Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
343 am EDT Monday may 25 2015
a strong warm front will push through the region today
and tonight with periods of showers and perhaps a thunderstorms...
mainly across central and northern areas. Behind this front...a very
warm and summerlike airmass will surge back into the region on
Tuesday. It will remain warm for the rest of the week along with
daily chances of scattered showers and thunderstorms.
Near term /until 8 PM this evening/...
as of 302 am EDT Monday...warm frontal boundary draped across
northern Great Lakes southeast into western New York with radar showing decent
shower/overrunning rainfall across western New York with that boundary.
This will continue to lift northeast across northern New York and Vermont today
with the eastern edge...away from best isentrophic lift and moisture
advection...witnessing less rainfall as it moves into dry airmass
with dewpoints only in the 30s. There is a descrepancy in the
models with the GFS trying to deliver 1/2 to 1 inch along Canadian
border and nam12 less than tenth of an inch. Although both agree
very little if any in southern Vermont as eluded to earlier. The
compromise of 1/3-1/2 inch along northern bdr with 0.1 to 0.25 inches
in central sections and less than a tenth in southern sections
Steepening lapse rates and marginal instability in the low to middle-
levels may allow for a few isolated thunderstorms to develop on the
back side of the front across northern New York later in the day.
High temperatures generally in the lower to middle 70s given cloud
cover and precipitation...though some areas far south and west could
see readings reach the upper 70s to near 80 if warm front makes it
through these area by late afternoon.
Short term /8 PM this evening through Wednesday/...
as of 302 am EDT Monday...no real changes from previous forecast
as consistency between models and model runs continues.
Warm front lifts north and east of forecast area tonight into
early Tuesday. Main threat of showers tonight along the candian
border Vermont and exiting SW to NE.
Partly to mostly sunny skies Tuesday along with much warmer
temperatures as 925 mb temperatures are prognosticated to reach +20 to +23c
which would support maximum temperatures in the valleys well into the 80s to
around 90 degrees. Much of the day will be dry with little forcing
mechanism to generate precipitation. However...can't rule out a few
isolated to widely scattered showers and thunderstorms from middle
afternoon into the night with some modest instability as forecast
area will lie in a modest instability/moisture axis in deep
southwesterly flow aloft with weak disturbances within the
flow...especially Tuesday night. Temperatures Tuesday night quite mild
with much of the region seeing lows in the 60s.
On Wednesday...southwest flow ahead of a cold front will advect
precipitable waters greater than 1.5 inches with increasing instability Wednesday
with approach of pre-frontal trough and upper support. Lifted indices
of -2 to -4 with 800-1200 j/kg of cape available, especially in the
afternoon. Bulk shear >30 kts with linear flow thus not looking at
much but an isolated strong storm not out of the question. Mainly
with these high precipitable waters ...looking at heavy downpours which is needed
right now. Maximum T forecast will be somewhat tricky dependent on
amount of sunshine..tad cooler but more humid...l-m80s.
Long term /Wednesday night through Sunday/...
as of 343 am EDT Monday...a weak frontal boundary will linger
across the region Wednesday night and Thursday...so will keep in
chance probability of precipitation for showers and thunderstorms. 00z European model (ecmwf) and GFS
models show this weak frontal boundary will move south of the
region Thursday night...so have lowered probability of precipitation and have gone with a
dry forecast for Thursday night. Models showing some differences
with the Friday forecast...with the GFS maintaing a dry forecast
for Friday...while the European model (ecmwf) has low to slight chance probability of precipitation for
showers and thunderstorms on Friday. Have opted to stay with the
super-blend probability of precipitation for Friday and will keep a mention of showers and
thunderstorms for Friday. European model (ecmwf) and GFS models in good agreement
in showing a dry forecast for Friday night...so have lowered probability of precipitation
for Friday night and have gone with a dry forecast.
European model (ecmwf) and GFS models bring a cold front east from the Great Lakes
on Saturday...but models show significant timing differences...with
the GFS faster and more progressive with the movement of the cold
front. The European model (ecmwf) is slower with the movement of the cold front
from the western Great Lakes on Saturday. Have opted to go with
the slower European model (ecmwf) model solution which bring the cold front into
the region late Saturday and Saturday night. The slower speed of
the European model (ecmwf) seems reasonable given the strong Bermuda high off the
East Coast on Saturday and Saturday night. Thus...will have a
chance of showers and thunderstorms in the forecast for Saturday
and Saturday night. European model (ecmwf) model has the cold front stalling out
across southern New England on Sunday. Have lowered the super-
blend probability of precipitation to slight chance for showers on Sunday. However...both
the GFS and European model (ecmwf) models now appear to be trending drier for
Sunday into Sunday night.
Aviation /08z Monday through Friday/...
through 06z Tuesday...mainly VFR conditions expected through the
period. A warm front will approach the region today from the
southwest. Models differ as to the amount of rainfall this warm
front will bring. Given the large temperature/dew point spread
shown by 06z Monday surface observations...expecting visibilities
with any rain showers will remain in the VFR category and ceilings
also to remain in the VFR category through the period. Expecting
southerly surface winds around 10 knots or less through the
Outlook 06z Tuesday through Friday...
06z Tuesday-12z Tuesday...a weak warm front will produce a period
of light rain showers with MVFR ceilings possible.
12z Tuesday-00z Wednesday...VFR in brief break from showers and
00z Wednesday-00z Friday...VFR with MVFR/IFR in afternoon showers
and thunderstorms, mainly during the peak heating hours.
00z Friday Onward...generally VFR conditions as weak high
pressure briefly builds into the region.