Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/21/20
Area Forecast Discussion
National Weather Service Quad Cities IA IL
551 PM CST Mon Jan 20 2020
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 255 PM CST Mon Jan 20 2020
1042+ MB arctic sfc high was centered upstream acrs the MO RVR
Valley, with eyes on sliding southeastward acrs northern MO by
Tuesday morning. Strong upper low that was a light snow/flurry maker
was seen on the current water vapor loop rolling southeast acrs
northeastern MO ATTM. As both these systems exit off to the east-
southeast, some temp modification will occur in return flow by mid
week, as well as some effects by approaching low pressure systems
that will be the next round of weather makers through the end of the
week.
&&
.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 255 PM CST Mon Jan 20 2020
Key Points:
*How cold to go tonight a fcst challenge with a mix of clouds and
clearing making for a variable temp regime, as well as any wind
chill impacts.
*Cold start to Tuesday may limit highs not much better than today
despite insolation and increasing southwest/southerly return flow
sfc winds.
Tonight...In sweeping subsidence behind northeast MO clipper eroding
much of the stratocu from the northeast this afternoon. This will
make for a challenging sky forecast tonight with some soundings
suggesting lingering stratus getting trapped under inversion aloft,
or possible redevelopment. As the passing upper level cyclone drops
acrs the TN Valley tonight, it may drag some of the more substantial
stratocu deck acrs east central IL westward acrs portions of the
local fcst area especially in the south. Any cloud deck will have
the potential to produce a few flurries tonight, but will keep the
fcst dry for now. Although there is the mix of clouds and clearing
tonight, will side with more clearing from dry in-wrapping
subsidence and thus the potential for colder low temps. Will
advertise lower single digits above zero in the south where there
will be the best chance for some clouds, while the clear areas dip
below zero. Some areas that stay mainly clear north of I80 may get
close to 5 below zero. There may be quite a bit temp variance as
well depending on depth of snow/ice cover and where clouds linger or
advect back in across. Guidance wants to go not as cold acrs
portions of northwest IL, but if those areas stay clear the longest
as well as down to the eastern I-80 corridor, fcst values probably
won`t be cold enough. With light sfc wind regime of 5 MPH or less
under passing ridge axis, wind chills should stay above advisory
criteria bu still cold of 10 to 15 below in clear sky areas. One
last factor to consider tonight, is if any fog/ice fog would develop
late as temps crash close to wet bulb values and sfc winds go light
or calm. Some of the HiRes solutions such as the HRRR develops at
least patchy fog mainly north of I-80 after midnight. This a low
confidence scenario with adequate sfc layer moisture at question and
will leave out fog mention for now.
Tuesday...as the sfc ridge slides off to the OH RVR Valley,
southerly return flow to take over locally with speeds to 10+ mph in
the afternoon. But after cold start to the day, despite expected
solar insolation, afternoon highs may not be much milder than this
Monday aftrenoon`s values.
.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 255 PM CST Mon Jan 20 2020
Precipitation will return for mid to late week, along with
moderating temperatures. The late week system is trending a bit
weaker and less organized than previous models depicted. The overall
impact will be an extended period of light precipitation, in the
form of snow, rain and possible drizzle, followed by the likelihood
for measurable light snow with the main system Friday. This will
likely be accompanied by widespread low clouds and periods of fog.
Dry weather and continued near to above normal temperatures are
expected through the weekend into early next week.
Tuesday night, warm advection commences with the passage of the
upper level ridge, leading to thickening cloud cover and steady to
rising temperatures through the teens to widespread 20s by sunrise.
A more active upper level pattern that follows will send a series of
weak shortwaves ahead of the main upper low that rolls through
Friday. The first round of precipitation will overspread the area in
the form of snow from west to east Wednesday as mid level lift ahead
of a shortwave interacts with deep moisture return. Current
indications suggest snow accumulations up to an inch possible over
eastern IA into northeast Missouri with much lighter amounts across
the east. This should be a rather wet snow as temperatures return to
the lower 30s. A period of weaker lift follows for Wed night into
Thursday, continuing the potential for light snow and a possible
rain or drizzle/snow in the south with minimal diurnal temperature
change holding readings largely in the 30s. Moisture advection over
the snow and cold surface conditions will also favor fog, but his is
not included in the forecast at this time.
Models have backed away from an organized single low lifting up from
the south with the introduction of greater energy in the form of a
shortwave and closing upper low in the northern stream that is shown
merging with the main upper low over the plains and mid MS valley
Friday. This leads to a much weaker low at the surface setting up
over the western Ohio River Valley, keeping an inverted trough with
at least light precipitation northwestward into the local area.
Colder air aloft wrapping around this developing low may still lead
to a few inches of snow over the forecast area, while surface
temperatures remaining much warmer than the past system point point
toward wetter, slushier snowfall. Still a lot of uncertainty with
this system and further changes are likely as the week progresses.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 550 PM CST Mon Jan 20 2020
VFR cigs expected through the period as the main weather concern
is the low potential for fog tonight. Guidance still tries to
produce some fog for northern TAF sites, but hasn`t shown up yet.
Will continue to monitor.
&&
.HYDROLOGY...
Issued at 1145 AM CST Mon Jan 20 2020
The recent stretch of bitter cold temperatures has lead to an
enhanced threat of freeze up ice jams along area tributary rivers.
This potential is greatest on the Rock River, mainly along the
stretch from Joslin upstream to Como. An ice jam was observed
yesterday upstream at Dixon, which briefly sent the river there
above flood stage. Cold temperatures and favorable flow levels on
the Rock River will create nearly ideal conditions for ice jams over
the next couple days and we will continue to monitor the situation
closely.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...12
SHORT TERM...12
LONG TERM...Sheets
AVIATION...Gibbs
HYDROLOGY...Sheets
Area Forecast Discussion
National Weather Service Medford OR
258 PM PST Mon Jan 20 2020
Updated aviation discussion.
.SHORT TERM...Low pressure is wrapped up offshore this afternoon, and
southerly winds ahead of this low are being observed from the
coast to areas east of the Cascades. Winds will ramp up through
the night, and we have Wind Advisories out for the Shasta Valley,
southern Rogue Valley, and portions of the East Side. South to
north forecast pressure gradients have trended higher today, so we
added the Rogue Valley Advisory to focus on areas from Phoenix
southward. We also bumped up forecast winds along the coast, but
since we only expect headlands to reach High Wind criteria (gusts
58mph or higher), we have not issued a High Wind Warning. Inland
winds will peak late tonight into early Tuesday morning, lasting
the longest east of the Cascades near Summer Lake. Rogue Valley
winds can be quite tricky, and this is a marginal case for a Wind
Advisory, but with MFR-RDD pressure gradients peaking at -8mb and
a moderately strong HRRR surface wind field, we are predicting
some areas will see sustained winds of 25 mph tonight and early
Tuesday morning.
There will be a quick shot of moderate to heavy precipitation with
the front. Midlevel flow is southwesterly, and this favors multiple
areas for snow impacts. The southerly component favors Northern
California and the Mount Shasta City area in particular, for a
period of moderate to heavy snow Tuesday. Snow will start early
Tuesday morning, and as the front moves through during the mid-
morning hours, snow levels will lower enough to affect areas at 3000
ft to include McCloud. We`ve adjusted the lower end of the Advisory
to include McCloud based on the consensus of latest model data.
Additionally, the westerly component to the midlevel wind favors a
period of moderate to heavy upslope snows in the Southern Oregon
Cascades...and some spillover snow over Highway 97. Snow levels will
start at 4000 to 4500 feet and lower to 3000 feet as the front moves
through Tuesday morning. We expect the period of heaviest snow to
occur between 4am and 10am, and one inch per hour snowfall rates are
likely at times.
Showery conditions are expected Tuesday afternoon, and snow will
continue to fall but will not be as heavy or steady as the morning.
A warm front is expected to move through Wednesday, and snow levels
will rise above 6000 feet by Wednesday afternoon. This means more
snow for the highest elevations and rain for the middle and lower
elevations. Most of the time warm fronts will bring a period of very
low clouds and some fog even in the late morning or early afternoon
areas to valleys west of the Cascades, so we expect a similarly
gloomy day for at least part of Wednesday. After the warm front
pushes through, less precipitation overall is expected on
Thursday.
.LONG TERM...4 PM Saturday through Tuesday morning...Saturday
Evening marks the start to a rainy weekend. A west oriented mid-
level jet will set up driving moisture onshore. A mid-level short
wave passes through the area near the start of this extended
forecast (4 PM Saturday) and a front later on Sunday. On Saturday
the disturbance creates strong warm air advection, bringing snow
levels up to about 6000 feet across the area. With the front on
Sunday, winds shift to the southwest, indicating Mt. Shasta may
see an uptick in precipitation. Also, snow levels should drop
slightly around 5000- 5500 feet for the area. Currently, snow is
not expected to reach Mt. Shasta city, but the NBM, including
other model blends, are showing a trend towards a light dusting in
this area and other than snow at Crater Lake, this to be the only
snow related impacts. Overall, the weekend precipitation should
remain rain for all but the highest areas, with no periods
appreciable snow accumulations occuring.
After sunday, model continuity begins degrade. The ECMWF and GFS
deterministic solutions begin to diverge. The ECMWF deterministic
and GEFS-mean show an open wave feature off the coast of British
Columbia being the driver to the weather on Monday. Whereas the GFS
deterministic develops a surface low instead of just a wave and
could be the difference between the start of the week being wet or
dry. Either solution does not bring much precipitation and impacts
look to be negligible for the start of the week. -miles
&&
.AVIATION...For the 21/00Z TAF Cycle...VFR conditions will prevail
through Monday afternoon. An incoming front will bring areas of
MVFR cigs/vsbys and local IFR cigs/vsbys in low clouds and rain to
the coastal waters this evening, moving onshore tonight with higher
terrain becoming obscured in low clouds, rain, and snow from the
coast to the Cascades. Snow levels ahead of the front will be 4500-
5000 feet MSL.
Low level wind shear will also be a concern this evening and tonight
at KOTH, KRBG, and KMFR until the front moves through. The front
will move through KOTH at 10Z, KRBG at 11Z, KMFR at 14Z and KLMT at
16Z.
Behind the front, the lower conditions will continue through the
remainder of Tuesday morning, but the precipitation will be showery
and snow levels will drop to 3500-4000 feet MSL. Conditions will
improve Tuesday afternoon and evening as the showers diminish, but
there will still be some MVFR cigs/vsbys around.
&&
.MARINE...Updated 230 PM PST Monday 20 Jan 2020...Southerly winds
will increase and seas will build this afternoon and evening as a
stronger front approaches from the west. This front will bring
gales and very steep wind-driven seas tonight followed by very high
and very steep long-period swell through Tuesday evening. Seas will
likely peak near 20 feet at 15 seconds during this time frame with
bar conditions becoming very hazardous. Winds and seas may briefly
lower Tuesday night, but another front, a warm front, will move
through the waters on Wednesday with a period of south winds that
could approach gale force again across northern areas. Seas will
remain very steep and hazardous due to increasing wind waves
combining with existing westerly swell. The weather pattern will
remain active late this week through this weekend with several more
fronts moving through. These fronts will likely generate winds and
seas at least at small craft advisory levels. -Spilde
.HIGH SURF...Models are showing significant westerly swell moving in
on Tuesday with wave heights peaking at 17-18 feet and a period of
15 seconds. This could result in higher than normal waves running up
the beaches with breaking waves in the 20-23 foot range. So, have
gone with a high surf advisory, mainly from Brookings northward.
High tides on Tuesday are at approximately 8-9 am and 10-11 pm. So,
those planning to be at the beaches on Tuesday should be aware of
the dangerous surf conditions. -Spilde
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 4 AM to 10 AM PST Tuesday for
ORZ029-030.
Wind Advisory from 1 AM to 4 PM PST Tuesday for ORZ030-031.
Winter Weather Advisory from 4 AM to 10 AM PST Tuesday for
ORZ027-028.
High Surf Advisory from 7 AM to 7 PM PST Tuesday for ORZ021-022.
Wind Advisory from 8 PM this evening to 7 AM PST Tuesday for
ORZ026.
CA...Winter Storm Warning from 1 AM to 2 PM PST Tuesday above 4500
feet in the for CAZ080.
Winter Weather Advisory from 4 AM to 2 PM PST Tuesday above 3000
feet in the for CAZ082.
Winter Storm Warning from 4 AM to 2 PM PST Tuesday above 4500
feet in the for CAZ082.
Wind Advisory until 10 AM PST Tuesday for CAZ081.
Winter Weather Advisory from 4 AM to 2 PM PST Tuesday for
CAZ083.
Pacific Coastal Waters...Hazardous Seas Watch from Wednesday morning
through Wednesday evening for PZZ356-376.
Gale Warning until 4 AM PST Tuesday for PZZ350-356-370-376.
Hazardous Seas Warning from 4 AM to 10 PM PST Tuesday for
PZZ350-356-370-376.
Gale Watch from Wednesday morning through Wednesday evening for
PZZ350-370.
$$
Area Forecast Discussion
National Weather Service San Francisco Bay Area
542 PM PST Mon Jan 20 2020
.SYNOPSIS...Mostly cloudy and seasonably cool conditions will
persist over the region today. There is a slight chance of
sprinkles or isolated light rain, but most areas should remain dry.
Rain chances increase region-wide late tonight into Tuesday as a
weak frontal system moves across northern California. Mostly dry
conditions are then expected for the remainder of the week, with
rain likely returning next weekend.
&&
.DISCUSSION...as of 01:45 PM PST Monday...Looks like the hi-res
short term models were right with today`s forecast. The HRRR for
instance indicated the best chance for showers actually reaching
the ground would be Monterey Area southward to Big Sur. Taking a
look at the afternoon KMUX radar imagery shows more defined
showers tracking NE over the Santa Lucia Mts. Automated gauges in
Monterey did actually show a tip around 1 PM. A few spotters and
media also reported a few drops making to the ground near Salinas.
even had brief rain here at the office. Not expecting much more
than a passing shower this afternoon and this evening. Any
lingering showers will end shortly after sunset this evening.
No major changes to the sensible weather forecast over the next
24-36 hours. The stream of subtropical moisture advecting in from
the southwest (high clouds and scattered showers today) will
slowly ease southward this evening and overnight. The next chance
for rain will be associated with a passing cold front, which is
currently off the PacNW Coast. The cold front is on track to move
toward the NorCal Coast tonight and then push through the Bay Area
on Tuesday. Warm advection light rain will develop over the North
Bay tonight and then precip will increase in coverage with the
cold front early Tuesday. Biggest initial impact will be to the
morning commute for the North Bay. Model trends have been slower
with the southward movement and steadier rain may not make it
into San Francisco until mid morning or early afternoon. The other
model trend noted has been to really weaken the front as it moves
southward. The rapid weakening is also trending drier the farther
south the front goes. Simply put - rains chances will be greatest
north of the Golden Gate in the morning Tuesday and may
completely fizzle by the time it reaches Monterey in the
afternoon. Definitely not on par with the fropa last week.
Rainfall amounts will generally be light with up to 1" far North
Bay.
Dry weather develops behind the front Tuesday night through
Friday. Medium range models are still showing precip returning
the region next week. Hopefully, the details will come into better
focus the next few days.
&&
.AVIATION...as of 5:42 PM PST Monday...For 00z TAFs. The focus of
light wet weather has remained mainly south today and is currently
pressing toward the Sierra Nevada with a warm front high aloft. VFR
tempo MVFR into the early evening, to the south where it`s rained
cloud layers have lowered to 2,000 feet to 5,000 feet agl. Wet
weather with lowering ceilings and visibilities develops Tuesday
and Tuesday night.
Vicinity of KSFO...VFR borderline MVFR in visibility, otherwise most
recent cloud ceiling is near 11,000 feet. VFR forecast for tonight
with probability 30% light showers developing Tuesday afternoon.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR-MVFR. Light and variable winds becoming
SE this evening persisting through Tuesday morning.
&&
.MARINE...as of 5:21 PM PST Monday...Southerly winds will gradually
increase tonight ahead of an approaching cold front that will push
through the coastal waters on Tuesday. A longer period northwest
swell will also begin to build over the waters tonight before
peaking midweek. This will generate hazardous seas conditions for
smaller vessels. Another long period northwest swell will then
arrive late week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 9 PM
&&
$$
PUBLIC FORECAST: MM
AVIATION: Canepa
MARINE: RGass
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Area Forecast Discussion
National Weather Service Mount Holly NJ
1011 PM EST Mon Jan 20 2020
.SYNOPSIS...
High pressure will continue to build into the region through
Wednesday before gradually weakening through late week. Low pressure
will arrive on Saturday bringing the next round of precipitation to
the area. This system will depart the area on Sunday.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Winds will continue to fall through the rest of the overnight
hours and will eventually decouple north of a boundary. Both the
HRRR and NAMNest only drag the boundary to TTN before starting
to slowly lift back north. Thus, there`s really high bust
potential in the temperature forecast because of the winds go
calm over the Pine Barrens, expect rapid radiational cooling and
temps to fall into the single digits. I tend to think that
solution is the one that will play out so I`ve kept forecast
lows on the cold side of the coldest guidance. It should be a
chilly one this evening.
Previous discussion...A cold afternoon in progress despite
plenty of sunshine. An upper- level trough will continue to
shift east of New England into this evening. Another upper-level
trough with a impressive mid level low center in the mid-
Mississippi Valley this afternoon will continue to dive
southeastward through tonight. Meanwhile, an upper-level ridge
entering the western Plains this afternoon and tonight will
gradually push strong surface high pressure eastward. We
therefore remain within a northerly flow regime on the east side
of the surface high.
While the center of the surface high is well to our west through
tonight, a tightened pressure gradient remains across our region.
This along with vertical mixing is resulting in a gusty wind this
afternoon, adding a wind chill factor. Despite this setup, it looks
like many areas will at least partially decouple tonight. This
should occur more and sooner in the sheltered areas (i.e. NJ Pine
Barrens). While it will be a very cold night (widespread teens and
some single digits), the temperature trend will depend on the winds.
We weighted the low temperatures much closer to the colder guidance,
especially in the typically colder locales, as the winds diminish
along with a lack of clouds. The low-level air mass is very dry
which also assist in getting temperatures colder. There could be
some mainly high level clouds in parts of the area toward daybreak
especially in the Pocono region, however this should not have any
significant impacts on the temperatures.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
An upper-level trough will dominate the East through Tuesday, with
this being comprised of two troughs. One of which amplifies once
again across New England and the second one slides across the
southeast states. These will have little affect on our sensible
weather as strong high pressure still centered well to our west
slides closer but does extend into our area. While the pressure
gradient is forecast to be still present, the overall mixing and
flow is weaker and therefore less wind is expected compared to today
(Monday).
It will be another cold day, with just slightly warmer afternoon
high temperatures compared to this afternoon (Monday). We used
mostly a MOS blend with continuity for the high temperatures. Lots
of sunshine expected, although some mainly high level clouds may
occur at times in some areas given the presence of the aformentioned
troughs aloft north and south of us.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
A relatively benign pattern is in store synoptically through the
latter half of the week with the next system forecast to impact the
area over the weekend. Upper troughing will pass to our south and
east through mid-week so north to northwesterly flow will prevail
aloft leaving high pressure in place at the surface and weak low to
mid-level flow. As the high pressure drifts slowly eastward and more
centered across the coast, it will weaken allowing for a general
warming trend through the end of the week as the airmass modifies.
The period will start with temperatures within a few degrees of
normal then will be 5-10 degrees above normal by Friday into
Saturday. Expect mainly clear but hazy skies through this period.
Would not be surprised if we see a few nights/mornings with areas of
fog or freezing fog and heavy frost given the stagnant airmass and
clear skies, espousal Wednesday night and Thursday night.
By midday Friday, a closed upper low will be making its way across
the Mississippi River Valley into the Ohio Valley then eventually
toward the Mid-Atlantic by Saturday. At the surface, a 2 part low
pressure system will be approaching the region from the south and
west. The initial low across the Ohio Valley will weaken then the
secondary low lifting north from the Gulf and across the Carolinas
will become dominant and intensify as it moves up the coast toward
the Mid-Atlantic. This low is forecast to briefly stall out over our
forecast area Saturday night then move slowly offshore on Sunday.
Clouds will be increasing from the west from this system throughout
the day Friday. Precipitation is then forecast to move in generally
from southwest to northeast early Saturday morning, perhaps even
before daybreak. Guidance still differs on the timing and
strength/coverage of this system with the GFS being the fastest as
of the 12Z suite. Can`t rule out a brief period of snow/sleet across
the entire area at precip onset (timing dependent), but this looks
largely like a rain event for the I-95 corridor and south/east. The
surface low will be tracking directly over the area and warm air
advection will be strong aloft and near the surface. Farther north,
a more prolonged period of wintry precip is probable, potentially
leading to some travel impacts on Saturday into early Sunday.
However, it currently appears that most of the area (especially
south of the Lehigh Valley and NW NJ) will see a transition over to
all rain Saturday evening and overnight as the low pressure center is
basically right over the forecast area. The low will be exiting the
area on Sunday and precip chances will diminish generally from west to
east through the day.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas.
Rest of the overnight...VFR SKC. North-northwest winds
diminishing to 5-10 knots in the evening, then becoming light
and variable at several terminals. High confidence on SKC;
moderate confidence on how quick the winds diminish.
Tuesday...VFR. Light and variable winds, becoming northwesterly
around 10 knots. High confidence.
Outlook...
Tuesday night through Thursday night...VFR. Mostly clear skies with
winds 5 kts or less favoring and northwesterly direction. High
confidence.
Friday through Friday night...VFR with clouds increasing and
ceilings decreasing. Winds becoming easterly around 5 kts. Moderate
confidence.
&&
.MARINE...
A cold northwesterly flow will continue through Tuesday, however it
will also be weakening some. Some downward trend in the surface
winds are noted this afternoon, however gusts to about 25 knots will
continue at least into this evening. Given trends, opted to cancel
the Small Craft Advisory for Delaware Bay. We will continue the
advisory for the NJ/DE Atlantic coastal waters (through midnight)
for now, although this may be able to be cancelled early (seas are
already down to 5 feet). For Tuesday, the conditions are expected to
be below Small Craft Advisory criteria within a continued north-
northwest flow regime.
Outlook...
Tuesday night through Thursday night...Sub-SCA conditions expected.
Fair weather with winds northerly around 5-10 kts.
Friday through Friday night...Initially fair weather and northerly
winds around 5 kts then building seas with winds becoming easterly
and increasing overnight to 15-20 kts. Conditions nearing SCA
criteria by daybreak Saturday.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
Synopsis...Staarmann
Near Term...Deal/Gorse/O`Hara
Short Term...Gorse
Long Term...Staarmann
Aviation...Gorse/Staarmann/Deal
Marine...Gorse/Staarmann
Area Forecast Discussion
National Weather Service San Diego CA
116 PM PST Mon Jan 20 2020
.SYNOPSIS...
A weakening Pacific trough will spread moisture and periods of high
clouds over southern California through tonight with some sprinkles
or light showers possible through early Tuesday. It will be cooler
through Tuesday, due to the increased cloud cover, onshore flow and
building marine layer. Fair, dry, and warmer weather returns for the
remainder of the week under ridging aloft and periods of weak
offshore flow. There is a small chance for showers again late
next weekend as a weak Pacific trough moves across the State.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
High clouds were widespread over much of the Southwest with some
breaks. Some weak echoes were indicated on radar, but these were
quite high in the atmosphere and not likely reaching the ground as
any significant rainfall. The sfc pressure gradients have
weakened considerably from yesterday, and the winds were turning
more southerly now with peak gusts of 25-30 MPH in the mts.
Offshore, about 525 miles WSW of San Diego at 1 PM PST, a more
energetic area of bubbling clouds was tracking steadily ENE. This
area will bring the best chance of measurable precip overnight. The
18Z NAM model run seems to have a good handle on it and has light
precip accumulations arriving at the Coast by midnight. The latest
HRRR run picks it up a few hours earlier.
A weakening trough just off the Coast will move inland overnight,
laden with high-level moisture. Due to the deep saturated layer
expected to arrive with it, some of this moisture is expected
to survive the trip earthbound as the marine layer deepens. Periods
of light rain or sprinkles are expected with some light
accumulations possible overnight. The best chance for accumulations
will be in the mountains where the dry, subcloud layer depth is
smallest.
The trough axis will swing rapidly east Tue morning, clearing the
high clouds and any lingering showers. Some lower marine clouds
could linger along and west of the mts into midday, but most areas
should see some sun and it will be slightly cooler due to the better
onshore flow and deeper marine layer.
Look for a nice stretch of weather to follow Wednesday into the
weekend as a ridge builds aloft and periods of weak offshore flow
aid the warm-up west of the mts. The models have been toying with a
trough late in the weekend into early Monday of next week, but
trends have been weaker, with overall ridging over the SW likely
inhibiting decent development. Even the ensemble members of both
models are unconvincing, so this one doesn`t hold much promise to be
a significant precipitation event, at this time anyway.
&&
.AVIATION...
202105Z...High confidence in thick 8000-10000 ft MSL based clouds
prevailing through the afternoon with locally SCT-BKN cigs 1000-2000
feet MSL at coastal airports intermittently through the afternoon.
Lower cloud bases push ashore after 05Z and into valleys after 07Z.
Moderate confidence in bases 1000-2000 feet MSL with ISO -SHRA
overnight into Tuesday morning.
&&
.MARINE...
An incoming west-northwest swell may produce 6-8 foot waves over the
southwestern portion of the coastal waters south of San Clemente
Island Wednesday into Thursday morning. Otherwise, no hazardous
marine conditions expected through Friday.
&&
.Beaches...
Swell and surf will build late Tuesday through Wednesday, which may
generate surf of 5-7 feet. The higher sets along with a long swell
period may lead to strong rip currents and hazardous swimming
conditions.
&&
.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...APR
Area Forecast Discussion
National Weather Service San Angelo TX
554 PM CST Mon Jan 20 2020
.AVIATION...
/00Z TAFS/
VFR conditions are expected to prevail through the next 24 hours.
A few scattered showers may develop Tuesday afternoon but the
better chances for more widespread showers will occur after 00Z.
Otherwise, gusty southerly winds will develop in the afternoon.
&&
.PREV DISCUSSION... /issued 246 PM CST Mon Jan 20 2020/
SHORT TERM...
Mid to upper level cloud cover is forecast to increase across West
Central Texas overnight. Low temperatures will be near to slightly
above seasonal normals, generally in the mid to upper 30s.
A weak upper level shortwave trough is forecast to track across West
Central Texas late Tuesday. Ahead of this feature cloud cover is
forecast to increase across the region through the day Tuesday. In
addition, lift from the shortwave trough will result in the
development of showers Tuesday afternoon, first across our western
counties, then spreading east by late afternoon. Rainfall amounts
through late afternoon are forecast to remain light, with most
locations seeing a tenth of an inch or less. Cloud cover and
possible showers will help to keep high temperatures on Tuesday
cool. Highs will be in the low to mid 50s.
LONG TERM...
(Tuesday Night through Monday)
All models suggest that Tuesday Night will be the wettest period,
with am area of showers moving across the area. ECMWF and the
latest HRRR have come in drier, while the GFS comes in fairly wet.
Models also suggest its coming in a little faster than earlier
forecast. With that in mind, have trimmed POP numbers back just a
tad Tuesday Night, mainly across the Concho Valley and Edwards
Plateau, and pretty much areawide on Wednesday. Rain chances are
high, just not as high as they were earlier.
Otherwise, rest of the forecast looks fairly quiet. Temperatures
will warm into the mid 60s for the weekend. Overnight lows will
be in the 30s and 40s. ECMWF and GFS both show another system
coming in early next week but given the uncertainty in the timing
between the models, have held off on POPs at this point.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 36 53 42 60 / 0 20 70 20
San Angelo 35 56 43 65 / 0 20 70 10
Junction 34 56 41 60 / 0 5 80 40
Brownwood 34 55 38 56 / 0 5 70 40
Sweetwater 38 52 44 62 / 0 40 80 10
Ozona 35 53 42 62 / 0 10 60 10
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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