Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/04/22
Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CST Mon Jan 3 2022
.SYNOPSIS...
Issued at 248 PM CST Mon Jan 3 2022
After a brief and modest warm-up on Tuesday, a cold frontal
passage early Wednesday morning will bring strong westerly winds
and nearly steady temperatures during the day before a sharp
cool-down occurs on Wednesday night. The next chance of snow comes
to central Illinois on Thursday.
&&
.UPDATE...
Issued at 900 PM CST Mon Jan 3 2022
A pressure gradient will slowly increase across central IL
overnight as a surface high pressure ridge moves farther to the
east and low pressure moves into and deepens in the northern
Plains. The resulting southerly wind should be modest, generally 5
to 10 mph, but increasing gradually toward morning. Temperature
falls should be limited as a result, and expect lows ranging from
17 in Galesburg to 24 in Lawrenceville. Cloud cover will be just
high and thin. Afternoon forecast package is on track with these
features, and no significant updates are needed this evening.
&&
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 248 PM CST Mon Jan 3 2022
Current day cloud phase satellite imagery depicts snow cover well,
with at least some snow cover detected at most locations
northwest of I-55. In addition, cloud cover is still hanging on
in southeastern portions of the forecast area with broken
stratocumulus observed mainly south of I-70. Blended sky cover
forecasts are not handling this well, so relied heavily on the
latest HRRR to incorporate current sky cover trends.
Light west/southwest winds have developed at most locations in
central Illinois as the surface ridge has moved off to the east of
the area. Expect fairly light south winds to continue through the
overnight hours, with a speed increase as well as some gustiness
developing after sunrise. The surface pressure gradient will be
increasing in response to the development of and movement of a
surface low across the northern Plains. South winds will be
elevated on Tuesday, and in addition daytime temperatures should
be the warmest of the week with highs in the mid 30s to mid 40s.
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 248 PM CST Mon Jan 3 2022
The shortwave trough digging from the northern Rockies into the
Plains/Midwest from Tuesday into Wednesday, and the associated
surface low, will bring the next cold front with it. Current
timing has south winds continuing into Tuesday night with the
front crossing central Illinois during the early morning hours on
Wednesday. Given the pressure rises behind the front and potential
for elevated wind speeds NBM wind speeds were boosted during the
Tuesday night - Wednesday night period. ECMWF EFI values north of
I-72 during this period are in the 0.7-0.8 range, indicating
deviation of the ensemble membership from climatology for the wind
speed forecast. Temperatures will struggle to warm at all during
the day on Wednesday, with a sharp drop anticipated on Wednesday
evening.
On Thursday, the next short wave trough is expected to affect
central Illinois. Unfortunately, there still isn`t great agreement
amongst guidance as far as the strength/track of this wave and
associated QPF amounts. WPC cluster analysis still shows about 55%
of members with a weaker wave and very light QPF, about 25% of
members with a stronger wave and greater than 0.25" south of I-72,
and the other 20% somewhere in the middle. Translated, odds
currently lean toward a light snow event for most of the forecast
area on Thursday but with potential for several inches especially
south of I-72. Snow ratios of 13-16:1 mean that it won`t take much
of a QPF change to change snow amounts substantially. Notably, the
ECMWF EFI for snow on Thursday depicts an area with values of
0.5-0.6 south of I-72 on Thursday, indicating deviation from
ensemble climatology toward an unusual event. These values are a
bit higher than yesterday, which is at least something.
Following Thursday`s short wave trough, winds potentially
continuing at 10-15 mph into the overnight hours along with
temperatures in the single digits to a bit below zero will combine
for some bitter cold wind chills. Wind chill temperatures by
Friday morning may fall into the -15 to -20 deg F range or even
colder.
Following another day with highs in the teens on Friday, expect
some warming on Saturday ahead of the next short wave trough,
with high temperatures expected to be back above freezing. A
chance of precipitation will exist southeast of the surface
trough. Both the GFS and ECMWF deterministic models bring the cold
front through early on Sunday morning with a return to colder
temperatures, but WPC cluster analysis shows this agreement may be
coincidental with about 35% of members delaying the front and
keeping temperatures relatively warm on Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 522 PM CST Mon Jan 3 2022
VFR conditions with increasing high clouds over the upcoming 24
hours. Winds S 5-10 kts overnight, increasing to 10-14 kts with
gusts around 20 kts after 12Z, and finally reaching 15-20 kts with
gusts 25-30 kts by 17Z-18Z.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...37
SYNOPSIS...AAT
SHORT TERM...AAT
LONG TERM...AAT
AVIATION...37
Area Forecast Discussion
National Weather Service North Platte NE
842 PM CST Mon Jan 3 2022
.UPDATE...
Issued at 842 PM CST Mon Jan 3 2022
Just upgraded the high wind watch to a high wind warning for
portions of the eastern Nebraska Panhandle, western Sandhills and
far southwestern Nebraska. Looking at the latest HRRR and NAM12
soln tonight and their H85 wind forecasts, feel confident enough
to upgrade the high wind watch to a warning for all counties
except Sheridan county. After coordinating with CYS, will leave
Sheridan county in a watch as there is some doubt as to how far
north the axis of high winds will reach. Went ahead and added
Perkins and Chase counties as HRRR and NAM12 Bufkit soundings
indicate mixing potential around 60 MPH centered around 1 PM MST.
For the high wind warning, it will run from 9 AM to 5 PM MST.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 350 PM CST Mon Jan 3 2022
The forecast concern in the short term will be high wind potential
on Tuesday with the arrival of an arctic cold front Tuesday night.
Surface low pressure will extend from southwest SD and western NE
12Z Tuesday as a prefrontal trough moves east during the morning. A
cold front will then drop southeast during the afternoon. This will
bring the potential for high winds to the western Sandhills and
southwest NE. The 18Z HRRR wind gusts support gusts to around 60 mph
across the eastern panhandle into Grant, Arthur, and Keith County
which remains within the current High Wind Watch area. The GFS and
NAM bufkit soundings do not support expanding the High Wind Watch
area. Used the NBM 90th percentile for winds, and windy conditions
will also occur elsewhere with gusts from 35 to 50 mph expected.
.LONG TERM...(Wednesday through Monday)
Issued at 350 PM CST Mon Jan 3 2022
The forecast concern in the long term will be significant snowfall
potential Wednesday into Wednesday night and bitter cold
temperatures through Thursday night.
Much colder temperatures will drop into western NE Tuesday night
with lows from 0 to 5 below north central and wind chills
approaching 20 below. Highs Wednesday only 5 to 10 above north to
the upper teens and low 20s southwest.
Computer models have come into better agreement on significant
snowfall across wrn Nebraska Wednesday into Wednesday night. There
are still track differences regarding the location of a 100 mile
wide band of snow ranging from swrn Nebraska to the northern
Sandhills. The SREF mean is farthest north, while the ECMWF and
NAM are nearest the current forecast. The GFS, on the other hand
is farthest south, although some members of the GFS also have
varying solutions further north. The current forecast continues
to focus the heavier snowfall in a 40 mile wide band centered
along highway 26 in the Panhandle and then southeast to along I-80
through North Platte and Brady.
This system will track southeast from WY into wrn and swrn NE.
Fairly strong isentropic upglide will be present on Wednesday, with
downglide increasing from west to east during the evening. Similar
to the recent snow event on Dec. 31 into Jan 1st, snow ratios
will be high, due to the presence of arctic air in place.
Currently using a 17-18:1 ratio Wed. into Wed. night. Within the
axis of highest QPFs, from 0.30 to 0.35 inches, resulting snowfall
totals of 5 to 6 inches are forecast. Higher ratios of 25:1 are
certainly possible, and have issued a Winter Storm Watch from 15Z
Wednesday until 12Z Thursday for the southeast panhandle into much
of west central NE. A very favorable snow growth environment
should develop in the arctic air. Frontogenesis and lift is strong
in the dendritic growth zone which, for this system, is quite
deep, from 550-850mb. This further increases the concern that a
light fluffy snow will occur with snowfall amounts greater than 6
inches in the heavier snow bands.
In addition to the snow, northeast winds will become north by
evening with frequent gusts from 15 to 25 mph. Blowing snow is
forecast. The wind chill values are likely to fall to 20 to 29 below
overnight Wednesday and possibly even colder, as temperatures
fall to 5 below to near 20 below. The latest forecast suggest Wind
Chill Advisories and Warnings may be needed across all of wrn and
ncntl Nebraska Wednesday night and Thursday morning.
Very cold Thursday, with highs only 5 to 15 above. Weak warm air
advection aloft begins on Thursday, to bring a slight chance for
light snow into Thursday evening, mainly across the western
Sandhills and north central NE.
A warming trend Friday into Saturday. The next upper trough moves
into the region Saturday, which is forecast to bring a cold front
into the area later Saturday into Sunday. Highs next Sunday will
be colder on the 30s, but should warm back up by next Monday as
upper ridging begins to build back in.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 606 PM CST Mon Jan 3 2022
Strong winds will be the main aviation concern over the next day.
Gusty westerly winds are expected across the region by late tomorrow
morning and continuing through the afternoon. Gusts up to 40 knots
could be possible especially in the afternoon. Winds diminish
slightly after sunset with the next chance of snow arriving after
00Z Wednesday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 9 AM to 5 PM MST Tuesday for NEZ022-023-
035-056>058-069.
Winter Storm Watch from Wednesday morning through late Wednesday
night for NEZ022-023-035-036-056-057-059.
High Wind Watch from Tuesday morning through Tuesday afternoon
for NEZ004.
&&
$$
UPDATE...Buttler
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Kulik
Area Forecast Discussion
National Weather Service Marquette MI
656 PM EST Mon Jan 3 2022
.SHORT TERM...(This evening through Tuesday)
Issued at 258 PM EST MON JAN 3 2022
GOES imagery and RAP analysis show a low-amplitude wave passing to
the north of Lake Superior today as increasing SW flow has brought
increasing temperatures back closer to normal this afternoon. Some
mid-level clouds are increasing upstream across northern WI in
response to WAA. Benign conditions are expected through the rest of
the day with only an isolated snow shower possible across the
Keweenaw. Moisture is shallow, but as a sfc trof crosses the lake it
could be just enough to spit out a few showers.
Tonight, winds veer around to E to SE as the weak sfc low pulls away
and a sfc trof approaches btwn two ridges. While this won`t amount
to much, there could be some add`l light snow showers across the
Keweenaw late tonight as easterly flow upslopes across the
Peninsula. More likely will be some lower clouds by tomorrow
morning. While winds relax tonight, clouds are expected to hang
around through the night...then then increase towards tomorrow
morning, which should help temps from crashing too much. Depending
on the cloud cover, temps will be around zero to the low teens above
zero where clouds persist the longest. Should any location go some
time without clouds, single digits below zero will be
possible...more likely across the interior and along the WI state
line.
Tomorrow, as the advertised mid-week low approaches from the
Dakotas, southerly WAA flow will increase cloud cover across the UP
with temperatures climbing up to around 30 across the east half.
Moisture remains limited throughout the day, so not expecting much
in the way of pcpn; however, there could be some isolated -shsn/fzdz
across the east with some assistance from Lake Michigan. Some
isolated shsn will continue across the Keweenaw, but moisture
remains limited so accums through the day aren`t expected. The aftn
will become breezy...especially across the east half. WAA
downsloping into along the Superior shore could bring gusts to
around 30mph for the aftn as well as along the Lake Michigan
shoreline.
.LONG TERM...(Tuesday night through Monday)
Issued at 347 PM EST MON JAN 3 2022
The start of the long-term period will be marked by the incoming,
well-advertised low that has decent definition in the lower
levels, but only briefly tightens up in the upper levels as it
crosses the Upper Great Lakes late Tuesday into Wednesday. The
system will be accompanied by PWATs approaching the 90% moving
average for early January (so just shy of a half inch). On Tuesday
night into Wednesday, models depict low-level frontogenetical
forcing initially offshore moving inland toward the SE across much
of the U.P. On Wednesday, a LLJ develops over the Great Lake of
Superior and noses into the U.P. At the surface, winds with a more
Erly component overnight Tuesday becomes more NErly to Nrly on
Wednesday. Putting all of this together, the picture comes
together to form a forecast of continuing to support watch (to
perhaps warning) level criteria for heavy snow within the areas
that already have a headline going. The ingredients come together
for the heaviest snow to fall in the late overnight to early
morning period for the Keweenaw and west, and in the first half of
Wednesday for Marquette and Baraga counties. Also note that
blowing snow becomes increasingly likely near and along Lake
Superior on Wednesday, adding to the less-than-ideal driving
conditions expected. But, this system snow becoming lake enhanced
event will turn into LES later Wednesday from west to east as the
responsible low continues its ENE trek. Supportive wind and
thermal profiles indicate the LES chances will persist for
portions of primarily the northern U.P. through much of the
remainder of this first full week of 2022, looking to taper off by
week`s end. However, the rest of this long-term period looks to
remain active as another system grazes past over the weekend.
The aforementioned (see discussion above) WAA late Tuesday will be
on the decline overnight, with CAA taking over Upper Michigan by
late Wednesday. Near normal temps overnight Tuesday into Wednesday
will be replaced by below normal temps for the second half of the
week, but then rebounding back toward normal over the weekend. The
coldest night looks to occur Thursday night into Friday morning,
with widespread single digits on either side of the zero degree
mark.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 656 PM EST MON JAN 3 2022
In the wake of a cold front that has passed CMX, lake aided
postfrontal low-level moisture and upslope flow should maintain IFR
cigs thru the evening. As the flow veers to a weaker upslope
northerly direction overnight, cigs should lift to low MVFR. Winds
will continue veering, settling to an easterly direction by morning.
This should result in cigs slipping back to IFR. There may be slight
improvement back to low MVFR in the aftn.
At IWD, front will be weakening as it approaches, so postfrontal low-
level moisture may not reach the terminal. Overall, VFR conditions
should prevail tonight, but there will be a period late evening into
the overnight where low MVFR cigs may occasionally appear. Expect
VFR on Tue. Approaching low pres system may bring -sn/MVFR cigs near
the end of the fcst period.
At SAW, VFR should prevail thru the evening. Low-level moisture
associated with the weakening cold front may lead to IFR cigs
developing late tonight. A developing light upslope se wind
developing Tue morning would then work to hold IFR cigs in place.
Some improvement to low MVFR possible by aftn.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 258 PM EST MON JAN 3 2022
Westerly winds to around 30 knots will remain possible through this
evening behind a passing low to the north of the lake. Winds will
relax tonight as they veer around to the E to SE for Tuesday,
increasing through the afternoon and evening as a low pressure
system approaches from the west. This low will pass through the
Mackinac Straits Wednesday afternoon. As this low moves through
Tuesday night, NE gales to 45 knots are expected across the west and
central, with a chance for a few hours of storm force gusts to
50kts. NE gales of 40 to 45 knots are expected across the east. As
the low pulls away on Wednesday, winds will become northerly with
gales to 40 knots possible through Wednesday evening. Freezing spray
may be heavy at times as the low builds waves upwards of 16+ft. High
pressure will return for Thursday and Friday, with seasonally light
winds to around 20 knots expected; however, a cold air mass will
remain over the lake with temps around 10 to the mid teens Thursday
and Friday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Watch from Tuesday evening through Wednesday
evening for MIZ001-003.
Winter Storm Watch from Tuesday evening through Wednesday
evening for MIZ002-009.
Winter Storm Watch from late Tuesday night through Wednesday
evening for MIZ004-005-084.
Lake Superior...
Gale Watch from Wednesday morning through Wednesday evening for
LSZ267.
Gale Watch from Tuesday evening through Wednesday evening for
LSZ266.
Gale Warning from 7 PM EST /6 PM CST/ Tuesday to 5 PM EST /4 PM
CST/ Wednesday for LSZ162.
Gale Warning from 7 PM Tuesday to 7 PM EST Wednesday for LSZ263-
264.
Gale Watch from late Tuesday night through Wednesday evening for
LSZ241>245-265.
Gale Watch from late Tuesday night through Wednesday afternoon
for LSZ240.
Lake Michigan...
None.
&&
$$
SHORT TERM...JAW
LONG TERM...lg
AVIATION...Rolfson
MARINE...JAW
Area Forecast Discussion
National Weather Service Phoenix AZ
400 PM MST Mon Jan 3 2022
.SYNOPSIS...
High pressure with dry and mostly clear conditions will be
persistent through the week. Localized freezing temperatures will
again be possible Wednesday morning, but mainly away from population
centers. Temperatures are forecast to warm to slightly above normal
readings starting Thursday, likely lasting through the upcoming
weekend.
&&
.DISCUSSION...
Upper level ridging has returned to the Desert Southwest with dry
southwest flow aloft. RAP analysis soundings show a very dry
atmosphere with PWAT near 0.15 inches this afternoon. Closer to the
surface, lingering cold air remains entrenched in the wake of the
previous storm system. This led to low temperatures in the 30s
across many lower desert locations once again this morning, albeit a
few degrees warmer than yesterday. A weak northerly gradient
increased wind speeds a bit along the foothills north and east of
Phoenix and contributed to the somewhat warmer lows seen there.
Upper level heights will continue to rise the next few days as a
strong area of high pressure builds in along the west coast and
Desert Southwest regions. This will allow for temperatures to warm a
few degrees each day. Temperatures will climb to above normal
readings by mid week and remain there through the coming weekend.
Wind speeds will remain very light for most of the week as well.
An upper level trough will pass well to the north on Tuesday,
slightly increasing the upper level relative humidity. Accordingly,
periods of high clouds are possible Tuesday and Wednesday, but
clouds should be thin enough that they will not impact daytime
heating much. The warmest daytime highs this week are likely to fall
on Thursday and Friday with readings topping out at around 70
degrees. The NBM shows about a 50% of reaching 70F or greater in
Phoenix by Friday. In Imperial and Yuma, the odds are 65-70%. The
amplified flow aloft later this week could eventually result in a
weather system diving southeastward toward our region over the
weekend, but the majority of ensemble guidance shows this system
merely lowering geopotential heights and bringing a slight dip in
temperatures on Saturday. WPC cluster analysis reveals that a
minority of ensemble guidance do allow for this trough to dig deep
enough to bring a slight chance of showers to the region. However,
this appears to be very GEFS-centric, with the EPS and GEPS
remaining completely dry and the latest NBM showing a less than 5%
chance of precipitation. The most likely outcome is for dry
conditions to continue with an increase in clouds, breezy
conditions, and a drop in temperatures for a few days.
&&
.AVIATION...Updated 2300Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
No weather impacts are anticipated through Tuesday evening with only
a few high cirrus decks. Trends in winds will be nearly identical to
the past 24 hours with prolonged periods of light and variable
character.
&&
.FIRE WEATHER...
Wednesday through Sunday:
Weak high pressure will dominate across the region through the
majority of the period with dry conditions prevailing through at
least Saturday. Temperatures will return to seasonal normals by the
middle of the week and likely slightly above normal by late week.
Aside from some occasional light afternoon breezes, winds will
generally be light through the entire period. Minimum RHs through
the period will mostly be in a 25-35% range, while overnight max RHs
mostly climb above 60%.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hodges/Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman
Area Forecast Discussion
National Weather Service Blacksburg VA
647 PM EST Mon Jan 3 2022
.SYNOPSIS...
High pressure will build across the region tonight, resulting
in significantly colder temperatures. The high will drift
overhead Tuesday, maintaining a mostly clear sky with light and
variable winds. A dry front is forecast to pass across the
region Wednesday, then stall to our south Wednesday night.
Thursday, an upper level trough dropping southeast from the
upper midwest is expected to result in a wave of low pressure
to develop along the stalled front to our south...which will be
the next opportunity for wintry precipitation.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 630 PM EST Monday...
Significantly colder tonight with potential for black ice.
Have slowed down the clearing on the western slopes of the
central Appalachians. Otherwise no changes in the forecast.
High pressure will build across the forecast area tonight,
passing overhead Tuesday. For areas with fresh snow cover, this
will set the stage for a very cold night tonight, temperatures
dipping into the teens. Some of the mountain valleys may see
readings dip into the single digits. Any snowmelt which occurred
today will refreeze with potential for patches of black ice on
roads and sidewalks.
Tuesday will feature a sunny but cold day. With temperatures
starting off well below freezing, it will take much of the day
to recover into the 30s. Southside may reach 40, but given the
fact the airmass is so dry (dewpoints in the teens) the wetbulb
zero will remain under 32 degrees through the day. As such,
expecting little or no snow melt Tuesday. If anything, the snow
may sublimate more than melt and/or compact due to the fact the
ground is not froze underneath. At any rate, still have an
opportunity to do some sledding.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 245 PM EST Monday...
High pressure gives way to another potential quick-hitting system
Thursday night...
Longwave trough centered over the Great Lakes with several
shortwaves embedded within the flow will continue to send quick
moving systems across the CONUS. Tuesday night into Wednesday,
surface low over the Great Lakes shunts high pressure east into the
Atlantic. Weak southwest/west flow will allow for mild temperatures
Wed/Thu ahead of a dry cold front that pushes through Thursday
afternoon.
The next system to keep our eyes on drops out of the northern Plains
on Thursday. The big question here is how far south this piece of
energy digs, along with how far west or east it is once it begins to
take on a negative tilt. Should things line up perfectly with a
negatively tilted trough over western North Carolina late Thursday,
another light snow event will be entirely possible for the mountains
of North Carolina, Virginia, and West Virginia as surface low
pressure tracks along the cold front, exiting rapidly to the
northeast. With the trend in the operational and ensemble guidance
trending a little snowier today, added in some light accumulations
mainly for the higher elevations Thursday night, but some still may
spill into the Piedmont. Details on this will be ironed out in the
next few days.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 245 PM EST Monday...
Cold air returns Friday as high pressure settles in with another
front approaching Sunday night/Monday morning...
Quick shot of cold air and potentially gusty winds will be possible
Friday morning behind a departing low pressure. Temperatures Friday
morning will features widespread teens for the mountains and 20s in
the east. For the mountains winds could be quite gusty at times and
wind chill values will be in the single digits to below zero at
times. We remain dry into Saturday as high pressure moves in
overhead and winds relax. Temperatures could potentially be even
colder Saturday morning with some single digits possible in the
higher elevations, especially if there is any snow cover.
Warmer on Sunday as flow turns back to the southwest in advance of
another cold front which will bring another round of rainfall Sunday
night into early Monday. High pressure returns once again for mid-
week.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 630 PM EST Monday...
High pressure will cross the Tennessee Valley this evening and
will be centered over Virginia Tuesday morning. As a result,
wind speeds will diminish overnight. By Tuesday afternoon, the
high will be offshore and surface winds will turn to the south
to southeast.
Have slowed down the clearing of the upslope clouds over the
west side of the Appalachians, similar to the HRRR and 3kmNAM.
Most locations will become VFR before midnight, but expect the
clouds to linger for most of the night at KBLF. Conditions will
be VFR for Tuesday.
Above average confidence for ceiling, wind and visibility.
.Extended Aviation Discussion...
Conditions will be VFR Tuesday night and Wednesday. Another
storm system will impact the region Thursday night and Friday
with potential for sub- VFR. Saturday will be another dry day in
between low pressure systems.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...PM
NEAR TERM...AMS/PM
SHORT TERM...BMG
LONG TERM...BMG
AVIATION...AMS/PM
Area Forecast Discussion
National Weather Service San Diego CA
113 PM PST Mon Jan 3 2022
.SYNOPSIS...
Returning onshore flow will bring cooler days, breezy conditions
over the mountains and deserts, and patchy low clouds to temper
overnight lows west of the mountains through Tuesday. A weak ridge
aloft and offshore flow will return fair, dry, and warmer conditions
midweek, with temperatures climbing back above average. Onshore flow
increases again to wrap up the week with more clouds, and a return
to cooler weather.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Satellite imagery at midday showed some high clouds drifting SE
across the State, and just beginning to affect SoCal. There were
some lower, marine clouds, but they were still well offshore and
showing no sign of advancing east across the Bight. The sfc pressure
gradient across SoCal was very weak, but there is an onshore trend,
and just after noon, we were just beginning to see some SW-W gusts
exceed 30 MPH at higher elevations. Winds should continue to ramp up
over the mountains and veer a bit more W-NW through tonight. We
could see a few of those lower clouds develop along the coast later
tonight, but trends suggest there won`t be much.
It will be cool again tonight, but not as cold as last night, with
patchy frost still likely well inland, in low, wind-sheltered areas
and in the lower deserts. Tuesday will still be fair and cool. There
may be a few morning clouds/patchy fog west of the mountains to
start out the day though. By Wednesday, a weak ridge will be
drifting east, approaching the West Coast. This will weaken the
onshore flow and trend us back offshore, along with rising heights/
thickness. This will result in the warmest day in some time as
afternoon temperatures climb to about average. The warmest day
should be Thursday, before the ridge weakens and another shortwave
pushes onshore for the weekend. We should see a surge in the marine
layer on Saturday, but other than that, it looks to stay dry and
cooler Friday and Saturday.
For Sunday, a new ridge pops up along the West Coast and our surface
winds turn back offshore. This means some warming should follow, and
at least from the ensemble perspective, that is the temperature
trend favored. There is a small chance that we could see some
precipitation over the weekend, but it is only a handful of the
GFS/ECMWF ensemble members that are highlighting this, so not
something to count on at this point, and it is not in the forecast.
&&
.AVIATION...
032100Z...A mostly clear sky will continue with just few-sct passing
high cirrus cloudiness. Low clouds haven`t made any headway towards
the coast today. HRRR shows the marine layer stratus remaining well
offshore. Given these trends, have amended to keep VFR prevailing
under a mostly clear sky through Tuesday at all terminals.
&&
.MARINE...
No hazardous marine conditions are expected through Friday.
Occasional gusts exceeding 20 knots are expected around San Clemente
Island Tuesday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE
PZ...NONE.
&&
$$
PUBLIC...10
AVIATION/MARINE/BEACHES...Gregoria
Area Forecast Discussion
National Weather Service Sacramento CA
220 PM PST Mon Jan 3 2022
.SYNOPSIS...
Mountain snow and Valley rain showers continue through Tuesday
along with strong winds. Another chance for wet weather possible
late in the week.
&&
.DISCUSSION...
Showers began over Shasta County and the Coastal Range early this
morning and are slowly moving inland this afternoon. Snow levels
began around 1500-2000 feet this morning for the northern
mountains. Based on area webcams, spotter reports, and snow level
radar observations, snow levels have risen to closer to 2500-3000
feet this afternoon as forecast. Snow levels will be higher over
the western Plumas County mountains and northern Sierra when snow
starts, around 4000-5000 feet. As the front moves through
interior Northern California late this afternoon and evening, NAM
3k and HRRR depict precipitation rates will increase, especially
snow amounts over the mountains north of Highway 50. This is also
when showers will move south through the Valley south of Shasta
County, though Valley showers will remain fairly light. Snow
levels will continue to rise to around 5000-6000 feet by tomorrow
morning across the region. The majority of snow and rain will
taper off by early tomorrow, with lighter showers continuing into
early Wednesday.
A strong upper jet is set up over Northern California/Southern
Oregon associated with the upper trough. Surface pressure
gradients have tightened over Northern California, causing winds
to ramp up over the area throughout the morning hours. Current
MFR-RDD gradient is around -10 to -12 mb, RDD-SAC gradient is
around -8 mb, and SAC-RNO gradient is around +9 mb. Northern
Sacramento Valley and adjacent foothills will see winds 20-30 mph
with gusts up to 35-50 mph. In the mountains, winds could be up
to 30-40 mph with gusts up to 45-60 mph, locally higher over wind
prone peaks, ridges, and canyons. Strongest winds will be
generally north of Interstate 80 for all elevations, and
especially in the Plumas County and Shasta County mountains.
These winds could cause damage to trees and powerlines,
especially combined with moderate to heavy snow in the mountains.
Mountain travelers should plan on difficult travel conditions,
reduced visibility, chain controls, travel delays, and potential
road closures this afternoon through tonight, especially during
the evening commute.
Ensembles show shortwave ridging forming over the eastern Pacific
and Northern California late Wednesday into Thursday. Dry weather
is expected for most areas except for a chance of warm air
advection showers over Shasta County. -HEC
&&
.EXTENDED DISCUSSION (Friday THROUGH Monday)...
Ensemble guidance is in agreement that another upper trough will
move through interior Northern California Friday, bringing another
chance of light to moderate rain to the lower elevations and snow
in the mountains, mainly for the Sierra and Western Plumas
County. Snow levels will be higher than with the current system at
around 5000-6000 feet. Ensembles and cluster analysis indicate
fairly high agreement that ridging will build for the weekend over
California, bringing dry weather, near normal temperatures, and a
chance of morning Valley fog. Uncertainty remain for early next
week as some guidance suggests a weak trough could bring another
chance of precipitation. However, clusters suggest a higher chance
that high pressure will continue into early next week. -HEC
&&
.AVIATION...
MVFR/IFR/ LIFR conditions in lowering ceilings and visibility
restrictions as a weather system moves through, mainly I-80
northward. In the Valley, LLWS with widespread southerly surface
wind gusts up to 35-40 kts possible N of I-80 and gusts up to
20-25 kts possible S of I-80 until 12Z- 15Z Tuesday. Southwesterly
surface wind gusts up to 60+ kts poss over higher mountain
terrain through 12Z- 15Z Tuesday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 7 AM PST Tuesday for Western Plumas
County/Lassen Park.
Winter Weather Advisory until 7 AM PST Tuesday for West Slope
Northern Sierra Nevada.
Wind Advisory until 4 AM PST Tuesday for Central Sacramento
Valley-Northeast Foothills/Sacramento Valley-Northern Sacramento
Valley.
Winter Storm Warning until midnight PST tonight for Shasta Lake
Area / Northern Shasta County.
&&
$$