundary and upper jet located just north of the international
border Saturday and Saturday night, along with a much less
substantial warm layer aloft. Hence, it develops convection across
the region Saturday afternoon and evening. If the GFS holds
true...deep layer shear of 30-45 kt indicates the potential for
strong to severe convection, capable of producing damaging wind
gusts and heavy rainfall. Please stay tuned for later forecasts as
hopefully subsequent model runs will come to a consensus on the
placement of convection.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 458 AM EDT Thursday...Cooler and drier air will finally return
next week as a cold front will push across the region on Sunday.
High PWATs/CAPEs indicate the potential for showers and
thunderstorms as this front moves through, with central and southern
sections of our forecast area seeing the highest chances due to
favorable timing of the frontal passage. Highs will be in the mid
80s to around 90. The rest of the week will see a return to more
normal temperatures behind the front. The airmass will be drier as
well. However, we`ll remain under cyclonic flow as an upper low
pinwheels over eastern Canada, which will keep at least a slight
chance of showers around through much of the week.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday...MVFR ceilings are hanging on at MPV and RUT
this afternoon, otherwise VFR conditions areawide. Isolated
shower possible across northern New York this afternoon with
brief visibility/ceilings reductions. Towards 12z tomorrow
clouds will begin to thicken and lower as precipitation chances
increase. Winds will increase out of the south/southeast this
afternoon between 5-10 kt with NE winds at KMSS around 5-8 kt.
have VCSH mentioned headed into tomorrow afternoon as chance for
showers increases across the area.
Friday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Saturday: VFR. Chance SHRA, Chance TSRA.
Saturday Night: VFR. Chance SHRA, Chance TSRA.
Sunday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance
Sunday Night: VFR. Slight chance SHRA.
Monday: VFR. Chance SHRA.
Monday Night: VFR. Slight chance SHRA.
Tuesday: VFR. Slight chance SHRA.