Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Binghamton New York
300 am EDT Tuesday Jul 7 2015
a weakening area of low pressure will move across the area early
today with scattered showers and embedded thunder...shunting
east of Interstate 81 later this morning. After a mainly dry middle
to late afternoon...a cold front will pass through tonight into
Wednesday with showers and a chance of thunderstorms. Another
system will possibly bring some showers and thunder
Thursday...followed by dry weather Friday through Saturday.
Near term /through tonight/...
230 am update...
what was an upper low...continues to weaken while opening up into
the west-southwest flow currently over our region. As it shears
out...scattered showers and occasional embedded thunder will
advect up the central twin tiers...then shunt mainly east of I-81
later this morning along exiting vorticity lobe. Not expecting
much out of the activity this morning...with dry conditions most
of the time and indeed some areas getting missed altogether.
Brief period of subsidence behind the wave...should yield mainly
dry conditions middle to late afternoon...however...cold front will
be inbound. Upper wave will run out ahead of the front and induce
a pre-frontal trough to sweep through this evening...followed by
the actual cold front late tonight into Wednesday morning. Showers
are likely...but thunder chances /initially fairly high in The
Finger lakes to central twin tiers region this evening/ will
diminish a bit as the activity heads east through the area with
loss of instability overnight.
Shear is quite limited with this system. Add unfavorable nocturnal
timing of front...and threat for organized severe thunderstorms
appears minimal. The bigger potential issue in this case is the
35-45 knots low level jet in the 850-750mb layer which will inject
moisture...surging precipitable water values to nearly 2 inches.
Right now it appears probable that the wave will be progressive
enough to prevent big problems. However...with that kind of moist
atmosphere and a warm cloud layer all the way up to around 15
kft yielding very efficient rain...it simply would not take long
for localized excessive rainfall to occur if showers-embedded
storms were to hang up and train for even a short amount of time.
At this point we will continue to mention potential of localized
water problems within our hazardous weather outlook.
With dewpoints edging into the middle to upper 60s...it will feel
rather sticky today...with highs well into the 80s for most of the
region. Given the moisture tonight...lows will be mainly middle 60s
to near 70.
Short term /Wednesday through Thursday night/...
cold front pushes through the forecast area Wednesday and then hangs up as a
stationary front over central PA. Some disagreement exists between
the models for midday Wednesday. NAM is quickest in pushing the
front into the Wyoming Valley and clearing out the southern tier
and Susquehanna region. European model (ecmwf) and GFS hang on to the precipitation well
into the afternoon along the i81 corridor. I edged toward the
faster NAM forecasts.
Another wave in the ul trough dips into the Great Lakes Wednesday
night, and a diffuse surface cyclone develops south of our forecast area. This
will keep the chance for showers and possibly a few thunderstorms
over New York and PA into Thursday evening.
Long term /Friday through Monday/...
minor changes made to the extended forecast based on latest HPC
guidance. Mainly lowered probability of precipitation for the end of the week and tweaked
models in decent agreement with the overall upper level pattern
and just minor surface feature differences...providing better forecast
confidence through this period than the last few days. The models
have been all over the place the last few days with respect to the
long term trends...but today they seem to be gripping onto a
solution and will move the forecast in that direction with the 12z
runs of the GFS and Euro having a very similar look. Northwest flow to
start the period as ridging starts to retro from the MS valley
into The Four Corners region of the Continental U.S.. over most of the
weekend weak surface high will keep the temperatures just above seasonal avgs
and conditions dry...late in the weekend a trough will start to
build across the Great Lakes and eastern Continental U.S....possibly cutting
off by next Monday. It is possible that this cut off low will
linger for awhile and produce a threat for very wet conditions
next week as precipitable waters look to climb. Its well into the future...and
things may change if the position of the cut off significantly
changes...but definitely something to watch.
Aviation /07z Tuesday through Saturday/...
weakening upper system will lift through the area this
morning...with scattered -shra and ceilings lowering into mainly MVFR range
/ksyr-krme should stay above fuel alt level/. We were able to back
off the amount of IFR...yet brief periods of IFR ceiling should still
occur towards dawn for kavp-kbgm-kelm thanks to combination of low
level saturation and spotty -shra. As the weak wave lifts
out...mainly dry VFR conditions expected for remainder of daytime
hours. However...moist cold front will approach this evening with
developing rain showers and possible embedded thunderstorms and rain reaching kelm-kith-
ksyr-krme towards end of taf period /kbgm-kavp to follow after
06z Wed/. Winds generally southeast 3-7 kts remainder of
overnight...veering to S or SW 6-9 kts during the day...see tafs
Wednesday through Thursday night...restrictions possible in scattered
shra/tsra...and possible early morning low clouds-fog.
Friday through Sat...VFR.