Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/18/21

Area Forecast Discussion...CORRECTED

National Weather Service North Platte NE

 804 PM CDT Sun Oct 17 2021

.UPDATE...
Issued at 802 PM CDT Sun Oct 17 2021

A forecast update is in place for slightly cooler low temperatures
across swrn Nebraska tonight. The forecast leans on the guidance
blend which verified fairly well Saturday night. Plus, the
evening upper air flights at Denver and North Platte show drier
air is in place and sfc winds should become light by morning. The
clear skies expected overnight, very dry air and predicted light
winds shown by the RAP model support lows in the lower to mid 30s
across swrn Nebraska.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 339 PM CDT Sun Oct 17 2021

Mostly quiet weather tonight and tomorrow will begin to give way
to the forecast area`s next chance for precipitation early
Tuesday morning. The upper level ridge axis will progress east
tonight and tomorrow as an upper level low moves into the western
United States. Southerly to southwesterly flow at 850 mb
overnight and the resulting WAA should keep surface temperatures
moderated despite clear skies with highs ranging from the mid 30s
in the southwest to the low 40s in north central Nebraska. Cooler
temperatures in the river valleys are possible once again.

Above average temperatures will continue on Monday. Southerly flow
and warm air pooling ahead of the cold front will bring temperatures
into the 70s, around 10 degrees above normal. Some high clouds may
develop during the day as moist upper air moves into western
Nebraska, but this will not have any major cooling to temperatures
at the surface. Winds will become gusty on Monday afternoon. The low
level jet will shift to the east and the pressure gradient will
steepen at the surface. The strongest wind gusts will be in north
central Nebraska, with speeds up to 30 mph. Elevated fire weather
conditions are expected due to this wind, but RH will be in the
upper 20s to low 30s across most of the forecast area, which may be
a limiting factor to fire development.

The cold front will begin to enter the western Panhandle from the
northwest late on Monday night. Ahead of the front, overnight lows
will be warmer compared to previous nights with lows ranging from
the low 40s in the Panhandle to the upper 40s in north central
Nebraska.

.LONG TERM...(Tuesday through Sunday)
Issued at 339 PM CDT Sun Oct 17 2021

As the center of the surface low moves east along the South
Dakota/Nebraska state line, the cold front will be dragged across
western and north central Nebraska through the day on Tuesday.
This will create a sharp contrast in temperatures across the
forecast area, with highs in the 50s in the Panhandle and highs in
the low 70s in north central Nebraska. Winds will shift to the
northwest and become gusty in the Panhandle and southwest
Nebraska. Most areas north of Interstate 80 have the potential to
receive precipitation, but the possibility increases towards the
South Dakota state line This system will be stratiform in nature
and QPF is generally forecasted to be less than an inch. As
temperatures drop overnight on Tuesday, some areas of the
Panhandle and Sandhills may receive snow or a rain-snow mix,
particularly in Sheridan County. Current models are pointing
towards low snow ratios and an increase in snow ratios could
result in higher snow amounts in those impacted areas. Will
continue to monitor for greater snow potential Tuesday night and
Wednesday morning.

The system will move east out of the forecast area by the end of the
day on Wednesday. Cloud cover will persist through in the northern
half of the forecast area, leading to another gradient in high
temperatures with the mid 40s in the north and the upper 50s in
southwest Nebraska. Behind the exiting low an upper level ridge will
begin to build again across the western United States, moving east
into the Great Plains. This will result in a gradual warming trend
through the rest of the week, with highs reaching the 60s by the
weekend. Some upper level moisture may lead to cloudy skies at that
time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 621 PM CDT Sun Oct 17 2021

VFR conditions expected to prevail through tomorrow evening. Some
high clouds pass through and winds remain gusty from the south
tomorrow afternoon, with gusts around 15 to 20kts possible.


&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...CDC
SHORT TERM...Meltzer
LONG TERM...Meltzer
AVIATION...Brown



Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 511 PM PDT Sun Oct 17 2021

.SYNOPSIS...17/927 AM.

A cold front moving through the area will bring a chance of light
rain and drizzle to the area tonight into Monday morning. There
will be cooling today and Monday before temperatures rise a
little through Thursday as high pressure redevelops. Another
chance for light rain develops over next weekend.

&&

.SHORT TERM (TDY-WED)...17/156 PM.

Synoptically, there is a 540 dam trough dropping down the west
coast to nearly the San Francisco Bay area. Over the next twelve
hours, this trough will drop far enough south and cut off,
bringing a little precipitation to at least the northern portion
of our area overnight. Another trough will follow on Wednesday
but that one will probably just clip the northern part of our
area. A ridge builds on Thursday bringing a brief break in the
pattern and the high temperature of the week, before another
trough extending from a closed Gulf of Alaska low brings impacts
the area beginning next Friday.

Skies are mostly clear over the area right now except for a few
over the Ventura Co mountains and some offshore clouds. Today has
been much cooler than yesterday due to falling heights and a to
moderate onshore flow. HRRR and local models are still showing
this reversal of the pressure gradients to bring near- advisory
level southerly and westerly winds to portions of the Antelope
Valley and the higher elevations of the LA county mountains this
afternoon and evening. While the fire weather indices are much
lower than yesterday, the combination of the gusty onshore winds,
low humidities, and critically dry fuels will bring elevated fire
weather conditions to the Los Angeles county mountains and
Antelope Valley this afternoon.

The trough will move into northern California tonight and a cool
cutoff upper low will form and then traverse the the state west to
east before moving into Nevada. As it moves, it will drag a weak
cold front into the Central Coast. The lift from the front along
with the cyclonic flow aloft will spin up a deep marine layer. The
front will bring a chance of rain to the Central Coast while the
rapidly deepening marine layer will allow for a chance of drizzle
or even light rain in Los Angeles County.

The front will rapidly weaken early Monday morning and will likely
not hold together long enough to be a rain producer for Ventura
and Los Angeles Counties, but the deep marine layer will continue
to produce drizzle and a slight chance of a shower. Rainfall
amounts from the overnight and morning hours, if any, should range
from a few hundredths to about a quarter inch in the upslope
locations. There will be fairly rapid clearing behind the front
starting in the Central Coast later in the morning and then
working through areas south of Pt Conception in the afternoon.
With the exception of the Central Coast most areas will see
another 8 to 12 degrees of cooling as the front passes. The
entire area will come in 8 to 16 degrees below normal.

Monday night should be clear and cold as the front and cold air
advection should wipe the marine inversion out, with chilly
overnight lows to all of the area.

A little ridge will provide a break between troughs and heights
could build to 578 dam on Tuesday. The onshore flow will markedly
lessen, and weak offshore could even set in. The sunny skies and
neutral to offshore flow will bring 6 to 12 degrees of warming,
but afternoon highs will still be 4 to 8 degrees below normal.  For
those interested in baseball weather, there shouldn`t be rain at
Dodger stadium Tuesday through Thursday, but there will be cool
evenings with overnight lows in the mid-50s.

On Wednesday the ridge makes way for a system moving into the
Pacific northwest. The tail end of the cold front associated with
this storm will bring a slight chance of light showers to northern
San Luis Obispo County.

.LONG TERM (THU-SUN)...17/200 PM.

A pop-up ridge pushes in from the southeast on Thursday, bringing
heights up to around 585 dam and the warmest temperatures of the
week. However, there will still be some slight onshore flow and
skies will likely be partly cloudy as mid and high level clouds
stream overhead is advance of the next trof, so things won`t get
too warm. Downtown LA will only hit around 75 degrees which is
still 4 below normal.

Ensembles point to a active weekend beginning on Friday as
another in the series of storms moves into north of the state.
There is still quite a bit of uncertainty with the exact track of
the storm, which has several little impulses. Right now the
Central Coast has about an 80% chance of some precipitation
beginning on Friday night while the LA area is only around 30%
beginning Saturday afternoon. Rain chances will continue off and
on through at least Sunday. It doesn`t look to be significant rain
maker. Temperatures will remain well below average during this
period of precipitation.

&&

.AVIATION...18/0010Z.

At 2345Z at KLAX, the marine layer was 1400 feet deep. The top of
the inversion was around 2200 feet at a temperature of 17 degrees
C.

A weak cold front and rapidly deepening marine layer will bring
a surge of low clouds and fog into the coastal slopes tonight/
Monday morning with areas of drizzle and 20-30 percent chance of
light rain, mainly in the 06z-18z time frame. Mostly expecting
MVFR cigs tonight, but could rise into VFR category by mid
morning Monday. Lower confidence in timing of ceiling
arrival which could be +/- 2 hours from TAF timing.

KLAX...Moderate confidence in TAF. MVFR cigs expected tonight,
potentially lifting to VFR category on Monday morning as marine
layer deepens rapidly. There is a 30 percent chance of light rain
or drizzle on Monday morning.

KBUR...Moderate confidence in TAF. MVFR cigs expected overnight,
potentially lifting to VFR category on Monday morning as marine
layer deepens rapidly. There is a 30 percent chance of light rain
or drizzle on Monday morning.

&&

.MARINE...17/920 AM.

Winds and seas are expected to remain fairly calm through this
afternoon. Late tonight into early Monday, NW winds will
strengthen from north to south ahead of an approaching frontal
system. Moderate confidence in winds strengthening to SCA level
from the Central Coast to San Nicolas Island by early Monday
morning. Confidence increases through the day on Monday as winds
strengthen further, with moderate to high confidence in widespread
SCA level winds Monday afternoon through late Monday night. SCA
level winds may spread into the western portion of the Santa
Barbara Channel during this time, but confidence is low to
moderate. Winds and seas are then expected to be below SCA levels
for all coastal waters Tuesday through Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

A storm system could affect the region next weekend.

&&

$$

PUBLIC...Rorke/jld
AVIATION...Gomberg
MARINE...Sweet/Stewart
SYNOPSIS...jld

weather.gov/losangeles