Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Buffalo New York
406 PM EDT Tuesday Jul 29 2014

cool temperatures will remain in place tonight with the chance for
lake enhanced showers east of Lake Erie. A surface trough will cross
New York Wednesday with a period of rain showers likely. The cool
pattern along with chances for showers will last through much of the
week as an upper level area of low pressure hangs over the Great
Lakes. Warmer air will return by the weekend but a lingering trough
aloft will continue chances of showers and possible thunderstorms.


Near term /through Wednesday/...
surface ridging is found across western and north central New York
this afternoon with a broad upper level low continuing to spin over
the Great Lakes and northeast states. Combination of the surface
ridging and weak upslope flow off the lakes will continue the
cloudy skies from western New York east to The Finger lakes. Diurnal
instability may still provide some scattered sprinkles but surface
ridging and cap at 800mb/6500ft will largely limit coverage and
intensity across western New York. East of Lake Ontario...much drier
air aloft as observed on water vapor imagery will keep just scattered/broken
fair weather clouds. Temperatures today will remain near 10 degrees
below late July averages. 12z buf radiosonde observation measured only +6c at 850mb
which is about -2sd. Highs will top out in the upper 60s to around
70 degrees with middle 60s across the colder spots.

Tonight any isolated sprinkles will taper off with lingering low level
cloud cover. July Lake effect will again become likely as BUFKIT
profiles indicate increasing lake induced cape to 1500 j/kg and
equilibrium levels rising over 30kft. Lake-850mb Delta t's will rise
over 13c. This instability will combine with a surface trough
approaching from just west of the lakes with an increase in low
level moisture for cellular lake enhanced showers to develop
northeast of Lake Erie and across Lake Ontario by daybreak. A risk
for waterspouts will also be present. Surface low temperatures overnight
will range from the upper 50s along the Lake Shores to the low 50s
across the inland southern tier.

The surface trough is forecast to shift across western New York
through the morning and early afternoon hours then across north
central New York through the afternoon and early evening hours.
Moisture convergence and lift along the front will bring a likely
probability of rain showers during these periods. Cool temperatures aloft
with lake induced equilibrium levels to 30kft will bring a possibility
for some graupel to fall within any heavier showers that develop
along the trough. Temperatures will warm a degree or two on Wednesday as
the southwest flow ahead of the surface trough raises 850mb temperatures to
near +8c.


Short term /Wednesday night through Friday night/...
an anomalously deep longwave trough will dominate the northeast
quarter of the nation through the short term period. A series of
lower amplitude shortwaves will rotate across the Great Lakes within
the mean longwave trough and provide several periods of enhanced
large scale ascent and moisture. The airmass is also cool enough to
support lake enhanced rain at times.

The airmass will be cool enough to support a lake response Wednesday
night and Thursday...with showers tending to focus over and east of
the lakes again. There may be enough instability left for a few
isolated thunderstorms Thursday afternoon. Finally Thursday night
the longwave trough will begin to pull out into Quebec...allowing
for some drying to take place across the lower lakes. Expect most
locations to be dry Thursday night with partial clearing. The
longwave trough over the east will finally pull away enough into
Quebec on Friday to bring a brief return to mainly dry weather.

Temperatures will continue to run below average through the period.
Highs on Thursday will be in the 70s and near seasonal averages on
Friday. Overnight lows will be cool...but cloud cover will limit
radiational cooling potential. Expect lows in the middle to upper 50s
on the lake plains and lower 50s inland.


Long term /Saturday through Tuesday/...
the broad longwave trough encompassing over 2/3 of the eastern
United States will slightly deepen and sharpen as a fairly strong
wave drops through the backside of this trough at the beginning of
this period. As this wave begins to round the base of the upper
trough increasing southerly flow and moisture will advect northward
along the East Coast and up The Spine of the Appalachians. This will
likely lead to an increasing threat of afternoon showers and
thunderstorms Saturday and to a lesser extent into Sunday.

Beyond Sunday...a great deal of model differences arise regarding
the timing of next system. The European model (ecmwf) continues to be a bit more
progressive with a Monday night and Tuesday time frame with a
frontal passage...right now leaning towards the faster solution with
another round of showers and thunderstorms with the front.

Temperatures overall will hover right around climatology through this
entire period with highs in the upper 70s to near 80f.


Aviation /20z Tuesday through Sunday/...
broken/overcast VFR ceilings remain across much western New York this afternoon
due to a cool moist flow off of the lower Great Lakes beneath a
trough of cold air aloft. Only scattered/broken VFR clouds are found toward
the Eastern Lake Ontario region due to the lack of lake influence
with a northwest flow in place. Isolated sprinkles may pop up this
afternoon but vcsh was removed due to surface ridging across the
region keeping a lid on development. Expect VFR conditions
tonight...with low VFR/MVFR possible closer to 12z as some lake
enhanced clouds and showers develop east of the lakes. A surface
trough will cross western and central New York Wednesday bringing
a period of showers and low VFR ceilings.

Wednesday night and Thursday...VFR/MVFR with scattered showers.
Saturday and Sunday...mainly VFR with chance showers and


upper level low will keep cool temperatures aloft across the Great
Lakes through much of the week. This will bring a chance waterspouts
tonight through Thursday for both lakes along with chances of lake
enhanced showers each night. Winds and waves will remain below Small
Craft Advisory levels.


rainfall the past two days has varied widely from around a half inch
for portions of the southern around an inch near Lake Erie
and east of Lake Ontario to significant rainfall totals across the
Genesee Valley. For our climate station in Rochester New York this
two- day rainfall event has brought some note worthy climate

Event rainfall Sunday and through 4 PM Monday totaled 3.84 inches of
rain in Rochester. There was 1.42 inches of rain on Sunday...and a daily
record of 2.42 inches of rain through 4 PM Monday.

This 2-day or "48-hour" event total of 3.84 inches places 6th
wettest of all 2-day rainfall totals in rochester's history. Below
are the top wettest 2-day totals in rochester's history which dates
back to 1871.

1 4.96 inches October 19-20 1873
2 4.21 inches August 27-28 1871
3 4.20 inches June 6-7 1980
4 4.19 inches August 28-29 1893
5 3.85 inches may 16-17 1974
6 3.84 inches July 27-28 2014

The recent rains have also bumped Rochester into a top 5 wettest
July on record. Below are a listing of the top 5 wettest julys on
record for Rochester new york:

Rank precipitation year

1 9.70 1947
2 8.08 1945
3 8.02 2006
4 7.51 2014
5 6.37 1897

There are still several days remaining in July...thus the final July
2014 precipitation total may increase.


Buf watches/warnings/advisories...
New York...none.



near term...Smith
short term...Franklin
long term...Arkansas

National Weather Service Glossary of Abbreviations