Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/29/23
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
855 PM PDT Sun May 28 2023
.SYNOPSIS...28/854 PM.
A strong onshore flow pattern will keep a persistent and deep
marine layer in place through the week. Night through morning low
clouds and fog with limited afternoon clearing will continue as
well. Areas of drizzle or light rain can be expected during the
night and morning hours through Tuesday. Temperatures will be
cooler than average for most of the week.
&&
.SHORT TERM (SUN-WED)...28/853 PM.
No clearing for many areas today, with current satellite imagery
showing extensive low clouds into the coastal slopes and foothills
of the Antelope Valley. Current ACARS data and pilot reports
showing a deep moist layer to around 4000 feet. This combined with
the strong onshore flow pattern (LAX-Daggett peaking at +9.5 mb)
resulted in cooler temperatures and gusty onshore winds today
across the interior, with the Antelope Valley only climbing to the
lower 80s. Wind gusts between 35 and 45 mph occurred across the
Antelope Valley this afternoon and evening, with isolated gusts
around 50 mph near Lake Palmdale. Some mid level moisture and
instability also generated some afternoon buildups over the
Ventura county mountains, but no storms detected on radar.
Closed upper level low pressure system near San Francisco will
drift southward and become centered off the coast of Point
Conception by Monday night, and is then expected to track
eastward across the forecast area on Tuesday. This pattern will
maintain the strong onshore flow pattern and deep moist layer
to around 5000 feet as depicted by the 00z NAM cross sections.
As a result, there will likely be areas of drizzle during the
late night and morning hours through Tuesday. With many of the
high resolution models and HREF ensembles showing some light
QPF, have introduced a slight chance (15-20%) of measurable rain
late tonight into Monday morning for much of the region,
especially the foothills and coastal slopes. A similar 15-20%
chance of light measurable rainfall is expected for late Monday
night into Tuesday morning. Minimal clearing expected on Monday
afternoon, with a slightly better chance of some clearing on
Tuesday afternoon as colder air aloft moves into the region and
may weaken the inversion. The upper low pressure system has had a
history of lightning across northern California today, and we will
have to monitor the potential for any convection as this low
moves down into our area in the next 24-48 hour time period. Some
afternoon cloud build-ups can be expected over the local mountains
on Monday and Tuesday. While still a low probability, the best
chance (10-15%) of any thunderstorms with this upper level low
pressure system would likely be Tuesday afternoon over the local
mountains, with the highest probability skewed towards the
Ventura county mountains. A slight cooling trend will continue
across the interior through Tuesday.
.LONG TERM (THU-SUN)...28/1236 PM.
That first upper low this week will be quickly followed by another
one Thursday, likely maintaining or even enhancing an already deep
marine layer with local drizzle possible and minimal change in
temperatures.
Following that a majority of the ensembles do show slight
improvement into next weekend with ridging developing along the
West Coast, though once again strongest much farther north over
the Pac NW. However, there is a 20-30 percent chance that the
trough will linger across southern California and result in little
or no chance in daytime highs. The most likely scenario is
temperatures warming to within a couple degrees of normal (ie.
still slightly below normal) with continued night through morning
low clouds and fog for coast/valleys.
&&
.AVIATION...28/2320Z.
At 2200Z, the marine inversion as KLAX was based at 3300 feet.
The top of the inversion was 5100 feet with a temperature of
14 degrees Celsius.
Overall, moderate to high confidence in 00Z TAF package. For
coastal and valley sites, moderate confidence in latest TAFs
with MVFR CIGs expected for all sites with a 20-40% chance of IFR
CIGs (except high confidence in IFR CIGs for KPRB overnight).
There is a 20-30% chance that MVFR CIGs will scatter out after
20Z. High confidence in desert TAFs.
KLAX...Overall, moderate confidence in 00Z TAF as MVFR conditions
are anticipated through the period. There is a 20-30% chance of
IFR CIGs 08Z-15Z. There is a 20-30% chance that MVFR CIGs will
scatter out after 20Z. No significant easterly wind component is
expected.
KBUR...Overall, moderate confidence in 00Z TAF as MVFR conditions
are anticipated through the period. There is a 30-40% chance of
IFR CIGs 08Z-15Z. There is 20-30% chance that MVFR CIGs will
scatter out after 20Z.
&&
.MARINE...28/121 PM.
For all waters, high confidence in current forecast through
Wednesday. For this period winds and seas are expected to remain
below Small Craft Advisory (SCA) levels.
Moderate confidence that Wednesday night widespread SCA level
winds, and borderline SCA level seas will spread over the outer
waters and the western portion of the Santa Barbara Channel.
&&
.BEACHES...28/121 PM.
Long-period south swell originating from the Southern Hemisphere
will move into the coastal waters through Tuesday. Strong rip
currents and elevated surf of local 3 to 5 feet will be possible
over the Memorial Day holiday weekend. There will be the potential
for hazardous rip currents and a Beach Hazards Statement may be
needed later this weekend.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Gomberg/MW
AVIATION...RAT
MARINE...Sweet/Schoenfeld
BEACHES...Sweet
SYNOPSIS...Gomberg
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
909 PM EDT Sun May 28 2023
.SYNOPSIS...
Low pressure over upstate South Carolina will continue to push
northward through Wednesday bringing increased shower chances,
cloud cover, and below normal temperatures to the region. Rain
chances begin to decrease while temperatures increase later this
week as high pressure builds back into the region.
&&
.NEAR TERM /UNTIL 7 AM MONDAY MORNING/...
Relative to the past 24 hours, the lower atmosphere has
significantly moistened up per ACARS soundings. There still
remains some dry air in the lowest 150-mb, but radar echoes
approaching from the southeast should further saturate the sub-
cloud layer. Current surface observations show dew point
depressions in the 10 to 15 degree range. While most approaching
showers are relatively weak in nature, some 35 to 40 dBZ echoes
have begun to emerge out of the Virginia Tidewater region. As
these showers lift toward the northwest, a brief moderate
downpour is possible over portions of central Virginia.
Aside from any enhancements along frontogenetic bands, a lot of
the activity will be loosely defined. There will likely be a
defined cut off where precipitation ceases as dry air sits to
the north. Some drizzle may squeeze out for areas north of I-70,
but these locations will largely remain dry overnight. In terms
of temperatures, enhanced cloud cover and persistent easterly
flow will hold temperatures in the 50s, locally into the low 60s
for the metro regions and along the Cheseapeake Bay.
&&
.SHORT TERM /7 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
A lull in activity is likely Monday morning. The highest
coverage of showers/storms is expected during peak heating each
afternoon Monday and Tuesday. Most of the model guidance now
keep rain chances low north of US-50, though that will
ultimately depend on how far north the frontal boundary makes
it.
The 12Z high res guidance today indicates a signal for possibly some
heavy rainfall along the eastern slopes of the Blue Ridge and in
parts of central VA. This area could see repeated rounds of rain
through Tuesday, and will be aided by orographic lift. Widespread
rainfall amounts of 0.25-0.75" are forecast south of I-66, with
isolated higher amounts of 1.00-1.25". Along the Blue Ridge,
rainfall amounts of 2-3" are forecast with isolated amounts up to 4"
possible. This could lead to isolated instance of flooding in poor
drainage and low-lying areas.
Afternoon temperatures over the next couple of days will reach the
upper 60s to lower 70s. Muggy overnight conditions with lows in the
50s to low 60s.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Shower and thunderstorm chances will continue with moderating
temperatures later this week. Overall not much change in the blocky
pattern with residual troughing moving across Canada and a gradually
flattening of the upper level ridge to the east. At the surface,
closed low pressure will continue to linger across the region while
gradually weakening and drifting offshore Wednesday into Thursday.
This will allow the chance for diurnal showers and thunderstorms on
both days with the higher coverage on Wednesday compared to Thursday
as an area of diffuse high pressure builds aloft. Although ensemble
and deterministic guidance show a bit of variance the tendency
remains for higher coverage of showers and perhaps a few
thunderstorms during the daytime hours Wednesday compared to
Thursday as the high builds in aloft. Precipitation chances do not
go to zero completely Thursday nor Friday although Friday appears to
be drier as high pressure continues build into the region.
Convection once again will be confined to the daylight hours, but
should be mainly terrain induced on both days with the potential of
one or two isolated showers/thunderstorms flaring up further east
along the bay/river breeze.
A backdoor cold front looks to drop into the region from the
northeast for the upcoming weekend ahead. 12z deterministic/ensemble
guidance continues to show some differences on the timing of front
along with the potential for showers and thunderstorms compared to
earlier runs from this morning. Latest guidance suggest a frontal
passage on Saturday afternoon and evening leading to increased
shower and thunderstorm chances across the region. The front will
quickly pass through Saturday night with high pressure building in
from the north Sunday into early next week.
Near normal temperatures are expected Wednesday with excess cloud
cover and showers. Highs by Thursday and Friday will warm back above
average with highs potentially around 90 degrees in most locations.
This trend will likely continue into Saturday ahead of the backdoor
cold front as 850 mb temperatures approach +12 to +16 degrees C.
Humidity values will also be on the increase as well with relief not
expected until the end of the weekend as cooler and drier air filter
in.
Forecast confidence in the long term periods remains moderate due to
large model spread for both precipitation chances and temperatures
within the mid and late week period.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
As a frontal boundary and associated area of low pressure lift
north from the Carolinas over the next couple of days, expect
sub-VFR conditions at most terminals, except for MRB where it
will likely stay VFR through the period.
Sub-VFR conditions are expected to hold off at most terminals until
late this evening to tonight, as clouds slowly move in from the
south. For DCA/IAD, steady MVFR CIGs arrive late tonight, and
could be followed by a period of IFR CIGs Monday morning to
afternoon, though confidence was not high enough to include in
TAFs at this time. CIGs could drop down to MVFR at BWI/MTN
sometime tonight or Monday.
A high coverage of showers is expected each afternoon through
Tuesday at CHO, with lower coverage at the other terminals. An
isolated thunderstorm is also possible, again the highest chance for
that is at CHO. VFR conditions could return Monday evening, though
confidence is low as it will depend on where the surface low tracks
and if clouds can lift.
Closed upper level low pressure will continue to linger through
Wednesday as high pressure builds aloft later this week. Periodic
sub-VFR restrictions remain likely through this time especially
during the early morning hours due to low clouds and the afternoon
with diurnally driven showers and thunderstorms. Confidence
continues to increase for VFR conditions returning Thursday into
Friday as high pressure builds back into the region. Sub-VFR
conditions potentially return with a backdoor cold front for the
first half of the weekend.
&&
.MARINE...
SCA conditions with gusts up to 20 knots continue through the
evening across the southern waters of the Chesapeake Bay and
tidal Potomac. The extratropical low over the Carolinas meanders
toward the area early in the week. Winds are forecast to decrease
this evening and tonight, but will likely pick back up to SCA-
level Monday afternoon in parts of the central/southern bay.
There is also a low chance for a few thunderstorms Monday and
Tuesday afternoons.
SCA level winds could linger into Wednesday although the pressure
gradient will continue to relax as low pressure weakens and high
pressure builds into the region. Winds will remain out of the
northeast Wednesday before switching to the south and southwest
Thursday and Friday. Sub-SCA conditions are expected during this
time.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ534-
537-543.
&&
$$
SYNOPSIS...EST
NEAR TERM...BRO
SHORT TERM...KRR
LONG TERM...EST
AVIATION...KRR/EST
MARINE...BRO/KRR/EST