Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
1011 am EDT Thursday Oct 2 2014
variable clouds will persist today into Friday as low
pressure departs east off the southern New England coast and weak
high pressure remains draped across our area. A strong early season
cold front will swing into the region for Saturday bringing a
widespread and welcomed soaking rainfall. Behind this front
temperatures cool back to more typical early October values for
Sunday into Monday of next week.
Near term /until 6 PM this evening/...
as of 1006 am EDT Thursday...have made several changes to forecast to
better capture latest cloud trends and temperatures. Current visible satellite pic
shows clring skies across most of northern New York into northern
Vermont...including parts of the cpv. Local btv 4/6km soundings Show
Low level moisture decreasing quickly by late this morning...with some
fair weather cumulus clouds developing this afternoon from surface heating. Will
show clouds dissipating this morning quicker in grids and
increased temperatures across the slv/northern dacks and into Vermont...based on
better surface heating from more sun. Temperatures will range from the l/M 60s
central Vermont mountains to l70s slv...with upper 60s likely here in the
Prior discussion...a burdensome...albeit generally quiet weather
forecast on tap again today as weak high pressure remains across
our area while 500 mb upper low drifts slowly off the southern New
England coast. Most problematic will once again be overall
coverage of clouds...and degree to which they burn off through the
day which will ultimately govern temporal/spatial trends in
temperatures. As early fall sun angle continues to lessen day by
day...we are finding it increasingly difficult to burn off our low
stratus...case in point yesterday. Used a blend of 925-850 mb
and/or 850 mb model blended relative humidity forecasts which suggest variably/mostly
cloudy skies this morning will gradually thin to pc in most areas
by this afternoon. However...I must admit confidence is not great
that all areas will see clearing...especially with such light
winds through the planetary boundary layer. Indeed...looking at midday soundings you
rarely see such light winds through the troposphere...even by July
standards. In fact...rap/NAM/GFS profiles all show values at 10
kts or less all the way through the 20 kft level at some point
through the morning/afternoon hours across our area. So safe to
say airmass change is not expected. Precipitation chances essentially zero
north of Rutland/Windsor counties...perhaps a departing
sprinkle/very light shower far southeast through middle
morning...that would be about it. Temperatures a blend of
available raw model datasets...suggesting maximum values ranging
through the 60s...perhaps a spot 70 here or there in areas of the
St Lawrence/Champlain Valley which see more sun today.
Short term /6 PM this evening through Saturday/...
as of 348 am EDT Thursday...partly to variably cloudy skies then
return (or continue) tonight into first half of Friday as lower to
middle level flow turns southerly and lingering moisture is advected
back north across our area from the south/southeast. Did trend on
the more optimistic side suggesting at least some partial breaks
in the clouds...though this could be wishful thinking if you
believe some of the deterministic solutions literal. Low
temperatures 46 to 54...coolest east with highs on Friday 65 to
73...mildest west. Probability of precipitation none.
By Friday night southerly flow continues to gradually increase ahead
of a strong early season upper trough and attendant cold front
across the Midwest/Great Lakes states. Skies trending clear/pc in most
spots through the evening hours...but clouds should quickly return
by the overnight hours as frontal zone draws closer with
widespread showers/rain pushing into the slv after 4 am or so.
Temperatures should run a tad milder than prior nights by a few
On Saturday aforementioned frontal zone swings through the region
with a widespread and welcomed rainfall expected. Model blended quantitative precipitation forecast
suggest areal amounts should average between 0.5 and 1 inch area
wide. This will be the first significant precipitation for our area
in nearly two weeks and likely the heaviest since middle August. Given
such dry antecedent conditions Hydro concerns will be minimal. Some
gusty south to southeasterly flow also possible along and
immediately ahead of the frontal zone...but latest nam12 925 wind
forecasts suggest higher...more problematic gusts are less likely than
prior indications. As we draw closer to the event later today into
Friday...higher res WRF data may add more insight. Temperatures
will be cooler given clouds/pcpn...mainly upper 50s to low
60s...perhaps a few middle 60s far east.
Long term /Saturday night through Wednesday/...
as of 331 am EDT Thursday...large-scale middle-tropospheric regime
change toward broadly cyclonic flow aloft will be underway to open
the period. Center of large upper low will remain over the
northern plains/Great Lakes region. Thus...the north country will
be in west to west-southwest flow and result in an increasing
unsettled weather pattern as series of shortwave disturbances
pinwheel around longwave trough/low. The extended continues to
benefit from good agreement among 00z/02 global models with
primary differences being in timing individual shortwave troughs.
Strong cold front will still be pushing across Vermont Sat night.
Likely to low categorical probability of precipitation for eastern Vermont/Northeast Kingdom
with sharper taper down across the rest of the north country.
Moisture-rich airmass continues to precede the front...with prognosticated
GFS precipitable waters of 1.5" being about 200% of normal for early October. One
interesting aspect inherent in today's GFS/ec and NAM/WRF guidance
is a secondary wave low that develops along front near NYC and moves
northeast into NH/ME. Feature is strongest in the NAM/WRF...but
majority of guidance shows an increase in forecast quantitative precipitation forecast across
northeast VT/greens. Curious to see if that unfolds as prognosticated. Quantitative precipitation forecast
from this event probably more beneficial given how dry it's been. A
partly/mostly cloudy Sunday. High chance probability of precipitation for lake effect rain
showers in favored lake effect belts in northern New York but largely dry
First in a series of weak disturbances aloft then skirts across
northern New York Sunday night with slight chance/chance probability of precipitation there but
mostly dry for Vermont. As longwave trough retrogrades slightly
Tuesday...a better-defined shortwave moves up from the Ohio Valley
with probability of precipitation trending toward high chance by Tuesday.
Temperatures in the period start off a few degrees below normal
(lower 60s) but trending back to near normal by early next
Aviation /14z Thursday through Monday/...
through 12z Friday...flight categories continue to be highly
variable across tafs early this morning with ceilings as low as
LIFR interspersed with patchy areas of mist. Gradual improvement
toward VFR is anticipated by late morning as shallow low level
inversion evident in soundings mixes out. Though most sites will
be VFR tonight...question will be if any marine stratus can work
its way back north underneath ridging aloft as suggested by model
925 mb relative humidity fields. Have indicated potential for MVFR ceilings at
mpv and rut. Fog will likely develop again at slk. Winds continue
Outlook 12z Friday through Monday...
12z Friday - 00z saturday: VFR under high pressure.
00z Saturday - 12z saturday: mostly VFR. Marked increase in winds
leads to potential low level wind shear concern for mss and perhaps pbg late. Best
shot at overnight fog at mpv with winds being lighter there.
12z Saturday - 12z sunday: sharp cold front moves through the
north country. VFR with gusty south winds ahead of the
front...briefly lowering to MVFR ceilings/visbys in rain.
12z Sunday onward: mostly broken/overcast VFR conditions. Potential for
lake effect rain showers at slk but unlikely to lead to visibility
restrictions. Possible overnight LIFR/vlifr fog at mpv and slk.