Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/03/20
Area Forecast Discussion
National Weather Service Columbia SC
1033 PM EDT Fri Oct 2 2020
A pressure ridge centered to the north of the area will extend
into the area over the weekend. The air mass will be cool and
dry through Saturday with moisture near the coast along stalled
frontal boundary but may spread into eastern South Carolina
Sunday with a few light showers. A dry cold front will move
through the area Sunday night. Temperatures will moderate next
week and mainly dry conditions expected.
.NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
Skies have cleared with sunset and temperatures are quickly
falling as radiational cooling conditions are optimal. Overnight
expect skies to remain clear and with light winds temperatures
will fall into the mid to upper 40s for most locations with some
outlying and typically cooler areas in the lower 40s.
.SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Saturday and Saturday night...Upper level trough axis west of the
area producing southwest flow aloft. At the surface, high pressure
to move from the Ohio Valley to the Mid Atlantic region. Northeast
surface flow will hold a dry and cool airmass in place. PWATs around
one-half inch. Under mainly clear skies, afternoon highs will warm
to the low and mid 70s with overnight lows in the mid 40s to mid
Sunday and Sunday night...The 12z NAM has come into agreement with
the GFS and ECMWF with mainly dry conditions. Low pressure moving
along a coastal front will hold most of the rain off the coast. Fast
moving clipper type system moves across the Mid Atlantic region
Sunday night as upper trough amplifies. Moisture limited and lift to
the north of the area so cold front should move through dry. Little
change in air mass with high temperatures in the low to mid 70s. Low
temperatures will be upper 40s and lower 50s as front will be weak.
The HRRR integrated smoke model indicated smoke aloft spreading over
the area on Sunday as the upper level trough deepens to our west,
producing a southwest flow. This smoke can be seen along the coastal
Carolinas and southern GA this afternoon.
.LONG TERM /MONDAY THROUGH FRIDAY/...
High pressure dominates early in the week. Models indicate
another moisture starved cold front moving through the region
Wednesday night with Canadian high pressure building in Thursday
and Friday. Tropical development in the Gulf of Mexico possible
during the period. Latest trends suggest dry conditions will
dominate across the Carolinas and east central GA as coastal
front moves further offshore.
Will continue with dry forecast with strong support from latest
GFS and ECMWF. Temperatures near or slightly below normal early
in the week with some clouds associated with coastal front and then
warming trend closer to normal Wednesday and Thursday, then cooling
down again Friday.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Dry air mass over the region, with light winds. Despite limited
low level moisture, cool air temps over warm waters tonight may
provide some localized shallow lake/river valley fog.
EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
expected through Saturday. Slight possibility of light rain and
some CIG restrictions Sunday mainly at KOGB, but confidence low
at this time. Models suggest that some smoke from western U.S.
wildfires may spread over the area on Sunday, and some minor
visibility restrictions are possible.
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
327 PM PDT Fri Oct 2 2020
.SYNOPSIS...Dry and unseasonably warm conditions are expected to
continue this weekend across the interior areas as strong high
pressure aloft persists. Marine clouds and fog are expected to
linger along the immediate coast for the next few days, briefly
clearing each afternoon then pushing back onshore each night. Inland
temperatures are expected to see a gradual cool down though the
.DISCUSSION...Little change to the forecast package this afternoon
as high pressure aloft maintains a stable and consistent weather
pattern. More robust west and northwesterly flow this afternoon
should help with smoke concerns...especially across the Humboldt
County coastal areas. Eventually by Saturday much of the smoke will
only be focused around the large fires while settling, focused
mainly over Trinity County per HRRR smoke modeling. For today
another warm afternoon will be observed over the interior areas
where max temps will once again be well above normal for early
October. Some relief is finally on the horizon as the ridge weakens
and heights and 850 temps finally fall a bit over the weekend for
some modest cooling. Forecast attention and confidence now turning
toward a major pattern change possible developing toward next
weekend. As the persistent ridge finally breaks down and moves east,
forecast models continue to hint at a weather system pulling in
tropical moisture from Hurricane Marie. At this time it is too early
to get overly excited about potential rainfall but models are in
agreement on brining in some rain, cooler temperatures and even high
elevation snow to northern CA next weekend.
.AVIATION...Fog and stratus plagued the immediate North Coastal Shore with
IFR/LIFR conditions persisting through afternoon. Much of the SKY
was OVC001/OVC002 at CEC and ACV, and VIS often reported less than
1/4SM. Around noonday, Visual Satellite Pictures confirmed that
skies were mostly clear beyond the immediate coast, but layers of
smoke continued to abound due to inland wildfires. For the remainder
of the afternoon, some improvement expected at the coastal airports.
However, improved CIG/VIS should be shortlived before deterioration
occurs again this evening. Inland areas...particularly in Mendocino,
MVFR CIGS were reported due to smoke. Smoke also filtered down to
surface levels. UKI reported IFR VIS into afternoon. Thinning smoke
is expected overnight. LLWS is again possible at UKI in the
evening/overnight as north winds above ground level (AGL) will
increase. These winds will be in the vicinity of UKI although the
stronger winds aloft have shifted southward, but approaching the
airport from the south still poses a LLWS flight hazard. /TA
.MARINE...Moderate northerly winds, mainly focused in the
southern outer waters, will continue to generate steep seas from 6
to 8 feet at 8 seconds through the weekend. These conditions will
expand into the northern outer waters and southern inner waters
on Saturday. Small craft advisory is now in place for the outer
waters and southern inner waters through Sunday. Conditions will
gradually improve Monday as the moderate northerlies pull away
westward. A longer-period westerly swell will be reinforced by on
Saturday around 6 feet at 15 seconds then slowly subsiding through
.FIRE WEATHER...A Red Flag Warning remains in effect for portions
of Southern Mendocino and Western Lake counties due to gusty north
and northwesterlies through this evening. This band of gusty winds
will coincide with an already very dry airmass over the entire
region. The strongest winds will occur at elevations above 1500 feet
and be most pronounced along the upper slopes and ridges. Winds have
weekend during the day today but relative humidity in that area has
remained very dry, and another pulse of northwest winds is likely
later this afternoon before wind significantly weaken overnight.
Focus beginning to turn toward next weekend as primary extended
models coming into agreement on the potential of a rain producing
front crossing areas north of the Bay Area. Given that it is still 7
days out it is hard to get excited about rain potential...especially
this time of year and the fact that it is on the heels of a major
blocking ridge. Nonetheless substantial rain amounts are being
depicted and even if those were reduced by 50% it would still bring
wetting rains to the large fires north of HWY 20...as well as
significantly reducing the widespread smoke.
CA...Red Flag Warning until 8 PM PDT this evening for CAZ264-276-277.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 1 PM Saturday to 7 PM PDT Sunday for
Small Craft Advisory from 7 AM Saturday to 1 AM PDT Monday for
Small Craft Advisory until 1 AM PDT Monday for PZZ475.
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Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
852 PM CDT Fri Oct 2 2020
852 PM CDT
The going forecast through Saturday morning is in good shape. As
was the case on the Day Shift, did continue to consider a Frost
Advisory for northwest Indiana where temperatures are in the low
40s as of just before 900 PM, which for the 2nd of October
diurnally would usually support at least mid 30s for lows. While
patchy frost is probable and areas of frost could occur,
satellite supports increasing clouds from the west likely to
result in flat-lining temperatures. Both the RAP and HRRR have
been consistent with that occurring in northwest Indiana. Will
continue to mention frost in that part of the forecast area but
confidence on more of a widespread frost remains below the
threshold of an Advisory. Elsewhere, patchy frost is possible
north of I-88 in northern Illinois given dew points in the mid 30s
and some upstream small holes in the clouds.
306 PM CDT
Through Saturday night...
Dry conditions are expected through Saturday afternoon with
surface high pressure and a dry low-level airmass in place.
Regarding overnight temperatures and the potential for frost:
with a completely clear sky, the floor on lows tonight is in the
lower 30s given the nicely dried-out surface airmass and
slackening winds. That said, the presence of thickening stratus
upstream across Minnesota, as well as plentiful mid- and high-
level cloud cover associated with an approaching system`s jet
streak cast a good deal of doubt that we`ll manage these types of
temperatures tonight. As a result, while we did give some thought
to a Frost Advisory for some of our typical cold spots, the signal
for sufficient radiational cooling potential through the night
seems too low to warrant any headline issuances at this point.
We`ll continue to keep an eye on upstream cloud trends this
afternoon and evening.
Another shortwave trough currently located over North Dakota will
traverse the ever-persisting upper longwave trough situated over
the region before encroaching our CWA late Saturday afternoon.
Sufficient DPVA, some frontogenetic forcing, and modest height
falls will allow for an expansive precipitation shield to develop
across the area Saturday evening, but QPF should be limited to a
few tenths at most before the shortwave exits on Sunday.
Temperatures should fall at a pretty good clip late Saturday
night into Sunday morning with the passage of a developing cold
front associated with this system, although likely not fast
enough to beat the intruding dry air and cessation of more
appreciable precipitation chances.
233 PM CDT
Sunday through Friday...
Some lingering rain, associated with Saturday nights weather
disturbance, will continue to be possible early Sunday morning,
but most areas should dry out by midday. The only exception to
this being over parts of northwestern IN near the lake. With a
reinforced shot of cool air over the lake, there will be some
potential for lake effect showers in this area, which could
persist into the afternoon before ending late. Otherwise, Sunday
is looking to be another chilly day across the area with highs
expected to remain in the mid to upper 50s.
Attention then turns to the next potential of frost Sunday night
into early Monday morning. Light winds are expected across the
area during this time as surface high pressure shifts over the
area. This in combination with, what at this time appears to be,
mainly clear skies could support good radiational cooling into
the low to mid 30s late Sunday night, especially for areas inland
from the lake and outside the more urban areas.
The surface high will shift to our southeast on Monday, with
winds turning southerly in its wake for Monday into Tuesday.
Moderating temperatures in this warm air advection pattern will
push highs back into the lower 60s for Monday, and potentially up
around 70 for Tuesday. A weather disturbance passing mainly to
our north on Tuesday may drop a weak cold front over the area
during the day, but this looks to do little to the temperatures as
the flow quickly shift back out of the southwest Tuesday night
into Wednesday ahead of a fast moving clipper system dropping
southeastward over Ontario. This system will result in a mild and
breezy day Wednesday, with a stronger cold front likely to shift
southward over the area during the afternoon. It continues to look
dry across the area with this frontal passage, so we continue to
advertise a dry forecast.
We only look to get a glancing blow at some cooler air in the wake
of this front, so we can expect temperatures to be in the lower to
mid 60s for Thursday. Thereafter, we look to get back into a mild
weather pattern, supportive of highs around 70 for next Friday.
For the 00Z TAFs...
For the Chicago area airports through Saturday:
- East-northeast wind speeds greater than 6 kt ending shortly
after 00Z, then becoming southerly on Saturday morning
- A few showers in the area later Saturday afternoon with an
increase in coverage after dark and likely trending to MVFR
After a late afternoon lake breeze, the wind speeds of 7-9 kt
will ease quickly by 00Z-0030Z. High pressure over the area
tonight will depart eastward Saturday morning allowing for
winds to turn southerly with speeds likely to remain below 10
kt most if not all of Saturday. While a lake breeze may develop,
confidence is high in this remaining east of ORD and MDW. The wind
will turn more northwest to north after dark Saturday and north-
northeast is possible but speeds look to be less than 7 kt.
VFR clouds will prevail through much of Saturday with temporary
breaks late tonight/early Saturday. Spotty showers on the
regional scale should be present Saturday afternoon with an uptick
toward sundown and after. Conditions should remain VFR after the
showers begin for a short period but then trend to MVFR with some
potential for IFR Sunday morning.
LM...Small Craft Advisory...IN nearshore waters until 10 PM Friday.
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Area Forecast Discussion
National Weather Service Reno NV
1244 PM PDT Fri Oct 2 2020
High pressure will remain over the region through the first week of
October, bringing warm afternoons, dry conditions, light winds, and
chilly mornings. General hazy skies will last across the region
A strong ridge of high pressure remains over the region with high
temperatures running 10-15 degrees above normal, but looking to
remain just shy of records. The very dry air mass will allow for
excellent radiational cooling with overnight lows continuing to drop
into the 40s for many valley locations, with 30s in the Sierra.
Based on latest high resolution HRRR smoke model along with
satellite data, it appears most of the smoke impacts will remain
aloft near and just east of the Sierra. This makes sense given the
overall light northeast flow in the low levels with a light westerly
wind around ridgetop level. Immediately downwind of ongoing
wildfires, smoke is likely to continue to bring air quality
concerns. We could see the return of lower level smoke spreading
farther into the eastern Sierra and western Nevada on Sunday as low
level flow returns more to the southwest.
The ridge remains fairly stagnant through the first week of October,
though does somewhat weaken the early part of next week in response
to an undercutting weak closed-low. Impacts from this are rather
minimal -- just a few degrees of cooling, but still well above
We continue to see signals in longer range ensembles for potential
wet and cooler weather starting around the weekend of Oct 10-11.
Approximately 3 out of 4 ensemble members from the EPS/GEFS/CMC are
showing signals of precipitation, with cooling temperatures. The
exact qpf numbers, however, vary greatly. This is likely due to what
is currently Hurricane Marie, how this system may evolve, and
whether remnant moisture will be entrained into upstream troughs.
Marie`s moisture moving directly into the region is an outlying
solution, with a 10% or less chance of occurring, but if it did,
much higher liquid totals are possible.
There is still a 25% chance that the moisture will remain north,
with light rain possible for far northern CA/NV and drier/breezy
conditions elsewhere. So, while we can say it looks like the
dominant ridge will weaken or break down, with a general downward
trend in temps, the exact impacts are still TBD. -Dawn
High pressure will keep light winds and cloud-free skies across
the Sierra and western Nevada through the weekend. Primary concern
continues to be the smoke and haze, which may impact ceilings and
visibilities for terminals through the weekend.
Smoke is slowly returning to the Tahoe Basin and portions of the
eastern Sierra today through Saturday. Visibility reductions
should only be around 4-5 miles for KTRK, KTVL, and KMMH. By late
Saturday into Sunday, more westerly flow develops and may bring
additional smoke and haze to the western Nevada terminals.
This will be heavily dependent on wildfire activity over the
next couple of days. For now it appears that the `old smoke` is
just lingering about the region. -Edan
For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Las Vegas NV
Issued by National Weather Service Flagstaff AZ
750 PM PDT Fri Oct 2 2020
.SYNOPSIS...A strong ridge of high pressure over the Western
States will lead to near-record high temperatures through
Saturday. North breezes can be expected through this evening,
especially down the Colorado River Valley. Conditions will remain
warm and dry through the at least Thursday.
.UPDATE...Made some minor changes to sky cover overnight as some
some thin high clouds are moving southward into the region. Also
adjusted the coverage of haze/smoke in far western portions of the
forecast area through Saturday.
.SHORT TERM...Tonight through Sunday.
Operational models are in good agreement showing the strong high
pressure to remain centered over southern Nevada and south
central California through Sunday. This will allow afternoon high
temps to be around 10 degrees above normal for the dates. Breezy
north winds have developed down Colorado River Valley this
afternoon. Light and variable winds are then expected through the
The HRRR Smoke Forecast continues to show wildfire smoke from the
southern Sierra to impact the northern portions of the Owens
Valley tonight into Saturday. Sundays weather is pretty much a
.LONG TERM...Monday through Friday. The warm high pressure system
is expected to slowly weaken and push eastward through Tuesday
night. Thus expect the dry weather to continue, through max temps
to lose a degrees or two each day. Progs are suggesting a return
to southwest flow aloft starting Wednesday that may persist
through Friday. Thus dry weather is expected as well as the
cooling trend in afternoon temps.
Strong high pressure will bring near record high
temperatures through Saturday. Max temperatures will start a slow
cool down on Sunday that lasts through next week, but will still
be around 5 degrees above normal on Wednesday. Dry conditions to
persist, with single digit RHs in the afternoon and poor to
moderate recoveries overnight. Other than some gusty northerly
winds down the Colorado River through this evening, the remainder
of the area is expected to see typical diurnal winds.
.AVIATION...For McCarran...Generally diurnal wind patterns
and clear skies are forecast through Saturday evening.
For the rest of southern Nevada, northwest Arizona and southeast
California...Little impacts expected through Saturday evening.
Smoke is expected to stay west of the Owens Valley through this
evening, but there is potential for smoke to move into this area by
early Saturday morning bringing some reduced visibility.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
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