Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/21/20
Area Forecast Discussion
National Weather Service La Crosse WI
1058 PM CDT Tue Oct 20 2020
.SHORT TERM...(Tonight through Wednesday)
Issued at 230 PM CDT Tue Oct 20 2020
Shortwave trough packing a little bit of a punch with good upper
level jet support, and perhaps more importantly, west-east running
frontogenetic support. RAP has picked up on a Fgen layer roughly
laying west to east across northwest WI, persisting through about
03z or so. An enhanced band(s) seem a lot more likely then they did
24 hours ago as a result. Meanwhile, a large swath of 1/2 mile snows
were falling across much of MN at early afternoon, all advancing
east/northeast. Warming has moved into southwest WI, but models have
tended to be too warm north of there, not compensating enough for
the lower dewpoints/wet bulbs and pcpn induced cooling. I-90 still
remains a good demarcation point for snow/wintry mix/rain and will
continue to hover that line there into tonight. Have decided to
upgrade Advisory to a Warning for Clark and Taylor counties in
northern WI based on the better threat for banding, not to mention
higher potential for 1" per hour snowfall rates (per HREF guidance).
Still have some of that early season melting to expect, but
snowrates should overcome that rather quickly. Might be my first
Winter Storm Warning ever issued in October in 29 years. I was fine
not doing one.
.LONG TERM...(Wednesday night through Monday)
Issued at 230 PM CDT Tue Oct 20 2020
Main focus Thursday into Friday is the potential for strong storms
Thursday. The 20.12z GFS/NAM are in good agreement with tracking an
impulse across the forecast area Thursday. The deterministic 20.12z
models all indicate strong moisture transport/convergence in
association with impulse/surface low. The 20.12z GFS/NAM show very
strong shear across the forecast area. However...bufkit soundings
suggest limited surface based instability...up to 1000 to j/kg
across the far southern forecast area. The 20.12z NAM shows 500 to
1100 j/kg 0-6km most unstable CAPE along surface front/low. Forecast
area will see thunderstorms...with limited instability potential for
severe storms remain low.
Main forecast concerns Friday night into Tuesday area temperatures
through the period. The 20.12z GFS/ECMWF are in good agreement in
digging upper level trough over the Northern Plains/Upper Great
Lakes region through the period. Shortwave trough moves across the
Central Plains Saturday night into Sunday night and spread rain or
snow across the forecast area. As disturbance moves southeast and
east of the forecast area...colder air advects into the Upper
Midwest and Great Lakes region. 20.12z GFS/ECMWF suggest 925mb
temperatures cooling to minus 6 to minus 8 degrees celsius by 12z
Monday. NAEFS temperature anomalies show minus 1 to minus 2 below
normal Sunday into Tuesday across the forecast area. High
temperatures Monday and Tuesday are expected to be middle 30s to
lower 40s and low temperatures will be around 20 degrees to lower
30s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1058 PM CDT Tue Oct 20 2020
As the storm system exits, remaining light returns/drizzle on
radar late this evening should push out of the area by 06Z. IFR
ceilings will likely persist at both TAF sites overnight, and can`t
rule out a dip to LIFR cigs at RST where lingering BR is also
likely to reduce visibility for a time overnight. Forecast
soundings are in decent agreement for the IFR cigs to quickly
scatter out towards 14Z with a return to VFR conditions.
Weak ridge of surface high pressure will drift overhead during the
day on Wednesday. Some hi-res models suggest isolated light
showers in the afternoon, but likelihood appears low so have kept
TAFs dry. There will be plenty of mid level clouds, however.
Winds will shift around to the southwest to west by the start of
this TAF period, changing direction but generally with a westerly
component during the day as the ridge moves overhead. Winds then
turn NE Wednesday evening.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 1 AM CDT Wednesday for WIZ032>034.
Winter Storm Warning until 1 AM CDT Wednesday for WIZ017-029.
MN...None.
IA...None.
&&
$$
SHORT TERM...Rieck
LONG TERM....DTJ
AVIATION...Kurz
Area Forecast Discussion
National Weather Service Charleston SC
1051 PM EDT Tue Oct 20 2020
.SYNOPSIS...
High pressure and a weak coastal trough will persist into late
week. A cold front could approach the region this weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1050 PM: The forecast remains on track. I will update to
make minor changes to sky and hourly temps.
As of 9 PM: KCLX detected a few weak returns over northern
Charleston County and few weak showers over the waters. Latest
HRRR indicates that rounds of showers will drift inland from the
Atlantic overnight. Inland, the primary concern will be the
development of fog. Guidance generally agrees that dense fog is
not expected. However, patchy fog should be common across the
inland counties after midnight.
As of 725 PM: A sfc trough will continue to push slowly inland
through the rest of this evening into late tonight. The trough
is expected to become stationary over the Midlands before dawn
Wednesday. Widespread fog and stratus should develop within the
trough, spreading into the inland counties late tonight. The
forecast update will maintain SCHC PoPs, thunder will be
removed. Patchy fog across the inland counties appears well
timed.
Previous Discussion:
Tonight: The synoptic pattern will be influenced by a deep
layered ridge to our northeast, and a mid level cyclone
positioned over the northwest Caribbean. Weak forcing will
mainly be the result of a trough located along the coast which
is expected to sharpen slightly this evening and begin to shift
onshore. Isolated showers are possible tonight through the early
morning, with the greatest chances nearest the coast in the
evening and trending inland overnight. A rumble of thunder is
possible, mainly in the southeast GA counties; however drier air
aloft and low instability will limit convection. Chance PoPs
along the coast are introduced through the evening, otherwise
slight chance PoPs dominate much of the forecast area. Low
temperatures will range from the mid/upper 60s over most of the
area to the low 70s along the coastline.
A steady influx of low level moisture from off the ocean is
expected to lead to the formation of stratus build down and
areas of fog overnight. The greatest coverage looks to be far
inland, where condensation pressure deficits are the lowest. Low
stratus could creep toward the coast near sunrise and dissipate
a few hours afterwards as winds increase and boundary layer mixing
initiates.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Deep layer high pressure will remain just northeast of the region
before gradually weakening late week ahead of an approaching cold
front. While significant upper level dry air will linger mainly
across the SC Lowcountry, low level moisture associated with a
coastal trough will increase rain chances. The best chance looks to
be across SE GA on Wednesday and Thursday where PWATs will be
between 1.5 and 1.75 inches. By Friday, moisture associated with TS
Epsilon will start to creep into the coastal waters and along the
coast before shifting inland throughout the day as high pressure
shifts further northeast. For each day, rain coverage should
generally be light and isolated to scattered. There is sufficient
instability so have maintained slight chance of thunderstorms for
each day and have also included mention over the coastal waters for
the overnight periods as well as during the day. High temperatures
will be in the low to mid 80s with upper 70s along the coast. Low
temperatures will be in the mid to upper 60s inland and low 70s
along the coast.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Global models continue to indicate that persistent deep layer ridge
to the northeast of the region will finally breakdown as a broad
upper trough forms over the central and southwest portion of the
country. This places the region in generally zonal upper level flow
through weekend, then backing to southwesterly Monday and Tuesday as
the upper trough sharpens well to the west and a ridge builds
southeast of the area. For the weekend, there could be some weak
upper level shortwaves moving through the zonal flow. The ECMWF
seems be more bullish with these disturbances than the GFS. For now,
have continued chance PoPs through the weekend. By Monday and
Tuesday, model consensus shows some drying, as the upper ridge
builds to the southeast, but there are considerable differences in
the timing/placement of the next strong cold front associated with
the upper trough to the west. The GFS is faster with the front, and
shows much higher potential for precipitation by later Tuesday,
while the ECMWF is a full 12+ hours later. For now, went with slight
chance PoPs during this period due to moderate to high model
differences. Temperatures are expected to remain 3 to 5 degrees
above normal into early next week.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
0Z TAFs: A sfc trough will continue to push slowly inland
through the rest of this evening into late tonight. The trough
is expected to become stationary over the Midlands before dawn
Wednesday. Widespread fog and stratus should develop within the
trough, leaving the KCHS and KSAV terminals on the eastern edge
of the stratus. It appears that periods of restrictions are
possible at the terminals after 7Z, peaking between 10-14Z. High
resolution guidance indicates that a patch of light showers will
pass near or over KSAV Wed morning, KSAV TAF will feature VCSH
between 14-17Z. Conditions should return to VFR by mid-morning
at KCHS and mid-day at KSAV.
Extended Aviation Outlook: Mainly VFR. Brief flight restrictions
possible during afternoon showers and isolated thunderstorms through
Saturday. There are some hints in the models of low clouds in the
mornings through at least Saturday.
&&
.MARINE...
Tonight: High pressure will dominate, although a weak inverted
trough will persist along the coastal waters producing isolated
showers overnight. The pressure gradient will remain somewhat
packed between high pressure to the north, and lower pressure in
the northwest Caribbean. This will produce mostly NE winds as
high as 15 kt with seas up to 4 or 5 ft within 20 nm of the
coast, and up to 7 ft on the outer Georgia waters beyond 20 nm,
where a Small Craft Advisory is still in effect.
Wednesday through Sunday: High pressure and a coastal trough will
prevail across the region. East-northeast winds will persist through
late Friday at 10 to 15 knots with occasional higher gusts, then
decrease to 5 to 10 through Sunday. As TS Epsilon shifts north-
northeast across the Atlantic, long period swell is expected to
increase and seas will remain elevated through the weekend. A Small
Craft Advisory will remain in effect for seas 5-8 ft through late
Sunday night for the outer Georgia waters. Seas could approach 6 ft
on Thursday through Friday for the nearshore waters. Otherwise, will
generally be 3-5 ft.
Rip Currents: Due to persistence, strong east-northeast winds and
increasing swell, opted to continue a moderate risk of rip currents
for Wednesday and Thursday. Due to long period swell generated by TS
Epsilon, an enhanced risk of rips is possible through the
weekend.
&&
.TIDES/COASTAL FLOODING...
South Carolina coast: Although astronomical tides continue to
decrease, persistent northeast winds of 10 to 20 knots are expected
to push tides into minor coastal flood levels during the late
morning/early afternoon high tide cycle on Wednesday and Thursday.
By Friday and into the weekend, the latest guidance indicates that
tides will peak just below coastal flood criteria.
Georgia coast: Tide levels are currently expected to remain
just below coastal flood advisory thresholds through the rest of
the week.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 7 AM EDT Monday for AMZ374.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...RFM
AVIATION...NED
MARINE...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Green Bay WI
1047 PM CDT Tue Oct 20 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 231 PM CDT Tue Oct 20 2020
The latest RAP analysis and satellite/radar imagery show high
pressure exiting the region into northeast Ontario. Meanwhile, an
intensifying shortwave trough is pushing a band of a little rain,
mostly snow into western Wisconsin and as far east as Marshfield.
This precip should should continue to spread northeast through the
rest of the afternoon. Temperatures have warmed into the middle
to upper 30s over north- central WI, but wet-bulbs remain below
freezing from Land O Lakes to Marshfield, and it didn`t take long
for precip to change to snow at Marshfield. Upstream visibilities
suggest some hefty snow accumulations on the order of 1" per hour
could occur once this changeover occurs. Despite warm ground
temperatures, the higher snowfall rates could still lead to
accumulations on roadways for the start of the evening commute.
Will add Wood County into the Advisory, particularly for the
northwest half of the county where slippery roads could be present
soon with temperatures near freezing. Forecast concerns continue
to revolve around snowfall amounts and impacts tonight.
Tonight...The potent shortwave will drive the band of precip
northeast across the region. Decent precip rates will likely
continue into the evening thanks to beefy mid-level fgen on the
nose of a 30-40 kt low level jet, as well as upper divergence. It
continues to look like there will be a sharp cutoff of precip
types and snow amounts, though it remains challenging to identify
where this cutoff will exactly occur. Strong lift in the dendritic
growth zone will likely lead to a band of 3-6" to the northwest
of this cutoff, while mainly rain will occur to the southeast.
Forecast snow amounts have been relatively consistent over the
past few days, and perhaps increased totals only slightly this
afternoon. Given the strong dynamics, wouldn`t be surprised to
see a few reports greater than 6". Will stick with a high end
advisory. Precip will be ending late tonight, and partial clearing
could start to occur over central WI by 12z.
Wednesday...Low clouds on the back edge of the system will
gradually erode from south to north over the course of the day.
But in the afternoon, will see a band of mid-level clouds return
to the region. So in the end, will see a partly sunny day with
highs ranging from the upper 30s to middle 40s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 231 PM CDT Tue Oct 20 2020
Lots of forecast challenges to contend with in the long term,
including rain, snow, and thunderstorm from Wednesday night into
Friday, and then the potential for more precip Sunday into Monday.
Wednesday night through Friday...Initially expect dry conditions
across most, if not all, of the forecast area early Wednesday
evening (00Z/22). Models have slowed down a bit with the arrive of
the low level WAA and therefore the precip. The arrival of the
WAA and increasing moisture late Wednesday night/Thursday morning
will bring a quick uptick in precip from south to north Thursday
morning. Precip types will initially be mixed, especially farther
north, where temperature are cold enough to generate snow. Expect
a changeover to all rain by Thursday afternoon. Additionally,
models show 400 to 800 J/kg of CAPE starting Thursday afternoon,
so will continue to mention thunder in the forecast, however,
still not expecting severe storms. SPC has included the entire
forecast area in the general thunder category for Thursday.
Meanwhile, with prolonged large- scale lift from the RRQ up the
upper jet and an approaching shortwave, and pwats increasing to
1.0 to 1.2 inches (about 200-percent of normal for late October)
expect to see a soaking rain from late Thursday morning into
early Friday, with the heaviest amounts occurring Thursday
afternoon and evening. Current QPF forecast has 1.0 to 2.0 inches
across the area from 06Z/22 to 18Z/23. As previously mentioned,
could see some localized urban flooding particularly in areas with
recently fallen leaves which may cause drain blockage. WPC
continues to highlight northern WI in the excessive rainfall
outlook for Thursday as well. By Friday morning the main surface
low moves northeast into southeast Ontario. Lingering shortwave
energy may keep some light showers around through the morning, but
precip should end by early afternoon with cooler and much drier
air filtering into the area.
Rest of the forecast...Surface high pressure builds into the area
on Friday night into Saturday and will see a quieter, but cool,
stretch of weather. Long range models are in slightly better
agreement with the Sun/Mon system. Current 12Z runs show a sfc low
tracking south of WI during this time, which would bring another
rain/snow precip event to the area. GFS has been the outlier,
keeping the system farther south, but has jogged more in alignment
with the EC and Canadian. Will continue to use a blended solution
for now with details to be sorted out in future issuances.
Thursday is the warm day of the week with highs ranging from the
low 40s in the north to the low 60s in the Fox Valley. Readings
will be 5 to 10 degrees cooler on Friday, and in the 30s to low
40s on this weekend.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1047 PM CDT Tue Oct 20 2020
The main TAF challenge for this period is the transition from the
rain/snow showers from the evening to the quieter overnight hours.
Fog and low cloud cover is expected to move in fairly quickly
behind the showers, which will keep a period of IFR and LIFR in
place early in the period for all sites. The densest fog will
impact AUW and CWA. As wind pick up again early tomorrow, expect
fog to mix out fairly quickly and a rapid rise in CIGs to MVFR.
VFR conditions will return by Wednesday afternoon and likely last
through the end of the TAF period. The next period of aviation
weather concerns will then likely be Wednesday night in the
overnight hours.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 AM CDT Wednesday for WIZ005-
010>012-018-019-030.
&&
$$
SHORT TERM.....MPC
LONG TERM......KLJ
AVIATION.......Uhlmann
Area Forecast Discussion
National Weather Service North Platte NE
654 PM CDT Tue Oct 20 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 343 PM CDT Tue Oct 20 2020
Main concern will be light snow chances tonight. Isentropic
Upglide increases late this evening across the northwest Sandhills
and spread east across north central NE overnight. The 290K
surface below 850mb remain quite dry. The better saturation will
remain across South Dakota tonight. Mesoscale models including the
HRRR and RAP indicate up to a tenth of an inch possible across
Sheridan and Cherry County after midnight, supporting chance POPS.
Will limit any mention to a slight chance remainder of nctrl NE
overnight. Snowfall accumulations up to a half inch possible
Sheridan and Cherry County. Little or no accumulation expected
further east.
On Wednesday, A warm front will lift into southern SD. This will
bring a southerly low-level flow leading to a warm up into the low
to mid 60s mainly west of Hwy 61, with slightly cooler
temperatures in the 50s for areas east. Dry weather is expected
for the day with southerly winds gusting up to 25 mph late morning
and afternoon.
Wednesday night, an upper trough will move across MT and WY. This
will bring a strong cold front south to just north and west of
the Black Hills. Across western NE, a southeast wind with
relatively mild low temperatures in the mid 30s to around 40 most
areas. Good isentropic upglide with low condensation pressure
deficits indicated below 850mb, then much drier aloft. This will
favor light rain or drizzle across the northeast half of the
forecast area. Temperatures forecast to remain above freezing, so
no freezing rain expected.
.LONG TERM...(Thursday through Tuesday)
Issued at 343 PM CDT Tue Oct 20 2020
The strong cold front will be quickly driven southeastward on
Thursday, moving just southeast of the area already by 18Z. A strong
1035mb Arctic high will move into eastern Montana and bring much
colder temperatures aloft and strong surface pressure rises into
the area during the afternoon. This will bring windy conditions as
northwest winds gusts of up to 40 mph across much of the area,
lasting into the late evening before the pressure rises relax a
bit. Behind the front, weak mid-level fgen will bring precipitation
chances up to 30 percent Thursday into Thursday evening mainly to
north central NE. Models show little or no measurable precip.
Initially, ptypes will favor rain but as cold air floods the area
we can expect a transition to wintry precipitation during the
afternoon and evening. Expect morning highs across the northwest
with falling temperatures most areas early afternoon. Highs near
previous forecast from the upper 30s/lower 40s nw Sandhills to
the mid 50s central and southwest.
Timing of ptypes to expect remain low confidence at this time.
Thinking predominant wintry precip will be snow but cannot rule
out a brief period of freezing drizzle in there as well. Will
need to monitor this potential in later forecasts. Regardless of
ptype, QPF is expected to remain a few hundredths or less.
As temperatures continue to fall through the evening, expecting
what will likely be the coldest morning of the season by Friday
morning. Air temperatures will fall into the teens and low 20s
and combined with winds potentially gusting around 15 to 20 mph
around sunrise, will see wind chill values from zero to 15 above.
Expecting a dry day for Friday as high pressure continues to build
in during the day with high temperatures in the mid 30s to around
40, around 25 degrees below normal for the third week of October.
Saturday through Monday will include active weather. A mid and
upper level trough in northwest flow will approach and move
through the region Saturday through Monday. Another shot of an
even colder airmass will arrive Saturday night and persist through
at LEast Monday. Forecast soundings saturday night from the GFS
will be cold enough for all snow for the ptype. The ECMWF,
however, is not as cold and therefore suggests a mix. A period of
mid level frontogenesis is forecast Saturday night into Sunday
morning, then weakening or ending. With the upper trough axis
remaining to our west into Monday, so snow chances will exist
Sunday night into Monday morning. Bitter cold temperatures for
October will occur Sunday and Monday with highs only expected to
reach the 20s and low 30s with morning lows in the teens and low
20s Sunday morning and low single digits to low teens Monday
morning with some locations threatening record lows. This will
allow wind chills to approach zero each morning. Looks slightly
warmer next Tuesday as westerlies aloft bring some downsloping and
highs to potentially reach the upper 30s to mid 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM CDT Tue Oct 20 2020
VFR conditions will continue the rest of the evening, then after
midnight a brief period of light snow is possible across the
northern Sandhills including KVTN terminal, at this time confidence
is low to medium in precipitation occurring, with only slight
chances possible at this time, so have mentioned light snow
showers in the TAF, but have did not reduce visibilities at this
time as snow chances remain low. Farther south across the
southern Sandhills into southwest Nebraska including KLBF
terminal, no precipitation is expected. Winds will increase
tomorrow afternoon out of the south southeast. The strongest winds
will be across the central and northern Sandhills.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Gomez
Area Forecast Discussion
National Weather Service San Francisco Bay Area
851 PM PDT Tue Oct 20 2020
.SYNOPSIS...Heightened fire weather concerns prevail in the hills
through much of the week due to gusty, dry offshore winds combined
with persistent low humidity. Locally gusty north to northeast winds
will continue at the higher elevations of the North Bay through
Wednesday morning before an afternoon lull and then stronger and
more widespread offshore winds Wednesday night for the North and
East Bay Hills through Friday morning. This winds are also
expected to expand locally to the Santa Cruz Mountains and San
Mateo coastline early Thursday morning. Temperatures will remain
warmer than seasonal averages today and Wednesday, but then cool
to near normal late in the week and into the weekend. Another
offshore wind event is possible in the hills from Saturday night
through Monday morning.
&&
.DISCUSSION...as of 08:50 PM PDT Tuesday...Most coastal stratus
observed on satellite earlier today has either mixed out or moved
southward toward the Monterey Bay, with only the smallest of
patches lingering around the Golden Gate bridge at this hour. It`s
been enough to drop visibility around KMRY to 1 statute mile and
near KWVI to 1/2 statute mile. Temperatures are expected to be
mostly in the 50s tonight with warmer conditions at higher
terrain.
However, the main weather story are the winds and fire concerns.
Winds in the North Bay Mountains are out of the north-northeast and
breezy, around 15 mph with gusts just under 20 mph. Offshore winds
are expected to increase over the highest terrain overnight with
gusts around 30 mph. While this appears to be a more low-end event
and confined to the North Bay Mountains, conditions are still dry
with the potential for fire starts to be present.
After winds subside Wednesday afternoon, increasing confidence
provided the justification to upgrade the fire weather watch to a
Red Flag Warning earlier today which will be valid Wednesday evening
through Friday morning. Winds will once again increase, stronger
than what is expected overnight tonight, and extend to the East Bay
and the Santa Cruz Mountains.
The rest of the forecast remains on track, as temperatures cool
toward the weekend for more normal values for this time of years.
There is still much that can be adjusted, but overnight lows could
dip into the 40s by the weekend. Speaking of the weekend,
unfortunately, the offshore winds do not appear to go anywhere.
There is still time for the forecast to be adjust, but some models
are indicating another offshore winds event keeping heightened
fire concerns present through Monday morning.
&&
.PREV DISCUSSION...as of 2:37 PM PDT Tuesday...The Rex Block over the
Eastern PAC is still very much in place this afternoon while the
amplified trough continues to extend over the entire CONUS. Down
at the surface, the Fort Ord Profiler has captured a slight
decrease in the marine layer depth along the Central Coast (down
to just over 1000 ft). The Bodega Bay Profiler tells a different
story: a rather shallow marine layer is currently evident(around
150 ft). This is evident in the SF oceanside cams, where the
shallow nature of the stratus has resulted in a picturesque fog
bank along the Golden Gate. This has translated into stations
measuring high RH values only along the immediate PAC shoreline,
while widespread moderate values in the 30-35% range are currently
being observed at North Bay stations just a few miles inland
(e.g. Santa Rosa and Petaluma). Further inland and above 1000 ft
in elevation, measured RH values are even lower: ranging in the
15-20th percentiles, with a few isolated locations in the low
teens. Winds are thankfully light this afternoon, with the highest
wind gusts measured at 20 mph at high- terrain stations (over
2500 ft).
The Red Flag Warning for the North Bay Mountains remains in effect
until 08AM PDT Wednesday. NE winds are expected to once again pick
up this evening and into tomorrow morning, albeit drier conditions
are expected in this instance. As such, critical fire weather
conditions cannot be overstated, not only for this current event
but for the remainder of the offshore wind events that are progged
for the remainder of this week. The next burst of offshore winds
following tonight`s event are progged to begin Wednesday night.
All Fire Weather Watches have been upgraded since this morning to
Red Flag Warnings. By the end of the day tomorrow, the air mass
over much of the interior will have substantially dried out, with
poor overnight humidity recoveries expected across the entire
interior and even along parts of the coast by the end of the
workweek. Essentially, this upcoming burst of offshore winds will
begin mixing down over the North Bay Mountains once again but is
also progged to become more widespread and extend into the East
Bay Hills and mix down into the East Bay Interior Valleys. Local
WRF, NAM, and HRRR runs this afternoon also capture the
development of a low-level jet feature that rapidly extends from
the North Bay and into the Santa Cruz Mountains sometime after
midnight. These winds will quickly dry out the area and. Are
expecting for the dry air mass to overrun the marine layer
influence along the entire SF Peninsula, with the exception of
the City of SF which due to geography will likely be spared from
the mixing down of these offshore winds. All in all, low- level
jet will rapidly descend over the East Bay and be diverted to more
of an easterly direction as it interacts with the Santa Cruz
Mountains and flows out into the San Mateo coast. This process
will then likely be observed again from Thursday night and into
Friday morning.
As for this weekend, increasing confidence regarding the third burst
of offshore winds that has been advertised for the last couple of
days. In both the GEFS and ECMWF ENS members, find that the
amplified trough over the CONUS will become less pronounced as a
series of shortwave troughs descend from British Columbia and into
the Great Basin. The upper-level ridge associated with the Rex Block
will remain in place through the weekend while heights fall across
the Mountain West. As a result, a sharp upper-level pressure
gradient will develop along the West Coast and our CWA will be
nestled in between the two synoptic features. Thus far our
observed offshore winds have largely been influenced by the nosing
of the upper-level ridge over Northern California. By contrast,
this weekend looks set to also include the influence of strong
northerly winds from the convergent quadrant of the shortwave
trough. Increasing confidence that this third burst will play out
and has the potential to be stronger than the burst before it. As
such, will be providing more updates to the potential for this
setup as newer model and ensemble runs come in.
&&
.AVIATION...as of 5:00 PM PDT Tuesday...A very shallow marine
layer will keep low clouds confined to the coast tonight. LIFR
conditions in the Monterey Bay Area later tonight otherwise VFR
clear. Offshore winds are developing over the North Bay Hills but
LLWS is not expected.
Vicinity of KSFO...VFR. Northwest winds to 15 kt decreasing after
04Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...LIFR after 08Z with bases near the
surface and vsbys reduced to 3-5 miles. Clearing rapidly by
midmorning.
&&
.FIRE WEATHER...As of 2:14 PM PDT Tuesday...First Red Flag warning
remains in effect through 8 am Weds for the North Bay hills. Its a
low end event but another shot of gusty winds will peak overnight
through about sunrise Weds, most focused around Mt Saint Helena
and the Napa hills.
Attention then turns to next round of Red Flags. Previous Fire Wx
Watches have all been upgraded to Red Flag Warnings. We also
included the East Bay Interior Valleys and coastal San Mateo in
this round of Red Flags. Initial Warnings start at 10 pm Weds for
the North and East Bay (including East Bay interior valleys).
Northeast winds will ramp up Weds night then peak early Thursday
morning as humidity values plummet. This will be a more widespread
event with gusts 40-50 mph frequent for the North/East Bay hills.
Winds will reach the higher ridges of the Santa Cruz mtns then crash
down towards coastal San Mateo early Thursday morning.
Winds to ease for a time Thursday afternoon but RH values will
continue to plummet as dry air spreads over the region. A second
burst of winds then occurs Thursday night into Friday morning,
this time with RH values exceedingly dry around 10-20% and NO
night time humidity recovery. For now this round of Red Flags is
set to end Friday at 8 am. The daytime hours of Friday will still
be dry as winds slowly turn onshore.
A reprieve of sorts from later Friday into Saturday. We are then
watching for a potentially stronger wind event sometime late
Saturday night but more likely Sunday into Monday. Confidence is
low to medium based on how trough carves out. However potential
for strong and damaging wind event is in the cards should worse
case scenario pan out with strong cold advection and support
through the troposphere where strong winds from aloft could mix
down into the valleys, and not stay confined to the hills as often
occurs.
This all will occur with fuel moisture readings (ERC) energy
release component reporting out with record dry levels.
&&
.MARINE...as of 02:11 PM PDT Tuesday...Increasing northwest winds
across the coastal waters tonight and through the coming days,
with gale force to near storm force, wind gusts expected in the
northern outer waters. Increasing northwest winds and hazardous
steep fresh swell from these gusty winds will bring hazardous
conditions for small craft vessels by midweek. Mixed seas will
persist with a moderate northwest swell and longer period
southerly swell.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Red Flag Warning...CAZ507
SCA...Pt Arena to Pigeon Pt 10-60 nm until 9 PM
GLW...Pt Arena to Pigeon Pt 10-60 nm from 9 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 5 AM
SCA...Pt Arena to Pt Reyes 0-10 nm
&&
$$
PUBLIC FORECAST: Diaz/DK
AVIATION: W Pi
MARINE: DRP
FIRE WEATHER: Walbrun
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Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
800 PM EDT Tue Oct 20 2020
.UPDATE...
latest RAP model has high pressure along the eastern seaboard
reaching northern FL over night as a trough of low pressure in
the northwest Caribbean sea pushes onshore the Yucatan Peninsula.
These two features will provide a rather robust and moist
easterly 1000-700MB flow tonight and through Wed. Forecast PWAT
values range from around 1.5 inches in the Nature Coast to over 2
inches in the southeastern and southern counties.
Most of the afternoon showers and isolated thunderstorms have or
will shortly wind down. However...showers are expected to traverse
areas generally to the south of the Tampa Bay region through out
the night. Mostly cloudy skies give way to partly cloudy during
the night with lows in the lower 70s. Forecasts looks good with
only minor near term adjustments.
&&
.AVIATION...
21/00Z TAFs. Anticipate a few TSRA TIL 02Z then BKN to OVC mainly
mid and high clouds overnight but ISOLD SHRA may track across the
terminals from SRQ south. AFT 14Z SHRA spread north and clouds
gradually lower but stay VFR. By 16-18Z ISOLD TSRA begin to track
near/over all the terminals. ENE to NE winds 06-11KT become E Wed
morning and gusty at times in the afternoon.
&&
.MARINE...
High pressure to the north and low pressure to the south will
maintain a tight gradient across the waters for the next few days
with robust winds at times. However winds have currently
slackened some...allowing the small craft advisory to end across
the near shore waters. But the advisory will continue overnight
offshore.
&&
.Preliminary Point Temps/PoPs...
TPA 75 83 74 88 / 20 60 20 40
FMY 74 82 73 87 / 30 70 40 50
GIF 74 83 74 86 / 20 50 20 40
SRQ 74 84 74 88 / 20 60 30 50
BKV 72 84 70 86 / 10 50 20 40
SPG 75 83 75 86 / 20 60 30 50
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...Small Craft Advisory until 10 AM EDT Wednesday for Waters from
Bonita Beach to Englewood FL out 20 to 60 NM-Waters from
Englewood to Tarpon Springs FL out 20 to 60 NM-Waters from
Tarpon Springs to Suwannee River FL out 20 to 60 NM.
&&
$$
UPDATE/AVIATION/MARINE...09/Rude
UPPER AIR...13/Oglesby
DECISION SUPPORT...13/Oglesby
Area Forecast Discussion
National Weather Service Tulsa OK
944 PM CDT Tue Oct 20 2020
...UPDATE...
.DISCUSSION...
Convection has slowly increased in coverage over the past 1-2
hours, and this trend will continue as 300K isentropic lift
continues to improve over the next several hours. Made some tweaks
to the near-term PoPs, with highest PoPs remaining focused across
northeast Oklahoma the remainder of the night.
Current low temperature forecast looks reasonable, with the HRRR
showing little movement in the warm front overnight.
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 56 81 67 85 / 70 20 0 0
FSM 65 82 64 86 / 10 0 0 0
MLC 67 81 65 84 / 10 0 0 0
BVO 52 71 64 85 / 80 20 0 0
FYV 64 78 60 82 / 30 10 0 0
BYV 60 78 62 84 / 40 20 0 0
MKO 62 81 64 84 / 40 10 0 0
MIO 53 74 64 84 / 90 40 0 0
F10 60 81 64 84 / 40 10 0 0
HHW 67 83 63 84 / 0 0 0 0
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...18