Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/09/18

Area Forecast Discussion

National Weather Service Binghamton NY

 1007 PM EST Thu Mar 8 2018

.SYNOPSIS...
A slow moving storm system over Northern New England will keep
snow showers over Central NY through at least Friday night. A
few inches of accumulation will be possible, especially in the
higher terrain surrounding the Cortland, Syracuse and Norwich
area. Temperatures will remain seasonably cool, with highs in
the 30s and overnight lows in the 20s.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
945 PM update...
Water vapor channels show two upper level features that will
affect NY and PA into the overnight hours. The first is an upper
level low that will cross east of PA overnight. This feature
will bring scattered snow showers and flurries mainly to
northeast Pa and south central NY overnight and then depart east
of these areas by 09z with a deep west to northwest flow of
fairly chilly and moist air becoming established across all of
central NY / northeast Pa. The other feature was the remnants
of an upper level low over Maine earlier today that will track
westward into Quebec late tonight and become an inverted upper
level trough. The water vapor channels show that moisture with
this feature will work from north to south into central NY and
northern PA overnight. Looking at the thermal fields, our area
will see remnant cold conveyor belt moisture from this upper
feature as the low and mid levels will actually be warm
advecting. Soundings show that moisture increases in the column
overnight and sure enough the hi resolution models bring light
simulated radar echoes south overnight to central NY and
northern PA by 12z Friday. So for the overnight have mainly
scattered flurries and snow showers with likely to categorical
snow showers farther north across north central NY late tonight.
Believe lake enhancement combined with synoptic moisture will
lead to higher POPs for light snow showers up there. Snow
accumulations will be around 1-2" overnight in our far northern
counties rest of area sees less than 1" overnight with many
areas see almost no accumulations.

Then for Friday, with cold air aloft under this broad upper
level low/trough and the stronger March sun, we actually see
some instability generated by afternoon. This will combine with
decent amount of lake enhanced synoptic moisture to lead to
scattered to numerous snow showers. Model mixed layer CAPEs
reach around 40-80 J/KG which isn`t that bad for snow showers.
The shear in the lowest 0-1 km layer was only 15-20 knots which
suggests a more celluar pattern of snow showers which lessons
the likelihood of banded heavy snow showers and potential snow
squalls. Looking at a local study this jives well as we would
need 0-1 km shear to be 30 knots or more for linear convective
structures. The NAMnest and latest HRRR both suggest celluar
convection breaks out with insolation in the afternoon. The
WRF_ARW and WRF_NMM both suggest linear convection. Based on
local study we will follow NAMnest and HRRR for this which
reduces the chances for major snow squalls. We will still have
higher POPs for snow showers especially in central NY.

Previous discussion is below.

300 PM update...

A broad upper level trough remains in place over the Northeast
this afternoon. A large upper level low continues to spin off
the Maine coast, and another upper level disturbance is evident
in the latest GOES-E imagery over Lake Huron. Plenty of strato-
cumulus cloud cover has develop under the unstable atmosphere
this afternoon, along with a few flurries/snow showers.
Temperatures have reached the upper 20s to mid-30s as expected.
The latter disturbance mentioned above will slowly rotate toward
the region later this evening. Behind this system a moist
northwest flow will become established, with snow showers
becoming likely late tonight in all of our NY zones, and also
the far N. Tier of PA. There will be a chance of snow showers
further south toward Towanda--Scranton and Wilkes-Barre.

Snow showers persist through the day on Friday as a well aligned
flow of lower and mid-level moisture continues to wrap around a
nearly stationary mid-level low center near Montreal. Forecast
model soundings indicate steep low level lapse rates below about
700mb...along with some surface based instability (up to 50
J/Kg). This should allow some heavier, convective like snow
showers and squalls to form over much of the area late Friday
morning and into the afternoon hours. These squalls could be
locally heavy at times, reducing visibility to under 1/2 mile
and creating hazardous travel conditions. Surface temperatures
will hold in the lower to mid-30s Friday afternoon, except some
upper 20s in the higher elevations of Central NY. Most locations
along and south of Rte-17/I-86 can expect 1 inch or less of snow
accumulation through the day Friday. Further north, snow amounts
will range from 1 to 3 inches...especially in the higher
elevations. Gusty northwest winds between 10-20 mph, with gusts
up to 25-30 mph can also be expected Friday.

By late Friday afternoon, evening and into Friday night
indications are that a well developed lake effect/enhanced snow
band will form along a 290-300 flow. This band should initially
form along a line from about Penn Yan to Marathon and Walton NY
late Friday afternoon. Latest model guidance is indicating a
good upstream moisture connection with Georgian Bay...which
should allow the snow band to extend a long distance off of Lake
Ontario. By Friday evening, the band should slowly drift north,
along a line from about Auburn/Geneva to Cortland,Norwich,
Oneonta and Delhi. The northern end of the band may be near
Syracuse at this time. The snow band could potentially produce
snowfall rates up to 1 inch per hour at times. The snow band is
forecast to continue drifting north Friday night, eventually
impacting the NYS Thruway corridor from Weedsport to Syracuse
and Utica/Rome. Overnight lows Friday night will be in the 20s
areawide. Outside of the main snow band, expect some scattered
snow showers/flurries across the NY Southern Tier and N. tier
of PA...meanwhile the Wyoming Valley region should be mostly
cloudy but generally dry. Forecast snow accumulations Friday
night look to range from 2 to 4 inches across the northern
Susquehanna Region, Northern Finger Lakes and the NY Thruway
corridor. 1 to 3 inches could fall in the western Catskills
(Delaware/Otsego Counties)...with an inch or less from the NY
Southern Tier and points south into Northeast PA.

Decided to hold off on any winter weather advisories at this
time and let the evening shift and/or midnight shift take
another look at possible accumulations. Main uncertainties
continue to be just how much snow will actually accumulate
during the day on Friday with the marginal temperatures and
stronger March sun angle now in place. Gut feeling is that most
of the accumulations will be above 1500 feet during the day
Friday, with more widespread accumulations into the lower
elevations Friday night.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Deep northwest flow continues bringing moisture into the area.
Cold pool aloft and late winter sun will add to the instability
so snow showers will increase through the day over much of the
area. Exception might be the downslope area of the extreme south
and southeast parts of the forecast area.

Snow showers taper off and end Saturday night as we lose heating
and the flow relaxes. On Sunday, still some instability but we
get some surface ridging so any activity will be light and very
widespread. High pressure builds in bringing a dry weather for
Sunday night.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Closed 500mb low drops into the area on Monday bringing moisture
and widespread snow showers as heating reacts with the cold pool
aloft. Surface flow remains northerly so there will be some lake
input, but main effect will be the additional lift provide as
the flow hits the higher terrain of central NY. Slow moving
system is still directly overhead on Wednesday so there`s little
reason to think the activity will taper off or end before
midweek.

Temperatures during the day will be near normal, in the 30s but
nights will be mild with the clouds and moisture.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Mainly lower VFR ceilings are present across all terminals. A
brief drop to IFR has occurred as of this writing at KAVP from a
localized snow shower. This should end quickly as per radar
trends so no amendment. We expect VFR most terminals through
06z with a few snow showers restricting ceilings and
visibilities to MVFR at KRME, KSYR between 01z and 04z at times
and KITH / KELM / KBGM between 07z and 12z with KBGM likely
seeing brief IFR conditions in this time period. For KBGM we
also expect MVFR ceilings and visibilities in snow showers by
12z. Then for all terminals by late morning Friday we have
ceilings between 2500 feet and 4500 feet with occasional snow
showers dropping conditions to LIFR at KSYR, KRME, KITH and KBGM
and IFR at KELM and MVFR at KAVP between 18z and 22z with the
afternoon heating, combined with cold air aloft and moisture.

Westerly winds be generally 5-12 kts tonight and West to northwest
winds 10-15 kts, with gusts 20-25 kts Friday during the day.

Outlook...

Friday Night through Saturday...Occasional restrictions from
ceiling bases/snow showers, especially CNY terminals.

Saturday Night/Sunday...Primarily VFR.

Monday/Tuesday...Chance of restrictions in snow showers.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$
SYNOPSIS...DJN/MJM
NEAR TERM...DJN/MJM
SHORT TERM...DGM
LONG TERM...DGM
AVIATION...DJN




Area Forecast Discussion

National Weather Service Bismarck ND

 920 PM CST Thu Mar 8 2018

.UPDATE...
Issued at 915 PM CST Thu Mar 8 2018

Some fog is expanding across the James River Valley north into
the Devils Lake Basin so have expended the fog further north. Once
again min temperatures are difficult to judge as they are rapidly
falling across the north central where the remnants of the
surface high remain. So dropped temperatures there 5 to 10
degrees.


UPDATE Issued at 556 PM CST Thu Mar 8 2018

Current radar trends show a large area of snow extending from
Glasgow MT southeast through Wolf Point to near Glendive MT.
Bowman radar shows virga but not much reaching the ground yet.
Web cams still look dry southwest. So will keep the POP trends
going for the evening as is. Current forecast looks ok so far.

&&

.SHORT TERM...(This evening through Friday)
Issued at 116 PM CST Thu Mar 8 2018

For tonight, an initial surge of warm air advection could produce
some light snow across western North Dakota after 00z and into
central North Dakota overnight. Any snow that does fall will be
light and amount to general a tenth of an inch or less.

A moist boundary layer, and light upslope winds may lead to fog
once again for the southern James and Missouri River Valleys. The
HRRR and SREF are hinting at perhaps even more widespread fog than
what is currently forecast, but confidence in fog developing
further north and west is not as high and therefore kept the
mention of fog isolated to the southern river valleys.

.LONG TERM...(Friday night through Thursday)
Issued at 116 PM CST Thu Mar 8 2018

A cold front will follow for Friday night/Saturday. With a lack of
moisture aloft leading to a lack of ice crystals, soundings
indicate the potential for periods of light freezing rain to mix
in with snow. Any periods of light freezing rain should be brief,
and with little moisture/lift to work with accumulation and
therefore impacts should be minimal. Breezy northwest winds 15 to
25 mph will develop behind the cold front Saturday. There should
be enough of a crust on the snowpack to limit drifting or blowing
snow, thus only patchy blowing snow seems reasonable at this time
with minimal or low impacts. Highs Saturday will reach the lower
to mid 30s. An upper level ridge takes control from the Northern
Rockies into the Northern High Plains Sunday through Wednesday.
Expect dry weather with a moderating trend, as highs will reach
into the 30s and 40s Tuesday and Wednesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 556 PM CST Thu Mar 8 2018

Low pressure centered across southwest Alberta Thursday evening
with an associated warm front through Montana is forecast to lift
northeast tonight and Friday. The warm front will be the focus
for snow across southwest and south central North Dakota tonight.
Fog is expected to form across the James river valley tonight an
possibly extend into KBIS-KMOT in moist southeast wind flow.
Expect deteriorating conditions to MVFR late this evening and
overnight with IFR conditions in FZFG at KJMS after 06z.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...WAA
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...WAA