Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Binghamton New York
959 PM EDT Wednesday Jul 30 2014
an upper level disturbance will remain over the area through late
week. This weather system will keep our temperatures cooler than
normal, along with a chance of showers or thunderstorms during
Near term /through Thursday/...
10 PM update...
all on track for tonight with WV hvg mvd into western sections of County Warning Area as
of 02z. Thus, showers are headed east with thunder hvg come to an
end in the last hour. Expect these will exit to the east and/or die
off by 04z. Skies looks to clear briefly in between waves possibly enough
to bring valley fog to the region ahead of next appchg shortwave. Thus have
added patchy valley fog to grids between 07z and 09z before clouds and precipitation
mvs back in. No other changes needed other than hrly tweaks to T/dew point values.
Previous discos below...
725 PM update...
WV imagery showing a well-defined shortwave skirting through western New York at
this time which has led to rain showers/thunderstorms and rain over The Finger lakes extending
down into northern tier of PA. Instability is waning with loss of
daytime heating as cores have dropped down below 18kft. Dropped hrly temperature
values in rain-cooled air but have not tweaked overnight mins with most
locales still expected to dip into the m50s with dewpoints still remaining
steady in the 50s.
Next WV currently moving into northern lower Michigan still on track to drop
into central Great Lakes after 09z this morning ldng to showers and
embedded thunder after this time. Current grids have this well in hand
with probability of precipitation looking likely through at least noon. No changes made bynd this
time as any little boundary left over from convection may be enough to
fire addnl storms drg the afternoon due to diurnal heating.
450 PM update...
updated probability of precipitation to go likely across finger lks, spreading east over the
next several hours. This is all in associated with WV dropping into wny at
this time. MLCAPES look meager around 500 j/kg in these areas. Freezing
levels up around 10kft, thus not expecting any severe this afternoon though some
storms may flirt with small hail and will bear watching radar for
the next several hours. Grids have already been sent.
4 PM update...
radar continues to show a few rain showers working east-NE into The Finger
lakes region...central southern tier of New York and into Bradford
County PA. Water vapor imagery continues to show an upper level wave
working ewrd into New York and PA for the afternoon. This is coinciding
with the time of maximum heating...providing some modest cooling
aloft to enhance some instability. Storm Prediction Center mesoanalysis Page shows
mixed layer convective available potential energy of between 250 and 500 j/kg mainly west of I-81.
Models generally are showing mixed layer convective available potential energy this afternoon
around 500 to 1000 j/kg with weak to modest shear profiles. Not
anticipating any severe weather given lack of strong shear and
instability but will be adding thunderstorms and rain to grids as 12z guidc is more
unstable than 06z and 00z guidc of last night. There really isn't
much of a trigger for convection either and I believe it will
remain fairly unorganized also limiting any severe threat. All the
acvty will wind down late this evening with the passage of the
short wave to the east. I used weather forecast office bgm/S local WRF 4km version for
timing of precipitation which looks right on target. I also blended with
surrounding offices for a better consensus forecast. So will have
chance probability of precipitation for rain showers and will add thunderstorms and rain shortly.
For tonight...rain showers and thunderstorms and rain will wind down after sunset and also with
the passage of the upper level wave to the east. Then another short wave...
presently seen well in the water vapor imagery heading southward
toward Lake Superior... will cross New York and PA Thursday morning. I expect
that there will be addtnl rain showers and even some thunderstorms and rain with this
feature. Model soundings suggest some instability too. The wave
will pass east by afternoon...the time of maximum heating so not
expecting anything significant in the way of intense storms. Convective available potential energy
likely will remain at best 500 j/kg. Shear will be strong Thursday am
but in the absence of any significant focusing ll boundary it is
possible that the convection has a hard time going given the lack
of significant instability. Still will have probability of precipitation for rain showers/thunderstorms and rain
focusing on the morning...lower in the afternoon Thursday.
Short term /Thursday night through Friday night/...
fairly stagnant weather pattern will set up across the area
Thursday night through Saturday. The middle to upper level trough
will set up over the Great Lakes and Ohio Valley with surface
high pressure off the East Coast. Deep south-southwest flow will gradually
bring higher dew points and increasing deep-layer moisture north-
northeast from the Ohio Valley to the northeast. Scattered showers
and thunderstorms can be expected each day mainly during the
afternoon and early evening. Coverage will be in the 30 to 40
percent range each afternoon lowering to 20 percent or less
overnight and during the morning hours. Cape values look to range
from 500-1000 j/kg both Friday and Saturday afternoon with deep
layer shear of 25-30 kts... both of these factors will be marginal
at best for any severe weather and given that widespread forcing for
lift will be weak not expecting much of a severe threat through
Saturday. Temperatures will be near normal with highs close to 80
and lows close to 60.
The pattern may become a bit more active on Sunday as models are
in good agreement showing the upper trough moving east across the area.
This forcing will bring a better chance of showers and
thunderstorms and have probability of precipitation increasing to 40 to 50 percent during
the afternoon. The approach of the upper trough may result in
slightly increased deep-layer shear on Sunday... while cape
values are forecast to remain unimpressive generally in the
500-1000 j/kg range. At this point it appears that a few isolated
severe cells can't be ruled out on Sunday given some forcing but a
significant event is not expected and nothing will be added to the
hazardous weather outlook at this time.
Long term /Saturday through Wednesday/...
overall upper pattern early next week continues the several month
trend of a ridge over the west and troughing over eastern North
America. At this point the pattern looks to be Delaware-amplified with
no significant systems crossing the area. As a result we expect
near normal temperatures with highs near 80 and lows near 60.
Probabilities of precipitation will be on the low side...
generally 20 to 30 percent each day with the best chance during
the afternoon and early evening.
Aviation /02z Thursday through Monday/...
complicated set of tafs...with remains of convection early on for
many terminals...fog later tonight for at least kelm and possibly
others...and then a vigorous upper wave passing through roughly 12z-
16z with at least showers and perhaps thunder. Temporary northwest
wind shift and restrictions krme-ksyr-kith-kbgm and then
kavp...otherwise light S to SW winds overnight with exception of
localized east-southeast wind krme. Confidence has increased in a gap in
cloud cover during predawn hours of Thursday morning...to allow
valley fog formation kelm including times of IFR visible 08z-12z. At
least MVFR figured late tonight krme...IFR not out of the
question. Then 12z-16z...a round of showers with next upper wave
that as of 00z is currently dropping across northwestern Great
Lakes region. Handled via tempo group with MVFR restrictions for
most terminals at this point. However...it should be noted that
despite morning timing...wave is strong enough to where cumulonimbus will be
possible within the showers. For now too much uncertainty to
include cumulonimbus in tafs...but cumulonimbus may be added in later taf sets if
confidence increases. Winds also to veer SW to west around 10 kts with
wave passage Thursday morning. Thursday afternoon...isolated or widely
scattered cumulonimbus possible simply due to instability of daytime heating
but the wave will have exited and so not much confidence.
Thursday ngt-Mon...restrictions possible each afternoon...in isolated to
scattered showers or thunderstorms. Also...possible valley fog
early each morning for kelm.