Area forecast discussion
National Weather Service Burlington Vermont
1019 PM EDT sun may 19 2013
Synopsis...
clouds and isolated...light rain showers will continue
overnight...followed by an increased chance of rain showers
Monday afternoon...with the potential for a couple of
thunderstorms as an a disturbance moves into the region with an
associated weak warm front. Upper level ridging will lead to a
dry night Monday night but a greater threat of showers on Tuesday
as the aforementioned warm front lifts northward across the north
country. Above normal temperatures will continue into the middle
of the week.
&&
Near term /until 8 am Monday morning/...
as of 1019 PM EDT Sunday...warm frontal boundary and associated
light showers along the cold side of the thermal gradient
continues to lift northeastward. Quantitative precipitation forecast amounts have ranged from a
few hundreths to a tenth of an inch with an additional few
hundreths expected through overnight. Temperatures may only fall a
couple degrees more under overcast and increasing warm- air
advection with lows near surface dewpoints in the 50s. Have maintained
slight chance precipitation probabilities by morning as a cool
front will begin to approach the north country from
Ontario/Quebec.
&&
Short term /8 am Monday morning through Tuesday night/...
as of 433 PM EDT Sunday...surface low becomes slightly more pronounced
with the associated front settling south of the region late
Monday...producing threat of showers and thunderstorms as it
heads south. Lifted indices less than zero will only reach the
southern half of the County Warning Area...with minimal cape values. Have
included mention of slight chance of ts in the afternoon for southern
zones. Upper level ridging will continue throughout the day with
northwest flow continuing aloft...which will also keep better
instability to the south. With mostly cloudy skies...southerly
flow at the surface for at least the morning...and 925mb temperatures
increasing to the middle teens...maximum temperatures will be in the l-u70s.
Monday night will see a break from precipitation daytime heating
ends...but continued cloud cover with min temperatures in the 50s.
Tuesday morning will start mostly dry but see chance probability of precipitation in the
afternoon as the front begins to lift back north as a warm front. Probability of precipitation
will continue to increase to 40-50 percent Tuesday night as the
warm front moves across the north country. Maximum temperatures in the m60s-
m70s with continued clouds and light flow. And min temperatures Tuesday
night will generally be in the 50s.
&&
Long term /Wednesday through Sunday/...
as of 433 PM EDT Sunday...transition from west to northwest flow
aloft to a more southwest flow aloft Wednesday through Friday
will result in an increased threat for showers and some
thunderstorms. Going forecast already has this idea handled well
and did not change from this thinking. The southwest flow aloft
is in response to an upstream upper trough which will not move
into the area until later Friday. As a result...a warmer and more
moist air mass will exist ahead of a frontal boundary. The
resulting instability will be sufficient enough and combined with
the lift associated with surface front/upper trough...the threat
for showers and some thunderstorms will be the rule. Should see
high chance to low likely precipitation probabilities for
Wednesday and Thursday. Upper trough exits the area on
Friday...so just a chance of showers will exist. One noticeable
feature on the backside of the upper trough will be the low level
cold air advection and we should see some below normal
temperatures moving into the area for the weekend. Could see a
few instability showers on Saturday with drier weather for
Sunday...the day of the Vermont city Marathon. At this
time...temperatures will be a few degrees below normal for The
Race.
&&
Aviation /02z Monday through Friday/...
through 00z Tuesday...have treated current very light showers
with p6sm -shra as observations indicate that the showers aren't
resulting in any significant reduction in visibility. Look for
these showers to come to an end from west to east by 03z.
Expecting mainly broken/overcast VFR ceilings for the rest of the
evening...though have tempo'd in some MVFR ceilings 03-06z at rut
and mpv given light southeast flow and lower ceilings that are in
place across parts of central New Hampshire and southern Vermont.
Winds will be mainly southerly 5-10kts through 12z Monday.
A frontal boundary will drop southward out of Canada on Monday
/between 13-18z/. Guidance has trended drier with the front...but
some limited instability at rut and mpv may trigger some isolated/scattered
showers and perhaps some thunder. Have indicated vcsh for this
potential from 15z Onward. Otherwise expect VFR conditions with
winds initially south at 5-10kts becoming northwest /west-
northwest at similar speeds upon frontal passage.
Outlook 00z Tuesday through Thursday... a frontal boundary
sagging southward from Ontario/Quebec brings the threat for showers and
possible thunderstorms for much of next week. The frontal boundary will
become quasi- stationary vicinity of northern New York and northern New England through
much of the period. Timing uncertainties currently exist but
anticipate several periods of MVFR and perhaps brief IFR
conditions during this time frame with showers and possible
thunderstorms...especially Tuesday and Thursday.
&&
Btv watches/warnings/advisories...
Vermont...none.
New York...none.
&&
$$
Synopsis...lahiff/kgm
near term...kgm/loconto
short term...kgm
long term...evenson
aviation...evenson/loconto
