Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/30/23
Area Forecast Discussion
National Weather Service Boston/Norton MA
948 PM EST Fri Dec 29 2023
.SYNOPSIS...
Less fog overnight than previous nights, as winds shift to the
southwest. Clouds dominate Saturday but not a washout, just a
few brief spotty showers along with a few breaks of afternoon
sunshine possible. More sunshine returns Sunday with seasonably
cool temperatures. Generally dry weather Sunday through mid
week, with moderating temps to above normal toward midweek. Low
pressure may impact the region Thursday, with higher
probabilities for rain vs snow. Drier and cold weather likely
arrives around Friday.
&&
.NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
945 PM Update...
Mixed bag of conditions across southern New England this
evening. In areas where light rain/mist has redeveloped,
ceilings remain low, but widespread improvement in ceilings and
visibility is being reported across much of eastern
Massachusetts. Some showers have blossomed across central CT
where we previously had PoPs of less than 10%. Utilized RAP
guidance to fill in the gap, but as precip moves eastward, light
rain/drizzle should end over the next 2-3 hours in CT.
Dense fog has developed along the immediate RI coastline (N.
Kingston reporting 1/4sm) thanks to SW flow and is expected to
pivot, in some form of 1/2-2SM, eastward across the Cape and
Islands over the next few hours. Relied heavily on the HRRR with
this update to account for anticipated cig and vsby reductions
overnight. Fortunately, SW flow will preclude any dense fog
from making it into the Boston metro area this evening.
730 PM update...
Fog and low clouds not as widespread as previous nights, as low
level winds are shifting to the WSW, along with slightly drier
air advecting into the region. Although, cyclonic flow
persists, so a few spotty light showers/sprinkles linger
overnight. This drier air will yield slightly cooler temps than
last night, with lows early Saturday morning mainly 35-40 across
the region.
&&
.SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY/...
Highlights
* Isolated to scattered showers Sat AM into the early afternoon.
Perhaps a few peaks of sun during the afternoon and a bit breezy
at times.
* Dry and quiet weather Sat night into Sun AM with more seasonable
temps. A bit breezy at times.
A trough will be over southern New England Sat AM. The trough will
lift into the Gulf of Maine by late in the day. Could see another
shortwave/trough lifting into New England behind it late in the day.
Despite that second trough will start seeing height rises as a ridge
builds into the Great Lakes Region. The ridge axis builds into
western New England by early Sun. Still stuck under a broad low on
Sat with a cold front sliding through. High pressure nudges in from
the southeastern US Sat night into Sun.
Will have another shot for isolated to scattered showers across
southern New England early Sat AM into the afternoon as the cold
front is sliding through. In wake of the cold front will have drier
air working its way in and perhaps some breaks of sunshine by the
afternoon. Overall haven`t changed the forecast too much in this
timeframe from the previous shift, but did bump our wind
speeds/gusts up Sat afternoon/night. Should get into WNW to NWly
cold air advection. Will not be too difficult in this regime to mix
down 20-30 kt wind gusts in a well mixed boundary layer. For now
hedged toward the lower end as some of the lingering clouds could
keep us from mixing as well, but this may need to be bumped up in
future updates if latest high res guidance is on track. High temps
top in the 40s across the region, but will see them cooling during
the afternoon quickly in wake of the front.
Have nudged down temps Sat night into early Sun due to the strong
WNW/NW cold air advection and clearing skies. At this point stuck
with the 30th percentile of guidance as it looks reasonable given
there still could be some mid/high clouds lingering. Lows generally
in the 20s, but coastal spots bottom out in the low/mid 30s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Highlights...
* Mainly dry weather and very pleasant with slightly above normal
temperatures New Year`s Eve through midweek
* Next chance of precipitation arrives around Thu, but lots of
uncertainty with the track of the low pres. Nonetheless, higher
probabilities for rain than snow given the lack of cold air
Temperatures...
At or above normal temperature regime this period across SNE, as
strong northern Pacific jet continues to flood Canada with a
maritime Pacific airmass. Temps seasonably cool Sunday and Monday
with highs in the upper 30s and lower 40s, along with overnight lows
in the 20s. A piece of this relatively mild maritime Pacific airmass
over Canada advects into SNE Tue and Wed, with highs rising well
into the 40s, especially Wed likely the mildest day next week.
Seasonably cool air returns late next week behind departing
coastal/ocean low around Thursday.
Precipitation...
Surprisingly all 3 ensemble systems (ECENS, GEFS & CMC Ens) are in
very good agreement this period regarding the timing and amplitude
of each short wave trough. Thus, above average forecast confidence
this period. Short wave ridging & a dry column provides pleasant
weather Sunday along with sunshine and a light west wind. A
positively tilted trough advects across SNE Monday, but given the
lack of moisture with this feature, we will keep a dry forecast for
Monday, just extra clouds. Trough exits offshore Tue with rising
heights into Wed along with drier than normal PWATs. Thus, more
pleasant weather with dry conditions both days along with sunshine.
This results in 4 day stretch of dry weather (Sun-Mon-Tue-Wed). The
next chance of precip arrives around Thu, as yet another southern
stream approaches SNE from the SW. Uncertainty on how far north this
feature tracks and if it merges with northern stream energy. Unless
phasing occurs with rapid trough amplification, given the lack of
antecedent cold air available, rain probabilities remain higher than
snow. However, still 6 days away so too early to rule out a given
scenario. Then drier and colder weather likely follows Friday.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z update...high confidence on trends, some uncertainty on
exact details and timing.
Mainly IFR/MVFR along with light spotty showers/sprinkles. Light
SSW winds. Definitely an important from previous nights.
Earlier discussion below.
-----------------------------------------------------------------
Tonight...Moderate confidence in flight categories and trends
A tale of two conditions with terminals either reporting
LIFR/IFR or VFR with LIFR/IFR constrained to terminals reporting
light rain/fog. Conditions will likely fluctuate at any given
terminal between flight categories all night, with confidence
highest in low cigs and vsby across Cape Cod and southern RI
given SW flow. Winds become a bit more westerly by daybreak
which should aid in lifting cigs towards MVFR/VFR at most
terminals.
Saturday...High confidence.
Starting off MVFR, but should improve to VFR by late AM/early
afternoon. Will have isolated to scattered showers late in the
AM through the early afternoon. Winds out of the W at 5-15 kts
and gusts of 15-20 kts during the afternoon.
Saturday Night...High confidence.
VFR conditions anticipated with gusty W to NW winds.
KBOS TAF...High confidence in trends, moderate in timing.
IFR this afternoon into the evening with spotty showers, drizzle
and light winds. Winds shift to the SW tonight and will
gradually improve to MVFR late. Scattered showers possible late
in the AM into the afternoon on Sat, but will be improving to
VFR during the afternoon.
KBDL TAF...High confidence in trends, moderate in timing.
Starting off IFR/LIFR with spotty showers and drizzle this
afternoon into this evening. Will see ceilings gradually improve
to MVFR late and borderline VFR by the Sat AM push. Winds shift
from the S to the WSW/SW tonight and W on Sat.
Outlook /Sunday Night through Tuesday/...
New Years Day: Mainly VFR, with local MVFR possible.
Monday Night: VFR.
Tuesday through Tuesday Night: VFR. Breezy.
Wednesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence.
Areas of drizzle this evening with spotty showers possible late
tonight. Expect SW winds around 10-15 kts with seas diminishing
to 2-4 ft. Have extended the southern waters SCA as winds and
seas will increase to SCA levels on Sat.
Saturday...High confidence.
Isolated to scattered showers as a cold front slides through.
Will have winds increasing out of the W/WNW at 10-20 kts during
the AM to 15-25 kts during the afternoon. Gusts of 20-30 kts
during the afternoon. Seas build 5-8 ft for the
south/southeastern waters and 2-4 ft elsewhere. Additional SCA
hoisted across portions of the southern waters. Please see the
SCA for more details.
Saturday Night...High confidence.
Any lingering showers tapering off during the evening. Winds out
of the WNW to NW at 10-20 kts and gusts 20-25 kts during the
evening lowering below 20 kts late. Seas lowering to 3-6 ft
across the south/southeastern waters and 2-4 ft elsewhere.
Outlook /Sunday Night through Tuesday/...
Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 10 AM Saturday to 1 AM EST Sunday
for ANZ232>235-237.
Small Craft Advisory until 1 AM EST Saturday for ANZ250.
Small Craft Advisory until 7 AM EST Sunday for ANZ254>256.
&&
$$
SYNOPSIS...Nocera/BL
NEAR TERM...Nocera/BL/KS
SHORT TERM...BL
LONG TERM...Nocera
AVIATION...Nocera/BL
MARINE...Nocera/BL
Area Forecast Discussion
National Weather Service Quad Cities IA IL
531 PM CST Fri Dec 29 2023
.KEY MESSAGES...
- Clipper system to bring a round of snow Saturday night into
Sunday (30-60% chance)
- Dry and seasonable temperatures for much of next week
&&
.UPDATE...
Issued at 528 PM CST Fri Dec 29 2023
HRRR runs have now shown a growing signal for fog over northeast
Iowa and northwest Illinois toward morning. I`ll be adding
patchy fog to the forecast for now, but will watch this trend
for introducing a period of possible dense fog toward morning.
Much of this will require complete clearing to occur, and a
strong drop in temperatures over the remaining snow cover.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 135 PM CST Fri Dec 29 2023
Weak ridge of high pressure builds into the area tonight
bringing clear to partly cloudy skies, light winds, and cold
temperatures. Lows should bottom out in the lower to mid 20s.
Can`t rule out some patchy fog/low stratus where winds go calm
for a while with the added moisture from melting snow today.
On Saturday, clouds should increase as warm air advection kicks
in. Highs will be in the 35-40 degree range.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 135 PM CST Fri Dec 29 2023
Saturday night and Sunday: Closed upper low/vigorous trough
dives out of Manitoba and across the Great Lakes region. The
trough will provide forcing but moisture is limited. Models
suggest the better forcing will remain across Wisconsin and
Michigan but a period or two of light snow should spread across
northeast Iowa and northern Illinois. Pops look to be in the 30
to 60 percent range with snow accumulations up to an inch.
Next week: El Nino alive and well with the main storm track from
California to the southeast United States. These are a series of
strong storm systems. Meanwhile, the polar jet will be well to
our north. This places the forecast area in a dry pattern with
seasonable temperatures. Highs will be in the 30s with lows in
the upper teens and 20s.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 528 PM CST Fri Dec 29 2023
Clearing will continue tonight, but towards morning, a period of
ground fog is possible, and I`ve included a temporary condition
of 1sm fog and a scattered LIFR cig. This is a placeholder for a
possible period of dense fog, mainly over the existing thin snow
covered areas. Otherwise, the VFR weather will be expected
through Saturday, with some mid clouds expected and west winds
under 10 kts.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
UPDATE...Ervin
SHORT TERM...Haase
LONG TERM...Haase
AVIATION...Ervin
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
309 PM PST Fri Dec 29 2023
.SYNOPSIS...Showers and isolated thunderstorms are forecast
tonight. Showers will continue on Saturday and then diminish on
Sunday. Drier weather is forecast for Monday followed by more
wet and unsettled weather Tuesday into Wednesday.
&&
.DISCUSSION...Quick moving front will depart to the southeast
this evening, followed by a cooler and showery modified polar
maritime airmass. Significant flooding concerns from excessive
rainfall with the plume of influx high PWATS remains low due to
short duration of heavy rain rates (over 0.30in/hr). None of the
main stem rivers are forecast to reach monitor stage, though
smaller rivers, streams and creeks will probably rise sharply and
the potential for nuisance advisory type flooding will need to be
monitored. Once again snow levels appear to remain high (6kft or
more) with no impacts expected for any of the mountain passes.
Snow levels will fall tonight into Saturday, down to 5000 feet,
however precipitation rates are forecast to diminish in the cooler
and showery air mass across NE Trinity County (Scott Mountain
Pass) and a winter weather advisory will not be necessary.
Showery activity and isolated thunderstorms will follow in the
cooler maritime polar air mass tonight, mainly across coastal
areas of Humboldt, Del Norte and Mendocino Counties. SREF and
HREF calibrated thunderstorm probabilities increase tonight into
the early morning hours of Saturday as the 500mb shortwave trough
splits. Steeper mid level lapse, low buoyant energy and long thin
CAPE profiles will be sufficient for low top storms given the
cooling 500mb temperatures (-25C) and weak upward forcing from
the 500mb shortwave trough. Freezing levels are forecast to stay
way too high (above 4500-5000ft) for any significant small hail
accumulations with CAPE less than 250J/kg. Granted HRRR indicates
higher pockets of CAPE for possible stronger updrafts. Thus,
isolated rice sized hail may reach the ground, though it`s
highly unlikely.
500mb trough axis will move across the area tomorrow and showers
will likely continue to spread onshore and develop over the
interior. 500mb ridging will build Sat night in advance of
another splitting/elongating 500mb trough. Deterministic models
and ensemble means were in agreement with the synoptic scale
progression of the cold core aloft heading southward and parallel
to the Central California coast. Some light and terrain-driven
showers are still possible, primarily for Mendocino, Lake and
eastern Trinity Counties with cool temperatures persisting aloft
(-20C at 500mb).
More pronounced ridging and warming aloft is forecast to build on
Monday as the next "bowling ball" in the line up heads toward the
West Coast. As is almost always the case this time over year,
especially after multiple days of rain, expect fog to form in the
interior and coastal valleys. The one day of dry and stable
weather will not last long as another storm in the parade will
bring more rain, perhaps high mountain snow and perhaps some
thunderstorms. Strong winds are certainly a possibility, however
the details are unclear. The GFS and ECMWF deterministic and
ensemble means are in much better agreement with the timing, but
there are subtle differences in small scale features. The flow
pattern appears to remain progressive and within the norm for NW
California for the first week of January. More precipitation will
probably impact the area late in the week or next weekend.
&&
.AVIATION...Low-level wind shear is the primary concern as winds just
above the surface remain strong as surface winds have backed off
from earlier today. Low-level wind shear conditions should finally
improved toward 12Z Saturday Ceilings have improved this afternoon
more than earlier predicted for the time being, but more waves of
showers are expected to bring ceilings back down to at least MVFR
later this evening, and perhaps lower visibility from showers with
heavier rain. Overall conditions should improve significantly after
12Z Saturday behind the upper level shortwave trough axis.
&&
.MARINE...Wind speeds continue to diminish today as well as seas.
Seas will lag a bit behind, so the gale warning will be replaced by
a hazardous seas warning this evening for all but the sheltered
northern inner waters. Extended the current small craft advisory for
northern inner waters through early Sunday morning mostly due to
seas, with all other waters falling suit after the hazardous seas
warning expires this evening. A series of long period swells are
still forecast next week with wave heights increasing by Tuesday
night.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
High Surf Advisory from 8 PM this evening to 6 AM PST
Saturday for CAZ101-103-104-109.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM PST Sunday for PZZ450.
Hazardous Seas Warning until 9 PM PST this evening for
PZZ455-470-475.
&&
$$
Visit us at https://www.weather.gov/eureka
Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka
For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service Goodland KS
223 PM MST Fri Dec 29 2023
.SHORT TERM...(This evening through Sunday Night)
Issued at 141 PM MST Fri Dec 29 2023
At the start of the short term period, the latest RAP analysis shows
the CWA between an upper air ridge to the west and an upper air low
over KY which yields a mostly northerly flow over the CWA this
afternoon. Current surface observations and satellite imagery
report clear skies and no precipitation with snow still on the
ground mostly in the northern half of the CWA. Going through the
rest of today, models show the CWA staying between the ridge-
trough upper air pattern with the CWA taking a more north-
northwesterly flow by the overnight hours. At the surface, dry
conditions are expected to continue through the rest of the day
with surface winds turning westerly by the overnight hours.
Overnight low temperatures for tonight are forecast to be between
the upper teens and the lower 20s.
On Saturday, forecast guidance shows the CWA staying underneath the
forward portion of the western ridge which gives the CWA a
northwesterly flow aloft through most of the day. At the surface,
precipitation is not expected for the region during the entire day.
A cold front is forecast to move through the CWA from the north
during the evening hours. Daytime highs for Saturday expect to be
in the upper 30s to lower 50s with areas still seeing snow on the
ground in the northern half of the CWA seeing the cooler daytime
temperatures. Overnight lows on Saturday night look to range
between the middle teens and lower 20s.
For the last day of 2023, models project the ridge to move more over
the CWA in the morning giving the CWA a more east-northwesterly
upper air flow. By the Sunday overnight hours, models forecast
the CWA upper air flow to turn north-northwesterly with the axis
of the ridge being over CO. At the surface, models show a surface
high traveling down from the Northern Plains and reaching the CWA
during the overnight hours. This high will allow for the cooler
air to remain in the region. Daytime highs for New Year`s Eve
range between the lower 30s and lower 40s followed by overnight
lows in the lower to upper teens.
.LONG TERM...(Monday through Friday)
Issued at 1225 PM MST Fri Dec 29 2023
The extended period starts out with a surface high clearing the area
which will allow for southerly winds to move in throughout the
day. ECMWF does have a tighter pressure gradient over the area so
may need to keep an eye on wind speeds for New Year Day but
currently doesn`t appear to be anything impactful at this time.
Through the remainder of the week a few quick moving troughs move
through the southern Plains; currently the one that needs to be
kept an eye on is the one late week. Deterministic runs of the GFS
keeps it south with no impacts to the area; the GEFS, ECMWF and
ECMWF ensembles all have some light qpf in the area however with a
more northern track. Light snow for the majority of the area
mixed in with a rain/snow mix to the south is currently favored
for this forecast package. After this, weak system the focus then
turns to another potentially stronger trough that guidance is
currently in agreement on emerging out of the SW CONUS.
Temperatures for the extended period are currently forecasted to be
near normal with highs in the 40s and lows in upper teens to low
20s. The two days with southerly flow (Monday and Thursday), high
temperatures were bumped up a few degrees due to the favorable
pattern for additional warming.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 222 PM MST Fri Dec 29 2023
KGLD...VFR conditions are expected throughout the entire 00Z TAF
period starting with northwesterly winds around 7 kts that turn
westerly by 04Z. At 15Z, KGLD winds become northwesterly once
again around 9 kts before becoming variable around 6 kts by 22Z
through the end of the TAF period.
KMCK...VFR conditions are also seen during the 00Z TAF period
beginning with variable winds around 6 kts that expect to become
north-northwesterly around 9 kts at 18Z through the rest of the
TAF period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...076
LONG TERM...Trigg
AVIATION...076
Area Forecast Discussion
National Weather Service Green Bay WI
536 PM CST Fri Dec 29 2023
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- 0.5-2" of snow possible Saturday night into Sunday as a clipper
system moves through the Great Lakes.
- Highest snow amounts expected across east-central WI, including
the Fox Valley Sunday morning.
- Short period of gusty north winds (20-30 mph) as snow ends
Sunday afternoon and evening could create minor blowing and
drifting snow on east- west oriented roads.
&&
.DISCUSSION...
Issued at 207 PM CST Fri Dec 29 2023
Short Term...Tonight and Saturday
Main forecast concerns will be on cloud trends late tonight and
whether any precipitation could work into parts of north-central
WI late Saturday afternoon.
The 19Z MSAS surface analysis showed a weak ridge of high pressure
that extended from the Upper MS Valley into western Ontario. A
weak area of low pressure over extreme northwest MN is a clipper
system headed in our direction. Visible satellite imagery
indicated skies had cleared over most of the area with some clouds
hanging over east-central WI.
The surface ridge (and its associated upper ridge) to move into
the western Great Lakes region tonight providing for mostly clear
skies and a light west-northwest wind. However, little change in
the air mass overhead could bring another round of low clouds and
patchy fog to parts of northeast WI after midnight. Confidence is
low as to exactly where/if these clouds actually develop. Models
bring the weak clipper low pressure into western Lake Superior
toward daybreak, but a lack of moisture ahead of this system would
preclude any precipitation. Min temperatures to range from the
lower 20s north, middle to upper 20s east-central WI.
This clipper will continue to move southeast and enter northeast
WI Saturday afternoon. However, upper support trails back to
northwest WI/northern MN where a mid-level shortwave trough to be
situated. Since both moisture and forcing are lacking through the
day, most if not all of the forecast area should stay dry. We will
see clouds increase in the afternoon and have kept a slight chance
pop over parts of north-central WI late in the day. Max
temperatures on Saturday to range from the lower to middle 30s
north-central WI, mainly upper 30s east-central WI.
Long Term...Saturday Night Through Friday
Snow...
Changes:
Only slight changes to snow totals from the previous forecast. Did
increase northerly winds a few miles per hour for Sunday afternoon
and evening as a tighter pressure gradient and increasing winds at
925mb could result in gusts of 20-30 mph, mainly for the Fox
Valley and east-central WI.
Details:
The main period of focus of the forecast is a clipper system
bringing a likely chance (60-80%) for snow beginning late Saturday
in northwest WI and spreading southeast before ending mid-Sunday
afternoon. The primary forcing with this system is an area of mid-
level convergence that is progged to pass directly over WI. One
factor that my limit snow accumulation is a lack of strong forcing through
the dendritic growth zone. Accumulations of about 0.5-2" are
expected with the highest totals across the Fox Valley and east-
central WI. There does look to be a short period Sunday afternoon
and evening during which gusty (20-30mph) north winds could create
some blowing and drifting snow, mainly impacting east-west
oriented road.
Uncertainty:
The primary area of uncertainty with this system is whether
northeast winds coming down the bay and lakeshore Sunday morning
could produce lake enhanced snow for a 3-4 hour period before
winds become more northerly by Sunday afternoon. It is likely
that given the short duration for which lake enhancement could
occur snow totals won`t be greatly increased, however, if the low
center continues to trend further east snow totals for areas south
of the bay and along the lakeshore may need to be increased.
Rest of the forecast...
Dry conditions are expected to return to the area for much of the
first half of next week with a high pressure system over the
southern CONUS extending into the region, a cold front associated
with a surface low tacking over central Canada could produce
light snow Wednesday morning, mainly across the Northwoods, but
impacts look minimal at this time. Another clipper type system may
also bring some precipitation towards the end of next week, but
given the that this system is a week out left NBM PoPs for now.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 530 PM CST Fri Dec 29 2023
Clear skies and light winds along with mild temperatures will
result in the formation of fog tonight. Numerical guidance
in the MAV/MET and the HRRR model not supporting it. The HiRes ARX
and NAM12 would support dense fog in spots. Since temp/dewpoint
spread across the far north are already less than 5 degrees, think
fog will be likely across much of the area overnight. This
thinking is supported by three sites along the Minnesota border
already tanking to a quarter to a half mile. Since temperatures
will be below freezing overnight, freezing fog could leave a thin
coating of icing on aircraft. Any low CIGS/fog should improve
Saturday morning. A round of light snow is expected Saturday night
into Sunday which could leave a few inches of snow resulting in
snow removal operations.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Kallas/GK
AVIATION.......Eckberg
Area Forecast Discussion
National Weather Service Raleigh NC
840 PM EST Fri Dec 29 2023
.SYNOPSIS...
A large upper level low will track eastward over and off the East
Coast through early Saturday. High pressure will build over the
Southeast states from late Saturday through New Year`s Eve. A cold
front and upper level trough will cross the region Monday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 840 PM Friday...
Forecast is in pretty good shape, with only small tweaks needed. The
latest surface analysis shows a couple of surface lows over the Mid
Atlantic/Delmarva coast. These low tilt westward in the vertical,
with the low just aloft (at 925-850 mb) seen on GOES imagery
spinning over central VA, while UA data shows the mid level
reflection near the WV/VA border. Multiple surface troughs extend
from, and are pinwheeling about, the Mid Atlantic lows. Passage of
one prominent vort max around the mid level trough base and upper
divergence in the left exit region of the upper jet (stretching from
the NE Gulf off the Southeast coast) provided sufficient deep lift
(working on minimal moisture through the column) to squeeze out some
showers over the N Piedmont over the last several hours (including
some graupel in the Triad late this afternoon, supported by a cool
low level wet bulb profile noted on RAP soundings). These showers
have since dwindled with the shearing vort lobe as they moved into
the N Coastal Plain, as the HREF mean indicated. We`ve even seen
some lightning flashes in central and E VA where the low level lapse
rates extending up into the mixed phase region have topped 6.5 C/km.
The stacked lows will continue to weaken as they lift ENE, leaving
us with mostly clear skies, although some low level moisture
breaching the NC and VA mountains may spill into our W sections, esp
over the next few hours. Temps are on pace to reach lows tonight in
the upper 20s to lower 30s. -GIH
Earlier discussion from 128 PM: The upper trough centered over the
Ohio Valley will move ENE through tonight. Meanwhile, an embedded
s/w disturbance in the SW flow ahead of the trough axis will help to
push a sfc cold front east across central NC through this evening.
Despite the current mesoanalysis which shows a fairly dry airmass
over us now, the HRRR continues to squeeze out a few brief high-
based low-qpf showers as the front crosses our area. These showers
will be possible between 20z and 00Z west of the Triangle and
between 22z and 02Z from the Triangle eastward. Otherwise, it will
briefly turn breezy for a couple hours along and behind the front as
NW sfc winds gust up to 20 mph. Behind the front we`ll see clearing
skies and CAA. Lows tonight a couple deg either side of 30.
&&
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 132 PM Friday...
A strong vorticity perturbation embedded within the cyclonic flow
aloft will push to our south early Saturday. A second perturbation
will cross our area late Saturday into Sunday. Devoid of ample
moisture and sfc forcing, dry weather will accompany these features
as they swing through and offshore. Periods of scattered cloudiness
can be expected, however, along with below normal highs in the upper
40s to around 50 in the south. As the upper perturbations push
through, forecast soundings indicate some decent mixing of stronger
winds to the sfc could be possible. As such, expect some gustiness
later Saturday morning to pick up into the 10 to 20 mph range into
the afternoon period. Winds will dissipate with sunset. Good
radiational cooling conditions are expected Saturday night, which
should allow lows to dip into the upper 20s to around 30 across the
south (colder temps possible at our traditionally cooler spots).
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 235 PM Friday...
New Year`s Eve will begin with low pressure over the Great Lakes and
high pressure over the northern Gulf of Mexico. Dry weather will
continue Sunday into Monday as the low moves over the mid-Atlantic
states and offshore. The GFS and ECMWF model camps still aren`t
coming into much agreement with how much precipitation there will be
along the cold front. The GFS/GEFS continue to show the bulk of the
precipitation south of the region where there is higher moisture
content, but do show rain extending as far north as southern
Virginia. Meanwhile, the 12Z ECMWF shows the bulk of the rainfall
remaining offshore and the 06Z EPS generally shows most of the
precipitation across eastern North Carolina, although rain could
reach as far west as Durham. Haven`t changed too much of this part
of the forecast, leaving a slight chance of pops most places Monday
afternoon and evening, then speeding up the departing precipitation
late Monday night.
Behind the cold front, high pressure will move in for Tuesday and
Wednesday before another low pressure system moves northeast from
the Texas coast Wednesday morning to the Carolinas Thursday morning
and off New England by Friday. This should be a quick moving system,
with the chance of precipitation moving in Wednesday night and
mostly moving east by Thursday afternoon. Despite some of the usual
differences in the models for a day 6 forecast, there was enough
agreement to add likely pops from the Triangle south and west. With
the low pushing east, the forecast is dry Thursday night and Friday.
Highs will be in the 50s. Lows will be in the upper 20s and 30s. The
temperatures will be warm enough that all precipitation should fall
as rain.
&&
.AVIATION /2320Z FRIDAY THROUGH WEDNESDAY/...
As of 620 PM Friday...
VFR conditions are expected through the TAF period. A front is
currently working it way across the area, in the vicinity of RDU as
of 23z. Brief gusts around 20 kts, light rain, and cigs around 3000
to 5000 feet accompany the front before quickly moving away from
terminals. Forecast to reach RWI around to shortly after 01z.
Locations may remain gusty for a couple hours post fropa before
ceasing beyond 3-4z. Mostly clear skies late tonight will fill back
in with patches of flat stratocu Sat afternoon with gusty conditions
15-20 kts through 22z. -Swiggett
Beyond 00z Sunday: VFR conditions are expected through the weekend.
Precip chances associated with an upper level trough and attendant
cold front moving into the area late Monday through early Tuesday
will bring the next chance for sub-VFR flight restrictions to the
Carolinas. -np
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Hartfield
NEAR TERM...Hartfield/np
SHORT TERM...Luchetti
LONG TERM...Green
AVIATION...Swiggett/np
Area Forecast Discussion
National Weather Service Las Vegas NV
730 PM PST Fri Dec 29 2023
.SYNOPSIS...A series of storm systems will move through the region
in the week ahead bringing cooler conditions and periods of
unsettled weather. The first system will arrive Saturday spreading
rain and high elevation snow across the region, followed by
additional light shower activity on Sunday. The next storm system
is set to arrive midweek which will bring somewhat lower snow
levels and additional precipitation potential.
&&
.UPDATE...Partly to mostly cloudy skies will continue over the
Mojave Desert and southern Nevada tonight as a storm system moves
into central California. No update necessary.
As of 7 pm, light to moderate band of rain was occurring along a
cold front moving into central California. Models indicate upper
trough still offshore will split tonight with southern stream
shortwave coming onshore around Pt. Conception early Saturday
morning. HRRR suggests rain band will stay intact tonight as it
progresses inland through the San Joaquin Valley and Santa
Barbara/Ventura Counties. New incoming hi-res guidance suggests this
band will become less organized as it encounters the southern
Sierra/southern California mountains Saturday morning as it starts
to move into the Mojave Desert and southern Great Basin. However
during the afternoon, anticipate scattered to numerous instability
showers to flare up primarily over the higher terrain under the cold
pool aloft. Those showers will dissipate by late evening as the
trough quickly shifts east into Arizona as the region lies under a
weak, transitory ridge Sunday morning.
&&
.SHORT TERM...through the weekend.
Our next weather maker is currently approaching the Northern
California coastline, spreading rain across coastal NorCal and
increasing mid and high clouds into the Great Basin and Mojave
Desert this afternoon. This trough will continue to progress
eastward tonight, and eventually close off into a small closed low
as it enters the Mojave Desert Saturday afternoon. While this
initial storm system is not especially strong, the low center
will move directly across far southern Nevada tomorrow afternoon
and evening, accompanied by a modest influx of low and mid level
moisture and cold air aloft. This will help promote fairly
widespread shower activity across our western zones Saturday
morning, which will spread into southern Nevada and northwest
Arizona during the afternoon and evening.
Rainfall expectations are very light for the lower desert
elevations, with sprinkles to a few hundredths being possible.
The higher elevations in the Spring Mountains, particularly near
Lee and Kyle Canyon, may squeeze out a few inches of snow during
the afternoon and evening hours, mainly above 7000 feet. Its worth
noting there is a fairly wide range of snowfall possibilities
around Mt. Charleston tomorrow with todays HRRR guidance more
bullish suggesting several inches, while some of the global models
are more pessimistic. Opted for a bit of a middle ground along the
lines of the HREF which favor amounts of 2-4 inches, but
uncertainty in snowfall forecast is higher than usual.
Shower activity will diminish late Saturday night, but additional
light shower activity will be possible Sunday afternoon and
evening, particularly north and west of I-15 with some increasing
upper level diffluence and an approaching shortwave moving in.
However, precipitation amounts through Sunday night are expected
to be quite light, ranging from simply sprinkles to a stray
hundredth or two.
.LONG TERM...Next week.
A Pacific trough will track to our south, roughly along the
southern international border on Monday with generally minimal
impacts expected. However, some lingering low PoPs persist across
the area with some scattered light showers possible through Monday
afternoon. Thereafter, a shortwave ridge will build in for Monday
night and Tuesday ahead of the next Pacific storm system making
its approach by midweek.
This next system will be a bit more robust than the previous
systems, and will be accompanied some colder air and lower snow
levels. That being said, there remains some lingering uncertainty
in the exact track, with some of the cluster guidance suggesting a
somewhat more southerly track (which has been a popular theme of
the season so far) which could cut into precipitation
expectations. Nonetheless, increasing precipitation potential is
anticipated Wednesday and Thursday, with snow levels falling into
the 4000-5000 foot range. This could result in some of the first
winter impacts of the season for some of our mountain travel
routes, so keep an eye on the forecast trends as things become
more clear.
Thereafter, yet another large Western trough is suggested in
extended range guidance by next weekend, which jives with the
current 8-14 day outlook by the CPC favoring below normal
temperatures and above normal precipitation as we head into mid-
January.
&&
.AVIATION...For Harry Reid...Winds will be light and diurnal through
the TAF period. SCT-BKN cloud cover will persist through the day
today aoa 15 kft before briefly clearing out Saturday morning. SCT-
BKN cloud cover will return around 20Z aoa 20 kft. However, there
remains a moderate chance of light rain on Saturday, with showers
possible in the vicinity of the terminal between 20Z and 04Z. With
light rain, ceilings could drop as low as 5 kft.
For the rest of southern Nevada, northwestern Arizona, and
southeastern California...Winds will be light and diurnal through
the TAF period, with the exception of KBIH, where gusty south-
southeast winds will pick up between 20 and 30 kts this afternoon.
KBIH gusts will gradually subside after sunset as they become light
and northerly by sunrise. SCT-BKN cloud cover will persist through
the day today aoa 15 kft before briefly clearing out Saturday
morning. Cloud cover returns to the region, with a slight chance of
light rain for southern Nevada Saturday afternoon.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Pierce
DISCUSSION...Outler
AVIATION...Varian
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