Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/05/23

Area Forecast Discussion

National Weather Service Burlington VT

 941 PM EST Sat Feb 4 2023

.SYNOPSIS...
Bitterly cold conditions this afternoon and evening will give way to
a warming trend on Sunday as surface high pressure shifts east of
New England. The next chance of precipitation, which should fall
mainly as snow, arrives Sunday night with a weak cold frontal
passage. More precipitation, this time mainly rain, is expected by
mid week.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 931 PM EST Saturday...Temperatures continue to rise slowly
but surely tonight with warm air advection riding winds from the
south and southwest. Blended in some HRRR to both hourly
temperatures and dew points, as our forecast was trending a bit
too high on dews for observations, and the HRRR seemed to have
the best idea on T and Td for the next several hours. Lowered
some of the winds ever so slightly, as conditions are a bit
calmer than expected under the ridge. Skies are now overcast for
most locations across the forecast area, but this could
fluctuate as lapse rates steepen throughout the day tomorrow and
mixing occurs. Some light snow showers or flurries are possible
across northern New York and potentially into Vermont tonight
with the passage of a warm front, included slight PoPs for that
in this update. Previous discussion below:

Previous discussion...Southwest flow will increase this evening
on the backside of the ridge and ahead of weak low pressure
lifting up west of the St Lawrence Valley. This will allow a
weak warm front to cross our area overnight, so the gradual
warming trend will continue tonight right into Sunday. Areas
east of the Greens will likely cool down a few degrees after
sunset since they`re the furthest removed from the warm front,
but even those areas should see climbing temperatures after
midnight. Therefore, lows will mainly occur early in the
overnight period, ranging from 5 to 10 below in the Northeast
Kingdom to around 10 above in the southern St Lawrence Valley. A
few light snow showers can`t be ruled out as the warm front
lifts through, but the vast majority of the region will remain
dry through Sunday morning. South winds increase through the
morning as well, especially in the Champlain Valley owing to
channeling, and temperatures will warm into the lower to mid 30s
areawide in response. The weak parent low will slowly move by
to our north late Sunday into Sunday night, and precipitation
chances will increase as its associated cold front approaches
from the west. The precipitation should start as rain as it
moves into the St Lawrence Valley late in the afternoon, but the
loss of daytime heating along with evaporational cooling should
allow the bulk of the precipitation to fall as snow as the
front gradually shifts east overnight. The snow will focus along
the western slopes of the Adirondacks and the northern Greens,
with an inch or two of accumulation expected. Elsewhere,
snowfall will be less than an inch, with much of the Champlain
Valley and central and southern VT to remain dry. Overnight lows
will be in the mid 20s to around 30.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 315 PM EST Saturday...Snow showers linger Monday morning across
the Adirondacks and northeast Vermont associated with the
aforementioned upper trough passage, but will quickly end by midday
as high pressure builds eastward from the Great Lakes over the
Northeast. Northerly winds on the front-side of the high will
provide a non-diurnal temp trend with morning temperatures in the
mid 20s west to mid 30s east gradually falling through the afternoon
to the teens and 20s by the evening. Under the center of the surface
and upper level ridge axis, lows Monday night will tail off into the
single digits and teens above zero under partly cloudy skies.

After a brief break of high pressure Monday night into Tuesday
morning, active weather returns again heading into Tuesday
afternoon/night as another lows looks to pass north/northwest of the
region. Boundary layers temps ahead of the system will be warmer
than the previous one with widespread mid/upper 30s and some 40s
Tuesday afternoon, offering a valley rain and mountain snow mix
Tuesday evening/night with the best chances for accumulating snow
being across eastern Vermont where light accumulations are possible.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 315 PM EST Saturday...An impactful period of weather remains
ahead for the middle to end of the work week and into the weekend
with a very convoluted upper level pattern evolving. Driest period
will be Wednesday and Wednesday night with high pressure briefly
building back into the region, but by Thursday morning the first in
a series of potent shortwaves embedded in a broad longwave trough
digging into the central US will advance through the Great Lakes and
northwest of the forecast area Thursday afternoon. Strong warm
advection associated with a southwesterly 50-60kt 850mb jet will
support temperatures once again rising above freezing with rain as
the dominate ptype through Thursday night outside of the highest
elevations where snow is likely. There also are indications of a
brief period of a wintry mix of sleet or freezing rain as well at
the onset, but given the poor resolution of guidance out this far
have kept the ptype rain/snow for now.

As this system exits the region Friday, attention will turn to the
next 2 shortwaves over the Great Lakes and southern states and
if/when they phase moving into the Friday night Saturday period. Too
early to tell what will evolve, but there is some agreement among
deterministic and ensemble guidance that the North Country will be
impacted somehow. Whether it`s more rain, mixed precipitation, or
perhaps a significant snow storm remains to be seen, but it`s
something to watch closely heading into midweek.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Through 18Z Sunday...Main threat to aviators will be LLWS with a
low level jet moving over the region 00-06Z. The shear layer
should be around 2000ft out of the southwest around 40kts. SFC
winds will be light and south for most terminals except MSS
which is keeping a NE wind due to channeled flow down the St
Lawrence Valley. South winds increase after 14Z with gusts to
20kts; this may limit LLWS somewhat as speeds begin to phase,
but expect some turbulence to remain. Otherwise, conditions
will remain VFR through 20Z with CIGs lowering west to east
20-06Z as a cold front moves into the North County.


Outlook...

Sunday Night: Mainly VFR, with local IFR possible. Chance SHSN.
Monday: Mainly VFR, with local IFR possible. Slight chance SHSN.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Windy with gusts to 30 kt. Likely SHRA, Slight
chance SHSN.
Tuesday Night: Mainly VFR, with areas MVFR possible. Likely SHRA,
Slight chance SHSN.
Wednesday: Mainly VFR, with areas MVFR possible. NO SIG WX.
Wednesday Night: VFR. NO SIG WX.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Hastings
NEAR TERM...Hastings
SHORT TERM...Lahiff/Storm
LONG TERM...Lahiff
AVIATION...Boyd/Hastings



Area Forecast Discussion

National Weather Service Medford OR

 429 PM PST Sat Feb 4 2023

Updated AVIATION Section

.SHORT TERM...KMAX-88D this afternoon revealing light returns
streaming south to north along the coast region and into Northern
California. A few mtn RAWS have measured a click (.01") in the
past few hours, but things are generally still quite dry.

A deep upper trough off the Oregon coast will gradually make its
way inland through the remainder of the weekend. Tonight a strong
short wave moving through the base of the trough will move
onshore into northern California helping to enhance upslope
precipitation there. Also, a strong surface low being advertised
in the high-res models is expected to move into the coastal waters
and move onshore around Reedsport near 12z. There is uncertainty
in the track of the low and we`ve generally been following HRRR
guidance and are expecting Gales. Winds on the coast will likely
get quite gusty in the overnight but we feel the event will
remain below warning gusts. Wind Advisory will remain for the
Shasta Valley, and local gusts may bump around advisory levels nea
summer Lake but we`ve also held off on a headline there. Also
looking for 15 gust 25-type winds in the Aslhand to Medford
region tonight.

Meanwhile inland, moderate snow rates should begin this evening
in the Mount Shasta region and last into early Sunday. A Winter
Weather Advisory is in effect there above 5000 feet. We considered
extending that Winter Weather Advisory across the South Oregon
Cascades and Siskiyous but no given period seems to threaten
substantial rates, and the heaviest accumulations will be above
above the most traveled routes. Hence no Cascades/Siskiyous
headlines for snow, but it will snow tonight through Sunday with
snow levels beginning near 5000 feet, falling to 4000 overnight,
then to near 3500 feet Sunday with totals of 5-10 inches looking
common. Stavish

.LONG TERM...(Monday through Saturday)...Upper ridging will
result in dry weather for Monday. The upper ridge will flatten out
Tuesday afternoon as the next upper trough approaches from the
west. Precipitation ahead of a cold front will move into the
marine waters and coastal counties Tuesday morning, then spreading
inland west of the Cascades Tuesday afternoon. However the Rogue
Valley could remain dry into Tuesday afternoon due to the westerly
component of the upper flow which typically results in
downsloping.

The front will move through the area Tuesday night, followed by an
upper trough with scattered showers that will become more isolated
as the upper trough axis shifts east during the overnight hours.

The upper trough moves east of the area Wednesday afternoon with
upper ridging building in Wednesday night, and lasting into next
Saturday with dry weather expected. This is being supported by all
members of the GFS ensemble members and the majority of the ECMWF
ensemble members. One thing to note: There`s good agreement an upper
trough will move east near 140W Thursday evening, with a split flow
developing Friday into Saturday with a cutoff low Saturday. However
the location of the low is well enough offshore to keep the best
chance of precipitation well south of our forecast area.
-Petrucelli

&&

.AVIATION...05/00Z TAFs...Southeast winds have surfaced this
afternoon at Medford where gusts recently reached ~30kt and at
Klamath Falls where a gust of ~40kt was recently reported. An
airport weather warning is in effect for Klamath Falls until
midnight for gusts greater than 35kt. Low-level wind shear is
expected where winds aren`t reaching the surface (at Roseburg).
Low pressure is expected to form along a front offshore this
evening, and then move onshore overnight. This could result in a
period of gusty winds at North Bend around 7-10z as offshore east or
southeast winds turn onshore from the SW or west.

VFR ceilings will continue this evening, but MVFR ceilings will
become more widespread overnight as the front and associated
precipitation moves into the area. The exception will be Medford
where VFR ceilings should continue through tonight due to
downsloping. However partial obscuration is possible later tonight
in the higher elevations surrounding Medford. Post-frontal showers
will continue with breezy conditions and a mix of VFR/MVFR on
Sunday. -Spilde

&&

.MARINE...Updated 200 PM PST Saturday, February 4, 2023...An
offshore front will continue to bring strong SSE winds to the
offshore waters this afternoon averaging 20-30 kt with gusts to 40
kt. Steep to very steep seas can be expected due to the combination
of building wind waves and west swell. A surface low pressure center
is expected to form along the front tonight and move quickly through
the waters from southwest to northeast between 7 pm (03z) and 4 am
(12z) PST. Recent hi-res model guidance is showing this low center
having a brief period of strong winds associated with it along with
a sharp wind shift from SSE to W (or even NW). For this reason, we
have expanded the gales to include the inner waters during this time
period. Then, the front will move onshore after 4 am PST (12z). Post-
frontal winds should ease to 15-25 kt (gusts to 30kt) from the WNW.
Fresh WSW swell will then combine with incoming long period W swell
to create steep, hazardous seas Sunday. Seas will build to around 14-
16 ft at 13 seconds Sunday evening, then will gradually subside
below 10 feet by Monday afternoon. Calmer conditions will last into
Monday night before another front and high and steep west swell
builds in late Monday night into Tuesday. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Winter Weather Advisory until 10 AM PST Sunday above 5000 feet
     for CAZ080-082-083.

Wind Advisory until 7 PM PST this evening for CAZ081.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 7 PM PST this
     evening for PZZ350-356.

     Gale Warning from 7 PM this evening to 4 AM PST Sunday for
     PZZ350-356.

     Gale Warning until 4 AM PST Sunday for PZZ370-376.

&&

$$