FXUS61 KBTV 251925
Area Forecast Discussion
National Weather Service Burlington VT
325 PM EDT Sun Jun 25 2017
Unsettled weather will continue across the region throughout the
entire week with a daily threat of showers and a few thunderstorms.
Some of the rainfall may trend heavy, especially later in the week
as a more humid airmass moves into the area. Temperatures will
remain close to seasonal early summer norms through the period.
.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 325 PM EDT Sunday...Scattered showers and a few heavier
thunderstorms continue across the area this afternoon in advance
of of a vigorous shortwave to the immediate north of Lake
Ontario. A few of the cells have produced small hail and gusty
winds, which is not surprising given relatively low freezing
levels near 9 kft and a near dry adiabatic sub-cloud layer. The
shortwave feature will progress bodily east across the northern
half of the area this evening when best threat of scattered
showers/isolated storms occur, then exit east overnight with
coverage waning. Lows a blend of available guidance showing
values mainly in the 50s.
More active weather still on tap for Monday as yet another strong
shortwave drops into the central Great Lakes area. Low level surface
trough boundary connecting today`s shortwave (then acoss the
Canadian Maritimes) to the Great Lakes feature will serve as focus
for low level convergence and additional showers/isolated
thunderstorms by tomorrow afternoon. Best coverage to occur during
peak heating hours of noon to 6 pm or so before covering slowly
wanes into the evening and especially overnight hours. Low to mid
level lapse rates are poorer than today and with cooler bondary
layer temperatures per 925-850 mb progs updraft strength in
covective cores will not be as robust. Thus no strong to severe
storms are expected. Highs tomorrow mainly from the mid 60s to lower
70s with lows Monday night from 45 to 55.
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 325 AM EDT Sunday...not much change in the overall
forecast for this period - still more unsettled weather. The
first half of Monday night will have a weak shortwave push
across the region. Models all show some disorganized convection
associated with the shortwave lifting southwest to northeast
through 08z, so have aligned the PoPs with a blend of some of
the hi-res models to show the evolution. One little feature to
see if it comes to pass will be the potential for a little bit
of lake effect showers come off Lake Ontario into the St
Lawrence Valley area first thing Tuesday morning thanks to some
cooler air aloft. A stronger upper trough approaches the area
Tuesday. Although there will be plenty of clouds and
temperatures on the cool side (upper 60s to lower 70s), the
temperatures aloft (around 500mb) are rather cold (near -22C),
so that should result in some instability to produce another
round of afternoon/evening showers and perhaps a few t-storms.
With the cold air aloft, wet bulb zero heights are quite low
(7000-8000ft), so chance for some small hail in any deeper
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 325 AM EDT Sunday...00z model suite still pointing toward
a continued lengthy stretch of unsettled weather. Not that it
will be cloudy and rainy continuously, rather we will see short
dry periods of 12-18 hours followed by 12-18 hour long periods
where scattered showers and t-storms will be around. At upper
levels, we will be in a region of fast mainly zonal (west to
east) flow with embedded shortwaves zipping through. It will be
these shortwaves, combined with daytime heating, that will be
the primary triggers for the convection. Given the uncertainty
in timing these shortwaves, it`s best to take a bit more of a
general approach to the forecast and use a model blend for day-
to-day PoPs. At this point, I don`t see anything indicating any
widespread severe weather through Friday.
GFS and ECMWF continue to show a more significant upper trough
develop to our west on Saturday, resulting in a deeper southerly
flow which brings in some very moist air (precipitable water
closes in on 2.0"). If this does come to pass, we could have
some hydro related issues by then, especially if we have enough
convective activity repeat across the same areas during the
week. Just something to watch at this point.
In general, temperatures will be slightly below normal through
much of the week though trending closer to normal late week as
the more southerly flow develops. Again, stuck with model blend
for temperatures, and there is considerable error potential if
we end up having much more sunshine than currently expected.
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Through 18Z Monday...Mainly VFR through the period with
scattered showers and thunderstorms through early evening.
Shortwave pushing across the area this evening driving scattered
showers and thunderstorm activity across the area. No severe
weather is expected though a few of the more robust storms could
produce small hail, gusty winds into the 30-40 mph range,
enhanced low level turbulence and brief MVFR/IFR conds.
Coverage of storms to wane this evening and overnight with loss
of surface heating and as shortwave exits east. Winds west to
southwesterly 6 to 12 kts and occasionally gusty into the 15-20
kt range through sunset, abating to light overnight. After 12Z
Monday VFR continues, but with an increasing threat of showers
and thunderstorms once again as we approach the 18Z time frame.
Given this will occur toward the very end of this forecast cycle
have omitted specific mention at this point. Winds continue
light west/southwesterly 5 to 10 kts.
Monday Night: VFR. Chance SHRA...Slight Chance TSRA.
Tuesday: VFR. Chance SHRA...Slight Chance TSRA.
Tuesday Night: VFR. Slight Chance SHRA...Slight Chance TSRA.
Wednesday: VFR. Chance SHRA...Slight Chance TSRA.
Wednesday Night: VFR. Slight Chance SHRA.
Thursday: VFR/MVFR. Likely SHRA.
Thursday Night: MVFR. Likely SHRA...Slight Chance TSRA.
Friday: VFR/MVFR. Chance SHRA...Slight Chance TSRA.