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Area forecast discussion 
National Weather Service Albany New York
750 PM EDT Monday Sep 1 2014

Synopsis...
high pressure will build east of the region tonight. A cold
front will approach the region late Tuesday into Tuesday evening
bringing showers and thunderstorms...and slightly cooler and
noticeably drier air will follow on Wednesday. The dry weather is
expected to continue the rest of the week.

&&

Near term /until 6 am Tuesday morning/...
as of 730 PM...water vapor loop continues to reveal a rather large
scale subsidence/drying along and east of i81. Latest mesoscale
reflectivity models appear to be too aggressive with the
convective development and have continued to cut back on probability of precipitation/weather
through this evening. Most of the convection remains upstream as
it will take some time to arrive. Based on trends...the cloud
cover and/or convective debris from the Great Lakes should hold
off until sunrise or later over most of the region. So...with high
level of moisture in the lowest levels /dewpoints have recovered
the past couple of hours/ and narrowing dew point depressions over
the region...some fog is expected tonight. Isolated showers are
possible in western areas toward sunrise. Temperatures should be
able to fall to similar levels as last night...maybe even a degree
or two cooler in spots...but still in the 60s to near 70f.

&&

Short term /6 am Tuesday morning through Thursday/...
clouds and coverage of showers and thunderstorms will increase
through the day as the cold front approaches. Some sun should help
temperatures reach well into the 80s for highs...but will depend on
the timing of the clouds and rain. Instability looks to be enough
to support strong thunderstorms with gusty winds and small
hail...with perhaps even isolated marginal severe weather.

Our region will be in the right entrance region of an upper jet
and a low level jet segment is expected to track through the
region for a bit of enhanced low level convergence. A decent
boundary layer equivalent potential temperature gradient should
provide some enhanced low level convergence as well. Precipitable waters could
be quite high...so the usual localized heavy rains and standing
water in areas of poor drainage could occur in thunderstorms.

Lingering showers and storms exit Tuesday night and some partial
clearing is possible by daybreak. Lows should be in the 60s...but
then deeper drying should occur through the day Wednesday with
more noticeable drop in the humidity. Boundary layer temperatures
cool a little but with considerable sunshine and west to northwest
winds...highs Wednesday in the middle 70s to lower 80s.

Dry weather continues into Thursday with just the start of warm
advection through the day. Quite a bit of sun once again expected
Thursday with highs in the upper 70s to middle 80s.

&&

Long term /Thursday night through Monday/...
the extended forecast opens up dry with high pressure over the
northeast shifting offshore with moderating temperatures and an
increase in humidity levels once again. A cold front will approach
the St Lawrence River valley...Great Lakes region...and Midwest
Friday afternoon into Saturday with a chance of showers and
thunderstorms. Cooler and drier conditions return for Sunday into
Monday of next week with Canadian high pressure building in from the
Great Lakes region and southeast Canada.

Thursday night into Friday...surface anticyclone moves off the southern New
England and Long Island coast. The middle level flow becomes zonal.
The forecast area could get under the anticyclonic shear side of the middle
and upper level jet. H850 temperatures may rise a couple of Standard
deviations above normal with the latest 12z GFS indicating h850
temperatures of +17c to +19c for Friday. A few thunderstorms may trigger
in advance of the cold front with a pre frontal surface
trough...especially late Friday PM west of the Hudson River valley.
Lows will be in the m50s to near 60f over the mountains and hills...with
60-65f readings in the valleys. Maximum temperatures were favored close to the
latest wpc values with middle and u80s in the valleys /a few 90f
readings in the middle Hudson Valley/...and u70s to m80s over the hills
and mountains humidity levels will be on the increase with surface dewpoints
mainly in the lower to m60s.

Friday night into Saturday...most active portion of the long term with
a cold front interacting with a moist and unstable air mass. The
timing of the boundary is still variable in the medium range
guidance with the 12z Canadian ggem the fastest...and the European model (ecmwf) the
slowest. We have favored a 12z GFS/wpc blend with a chance of showers
and thunderstorms Friday night...and the best chance of showers and
thunderstorms south and east of the capital region Saturday
afternoon...some of which could be strong if sbcapes of 1000-2000
j/kg are realized. Nonetheless...a chance of thunderstorms was kept in
the forecast on Saturday. Maximum temperatures will depend on the timing of the
front and its associated cloud cover. Lows will be in the middle and
u60s south and east of the capital region...and u50s to l60s mainly
to the north and west. Highs on Saturday are in the m60s to m70s
north and west of aly...and u70s to m80s to the south and east.

Saturday night into Sunday...showers and isolated thunderstorms will
be ending with the front pushing through the southern tier. Some of the
guidance has a weak wave form along the boundary...and move across
New England. A strong surface high will be building in from Midwest and
west-central Great Lakes region. There maybe a few isolated showers over
the north country of New York and the northern dacks...but Sunday was kept dry
at this point with much cooler temperatures...as h850 temperatures fall to +2c to
+8c from northwest to southeast over the forecast area. Lows by Sunday morning will
be in the m40s to m50s over most of the area with more comfortable
humidity levels...and highs will be cool in the u50s to m60s over
the hills and mountains...and mostly u60s to l70s over the valleys with
breezy conditions.

Sunday night into Monday...the cool Canadian air mass will continue
over New York and New England. The surface anticyclone will be positioned
near southeast Ontario and northern New York Monday morning with mostly clear and cool
weather. Lows will be widespread in the 40s to l50s with highs once
again in the 60s to l70s.

&&

Aviation /00z Tuesday through Saturday/...
initially...VFR conditions across the entire region. However...low
stratus/fog/mist will redevelop overnight with an increased
probability for IFR conditions. Looking at the trend 24 hours
ago...we will attempt to follow a similar trend in this set of tafs.

Fog and/or low stratus should burn off Tuesday morning within a
couple of hours of sunrise. Then we shift our attention to the
approaching cold front. This will set the stage for scattered
convection from around the noon hour and continuing into the
afternoon hours. At this time...we will place a prob30 and
continue to adjust timing per trends as they evolve during Tuesday.

Outlook...

Tuesday night: high operational impact. Likely rain showers...tsra.
Wednesday: no operational impact. No sig weather.
Wednesday night: no operational impact. No sig weather.
Thursday: no operational impact. No sig weather.
Thursday night: no operational impact. No sig weather.
Friday: no operational impact. No sig weather.
Friday night: moderate operational impact. Chance of rain showers...tsra.
Saturday: moderate operational impact. Chance of rain showers...tsra.

&&

Fire weather...
high pressure will build east of the region tonight. A cold
front will approach the region late Tuesday into Tuesday evening
bringing showers and thunderstorms...and slightly cooler and
noticeably drier air will follow on Wednesday. The dry weather is
expected to continue the rest of the week.

Relative humidity values tonight and tomorrow night should be 80 to 100 percent
with fog and dew formation tonight. Minimum relative humidity values Tuesday
afternoon are expected to be in the 50 to 70 percent range as
showers and thunderstorms increase in coverage across the region.
After the frontal passage...minimum relative humidity values Wednesday afternoon
should range between 40 and 50 percent.

West to southwest winds at less than 15 miles per hour this evening should
become south by Tuesday morning. Southwest winds at 15 miles per hour or
less will become west to northwest Tuesday night at less than 15
miles per hour. Winds should shift to northwest at around 15 miles per hour Wednesday.

&&

Hydrology...
there were pockets of one inch or more of rainfall...mainly north
and south of the capital region on Sunday. Most areas however
received well under an inch of rainfall. There was little if any
impact on main Stem rivers since we had been dry before this rain
moved in.

Any isolated showers or thunderstorms through Tuesday morning
should have no impact on our watershed.

Tuesday could be a different story. We expect showers and
thunderstorms during the afternoon and evening. Average basin
rainfall looks to be mainly under an inch so once again we do not
expect many if any rises on the rivers. However...rainfall could
be locally heavy producing the usual ponding problems.

Drier weather returns by Wednesday...lasting through the remainder
of the workweek.



For details on specific area rivers and lakes...including observed
and forecast river stages and lake elevations...please visit the
advanced hydrologic prediction service /ahps/ graphs on our website.

&&

Aly watches/warnings/advisories...
CT...none.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...NAS
near term...bgm/NAS
short term...NAS
long term...wasula
aviation...bgm/wasula
fire weather...NAS
hydrology...NAS



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