Area forecast discussion
National Weather Service Buffalo New York
1049 am EDT Thursday may 23 2013
Synopsis...
low pressure tracking north of Lake Ontario will drag a cold front
across our region this afternoon. Showers will linger behind the
front tonight...then diminish from west to east on Friday as drier
air works east across the area. Much cooler air will also follow the
front tonight and Friday.
&&
Near term /through tonight/...
late this morning a surface low is found just to the north of Lake
Ontario with a cold front back across the far western end of Lake
Ontario and down along Lake Erie. This places our County Warning Area still within
the warm and humid sector...though not quite as warm and humid as
recent days. Regional radars are showing the beginning of a line of
showers and thunderstorms ahead of the cold front across wny and
slowly advancing eastward.
As the surface low moves across southern Quebec today...the trailing
cold front will cross western and central New York during the
afternoon. While instability will not be that favorable...
large scale lift associated with the front and approaching upper
level trough will result in more widespread showers compared to what
we saw the previous two days. Will continue with a chance for
thunderstorms across the southern tier and Genesee Valley eastward
where the instability will be a little greater.
Behind the front...temperatures will likely hold steady or slowly
fall during the afternoon...especially across the far west where
readings may dip into the upper 50s by late afternoon.
Tonight...the cold front will drift to the New England coast while
the axis of the upper level settles over western New York. Abundant
moisture lingering behind the front and the lift associated with the
upper trough will keep showers going through the night. Modest cold
air advection behind the departing surface front will allow
temperatures to cool through the 40s.
&&
Short term /Friday through Sunday/...
cooler air will filter into the region behind the cold front on
Friday as a sharp upper level trough axis moves slowly across the
region from west to east. Although model qpfs are on the light
side...expect a solid area of non-convective precipitation
associated with the upper trough with categorical probability of precipitation. Highs will be
notably cooler...with temperatures only in the 50s on Friday.
The upper level trough will slowly track east...and is forecast to
eventually close off across New England on Saturday. There is some
disagreement in model guidance in how quickly and where the closed
upper low will ultimately develop. In general...00z runs of the American
NAM/GFS/sref models are slower in closing the low off which would
keep it well to the east of our region. The European/UKMET/ggem
close the low off more quickly and further to the west. If the
latter verify...clouds and some showers to linger in the Eastern
Lake Ontario region throughout the weekend. At this point...feel an
ensemble of all available guidance is the best approach until
guidance comes into better agreement.
Either way...expect areas west of Rochester will remain dry...and
with a fair amount of sunshine. East of Lake Ontario may see a
shower...depending on the position of the upper low. Temperatures
will be below normal through the period...but will gradually
moderate during the weekend. Expect highs mainly in the lower 60s on
Saturday and the middle to upper 60s on Sunday. Significantly cooler
temperatures are possible east of Lake Ontario...where clouds and
perhaps some showers will keep things cooler.
On Friday night there is a potential for patchy frost in the
interior valleys of the southern tier. A modest pressure gradient
should prevent widespread frost...however temperatures in the
sheltered valleys may push the freezing mark. Lows should be
slightly warmer on Saturday night...in the upper 30s to lower 40s.
&&
Long term /Sunday night through Wednesday/...
the upper low across New England will weaken and exit into the
Canadian Maritimes...leaving cool Canadian high pressure across our
region for the majority of the period. This will result in a quiet
weather pattern with no precipitation expected. The dry airmass in
place will likely result in a wide diurnal range in temperatures.
The coolest period looks to be Monday with overnight lows falling
into the middle 30s and lower 40s and highs in the middle to upper 60s.
These temperatures would suggest some frost potential especially for
the normally colder locations of the southern tier and areas east of
Lake Ontario. It is likely that headlines will be needed at some
point during this period.
A gradual warming trend will then occur through middle week as the high
shift slightly to the east allowing for a more southerly flow with
highs reaching normal or slightly above normal by middle week with
readings in the 70s.
&&
Aviation /15z Thursday through Monday/...
scattered to numerous showers will continue to lift north across the
area early this morning. Some of the showers across western New York
will be heavy enough to lower visibilities to MVFR for brief periods.
There should be enough wind during the early morning hours to
preclude the development of fog despite the very moist airmass in
place.
A cold front that trails low pressure over southern Quebec will
cross western and central New York this afternoon. The will provide
additional focus for showers...especially during the afternoon as
the bulk of the rain begins to take residence behind the surface
cold front. Ceilings/visibility should initially be VFR...then drop to MVFR
late in the day as temperatures cool while abundant moisture remains
in place.
Showers will continue behind the front tonight as the upper level
trough works into New York state. The presence of abundant moisture
..cooling temperatures and a northerly upslope flow behind the
departed front will likely result in widespread MVFR to IFR
conditions.
Outlook...
Friday...MVFR improving to VFR as showers diminish.
Saturday through Monday...VFR.
&&
Marine...
low pressure centered just north of Lake Ontario will move slowly to
the northeast and push a cold front across western and central New
York this afternoon. A brisk northerly flow behind the front will
likely result in Small Craft Advisory conditions tonight through Friday morning.
&&
Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory from midnight tonight to noon EDT Friday
for lez040-041.
Small Craft Advisory from midnight tonight to 2 PM
EDT Friday for loz043-044.
Small Craft Advisory from midnight tonight to noon EDT
Friday for loz042.
Small Craft Advisory from 2 am to noon EDT Friday for
loz045.
&&
$$
Synopsis...tjp
near term...Thomas/tjp
short term...apffel
long term...apffel/tma
aviation...tjp
marine...tjp
