Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
934 PM EDT Thursday may 28 2015
a ridge of high pressure will build into the region tonight and
will remain over the north country through Friday night. A strong
cold front will move slowly southeast from Canada on Saturday
afternoon and overnight. Another ridge of high pressure will bring
drier cooler weather for the beginning of next week.
Near term /until 8 am Friday morning/...
as of 934 PM EDT Thursday...isolated showers still exist across
the northern half of Vermont tonight and have adjusted the
forecast to account for this. Thus have slowed the exit of
precipitation chances until after midnight as well as the clearing
across Vermont. Remainder of forecast in good shape.
Short term /8 am Friday morning through Saturday night/...
as of 430 PM EDT Thursday...surface high pressure builds over the
region for Friday and Friday night. Warm temperatures continue to
be 10 to 15 degrees above seasonal normals. On Saturday and into
Saturday night the weather becomes more active as a strong cold
front will approach from the northwest. GFS and European model (ecmwf) have slowed
down with this feature and bring the front through after 00z
Sunday now. The timing of this front will limit severe potential.
Precipitable waters will be high as a feed off the Gulf streams northeastward
along the frontal boundary. Only modest lapse rates
though...pretty weak instability...though some cape does show up
on the sref and NAM. Strong shortwave trough passes well north of
our area...feel stronger storms may coincide and remain north of
the international border. Will continue to monitor potential for
severe thunderstorms Saturday afternoon and overnight.
Long term /Sunday through Thursday/...
as of 136 PM EDT Thursday...the overall pattern in the extended
remains the same from the previous forecasters line of thinking
for Sunday through Wednesday of next week. The line of showers
from the advancing cold front will push through the area on
Saturday and so there will only be a few lingering showers mainly
in the southern portion of Vermont as the front will likely be
aligned in southwest to northeast over central Vermont. Nearly all
the instability will be gone as the atmosphere will be stabilized
behind the front so the decent shear over Canada will all be well
north of any instability.
After the lingering Showers Pass through the area Sunday morning,
high pressure will build into the forecast region resulting in
drier and cooler weather next week. Expect daytime temperatures to see a
warming trend through the week with sunday's highs in the 60s and
by Wednesday we will see a return of maximum temperatures in the upper 70s
with the potential for 80s in the valleys. Overnight lows Monday
behind the front will see the best chance for some light frost as
temperatures will drop into the lower 40s to upper 30s. Right now the
forecast doesn't include any mention of frost because temperatures will
hover above 36 degrees on Monday. From there we will see the
gradual return to near normal overnight lows through the early
portion of next week.
Aviation /02z Friday through Tuesday/...
through 00z Saturday...still have leftover MVFR stratus around at
slk and mpv, but tafs should go VFR in short order. Outside of
some radiational fog/mist at slk mpv and mss, VFR will prevail
through the rest of the taf period.
Deep-layer subsidence now over St. Lawrence Valley will clear out
any leftover stratus through 03z, with all tafs going VFR for a
brief period. Aviation focus then shifts to potential for
IFR/LIFR mist/fog. At slk, present T/dew point spread is 3 degrees and
clearing skies should allow for temperatures to fall below crossover
readings by 03z. Given wet ground from today's earlier
showers/storms and aforementioned narrow T/dew point spread, feel best
shot at LIFR fog is at slk and i've shown such in tempo group.
I've also indicated 1-3 sm br at 06z at mpv as clearing looks to
be a bit later. Northwest winds will go light/variable.
Any mist/fog Burns off quickly once insolation begins into the
early morning hours, with VFR/few fair weather cumulus dotting the tafs
thereafter. Light and variable winds initially, becoming southerly
under 10 kts later in the day as center of surface high shifts
off the southern New England coast.
Outlook 00z Saturday through Tuesday...surface high pressure with VFR
conditions continue into Friday...before another front with more
storms occur on Sat afternoon into Saturday evening. Some patchy
fog/br is possible at mpv/slk and Rutland on Saturday morning.
These storms will contain localized gusty winds...brief heavy down
pours...and frequent lightning. Look for breezy south to southwest
winds at 15 to 25 knots to develop ahead of approaching surface
boundary on Saturday. A wind shift to the northwest will occur
behind the boundary on Sunday. Monday will be mostly dry with VFR