Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/03/18
Area Forecast Discussion
National Weather Service Bismarck ND
854 PM CDT Tue Oct 2 2018
.UPDATE...
Issued at 852 PM CDT Tue Oct 2 2018
Based on NDDOT webcam and surface observation trends, issued a
Dense Fog Advisory through 12 UTC for northwest and far north
central North Dakota. An advisory may be needed later tonight for
south central North Dakota and the James River Valley.
UPDATE Issued at 634 PM CDT Tue Oct 2 2018
Fog potential tonight, precipitation tonight and Wednesday, and
strong winds on Wednesday highlight this update.
Fog and drizzle continue to develop across south central North
Dakota as of 00 UTC. The HRRR/NBM/RAP/GFSLamp through their 22
UTC iterations maintain the stratus and expand the fog through the
night across the south central and James River Valley, and
possibly towards the Dickinson and Hettinger areas. This seems
likely given the observed trends with light southerly surface
winds maintaining the low level moisture with dew points in the
upper 40s and lower 50s. A Dense Fog Advisory may be needed.
As of 00 UTC, a quasi-stationary front across western into far
north central North Dakota will begin to propagate southeast as a
cold front tonight, and clear the James River Valley by mid day
Wednesday. Precipitation will increase on the cool side of this
boundary late tonight into Wednesday morning with the arrival of
the leading impulses ahead of the potent shortwave. Precipitation
should be in the form of rain tonight across the north,
transitioning to snow Wednesday morning along and north of US
Highway 2. Across the southwest and south central, scattered rain
showers are possible late tonight into Wednesday morning, with a
thunderstorm not out of the question given the steep mid level
lapse rates.
Regarding winds for Wednesday, the 22 UTC RAP and 18 UTC NAM low
level wind fields are stronger than the 18 UTC GFS in strong cold
air advection and pressure rises behind the cold front. The
NAM/RAP would support a Wind Advisory, especially south of US
Highway 2. Will continue to monitor trends in the guidance through
the evening. High temperatures on Wednesday are likely to be
reached overnight, with falling temperatures through the day.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 111 PM CDT Tue Oct 2 2018
Concerns for this forecast period involve accumulating snow
across northwest North Dakota late tonight and Wednesday morning,
then gusty winds across much of central and southwest North
Dakota Wednesday afternoon.
First, the h500 flow is setting up to bring a shortwave trough from
the northwest CONUS through the northern plains by Wednesday
afternoon. This will set up broad lift across the region tonight
and Wednesday morning. As the baroclinic zone slides south
through the region tonight, we expect a brief period of enhanced
vertical motion as isentropic lift and frontogenetic forcing
briefly line up. Temperatures will be around the critical
threshold for snow across the north central and northwest, where
we expect one to two inches of accumulation across the far
northern tier of counties from divide through Bottineau Wednesday
morning.
Second, subsidence behind the shortwave will enhance momentum
transfer resulting in increasing northwest winds Wednesday
afternoon. The NAM in particular indicates this, with potential
wind gusts to 45 mph for one to 3 hours. However the GFS is more
subdued, suggesting 25 to 35 mph winds. Will hold off on wind
advisory for now.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 111 PM CDT Tue Oct 2 2018
The extended forecast will encompass two periods of concern for
early winter weather events. First, a negatively tilted h500
trough will migrate northeast into the northern plains from
southern California on Thursday night and Friday, spreading
precipitation across the region. Temperatures again will be near
the critical threshold for rain and snow, with the possibility of
accumulations mainly across the north and east central. The
difference of one or two degrees in temperatures here will
dictate more or less snow, so uncertainty remains high for how
far south the snow will reach.
The remainder of the long range will be dominated by a large slow
moving upper low across the western CONUS. Much uncertainty
remains with this feature, as models have been increasing the
strength of a ridge over the east coast, which may hold up the
progression of this low, per the European. If this becomes the
favored solution then warmer air can be expected across the
northern plains. If not, then the possibility of more
accumulating snow exists per the GFS. Either way, the QPF from
this storm will be rather substantial for this time of the year.
Will continue to highlight the uncertainty in the weather
messaging.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 852 PM CDT Tue Oct 2 2018
IFR stratus and fog this evening will expand across south central
North Dakota and the James River Valley tonight, with LIFR/VLIFR
visibility in fog developing. This includes KBIS and KJMS. The
stratus and fog may approach KDIK late tonight into early
Wednesday morning, however, this is somewhat uncertain. A
stationary front across western through north central North Dakota
as of 00 UTC will move southeast as a cold front overnight into
Wednesday morning. LIFR/VLIFR stratus and fog will expand tonight
behind this front across the northwest and north central
impacting KISN/KMOT. Rain will develop across northern North
Dakota tonight, changing to snow Wednesday morning with IFR
conditions. Scattered rain showers, and perhaps a thunderstorm,
are possible tonight into Wednesday morning southwest and south
central. Strong northwest winds with gusts of 30-40 kts will
develop Wednesday across most of western and central North Dakota.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 7 AM CDT Wednesday for NDZ001>003-
009>011.
&&
$$
UPDATE...PA
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...PA
Area Forecast Discussion
National Weather Service Boston/Norton MA
1045 PM EDT Tue Oct 2 2018
.SYNOPSIS...
Low pressure over the Eastern Great Lakes will cross New England
tonight, bringing showers and a few thunderstorms along with
some heavy rainfall. Clouds may linger Wednesday morning, but
high pressure will build in with dry and seasonable temperatures
weather the rest of the day. An unseasonably warm afternoon is
on tap for Thursday ahead of an approaching cold front. Dry but
seasonably cool weather follows Friday and Saturday. Well above
normal temperatures are expected at times next week and in fact
some record highs may be challenged.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
No major changes to the forecast this evening. Tried to time out
rainfall chances based on observed radar trends. Last few runs
of the HRRR appear to have the correct idea on placement, but
the timing is off by a couple of hours on the slow side.
Latest surface observations indicate a low pressure near
Syracuse, NY, moving east along a front draped across southern
New England. A mesolow was also noted near Boston. This low
pressure will continue to move east overnight. Still expecting
drier weather to develop after midnight, but it may be closer to
daybreak before threat of rainfall ends across the western half
of southern New England.
Not anticipating much change to temperatures, which should
remain within a few degrees of where they are this evening.
Previous Discussion...
Main action through early this evening has been across the
southern portion of Hartford and Tolland counties. Some
locations picked up a quick 1.50 to 2 inches of rain in an
hour...leading to some street flooding. Currently...mainly heavy
showers moving across RI and SE MA but there remain a few
embedded t-storms.
Overall...heavy showers and embedded t-storms will continue
to track across the region overnight with a strong shortwave/forcing.
The greatest risk for flash flooding/severe weather will remain
southwest of our region where the better instability resides. We
still need to monitor the risk for localized flooding and a low
probability for isolated severe weather overnight across our
CT/RI and SE MA zones. However...confidence in our region is not high
enough for any SVR/FFA headlines at this point but will continue to
monitor.
Otherwise...models have been too aggressive in lifting warm front
northward. The front currently runs along a line from BDL..to
SFZ...to near OWD. The front should lift a bit further north over
the next several hours...but some high resolution guidance
especially the 4 km NAM shows a meso-low shifting the winds back
to the northeast across northeast MA and possibly further
southwest. In fact...parts of northeast MA may never see the
warm front cross the region. Will have to watch for areas of fog
in this region...especially in areas where cooler air works back into
the region. Temps will be in the 50s north of the front and 60s south of the
front.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Leftover convection over Cape Cod and Islands Wednesday morning
during the commute, but this will move offshore. Weak high
pressure trails the shortwave and crosses our area during the
afternoon/evening. Expect a dry day with increasing sunshine.
Temps at the top of the mixed layer would support max temps in
the low to mid 70s. Light winds will support local sea breezes
in the usual locations.
Dry weather continues into Wednesday night, although light south
flow will bring increased moisture and may support some fog and
low clouds overnight.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Unseasonable warmth expected Thu afternoon
* Dry and cooler with seasonable temps Fri/Sat
* Near record high temperatures possible at times next week
Details...
Thursday...
Approaching cold front will result in anomalous mid level warmth
overspreading southern New England. 850T rise to between +16C and
+18C by Thu afternoon along with southwest surface winds. This
should result in afternoon high temperatures in the upper 70s to
around 80 in many locations.
The cold front will cross the region late Thu into Thu night. There
is not much instability/forcing ahead of this front...so not
expecting much more than the risk for a few brief showers.
Friday and Saturday...
Canadian high pressure will build south behind the cold front Fri
into Sat. This will result in the return of cooler/seasonable
temperatures along with dry weather. High temperatures both days
will mainly be in the 60s, with the cooler day being Friday
especially along the coast.
Next Week...
Anomalous upper level ridge will build north into southern New
England. This will result in above to well above normal
temperatures at times. Given this setup...the potential for
afternoon highs reaching into the 80s for a couple days is a pretty
good bet. In fact...we could be looking at near record high
temperatures for a day or two. The one fly in the ointment is a
potential backdoor cold front that could cool us down a bit. Timing
is highly uncertain...but most guidance is indicating the best
chance for these briefly cooler temps would be Mon.
Dry weather looks to dominate for the first half of next week given
upper level ridging in control. We can not rule out a few showers
on Monday with the backdoor cold front...but does not look like much
at this time.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Tonight...High confidence. IFR to LIFR conditions in showers
and isolated t-storms in most locations early this evening will
persist overnight. MVFR-VFR conditions across the Cape/Islands
will deteriorate to IFR-LIFR thresholds overnight.
Wednesday...Moderate confidence. IFR to even LIFR conditions may
persist for at least part of the morning...especially across
eastern New England. Improvement occurs from west to east...but
timing uncertain
Wednesday night...High confidence.
VFR, with IFR possible in patchy BR.
KBOS Terminal...Moderate confidence.
KBDL Terminal...Moderate confidence.
Outlook /Thursday through Sunday/...Moderate to High Confidence.
Thursday: Mainly VFR, with local MVFR possible. Breezy.
Thursday Night: Mainly VFR, with areas MVFR possible. A slight
chance of rain showers.
Friday through Friday Night: VFR. Breezy.
Saturday through Sunday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...
Tonight...Low pressure moves east across New England tonight,
pulling a cold front across the waters later tonight. Clouds and
fog may linger through the early night, with best chance for
showers and scattered thunder during the mid and late night.
Poor visibility during the night. South to southwest winds gust
to 25 knots, with 5-6 foot seas on the outer waters. A Small
Craft Advisory continues for all waters.
Wednesday...The cold front and showers move offshore and out to
sea on Wednesday morning. High pressure moves over the waters
with dry weather.Winds turn out of the north with diminishing
speeds, but with sea breezes near the coast. Seas 5-6 feet on
the outer waters will subside during the afternoon.
Wednesday night...Winds remain less than 25 kt and most seas
will be less than 5 feet. Parts of the outer waters may have
seas near 5 feet. Developing fog may lower vsbys to 1 to 3
miles.
Outlook /Thursday through Sunday/...Moderate to High Confidence.
Thursday: Winds less than 25 kt. Seas up to 5 ft.
Thursday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain
showers.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 9 ft.
Friday Night: Winds less than 25 kt. Rough seas up to 9 ft.
Saturday: Winds less than 25 kt. Areas of rough seas.
Saturday Night through Sunday: Winds less than 25 kt. Local
rough seas.
&&
.HYDROLOGY...
As noted, precipitable water values build through the evening,
then top out around 1.75 inches tonight before diminishing
toward morning. The combination of deep moisture and strong lift
is expected to bring local downpours that could cause 1-2
inch/hour rain rates in spots, which could cause some
urban/small stream/poor drainage flooding. Previous rain has
been substantial, but it has also had some time to drain off.
Sufficient uncertainty on amounts and coverage to hold off on a
watch, but we will continue to monitor this rainfall.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 9 AM EDT Wednesday for ANZ231>234.
Small Craft Advisory until 4 AM EDT Wednesday for ANZ230-236-
251.
Small Craft Advisory until 10 AM EDT Wednesday for ANZ235-237.
Small Craft Advisory until 4 AM EDT Thursday for ANZ250-
254>256.
&&
$$
SYNOPSIS...WTB/Frank
NEAR TERM...Belk/Frank
SHORT TERM...WTB
LONG TERM...Frank
AVIATION...WTB/Belk/Frank
MARINE...WTB/Frank
HYDROLOGY...
Area Forecast Discussion
National Weather Service Cheyenne WY
946 PM MDT Tue Oct 2 2018
.UPDATE...
Issued at 932 PM MDT Tue Oct 2 2018
The main near-term concern for tonight is the potential for strong
winds in the wind prone areas of southeast Wyoming. Uncertainty is
high for the Bordeaux area, as several high-resolution models have
trended toward showing minimal eastward progression of the surface
trough. This would limit potential for 50+ knot gusts. However, we
have seen an up-tick in low-level gradients along/w of the Laramie
Range. The H85 CAG-CPR gradient could approach 60 meters by around
15z Wed. Despite fairly modest H7/H85 flow over ARL, mountain wave
activity may be sufficient for a few 60 MPH wind gusts as the HRRR
has suggested over the last several runs. In addition, a 2 to 3 mb
pressure gradient over the I80 summit could also lead to a few 55-
60 MPH wind gusts near Vedauwoo/Buford. Issued a High Wind Warning
for ARL/VDW, as well as BRX despite the uncertainty. The peak wind
gusts should occur around 15z Wednesday. Updates have been sent.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 145 PM MDT Tue Oct 2 2018
Mid-to-high level moisture continues to stream into the region
ahead of Rosa`s remnants. Showers can be seen on radar across
western Colorado; these showers will reach portions of Carbon and
Albany Counties later this afternoon, with only denser areas of
cloud cover noted elsewhere. Behind Rosa, an upper-level zonal
flow will set in overnight. Under this pattern, the area of
concern will be the I-25 "wind" corridor between Chugwater and
Wheatland. A deep, shallow inversion will set up on the lee side
of the northern Laramie Range overnight, prohibiting the stronger
flow aloft from mixing down to the surface. However, the inversion
looks like it`ll break in the early morning hours which will
allow for mixing down to the surface. Additionally, a lee surface
low will develop shortly after the inversion breaks. This set up,
along with funneling through the local terrain, will bring strong
and gusty winds from the west and southwest across the I-25
corridor near Bordeaux from about 0300 to 0900 MDT. A high wind
watch is out for this period and will continue to be accessed as
the event approaches.
Moving into Wednesday afternoon, cloudy and windy conditions will
prevail as the next upper level low pressure system moves in from
the west. A mid-level vorticity maximum will be ejected from the
flow and move across the region through the day Thursday. This
will aid in the continuation of windy conditions across the whole
of the region, in addition to rain showers, for the duration of
the day.
.LONG TERM...(Thursday night through Tuesday)
Issued at 145 PM MDT Tue Oct 2 2018
Long term forecast continues to be tricky with respect to an
amplified flow pattern. Hemispheric water vapor continues to show a
favorable regime for the development of a progressive amplified
mid level flow regime. An amplifying downstream subtropical ridge
and large west coast trough will be key in the placement of
individual features.
Friday, a shortwave trough is progged to eject over the front range
bringing showers and possible storms. WInds aloft will be increasing
thanks to a mid level jet of 55 to 60 kts. Some concerns for high
winds along and behind a cold front were noted. Winds were
increased in the grids. Multiple rounds of precipitation are likely
as a weak lee side low moves through south central Wyoming and
into the plains. Showers and possible high elevation snow will
develop Friday and continue through Saturday. This appears to be the
first chance of the season for significant high elevation snow. This
does however depend on the placement, the timing, and the strength
of the colder air from a canadian maritime high.
Sunday, potential exists for a very strong lee low to move close to
the area brining heavy precipitation. A large 500 mb trough with
strong DPVA and an attendant 90kt jet streak is expected to move
into the Great Plains Sunday morning. Should the strong low develop
in northern colorado, upslope flow with showers and embedded
thunderstorms will be likely. Currently, models are split. The
Canadian and the ECMWF show a low developing much further
south, while the GFS and the new FV3 continue to show a very deep
sub thousand millibar low in northern/central Colorado. GFS Ensembles
show good clustering of the lows in this region, lending some
confidence to the GFS solution. EPS solutions are a bit broader and
weaker with the surface low but overall deeper and more closed off
with the trough. While exact confidence is not high, both models
show very strong lift over the front range with ample moisture for
precipitation. A strong artic cold front will also bring the cold
air necessary for winter weather Sunday night through tuesday.
Should the timing of the cold air and the strong lift coincide,
mountains may see heavy snowfall for the first time this season.
This will need to be watched closely over the next few forecast
cycles. Regardless, both solutions favor a wet and cooler regime
than the warm september temperatures we have seen.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 613 PM MDT Tue Oct 2 2018
VFR prevails. Rain showers will likely become more widespread this
evening/overnight, mainly across Carbon county as remnant moisture
from Rosa continues to stream northward. Ceilings at KRWL may fall
to near 3000 feet at times. Otherwise, expect SCT to BKN sky cover
between 5k and 15k feet AGL for most terminals. Gusty winds likely
to develop across much of the region on Wednesday, with gusts over
30 knots common.
&&
.FIRE WEATHER...
Issued at 145 PM MDT Tue Oct 2 2018
Critical conditions no longer as moisture streams in from the
south and west today and cloud cover increases and lowers across
the region. Rain showers and a slight chance for thunderstorms
expected nearly each afternoon/evening through the extended.
Windy conditions are expected overnight tonight and through the
day Wednesday and Thursday. Snow possible as early as Friday
across the higher elevations. Snow levels will lower as we move
into next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 6 AM to noon MDT Wednesday for WYZ106-110-
116.
NE...None.
&&
$$
UPDATE...CLH
SHORT TERM...AB
LONG TERM...AL
AVIATION...CLH
FIRE WEATHER...AB
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
801 PM PDT Tue Oct 2 2018
.SYNOPSIS...02/731 PM.
Light to moderate rain will fall across the region tomorrow with
a slight chance of thunderstorms. Showers may linger into Thursday
morning. Temperatures will remain below normal into next week
though with some warming on Friday and Saturday.
&&
.SHORT TERM (TUE-FRI)...02/801 PM.
***UPDATE***
Overall, the weather looks to be behaving as forecast. Latest
radar shows some showers off the Central Coast which should start
to move onshore later this evening. Elsewhere, will expect
continued cloudy skies this evening with some isolated showers or
sprinkles as atmosphere continues to moisten up.
Current look at latest high-resolution model data as well as QPF
analysis indicates current forecast looks very much on track.
Steady rain will develop over the Central Coast tonight then
across Ventura/LA counties during the day on Wednesday. Current
QPF numbers, as stated below, still look good. Models are still
indicating a decent amount of instability as the front moves
through. So, the slight chance of thunderstorms late tonight and
Wednesday looks good.
No significant updates to the forecast are planned at this time.
***From Previous Discussion***
Upper low sliding south now which has effectively shut off any
eastward propagation of the frontal band, the leading edge of
which remains about 60-90 miles west of the Central Coast. There
were a few showers out ahead of it that brought a few drops of
rain to parts of SB/SLO Counties earlier today. Not much since
then and probably not much more until at least this evening.
Models have been consistent showing the low levels moistening up
this evening under light to moderate southerly flow while the
frontal band remains offshore. The HRRR and NBM are the only
models showing precip over land this evening and this is a
reasonable scenario assuming the low levels moisten up as both the
GFS and NAM expect. Best chances this evening will be south of Pt
Conception, especially upslope areas, with amounts generally under
a tenth of an inch.
The main action expected later tonight into Wednesday once the
upper low finally starts moving east again and that main frontal
band moves towards the coast. Upper level diffluence along with
some vorts moving around the low will provide a favorable
environment for thunderstorm formation along that band which will
progress slowly east through the day. Models continue to advertise
small pockets of heavier precip developing later tonight, likely
with thunderstorms. Don`t have much confidence in the precise
locations of these but it does provide evidence that convection
will be a factor. Outside of convection rainfall amounts and rates
should be well below critical levels. However, brief heavy rain is
possible with thunderstorms and while most convective rates
should top out around a half inch per hour there`s a non-zero risk
of a storm forming over the recently burned area with rates
reaching critical levels. For SB/Ventura counties the most likely
period of time would from mid to late morning Wednesday through
mid afternoon and from noon to 8 pm for LA County.
Previous rainfall forecast still looks on track, generally a half
inch or less for most lower elevation locations and up to an inch
in the foothills/mountains. And obviously higher amounts possible
where thunderstorms develop. Showers expected to taper off
Wednesday evening but could still be some lingering light showers
into early Thursday. After that dry and warmer Thu/Fri under
mostly clear skies. Likely some locally gusty north to northwest
winds developing across SB/SLO counties and adjacent coastal
Friday and Friday evening.
.LONG TERM (SAT-TUE)...02/134 PM.
Models have been consistent the last few days showing a cold
upper level trough setting up across the western third of the US
this weekend through early next week while a monster ridge
develops along the east coast. This combined with a strong onshore
trend Saturday will bring cooling to most of the area. Then Sunday
through Tuesday the GFS is indicating a huge eddy circulation
developing that will rapidly spin up the marine layer to over
5000` deep south of Pt Conception (especially Ventura and LA
Counties) and it even generates some light rain. The ECMWF is a
little farther east with the trough and not nearly as cold and
gloomy. For now have trended towards the colder/cloudier GFS
solution with highs mostly in the 60s to lower 70s for
coast/valleys. Areas north of Pt Conception would be a little
warmer and generally cloud free in this scenario.
&&
.AVIATION...02/2216Z.
At 2130z, the marine inversion at KLAX was based at 800 feet. The
top of the inversion was 1700 feet with a temperature of
20 degrees Celsius.
Overall, low to moderate confidence in 00Z TAF package. Moderate
confidence through early Wednesday in VFR conditions for all
sites. Main concern will be cold front forecast move through on
Wednesday. All sites should receive steady rain, but confidence in
timing is low. There will be a 20% chance of thunderstorms on
Wednesday for all sites.
KLAX...Overall, moderate confidence in 00Z TAF. There is a 20%
chance of MVFR CIGs 02Z-16Z. High confidence in rain with MVFR
conditions on Wednesday, but low confidence in timing. There is
a 30% chance of east winds 8-10 knots 14Z-20Z.
KBUR...Overall, moderate confidence in 00Z TAF. There is a 20%
chance of MVFR CIGs 02Z-16Z. High confidence in rain with MVFR
conditions on Wednesday, but low confidence in timing.
&&
.MARINE...02/800 PM.
For the Outer Waters, moderate confidence in current forecast.
There is 30% chance of Small Craft Advisory (SCA) level southeast
winds tonight and Wednesday. High confidence in SCA level
northwest winds Friday through Sunday with a 30% chance of Gale
force winds.
For the Inner Waters north of Point Sal, high confidence in
current forecast. There is a 70% chance of SCA level northwest
winds during the afternoon/evening hours on Saturday and Sunday.
For the Inner Waters south of Point Conception, moderate
confidence in current forecast. There is a 50% chance of SCA level
winds across western sections Friday through Sunday during the
afternoon and evening hours.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (FRI-TUE).
Gusty northerly winds possible across SLO/SB Counties Friday and
Saturday.
&&
$$
PUBLIC...MW/RAT
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kj
weather.gov/losangeles
Area Forecast Discussion
National Weather Service Blacksburg VA
836 PM EDT Tue Oct 2 2018
.SYNOPSIS...
High pressure across the region will maintain overall dry
and warm weather through late in the week. A cold front will
sag southeast into the area later Friday resulting in a chance
of showers and storms. High pressure then returns to the region
for the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 830 PM EDT Tuesday...
Weak moisture convergence zone/surface trough along the
southern Blue Ridge has resulted in a few showers developing
just after sunset as dewpoints maxed out at dark. However given
lack of much instability and support aloft, expect these to fade
soon so only carrying an isolated shower during the next hour or
so over the southwest. Also appears band of convection over
northern West Va, well ahead of the front to the northwest, will
also fade with loss of heating and supported by the latest HRRR
which keeps most of the showers to the north overnight. Cant
totally rule out a shower far northwest sections late within the
trailing northwest flow, so keeping in a low pop in part of the
I-64 corridor. Otherwise appears enough clearing to promote at
least patchy fog development valleys, and where earlier showers
occurred with perhaps dense fog in spots over the west. Nudged
lows up slightly mainly east in response to higher dewpoints
although should still see readings in the upper 50s-mid 60s
given radiational cooling again overnight.
Previous discussion as of 215 PM EDT Tuesday...
Weak cold front approaching from the northwest is helping to
generate scattered showers/thunder across the Appalachians and
central mid Atlantic region early this afternoon. The front
will wash out across the region tonight then lift back
northward tomorrow. Surface winds look to remain light/variable
while the low level flow becomes predominately northwest.
Expect this will keep clouds and some showers at the higher
terrain in light upslope flow. Fog potential is challenging
overnight since some upslope clouds west of the ridge will
impede cooling, but if clouds become scattered there will be
windows of time when fog can develop, even moreso if cloud
coverage is less than anticipated.
Any fog/stratus/lingering upslope showers will dissipate
Wednesday morning. Guidance is hinting at some development of
showers/thunder along the southern Blue Ridge into the mountains
of NC tomorrow afternoon with weak upslope flow coupled with
some short wave energy and isentropic lift.
Temperatures will remain well able normal with lows tonight in
the low/mid 60s and highs Wednesday in the low/mid 80s east of
the Ridge to mid/upper 70s to the west.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 235 PM EDT Tuesday...
Large ridge aloft centered over the mid-Mississippi Valley will
build northeast through Friday night. This ridge will reach the
southern Appalachians by Friday. Any isolated showers or
thunderstorms Wednesday afternoon will diminish quickly Wednesday
evening with the loss of solar heating. The best chance will be in
the northwest mountains of North Carolina. It will remain warm and
humid Wednesday night with low temperatures ranging from the mid 50s
in the mountains to the mid 60s in the piedmont.
With 850 mb temperatures from 14 to 17 Celsius combined with
partly sunny skies Thursday will warm high temperatures to the mid
70s in the mountains to the mid 80s in the piedmont. Scattered
showers and isolated thunderstorms will form ahead and along the
cold front as it drop southeast Thursday.
Thursday night into Friday, the cold front will reach northern
portions of the Mid-Atlantic region. The challenge of the forecast
is how far south the surface boundary progresses. The best chance of
clouds and a few rain showers will occur Thursday night across
northwestern portions of the forecast area. Low temperatures
Thursday night will remain mild with readings from around 60 degrees
in the west to the mid 60s in the east.
Northerly flow associated with a strong Canadian surface high over
the St. Lawrence River Valley should propel the backdoor front and
wedge southward Friday into Friday night. High temperatures Friday
are tricky with wedge and clouds. It will still be mild but cooler
from around 70 degrees in the north to the lower 80s in the south.
Utilizing the Superblend for pops on Friday. Clouds and the
potential for showers will continue Friday night into Saturday
morning. Low temperatures Friday night will vary from near 60
degrees in the mountains to the upper 60s in the piedmont.
Overall forecast confidence is moderate.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 235 PM EDT Tuesday...
A broad upper ridge across the Southeast will amplified to the
northeast into the weekend, then shifts east into the Atlantic early
next week. The zonal flow across the northern tier of the county
will keep the deeper convection to our north. Shortwave troughs
rotating in the westerly upper flow may enhance convection across
the west. The question remains on how long the ridge will keep the
best chances of showers or thunderstorms well to our northwest.
As we head into the weekend and early next week, isolated to
scattered diurnal convection will be possible mainly across the high
terrain.
Temperatures will average around 10 to 19 degrees above normal with
highs in the 70s to the mid 80s and lows in the mid 50s to mid 60s.
Forecast Confidence Levels: Moderate
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 650 PM EDT Tuesday...
Isolated showers continue to fade across the region this evening
and expect most will have dissipated after sunset. This should
lead to mainly VFR this evening with perhaps a few spots seeing
enough strato-cu for MVFR cigs at times over the mountains. Any
showers or storms closer to the front to the north should
weaken with perhaps an isolated shower making it to the KLWB
vicinity after dark.
Otherwise weak cold front to the north will stall out overnight
before lifting back north on Wednesday. Flow should become light
northwest later tonight making for weak upslope flow into early
Wednesday. Expect this will keep clouds around at the higher
terrain in light upslope flow espcly KBLF/KLWB later tonight.
Fog potential remains uncertain given drying in spots today but
also isolated heavier downpours from earlier. Appears may see
some stratus across the mountains evolve into sub-VFR vsbys in
fog. However question remains with residual cloud cover
elsewhere as more canopy could reduce radiation cooling aspects
late. Does appear that KBCB may see enough clearing to drop to
IFR/LIFR after earlier showers with KLWB possibly seeing the
same. Fog should be a bit more patchy out east with overall MVFR
expected although KLYH could go lower right before daybreak
where clouds look even less.
Any fog/stratus will dissipate by mid morning Wednesday. However
lingering upslope flow could keep sub-VFR cigs lingering around
KBLF until afternoon. Otherwise expect diurnal heating to
generate some MVFR cumulus mid morning that will lift to VFR
during Wednesday afternoon. Any shower threat appears quite
isolated so wont include mention as well.
Winds will generally be light westerly with no significant
impact to aircraft operations.
Average confidence most elements, below average for IFR
vsby/cigs overnight.
Extended Discussion...
High pressure at the surface and aloft will dominate the area
into late this week. A front approaching the Mid Atlantic
region on Friday may generate scattered MVFR showers and
thunderstorms. High pressure will build in from the north in the
wake of this boundary resulting in mostly VFR outside of
isolated showers Saturday, and perhaps low clouds within a
developing wedge by Sunday.
There will also be potential for for late night/early morning
fog in the valleys each morning.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/MBS
NEAR TERM...JH/MBS
SHORT TERM...KK
LONG TERM...KK
AVIATION...JH/MBS
Area Forecast Discussion
National Weather Service Topeka KS
1100 PM CDT Tue Oct 2 2018
...AVIATION UPDATE...
.SHORT TERM...(This evening through Wednesday)
Issued at 351 PM CDT Tue Oct 2 2018
Warm front has mixed north with gusty SSW winds at most locations
and temps in the 80s. Isolated showers were fairly persistent over
southeast Kansas and could see one or two reach east central
Kansas before sunset as ML CAPE lingers but a lack of near-surface
ascent should allow for a dry evening. Models are consistent with
modest isentropic upglide developing from 310 to 315 K as the low-
level jet increases overnight in response to surface cyclogenesis
moving across the Dakotas as the strong upper wave over southern
British Columbia this afternoon pushes east. Neither moisture
profiles nor instability aloft are impressive however. A weak wave
in the west-southwest flow aloft could pass through and aid in
ascent, but at this point am not expecting anything more than very
isolated activity in the 6Z-15Z window. The low-level jet should
allow for fairly steady overnight temps and increasing surface
winds, with a very warm and breezy to windy Wednesday before the
front associated with the aforementioned wave enters from the
north-northwest late in the afternoon. Models continue to be
rather dry with this front through the afternoon though ML CIN
values do drop to around 50 J/kg. With current dewpoints in a
well-mixed boundary layer to the south around 70 F, will err on
the side of caution with a less-capped atmosphere and add a small
chance for thunderstorms late in the afternoon. ML CAPE around
1500 J/kg and 25 kts of deep-layer shear suggest a small severe
weather potential in wind and hail until early evening when
instability diminishes.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 351 PM CDT Tue Oct 2 2018
The front becomes more zonal into the evening with more coverage
expected as moisture convergence increases. Nearly zonal flow
aloft could lead to some training and some locally heavy rainfall
though some continued southerly movement to the boundary is
anticipated. East to northeast surface winds behind the front and
the approach of the weakening upper wave off southern California
coast this afternoon leads to a better isentropic lift scenario
for decent precip chances Thursday into Thursday night. The next
upper wave brings the front north late Thursday night with steady
to rising temp potential and another front in the vicinity Friday
into Friday night. Discrepancies in the front`s position Friday
continue to vary considerably but severe weather potential could
develop in some solutions. The front likely will be to the
southeast by Saturday though southwest flow aloft downstream of a
developing Four Corners low keeps some potential for elevated
precip in place for much of the weekend. Much of the area should
be back in the warm sector for Monday with another frontal passage
possible Monday night into Tuesday as a wave ejects northeast from
the southwest trough. There are many questions for where and when
the best excessive rain potential will be through these periods,
but several rounds of moderate to heavy rainfall appear possible.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday)
Issued at 1100 PM CDT Tue Oct 2 2018
Not a lot of change in forecast thinking. With the RAP and NAM
showing the pressure gradient increasing through sunrise and
surface winds already gusting, think it is less likely the
boundary layer would decouple causing LLWS. Otherwise models
continue to show a stratus deck developing by sunrise. Confidence
in CIGS being below 3 KFT is marginal so will keep a VFR forecast.
Although is is not impossible the status could come in between 2
and 3 KFT. Some of the 00Z guidance suggests convection along the
front may hold off until it is south of the terminals. Think there
is some potential for TS in the evening, so will include a VCTS.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...65
LONG TERM...65
AVIATION...Wolters