Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
644 am EST Sat Feb 28 2015
high pressure ridge will remain over the area through early
Sunday. A wave of low pressure will bring widespread light snow to
the area from Sunday afternoon through Monday. Another stronger
area of low pressure will pass to our west Tuesday night and
Wednesday...mixed wintry precipitation is expected with this
system along with gusty winds. Colder weather will once again
return for the end of the week.
Near term /until 7 PM this evening/...
as of 641 am EST Saturday...Saturday will be very similar to
Friday...even slightly warmer. Strong ridge of surface high
pressure remains over the area. Dry weather with mainly sunny
skies are expected. Have continued with previous forecasters
thinking and gone above MOS guidance for high temperatures today.
Short term /7 PM this evening through Monday/...
as of 411 am EST Saturday...first part of the day Sunday will be
much like the previous 2 with surface high pressure still over the
area...though it will slide eastward during the day allowing for
an increase in middle-upper level clouds during the afternoon hours.
Wave of low pressure and front extending out ahead of it will
approach our forecast area and by Sunday afternoon have mentioned
chance for snow increasing from south to north across our area.
Pressure gradient increases...will see south-south-southwest winds 10-15
miles per hour...the highest gusts will be in the Champlain Valley during the
afternoon. Increasing 850-700mb warm air advection and isentropic ascent allows
widespread light snow to develop from SW-NE during Sunday evening.
Should see periods of light snow continuing through the overnight
hours with 2-3" of accumulation by daybreak Monday in most spots.
Overcast skies and continued light S-SW winds will keep temperatures from
falling much Sunday night with overnight lows mainly in the middle-
upper teens. On Monday as low pressure moves northeast of the area
will see wrap around northwest upslope snow showers through much
of the day.
Long term /Monday night through Friday/...
as of 402 am EST Saturday...dry and colder weather returns for
Monday night and much of Tuesday as ridge of high pressure moves
across the area. Temperatures Monday night will drop below zero across
much of the area...with highs on Tuesday in the 20s. The high will
depart to the east Tuesday afternoon...with clouds quickly
returning along with the chance of some light snow by evening
across northern New York. Precipitation chances then increase
Tuesday night with approach of low pressure and associated warm
front from the Ohio Valley and lower Great Lakes. Latest guidance
continues to suggests that the low will take a track up through
the St Lawrence Valley on Wednesday...which would allow for milder
air to stream into forecast area. GFS indicating a deeper surface
low and is more aggressive with the warming than European model (ecmwf). GFS
depicting 850 mb temperatures around +4c with European model (ecmwf) barely above 0c. The
answer likely lies somewhere in between. Expect precipitation to
begin as snow everywhere...then transition to a wintry mix
overnight. With precipitable water values climbing to near .75
inches...it is shaping up as a moderate precipitation event...with
best forcing indicated Tuesday night with overrunning associated
with warm air advection. Strong southwesterly 850 mb jet will
result in some shadowing issues in some areas...and enhanced
precipitation in others.
During Wednesday surface low tracks up through St Lawrence Valley
across southern Ontario/Quebec. Associated cold front will move
across the north country during the afternoon. Steady mixed
precipitation may change to just rain in many locales before
tapering to scattered snow/rain showers during the day. Lingering
snow showers possible Wednesday night into Thursday as upper trough
moves across region and temperatures turn colder once again. With upper
trough lagging...will have to watch for potential wave formation
along surface boundary to our south...which could result in another
period of steadier precipitation during this period...especially
across southern areas. After a mild day Wednesday with temperatures in the
30s to around 40...its back to below normal Thursday with readings
mainly in the 20s. Cold and dry weather Friday as high pressure
builds across the region.
Aviation /12z Saturday through Wednesday/...
through 12z Sunday...VFR expected through the period with
generally clear skies and light winds as high pressure remains
over the region. Exception is slk which will see some low clouds
this morning with occasional MVFR conditions. Winds light westerly
except southwest and a bit gusty at times at mss/slk today.
Outlook 12z Sunday through Wednesday...
12z Sunday-18z Sunday...mainly VFR with high pressure.
18z Sunday-00z Tuesday...developing warm front and associated
weak area of low pressure will increase the clouds with snow
likely by 00z Monday. Expect MVFR with periods of IFR.
00z Tuesday-18z Tuesday...VFR conditions under high pressure.
18z Tuesday Onward...increasing chance for MVFR/IFR in mixed
precipitation as warm front approaches from the southwest.