Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
831 PM EDT sun Mar 29 2015
a cold front moving east from the western Great Lakes will bring
a chance of rain and snow showers to the north country on Monday.
After a brief cool down Tuesday and Wednesday...a warming trend
will lead to temperatures in the middle 40s to low 50s by the end of the
Near term /until 6 am Monday morning/...
as of 808 PM EDT Sunday...satellite loop showing high clouds
moving into the region from the Great Lakes at this time. These
clouds are ahead of a cold front. Current forecast looks good at
this time...so no changes have been made.
Previous discussion from 350 PM EDT Sunday...tricky temperature forecast
tonight as we will start out with clear skies but at the same time
the pressure gradient will be increasing ahead of a frontal system
moving through Wisconsin this afternoon. Think the cooler readings
will be in eastern VT, especially nek where it will be in the
teens. Warmer to the west in the St.Lawerence valley which is
already under the influence of a strong pressure gradient and
gusty winds, so low temperatures west of The Greens and St.Lawrence
Valley will be mainly in the 20s with steady or rising temperatures
toward morning as a strong low level jet with 30 to 50kts of SW
flow at 850mb pushes into the region. There will be an increasing
clouds and a chance of snow showers after 06z in New York and toward
morning in VT, with decent qg forcing for ascent but not not much
moisture so expecting much in the way of accumulation.
Short term /6 am Monday morning through Tuesday night/...
as of 350 PM EDT Sunday...the first of two frontal systems will
be approaching northern New York in the morning but with the S-SW flow expect
the temperatures in the boundary layer to support any show showers in the
higher terrain mixing with rain in valleys by 13-16z. Models
suggest a brief dry slot aloft possible around that time as well
just ahead of the first front which should be reaching the
Champlain Valley around 18z or so. Steep low-level lapse rates and
even some low values of cape, so some gusty rain or snow showers
may accompany the cold front as it move through with winds
shifting around to SW-W. Temperatures during the day will warm into the
low to middle 40s under moderate and gusty south westerly flow of 25
to 30 kts with overcast skies. The southerly flow during the day
on Monday will support continued warming to near normal as 850
temperatures climb to -5c. Highs in the middle 40s in the valleys and upper
Winds will gradually shift from west to northwest with upslope
flow developing Monday night behind a secondary cold front. Temperatures
cool enough so that any rain showers will be changing to snow
showers. Froude numbers expected above 1 most of the persistent snow
shower expected at the summits and slightly on the Lee side of The
Greens. A dusting to an an inch will be possible for most places
with very little in the Champlain Valley. Over northern New York
and the northern greens into northeastern Vermont some of the higher
terrain may get 1-3" inches of snow with higher amounts at the
summits. Expect lows overnight behind the cold front to be similar
to Sunday night in the middle 20s.
Tuesday behind the surface front an upper level trough will pass
through the region with north westerly flow. Any leftover
orographic snow showers or flurries over the Adirondacks and The
Greens will be ending. 850 temperatures will be running about -9c on on
Tuesday which will will stay on the cooler side running in the middle
30s to near 40 across the area.
Tuesday night light northwest flow continues as a surface high
moves over the Great Lakes. Should be just enough wind and moisture
around for partly cloudy skies to prevent the bottom dropping out
of the low temperatures but still chilly in the teens to around 20
for most of US.
Long term /Wednesday through Sunday/...
as of 350 PM EDT Sunday...extended period picks up on Wednesday
with northerly low level flow and 500 mb trough exiting the
region. Surface ridge builds through Wednesday, then by Thursday
morning low level flow returns to southerly with high shifting to
the east. Will get some sun under the high pressure, but cool air
will limit maximum temperatures. 850 mb temperatures at 18z Wednesday only -13c, and
925 -7 both support maximum temperatures in the low 30s. Low level wind
begins to shift around to the west to southwest by Thursday
morning, but warm air advection doesn't take hold overnight and
lows still a chilly teens to lower 20s.
For Thursday 500 mb trough reaches the northern Great Lakes with the
500 mb ridge Easter over New England and Quebec. European model (ecmwf) showing
higher amplitude with its trough/ridge combo. At the surface low
pressure is placed a little ahead of the upper low. GFS has a
prefrontal trough racing well ahead of the synoptic low, actually
placing it under the upper ridge. European model (ecmwf) is a little slower, lagging
precipitation timing by about 12 hours. GFS seems a little speedy given the
upper pattern. Either way with southerly flow on Thursday
temperatures forecast to warm into the 40s with chance probability of precipitation for rain
in the warm air. For Thursday night probability of precipitation into likely category with a
blend of European model (ecmwf) and GFS.
For Friday previous runs of GFS and European model (ecmwf) had differences with European model (ecmwf)
witholding cooler air and forecasting a high of 64 at btv on Friday.
As appealing as this sounds it is too warm, and 12z European model (ecmwf) is more in
line with other guidance and maximum temperatures in 40s to low 50s Friday.
Showery Post frontal air with northwest to north flow and cold air
advection will bring Friday night lows back down to the 20s.
For Saturday both models in overall agreement of a secondary
shortwave trough rounding the base of the upper low and a
reinforcing shot of cold air at the surface with some light snow
showers late Saturday/early Sunday. Highs both Saturday and Sunday
to hold in the 30s, with Saturday night in the teens to low 20s.
Cold air this time of year doesn't have the teeth it had a month
ago, but we still can't seem to shake loose.
Aviation /01z Monday through Friday/...
through 00z tusday...VFR/sky clear to start the period... but
will see an increase in clouds and chances for rain/snow showers
after midnight and on Monday along with increasingly gusty winds
and some low level wind shear. Tonight...increasing middle/High
Deck of clouds and strengthening low level wind field will lead to
low level wind shear at mss/slk/mpv/rut and gusty south winds up
to 20-21 knots at btv. Will see lower ceilings and periods of
rain/snow showers encroach upon taf sites by 08-12z with areas of
MVFR/possibly IFR developing and continuing for most of the
day...again periodically. Btv/pbg least likely to be affected by
reductions to ceilings/visibilities due to downsloping
south/southwest flow. All taf sites will see marked increase in
surface winds with gusts 20-30 knots Monday morning and into the
Outlook 00z Tuesday through Friday...
00z Tuesday through 06z Tuesday...periods MVFR/IFR ceilings/visibility in
rain or snow showers with low pressure system moving west to east
out of Great Lakes.
06z Tuesday through 00z Wednesday...mainly VFR conditions...but
localized MVFR with scattered mountain snow shower activity (possibly
including slk/mpv) Tuesday morning. Hir terrain obscured at times.
00z Wednesday through 12z Thursday...mostly clear with high
pressure in place.
12z Thursday through Friday...MVFR ceilings/visibility possible in scattered
rain showers with approaching low pressure system. Potential for
gusty south/southwesterly winds and low level wind shear.