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Area forecast discussion
National Weather Service Binghamton New York
129 am EDT Tue Apr 24 2018

Synopsis...
high pressure will reside over the region overnight only
gradually increasing clouds. Clouds will continue to increase
through the day on Tuesday with a low pressure system that will
bring periods of rain late Tuesday through the middle of the
week. Expect generally dry and seasonable weather Thursday night
and Friday.

&&

Near term /through today/...
1030 PM update...updated to tighten up the onset times for the
rain Tuesday into Tuesday evening. Used the namnest 3 km
simulated reflectivity as well as the hrrr reflectivity.
Generated hourly pops from these fields and start times are more
defined from previous shift which is typical as we get closer
to the onset time.

The basic dynamical set-up is another southern branch upper
level low over the southern U.S which will track slowly east-
northeast tonight and Tuesday. This feature has a well developed
low-level cyclone which tracks northeast reaching the southern
Appalachians and NC/Virginia by 00z Wednesday. A southeasterly low-
level jet will increase and tighten up across Virginia/WV and western
and southern PA Tuesday with strong low-level moisture
advection. This jet will also support strong isentropic lift on
the 290-300k surface Tuesday in New York and PA. Aloft this upper
level low will merge into a northern branch upper level wave
Tuesday night with strong upper level divergence. Hence it will
support a swath of rain spreading across New York and PA into Tuesday
night.

Models indicate that most of northeast PA and central New York will be
rain free Tuesday. Some light showers could affect areas from
The Finger lake southeast to the Poconos mid to late afternoon
Tuesday. The bulk of the rain looks like it comes Tuesday night.

We are not expecting enough rain to cause any flood issues.
Rainfall totals should range from around one half inch in The
Finger lakes to near an inch in the Poconos/Catskills.

730 PM update...
a little cirrus was heading north but the night will feature
mainly clear skies and chilly temperatures but milder than last
few mornings due to southerly winds. Some protected valleys east
of Binghamton will likely de-couple and see temperatures back
down to the upper 20s and lower 30s Tuesday am. Rest of
forecast area will see minimums in the mid 30s to lower 40s.
Didn't make any significant changes to previous forecast.

330 PM update...

Clear skies and warm temperatures will be the
rule for the rest of this afternoon and early evening as high
pressure remains firmly in control of our weather. Few to
scattered cirrus clouds move in from the south late this evening
and into the overnight period. With clear skies and light south
winds expect temperatures to fall off rather quickly after
sunset this evening..but likely not as cold as yesterday
evening. Temperatures should begin to level off, holding fairly
steady late tonight as clouds and moisture increase. Overnight
lows will be in the mid-30s to lower 40s areawide.

Tuesday starts off mostly cloudy in NE PA and partly cloudy
across central New York. Clouds continue to increase from south to
north through the morning hours...so that by midday or early
afternoon the entire County Warning Area should be mostly cloudy. Conditions
will stay dry through the morning hours. Then, a slight chance
to chance of showers will slowly move into our forecast area
from the southwest. With a Dry Ridge of high pressure still
hanging on over the far eastern portion of the forecast area
expect the northeastward progress of the rain showers to be
very slow...reaching the I-81 corridor by around 5-8 PM.
Rainfall amounts during the day on Tuesday are looking very
light, with just a few hundredths of an inch from I-81
west...especially in Steuben, Bradford and Luzerne counties.
Temperatures remain mild, but slightly cooler then today. Highs
will be in the upper 50s to mid-60s.

&&

Short term /tonight through 6 PM Wednesday/...
330 PM update...

Very little change to the short term forecast period, as it
still looks unsettled and wet.

Rain will continue to overspread the region Tuesday night and
Wednesday as a short wave passing through the Great Lakes phases
with a cut-off upper low moving from the srn appalachian mtns
newd to near New Jersey. A weak surface low associated with this system
will track out ahead of the upper low from the Carolinas to the
New England coast. A push of warm moist air northward ahead of
the low will prime the air mass for widespread rain showers into
Wednesday. The most favorable period for moderate rain will be
during the day Wednesday with the sfc low near the Delmarva
Peninsula resulting in tight thermal packing within a moderate
baroclinic zone lifting north through tonight across ern PA and
east-central New York. The development of a weak-MDT layer of mid lvl
f-gen should be enough to enhance precipitation efficiency
during the late morning and afternoon hours on Wednesday.
Guidance is hinting at some marginal instability over the far
southeastern portion of our cwa, but not enough confidence to
add any thunder into the forecast at this time. Rainfall amts
from Tue night through Wednesday should range from 0.5 to 1
inch...with locally higher amts in the elevated regions of the
Poconos and Catskills.

Temperatures will remain fairly mild Tuesday night and Wednesday with
highs in the 50s to near 60 and lows in the 40s.

&&

Long term /Wednesday night through Monday/...
300 PM update...

Start of the period cold rain on back side of surface low and
upper level trough in eastern New York. The rain and low lift
northeast Wednesday night and Thursday. Rain may continue into
Thursday night in the far northeast. Temperatures at low levels
stay above freezing so precipitation should remain as rain.
Cooler highs Thursday in the 50s under the trough and with
neutral advection. Lows Thursday night in the mid and upper 30s.

Weak ridging aloft and weak surface high on Friday before the
next system approaches Friday night. The weekend system a cold
front and narrow but deep upper level trough moving in from the
west. Ahead of this is a coastal that stays well east of the
area. Rainfall amounts look light centered on the daytime
Saturday. Highs in the 50s Saturday. Sunday a large surface
high and upper level ridging moves in with dry mild air. The
high moves to the coast Monday but the region stays dry. Highs
in the 50s Sunday rise to the upper 50s and lower 60s Monday.

&&

Aviation /06z Tuesday through Saturday/...
06z update... if anything, the latest data continues to suggest
a further slowing with the onset of steadier rain/restrictive
conditions. As such, it now looks like VFR will hang on into the
early evening hours, with MVFR-fuel alternate restrictions not
developing until the 00-03z, Wednesday time frame.

S-southeast surface winds of 5-10 kt through much of this morning, may
become a bit gusty this afternoon/evening (gusts of 20-25 kt
likely).

Outlook...

Wednesday-Thursday... restrictions likely with rain showers.
High confidence.

Thursday night and Friday...generally VFR. Moderate confidence.

Friday night and Saturday...some restrictions possible in
scattered rain showers. Lower confidence.

&&

Bgm watches/warnings/advisories...
PA...none.
New York...none.

&&

$$
Synopsis...mjm

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