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Area forecast discussion 
National Weather Service Buffalo New York
810 PM EDT Monday may 4 2015

a weak cool front will sag across our forecast area early
tonight to produce some badly needed showers and possibly a
couple thunderstorms...but significant rainfall amounts are not
expected. The front will stall over Pennsylvania on Tuesday...
while high pressure will drift across the Great Lakes region.
Other than a shower or two over the southern tier on Tuesday...
dry weather with above normal temperatures can be expected
through the rest of the week.


Near term /through Tuesday/...
an area of light showers drifting eastward across the region
early this evening associated with a pre-frontal trough. Main
surface cold front still upstream making its way across southern
Ontario. Forcing with this feature looks limited with very little
in the way of activity associated with it. Instability waning and
with lack of forcing from the cold front will remove mention of
thunder for tonight...but we still could see some scattered
shower activity develop across the area with the fronal passage
later tonight.

For Tuesday...the frontal boundary is expected to stall across
Pennsylvania. The bulk of any surface based convergence will thus stay
south of the PA border...although the airmass will still be somewhat
unstable over the southern low chance probability of precipitation will remain in
place for showers and a stray thunderstorm. Otherwise...skies should
at least partially clear over much of the region as high pressure
will build across the lower Great Lakes.

There will be a little cooling behind the 850 mb temperatures will
drop back to around 8c. Nevertheless...we will stay on the warm side
of normal as most areas will reach into the upper 60s to lower 70s.


Short term /Tuesday night through Thursday/...
a frontal boundary will stall just to the south of our County Warning Area on
Tuesday night. Most model guidance develops a convective wave along
this...but differs on the timing and position of the front which
lowers forecast confidence. This will probably be just showers...but
can/T rule out a few thunderstorms Tuesday evening. Model consensus
suggests the best chance for precipitation is across far southern
areas which is closest to the front. Otherwise a broad area of high
pressure will expand across the Great Lakes region and clear out the
region from north to south. Low temperatures should generally be in
the 40s...with the coldest temperatures to to north where clear
skies and light winds will bring good radiational cooling

Medium range model guidance is in fairly good agreement with the
frontal zone expected to wash out to our south as high pressure
becomes established across the region on Wednesday. The 12z
ggem/European model (ecmwf) both hang onto some showers across Chautauqua County...but
most other guidance is dry for Wednesday.

The surface high will continue to influence our weather through
Thursday while the upper level ridge axis gradually shifts from the
Central Lakes to the lower Great Lakes region. This should bring
another couple days of exceptional Spring weather. Highs should
average in the 70s on Wednesday and then range from the middle 70s to
lower 80s on Thursday. The exception will be along the immediate
lakeshores where the light gradient flow will allow a lake breeze to
develop each afternoon near the lakes. There may be an isolated
shower across interior portions of the southern tier Thursday
afternoon...otherwise expect fair weather and mostly clear skies.


Long term /Thursday night through Monday/...
a Summer-like pattern will set up for most of the long term period
with upper level ridging across the northeastern states through the
period. Initially this ridge axis will be across our region...but
this axis will shift to the east through Monday which will set up a
progressively more moist flow. GFS/ECMWF/ggem guidance is in fairly
good agreement on the big picture...with the 12z GFS faster
breaking this ridge down than the ggem.

This will bring much above normal temperatures to the region for
Friday and Saturday...with widespread highs in the 80s likely.
Temperatures will be a bit cooler along the lakeshores. There is
a small chance for mainly diurnally driven showers or
thunderstorms during the afternoon hours...but the vast majority
of this timeframe should remain dry.

The chance for precipitation will increase Sunday and Monday as a
deep south-southwest flow aloft brings in progressively more moist air.
GFS/European model (ecmwf) consensus quantitative precipitation forecast increases with the pattern shift with a good
chance of showers and thunderstorms...especially during the
afternoon hours. Daytime highs will still be warm...but not as much
so with the increased cloud cover. Highs should average in the upper
70s to lower 80s on Sunday and Monday.


Aviation /00z Tuesday through Saturday/...
VFR conditions will remain in place this evening...despite the
arrival of a cold front with its associated showers. As we push
deeper into the night...ceilings will near MVFR levels at most sites
between 06z and 12z...with ceilings dropping to IFR levels across the
higher terrain of the southern tier.

On Tuesday...the aforementioned cold front will be stalled over
Pennsylvania while mainly VFR ceilings will be found across western
New York and certainly the Eastern Lake Ontario region. While
there will be the potential for a shower south of Buffalo and
Rochester...the bulk of the day will be rain free. A thunderstorm
cannot be ruled out across the southern tier.

Tuesday night...mainly VFR.
Wednesday through Friday...VFR.
Saturday...mainly VFR with a chance of MVFR in rain showers.


a cold front will settle across the lower Great Lakes tonight. A
weakening pressure gradient will lead to a lessening of the

On Tuesday and Wednesday...high pressure over the lower Great Lakes
will only produce light winds and negligible waves.


Buf watches/warnings/advisories...
New York...none.



near term...rsh/tma
short term...apffel
long term...apffel

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