Scientific Forecaster Discussion
fxus61 kbgm 182355
Area forecast discussion
National Weather Service Binghamton New York
755 PM EDT Thu Jul 18 2019
a hot and humid airmass remains over the region through at
least Saturday and heat index values could reach dangerous
levels Friday and Saturday afternoon. It will be partly sunny,
with chance of thunderstorms through the weekend as several
disturbances pass through the region. Cooler high pressure
builds into the area the start of next week.
Near term /through Friday night/...
3 PM update...
... Heat expected Friday and Saturday...
Stationary front remains to our south/southeast today. With
heating this afternoon, showers and storms will develop along
this front and a few storms could leak into NE PA and southeast NY, but
the bulk of the area will remain dry.
Main impacts this period will be due to excessive heat Friday
and to start the weekend. Heat index values will likely climb
above 105 for valley and urban locations tomorrow, but
conditions will be less oppressive in rural and mountain areas.
A excessive heat warning has been issued through Saturday and a
heat advisory is now in effect for northern Oneida, Otsego and
Delaware counties, where conditions will be slightly cooler.
Showers and thunderstorms may develop tomorrow afternoon and
evening as we remain along the periphery of an upper ridge.
There will be plenty of instability with cape values over 2000
j/kg and moderate deep layer shear in westerly/northwesterly
flow aloft. NAM is indicating a few weak waves pushing through
the flow late Friday afternoon and evening which could provide
enough ascent to kick off scattered storms. However, it is more
likely that convection initiates along convergence from lake
breeze in the afternoon and slowly pushes eastward into our
forecast area. Isolated damaging wind gusts will be the main
threat from these storms.
Short term /Saturday through Saturday night/...
oppressive heat and humidity expected during the short term
period as a flat upper level ridge builds over the region.
Excessive heat warnings and heat advisories are now in effect
through Saturday for the entire region. Near record highs
expected, in the low to mid-90s areawide. Surface dew points are
progged to reach 72-76 as well, which will produce dangerous
heat indices between 105-110 in the urban valleys; and 95-100
over the higher elevations. At this time Saturday appears likely
to be the hottest day this week. Confidence in reaching these
temperatures and heat indices is now high. Latest guidance
continues to show 850mb temperatures reach around +22c as an
elevated mixed layer approaches from the west. Low chance for a
few late day or evening thunderstorms, especially across our
central New York zones, otherwise expect partly sunny skies. If
thunderstorms are able to develop and break the mid level cap,
there could be gusty winds and heavy downpours. These showers
and storms could linger into Saturday night...again, mainly
north across central New York. Staying warm and muggy overnight, with
lows only in the low to mid-70s.
Long term /Sunday through Thursday/...
a frontal boundary slowly drops south across central New York during
the day Sunday. This should allow for a better chance of showers
and thunderstorms, as instability remains high ahead of the
front. Decent jet support as the upper level trough drop into
Ontario, will allow for modest deep layer shear around 30-40
kts, therefore will need to watch for some stronger well
organized convection. Still some minor discrepancies in exactly
how fast this boundary moves through the region. South of the
front the heat and humidity will continue; although not as hot
as Saturday as the cloud cover and t'storms will limit the
temperatures a bit. Still expecting highs 88-93 from the
southern tier of New York south into NE PA....with low to mid-80s
further north in central New York.
Sunday night and monday: the aforementioned frontal boundary
tries to stall, or only very slowly moves south and east. Again,
some model differences in the exact position and timing of this
slow moving front. For now, continued with higher chance pops
for more showers/storms across the south-east half of the cwa,
fading to low end chance or slight chance up across the north.
Temperatures and dew points will continue to lower as the cooler
air mass advects in and cloud cover remains higher. Highs are
only forecast to reach the upper 70s to lower 80s, with lows in
Tuesday and wednesday: upper level trough moves over the region
putting US in a northwest flow regime. Still minor differences
in the guidance, but there does appear to be surface ridging and
drier low level air moving in. Therefore, current forecast is
calling for partly sunny and generally dry weather these two
days, with much more seasonable temperatures and low humidity.
Highs will be 75-80 and overnight lows in the 50s.
Thursday: actually fairly good agreement in the guidance that
the upper trough sharpens as energy moves into the upper Great
Lakes next Thursday. This could bring another frontal boundary
through the area, with a better chance for showers and
thunderstorms. Seasonable temperatures.
Aviation /00z Friday through Tuesday/...
mainly VFR conditions are forecast for this taf period. Fair
weather cumulus is dissipating but a weakening mid level wave
will keep scattered mid clouds overnight. At kavp, stratus is
likely overnight with occasional alternate required conditions
between 08z-12z. On Friday, scattered to broken cumulus is
forecast around 4-5k feet with ceilings mainly in the
afternoon. Scattered convection could occur late afternoon/early
evening but not included at this time due to uncertainty in
Light and variable winds overnight becoming southwest 5-10
knots on Friday.
Friday night through Saturday...weak passing disturbances
provide chances for showers and storms yet VFR most of the time.
Potential valley fog each night especially at kelm, but it will
depend on how much debris clouds are leftover from daytime
showers and thunderstorms.
Saturday night through Sunday night...better chances for
scattered showers and thunderstorms and associated restrictions
as a frontal boundary slowly moves through the region.
Monday and Tuesday...still at least a small chance for showers
and thunderstorms with associated brief restrictions.
PA...excessive heat warning from noon Friday to 8 PM EDT Saturday
New York...excessive heat warning from noon Friday to 8 PM EDT Saturday
Heat advisory from noon Friday to 8 PM EDT Saturday for nyz009-