Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/26/17
Area Forecast Discussion
National Weather Service Bismarck ND
952 PM CDT Fri Aug 25 2017
.UPDATE...
Issued at 934 PM CDT Fri Aug 25 2017
Upper level low continues to track from north central into
northeast ND. Convection over South Dakota seems to have inhibited
the moisture return into the southeast portion of the CWA this
evening, with secondary surge of precipitation likely poised to
lift into far southeast ND or WC MN. We could see a sprinkle or a
little drizzle in the far eastern portion of the CWA tonight but
not enough for a mention of precip, thus we have removed
precipitation chances for the rest of the night.
The main focus will be on potential fog development. Lower
boundary layer remains quite moist, with generally light winds
expected overnight. Latest satellite imagery shows mainly clear
skies over western and much of south central ND, with some breaks
in the higher clouds developing north central. It remains cloudy
over the James River Valley into the Turtle Mountains. Currently
any limits to visibility are over the James River Valley and
points east where we had recent rainfall. Low stratus remains here
also, so the extent of dense fog remains in doubt.
Farther west, over central and western ND, dewpoint depressions
are generally 2-4 degrees, but as of yet, no fog. Last several
iterations of mesoscale models indicate low stratus/fog developing
around midnight across central ND and spreading west. We utilized
a blend of mesoscale models to depict the development of
stratus/fog tonight. Currently this develops areas of fog across
most of western and central ND. At this time it looks like the
most likely areas for dense fog would be the Highway 83 corridor
and the I94 corridor from Bismarck to near Dickinson, from around
10Z to 14Z. With some doubt about whether it will be more stratus
or dense fog, and with the development of dense fog forecast to be
late tonight into Saturday morning, will not issue any advisory
at this time. Would not be surprised though if one is needed
on the overnight shift.
UPDATE Issued at 724 PM CDT Fri Aug 25 2017
Quick update to clean up pops this evening. Maybe another hour of
showers over the far southeast CWA, otherwise just isolated
showers expected. Removed the mention of thunder for the rest of
the night.
UPDATE Issued at 600 PM CDT Fri Aug 25 2017
A weak upper level system will track across north central and
northeast ND tonight keeping a chance of showers over central and
eastern ND. A weak surface flow and a moist lower boundary layer
will lead to conditions favorable for fog development tonight. A
limiting factor, at least initially will be cloud cover. Currently
extensive mid and high level clouds cover all but the far
southwest portion of the CWA. As we lose the higher clouds
overnight, the fog potential should increase. Most of the
mesoscale models are indicating widespread low ceilings and fog
across much of western and central ND. Currently this is handled
well with the going forecast. Will need to monitor for possible
Dense Fog highlights later tonight.
For the update, we adjusted pops based on latest radar. Utilized a
blend of current pops with the time lagged HRRR to generate pops
for the evening and overnight hours. Also lowered sky cover over
the southwest this evening.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 235 PM CDT Fri Aug 25 2017
Main concerns in the short term include thunderstorms chances
this afternoon and tonight followed by fog potential with clearing
skies tonight.
This afternoon showers and scattered thunderstorms formed along
and north of a short wave trough moving through central South
Dakota. This feature will move east with keeping best instability
and shear south but with enough instability north for widely
scattered thunderstorms.
Clearing skies tonight as the trough moves east will allow fog to
form in the areas that received rain today. The RAP/HRRR CAM
models spread fog across teh area and will only limit the fog
where clouds may remain longer in the James river valley.
.LONG TERM...(Saturday night through Friday)
Issued at 235 PM CDT Fri Aug 25 2017
The main feature in the extended period will be the development of
a significant h500 ridge across the northwest CONUS by early next
week. The result will be dry weather as the majority of short
wave energy will by shunted north and broad subsidence will
bring a warm thermal ridge into the eastern highs plains. This
will bring warn and dry weather for the region, especially west
where highs will touch the lower 90s by mid week. Temperatures
will be cooler by still mild high highs in the 80s across the
east.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 934 PM CDT Fri Aug 25 2017
Widespread IFR-LIFR cigs and vsbys expected late tonight into
Saturday morning at all TAF sites. Fog/stratus will slowly give
way to VFR conditions during the morning hours on Saturday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...TWH
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...TWH
Area Forecast Discussion
National Weather Service Columbia SC
1015 PM EDT Fri Aug 25 2017
.SYNOPSIS...
The forecast area will be between a frontal boundary off the
Southeast Coast and high pressure ridging southward along the
Appalachians over the weekend. An area of low pressure will
develop along the front and lift northeastward. The low will be
off the South Carolina coast Monday.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Evening showers have generally come to an end across the area or
shifted westward into central Georgia. Frontal boundary remains
stalled offshore with generally easterly winds across the
forecast area. There is the possibility of some stratus clouds
redeveloping late tonight, especially along the eastern Midlands
and CSRA where there was some rainfall but confidence is
limited as some drier air should also be advecting in from the
northeast. Overnight lows expected to be in the upper 60s to
lower 70s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
There will be a tight moisture gradient between dry high
pressure ridging southward along the Appalachians and the front
off the Southeast Coast. The gradient diminishes forecast
confidence but the NAM, GFS, and ECMWF keep deeper moisture east
of the forecast area through Sunday and we have continued the
dry forecast. Wind and mixing should help prevent early morning
fog but there may be considerable stratocumulus at times in the
northeast flow. Moisture may become a bit deeper Monday because
of wrap-around moisture associated with low pressure slowly
lifting northeastward along the front. The guidance consensus
supports a small shower chance Monday mainly in the east
section. Leaned toward the lower high temperature guidance
because of the northeast flow and cloudiness. Favored the
higher low temperature guidance because of expected mixing.
Followed the GFS and NAM MOS for the wind forecast.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The GFS and ECMWF display low pressure off the coast lifting
northeastward and farther away from the forecast area Monday
night through Tuesday. Weak surface troughing and moisture are
depicted lingering in the wake of this system through Friday.
The models show upper troughing mainly lifting north of the area
by Wednesday. The models keep the remnants of Harvey well west
of the area through the period. The GFS and ECMWF MOS support
near normal temperatures and chance pops through the medium-
range period.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Surface high pressure to our north, with trough/frontal
boundary near the coast or offshore, providing a general NE low
level flow over our forecast area. Lingering convection late
this evening will not affect the TAF sites. Latest LAMP and
HRRR guidance continues to lean towards a more optimistic
forecast during the early morning hours on Saturday so will keep
VFR conditions, which should continue past sunrise through the
end of the TAF period.
EXTENDED AVIATION OUTLOOK...No significant impacts expected
through Sunday, with some possibilities of late night/early
morning stratus. Increasing precipitation chances Monday through
Wed.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Forks ND
941 PM CDT Fri Aug 25 2017
.UPDATE...
Issued at 941 PM CDT Fri Aug 25 2017
Latest high resolution guidance and radar imagery is indicating
that the stronger storms stretching from near Sioux Falls SD up
toward Willmar MN are sapping some of the expected pcpn for our
southern FA. Some stronger echoes did move up through Elbow Lake
and Grant County MN, where Elbow Lake picked up over a half an
inch of rain. However, outside of possibly Otter Tail and Wadena
counties, will reduce pcpn chances and amounts. Areas north of a
Wahpeton to Park Rapids line may only see some very light showers
or drizzle. Although clearing is still west of the FA, there has
been some fog in the Valley City ND area as well. Will keep fog
mentioned from Devils Lake down through the Valley City area
overnight.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 325 PM CDT Fri Aug 25 2017
Water vapor shows Short wave moving into western SD and the nose
of the upper level jet on its south end. This is causing a large
increase in convection btwn Aberdeen and Pierre just west of
surface warm front which was from just east of Aberdeen to
Valentine Nebraska. Low pressure in south central SD will move
east-northeast thru the evening and night into west central MN
overnight. HRRR model seems too far north with sfc low and thus
too bullish with qpf in SE ND. Main convection should stay just
south of ND border and then ENE into the far SE fcst area with
bulk of heavier rainfall south of there to areas west of the Twin
Cities thru tonight. High chance to likely pops Park Rapids to
Wahpeton east this evening/tonight. Some light rain showers
possible north of there but how far north is the question with
prospects for much Grand Forks north and west in doubt.
Band of showers in W ND has been moving very slowly east and is
associated with a short wave and sfc boundary in eastern
Saskatchewan and far western ND. This boundary will move only into
central ND tonight and then basically wash out Saturday as low
pressure moves east thru central/eastern MN.
Low level moisture will continue to move northward and with it
gradually lowering ceilings and some fog potential mainly DVL
region closest to sfc boundary in central ND.
.LONG TERM...(Saturday night through Friday)
Issued at 325 PM CDT Fri Aug 25 2017
Saturday night into Sunday will see the clouds and showers
gradually move east with sunshine returning to E ND and the RRV
Sunday while clouds hold in the far eastern fcst area until late
in the day.
For Sunday night through Tuesday, dry high pressure will build into
the Dakotas and the Central Plains. A complex upper level pattern
develops over the U.S. as Hurricane Harvey blocks moisture from the
Gulf with strong trough building over the Midwest and a ridge
building into the Northern and Great Plains. For the forecast area,
this pattern yields dry and warmer weather. Models are indicating
near to slightly above normal temperatures for much of next week,
but given the persistent dry weather, wouldn`t be surprised to see a
larger diurnal swing with highs in the 80s or even near 90 and lows
in the 50s for Monday and Tuesday.
For the second half of the week, it looks more likely that rain
chances will return. Slight chances for scattered showers and storms
exist for Tuesday night through Thursday night as a boundary moves
in from the north, but these rain chances will be on and off and not
widespread. Based on current trends and Harvey still looking to
control the Gulf moisture supply, it looks more likely that this
would be a weak and drier boundary washing out over the area. Better
shower and storm chances move in for the Friday and into next
weekend as the Gulf moisture supply opens up again and a stronger
system approaches the Northern Plains from the Northern Rockies.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 648 PM CDT Fri Aug 25 2017
The TAF sites have dropped into the MVFR range, and will hold that
way tonight into portions of Saturday. Ceilings may briefly drop
even lower late tonight. Not sure about the possibility of fog, so
did not mention any at this point. The showers will primarily
affect KFAR and KBJI, but only mentioned VCSH for now. If the
showers are more impending, will amend the TAFs as need be.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Godon
SHORT TERM...Riddle
LONG TERM...BP/Riddle
AVIATION...Godon
Area Forecast Discussion
National Weather Service Goodland KS
515 PM MDT Fri Aug 25 2017
.UPDATE...
Issued at 438 PM MDT Fri Aug 25 2017
Added patchy fog to late night tonight and morning period
Saturday. Majority of guidance now supports influx of low level
moisture from the south late tonight and possible stratus/fog
(ARW/NMM/RAP/HRRR/HRRRx/NAM/SREF). If signal is still in place
later this evening I will consider increasing coverage.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 235 PM MDT Fri Aug 25 2017
May see an isolated thunderstorm or two in the northwest 1/3 of
the area through sunset or perhaps early this evening along a sfc
convergence area where moisture in the 700-500mb column is
forecast. Otherwise just a few mid and high clouds moving through
from the northwest. It should be noted that the NAM is continuing
to advertise abundant boundary layer moisture moving into the area
(mainly east of the CO/KS border) from the southwest after
midnight. Latest HRRR/experimental HRRR also now showing
indications of moisture return although not quite as far
northeast. Fog is certainly possible if the model visibility
forecasts are correct. Given the recent indications in the models
will let evening shift get a look at more model runs and 00z data
before possibly adding fog and increasing cloud cover.
On Saturday a surface trough is forecast in the mid to late
afternoon hours generally from near McCook to Burlington to Kit
Carson Colorado. There is a bit of moisture in the 850-500mb layer
and some low level convergence along the boundary. May see an
isolated thunderstorm or two as a result around 00z Sunday.
Afternoon temperatures should peak in the mid 80s to low 90s.
.LONG TERM...(Saturday night through Friday)
Issued at 155 PM MDT Fri Aug 25 2017
Saturday night-Sunday: Minor changes were made to the afternoon
forecast today to take into account latest guidance and
observations. A cold front will be grazing the central High Plains
Saturday afternoon. This will give way to instability over our
region, with our highest chance of thunderstorms appearing around
Saturday night into Sunday. Residents should not rule out strong
winds and small hail.
Monday-Thursday: Expecting mostly clear skies throughout the
reminder of the long term forecast. Highs will be in the mid to
upper 80s with lows in the upper 50s and lower 60s. No severe
weather threat is expected at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 515 PM MDT Fri Aug 25 2017
Isolated showers or thunderstorms may move into northwest Kansas
and southwest Nebraska around sunset before quickly dissipating.
Confidence is highest in possible showers at KGLD, with less
confidence in thunderstorms reaching either terminal. Added VCSH
at KGLD and left this out of KMCK.
Late tonight low level moisture increases, and stratus/fog may
begin to develop in northwest Kansas south of Interstate 70. If
this happens as current guidance indicates 3-6sm would be possible
around 12Z at KGLD, with VFR conditions prevailing at KMCK. Some
guidance is showing stronger signal for IFR (or lower) conditions
impacting KGLD. Confidence is not high enough to prevail these
conditions at this time, but this will need to be monitored.
Additional thunderstorm activity may develop late in the TAF
period Saturday at KGLD and KMCK, but better chances appear to be
after 00Z (end of current valid time).
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...DR
SHORT TERM...99
LONG TERM...EV
AVIATION...DR
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1040 PM EDT Fri Aug 25 2017
.SYNOPSIS...
High pressure building across the region will introduce an extended
period of unseasonably cool conditions that is expected to last
through the weekend. Increasing moisture early next week will result
in expanding coverage of showers and thunderstorms. Tropical
moisture may spread north out of the Gulf and into the Southeast
later next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1035 pm EDT: Late evening HRRR runs continue to indicate
spotty showers around the region overnight, with the best
concentration along the eastern slopes of the mountains and the
adjacent NC foothills. This appears reasonable given the layers of
easterly flow in the VAD wind profiles, and isolated PoPs will thus
be featured in these areas through daybreak Saturday. Otherwise,
expect scattered clouds to persist overnight due to the higher level
cirrus in the NW flow aloft, and occasional lower stratocumulus in
the more easterly flow at lower levels. Patchy mountain valley fog
is likely.
Meanwhile, surface high pressure will continue to ridge southward
across the region from the Great Lakes area through Saturday. This
will keep northeasterly flow in place near the surface and inhibit
dewpoint and sbCAPE recovery somewhat. Some minimal instability is
still indicated in model profiles Saturday afternoon which could
combine with meager upslope flow into the mountains to produce a few
showers and isolated thunderstorms. Isolated to scattered PoPs will
be featured in these high terrain areas for primarily tomorrow
afternoon. Maximum temperatures will remain at least a category
below climatology throughout.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 130 PM EDT Friday: The short term will begin with a broad
upper trough in place down the Eastern Seaboard, a bit of shortwave
ridging across the OH Valley, and another trough pushing into the
western Great Lakes. Surface high over southeast Canada will begin
to ridge down the East coast under the confluent flow aloft between
the ridge and eastern trough, setting up a classical CAD event for
us. While Harvey, sitting over SE TX, won`t be a player for us, a
tropical wave over the FL Peninsula will lift NE into the south
Atlantic bight, pushing up the GA/SC coasts through the short term
period. This will sort of squish the damming wedge into western NC,
with a fairly strong pressure gradient and thus winds generally 10-
15 mph out of the NE as we move through the period. Easterly flow
from the tropical wave, or potential tropical depression (currently
40% chance of tropical development), will bring precip into eastern
NC toward the end of the period. By this time, the incoming Great
Lakes trough will deepen into a closed low somewhere over the
Midwest with its own attendant moisture approaching the area. All in
all, the short term is fairly quiet with a continued cooling trend
(highs 3-6 degrees below normal Sunday and 6-10 degrees below by
Monday) as the damming strengthens.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 200 PM EDT Friday: The extended forecast is quite a bit more
complicated, with several factors in play, including the Great
Lakes/Midwest upper low, the tropical wave/low off the NC coast, and
Harvey still producing catastrophic impacts over TX. Aforementioned
tropical wave/low off the NC coast will continue to lift NE as we
start the period, with low-level easterly flow bringing quite a bit
of moisture into E NC, with a corresponding increase in pops
especially for eastern zones on Tuesday. With the increasing cloud
cover, Tuesday should also be the coolest day with highs 8-12
degrees below seasonal normals, more significantly in the NW NC
Piedmont areas. The cold dome will be eroding as we move forward on
Tuesday with the approach of the northwestern low, but despite the
cooler temperatures, weak WAA atop the cold dome plus PVA/upper
jetlet moving overhead may lead to enough synoptic lift for a few
thunderstorms to develop with may be 500 J/kg CAPE to work with and
30-40kt deep layer shear.
By Wednesday, the coastal low will be racing to the northeast and no
longer a factor. Upper Midwest trough will open and damp, with a bit
of ridging trying to build in from the Atlantic ridge. The big
unknown will be Harvey which at this point does not look like it
will phase with the broadening upper trough, but rather remain in
place...continuing to rain...somewhere over SE TX. However, with the
increasing gradient aloft between the upper Atlantic ridge and the
northern trough, moisture from Harvey will begin to get picked up
and spread ENE over the Deep South and toward the Southern
Appalachians. Despite slightly increasing thicknesses and with the
damming eroded by Wednesday afternoon, increasing cloud cover will
generally counteract most resulting temperature increase, with highs
still a good 6-10 degrees below normal, with only minor increases as
we move toward the end of the period. Should see an increase in
convection by midweek as well, with the increasing moisture and
enough CAPE for isolated to scattered thunderstorms. Quite a bit of
uncertainty with how much moisture will make it to the area and what
other synoptic and mesoscale features will be in play that may
enhance pops, so have generally capped them at chance for now. The
remnants of Harvey are progged (for now) to remain over TX with no
direct threat to our area, but the moisture advection will continue
past the end of the period.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: Strong surface high pressure centered to the
north of the region will keep generally drier weather in place
across the area through the TAF period. However, an easterly fetch
of improving Atlantic moisture at low levels will try to make
inroads across the coastal plain and central piedmont of the
Carolinas. This should contribute to a steady uptick in
stratocumulus/cumulus through the period, with slowly improving
shower chances primarily near KAVL in the mountains. Expect mainly
steady NE winds at 10 kt or less across the piedmont and foothills,
with more variable winds at KAVL in the French Broad Valley. Fog
potential at KAVL could be briefly inhibited by higher cirrus
overnight, but at least MVFR restrictions look likely around
daybreak Sunday.
Outlook: Very gradual moistening will continue into early next week,
with some afternoon showers possible - mainly over the higher
terrain. Moisture improves on Tuesday, after which more widespread
showers are expected.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 95% Med 75% Med 78% High 100%
KHKY High 100% High 91% Med 73% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 90% High 81% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...Wimberley
NEAR TERM...HG
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...HG
Area Forecast Discussion
National Weather Service Medford OR
317 PM PDT Fri Aug 25 2017
.DISCUSSION...Thursday brought a brief break from heat and smoke to
much of the forecast area. Today, we have begun transitioning to
a hot, dry pattern. Temperatures and smoke will increase over the
next few days. The challenge is determining the extent to which
smoke will limit high temperatures. Model guidance indicates
temperatures could exceed 105 degrees in west side valleys, and
reach the upper 90s in east side valleys Sunday and Monday.
However, considering the amount of active fires in our forecast
area, high temperatures shouldn`t hit those extremes... but should
still be well above normal. Expect highs around 100 in west side
valleys and the lower 90s in east side valleys beginning tomorrow
and peaking Sunday and Monday. Combined with smoke impacts, this
could create dangerous conditions for sensitive groups.
A thermal trough along the coast will maintain strong north to
northeast winds long the coast tonight. Winds will start diminishing
tomorrow as the thermal trough weakens. Expect some patchy fog along
the coast early tomorrow morning, but the marine layer should be
fairly thin, so expect that to be relatively short-lived. Sunday
morning, winds will transition from offshore to southerly, as the
thermal trough weakens, thus expect a fickle finger of fog to make
its way into the Brookings/ Crescent City area.
Sunday afternoon and night, models indicate moisture advection and
very slight instability over the East Side, but don`t see much of a
trigger until late Sunday night, and instability will have
diminished by that point.
Monday, Tuesday, and Wednesday afternoon and evening, expect several
shortwaves embedded in broad southwesterly flow to meander into the
area. These will bring the possibility thunderstorms east of the
Cascades Confidence in this forecast is low, and will need to be
fine tuned as instability and moisture are borderline.
The smoke forecast will continue to need to be updated with each
forecast, but for now do not see any significant breaks. Much will
depend on fire activity, but in general expect smoke to diminish at
night, and worsen in the afternoon over the next several days.
-MSC
&&
.AVIATION...25/18Z TAF CYCLE...Along the coast...stratus
has eroded and VFR will prevail the rest of this afternoon
into this evening. A shallow marine layers will likely bring
IFR/LIFR low clouds/fog back to OTH tonight between 08-10Z,
lasting until 16Z before becoming VFR again. An area of mainly
VFR though will occur south of Cape Blanco to Brookings with
shallow marine clouds/fog in the vicinity of Brookings after 09z.
Smoke from the Chetco Bar fire will also occasionally reduce
visibility to MVFR/IFR in and around Brookings.
Since the marine layer will be much shallower than the past
couple of nights, we are not expecting clouds in the Umpqua
Basin. However, almost all inland areas will have to deal with
reduced visibility (MVFR and occasional IFR) due to wildfire smoke.
Latest HRRR smoke projections show low-level smoke will impact MFR
again this afternoon as well as LMT, which could linger through the
night. By far, the thickest smoke will be in western Siskiyou County
valleys, the Applegate Valley and near the High Cascades/Umpqua
North complexes, where visibility could be reduced to just a few
hundred feet at times. -Spilde
&&
.MARINE...Updated 230 PM PDT Friday 25 August 2017...High pressure
is offshore with a thermal trough along the coast. Gales south of
Port Orford beyond 5 NM from shore will reach a peak this evening
and persist through late tonight. Meantime, small craft advisory
conditions will persist elsewhere. Winds will slacken on Saturday as
the high weakens and thermal trough moves inland. But, advisory
conditions will persist through Saturday night with gusty winds in
the outer waters and fresh swell near shore. Winds and seas will
continue to diminish Sunday into early Tuesday. Northerly winds will
trend higher again Tuesday into Friday with gales possible south of
Cape Blanco late in the week. -DW
&&
.FIRE WEATHER...Updated 120 PM PDT Friday, 25 August 2017...
...AN EXTENDED PERIOD OF ACTIVE BURNING CONDITIONS EXPECTED TODAY
INTO EARLY NEXT WEEK...
The thermal trough along the southern coast will continue to deepen,
resulting in stronger offshore northeast winds, especially over the
Coast Range and into portions of western Siskiyou County. It should
be noted up front that this thermal trough is NOT expected to be as
strong as the one last week/weekend. However, this one presents a
potentially dangerous situation, particularly in southern Curry
County where the Chetco Bar fire is burning and within just a few
miles of the coast. The region will really dry out beginning tonight
with poor humidity recoveries and a continuation of gusty NE
offshore winds. Rapid fire spread impacts could be significant. With
a mid level Haines of 6 we have extended Red Flag through the Day
Saturday. Models are showing a mid level haines of six daily through
monday, but will wait to see how the fire behaves Saturday before
raising the watch Sunday to a warning and extending it to Monday.
Model guidance shows the lowest RH recoveries Saturday night into
Sunday, but NE winds should ease. The thermal trough will gradually
weaken and move inland Sunday into Monday. So, along the coast,
we`ll see increasing onshore flow by early next week with higher
humidity and less wind. However, with the thermal trough moving
inland, fires burning across the remainder of the area will be
susceptible to increasing fire behavior due to a very dry, unstable
air mass. Model guidance is showing high level Haines value of 5
and, in some places, high level Haines 6, which could lead to plume
dominated fire. Although the Haines is indicating just below a six
along the Cascades Sunday, the thermal trough moves inland that day
and that usually results in very active fire behavior and have
raised it to a 6 and issued a watch for Sunday on active fires along
the Cascades.
In the extended, there is still some uncertainty with how fast the
upper level ridge will break down, but it does appear that at least
slight decrease in high temperatures will occur with more marine air
pushing farther inland west of the Cascades after Tuesday.
Thunderstorm potential is low, but increases a bit toward midweek
with the best chance east of the Cascades.
/FB/Sven
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 7 PM this evening to 9 PM PDT Saturday for
ORZ618-619.
Fire Weather Watch from Sunday morning through Sunday evening
for ORZ618-619.
Fire Weather Watch from Sunday afternoon through Sunday evening
for ORZ617-622-623.
CA...None.
Pacific Coastal Waters...Small Craft Advisory until 2 AM PDT Saturday for PZZ350-356.
Gale Warning until 2 AM PDT Saturday for PZZ356-376.
Small Craft Advisory for hazardous seas from 2 AM Saturday to 5
AM PDT Sunday for PZZ350-356-370-376.
Small Craft Advisory until 5 AM PDT Sunday for PZZ370-376.
$$
MSC/SBN/DW
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
937 PM EDT Fri Aug 25 2017
.SYNOPSIS...
A front will remain stalled off the coast through the weekend as
high pressure builds in from the north. An area of low pressure
is forecast to develop along the stalled frontal boundary off
the Florida coast this weekend then slowly lift northeast along
the Southeast coast early to mid next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 935 PM Friday...All precipitation has ended for the moment
near the coast and have dropped PoPs until after 06z. HRRR and
RAP indicate a few spotty showers redeveloping along the coast
as we head toward morning and will have a slight chance PoP
immediate coast. No changes needed to forecast temperatures
with lows mid 60s inland to lower 70s coast.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
As of 345 PM Friday...No major changes to the forecast with the
majority of the are remaining dry except for along the coast.
Slightly better instability tomorrow with MLCAPES around 500
j/kg, may lead to at least a few storms making it just onshore
by afternoon. A frontal boundary that is stationary now does
more toward the coast late in the day as a warm front, which may
be enough to generate a few showers or storms. It will be
another comfortable day with dewpoints holding in the 60s and
temps in the lower to middle 80s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
As of 330 PM Fri...Below normal temps expected this weekend and
through most of next week, with slow warm up late week.
Unsettled conditions are expected this weekend and early next
week, as an area of low pressure is forecast to develop along a
stalled frontal boundary along the southeast coast, and may
strengthen into a tropical cyclone. However, much uncertainty
remains regarding this system.
Saturday Night and Sunday...Strong high pressure will build
behind a cold front that will remain stalled off the southeast
coast. Still, widely scattered showers will possible along the
coast, while further inland it should remain mostly dry. More
widespread showers will creep into coastal sections Sunday
afternoon, and have chance PoPs for this. Low level thickness
values, and NE flow, support below normal temps with highs in
the upper 70s to mid 80s and overnight lows in the low/mid 60s
inland and upper 60s/low 70s along the coast.
Monday through Wednesday...Models are still on board for
development of a tropical low pressure system currently near the
west coast of Florida. The low will slowly strengthen over the
next couple days and travel up the stalled front that is over
the Gulf Stream. CMC still strengthens the potential system the
most, while the GFS and EURO offer a weaker solution. The GFS
and EURO are closer to the coast, while the CMC is a bit farther
off the coast, but not much. It remains to be seen what will
develop, as models have struggled with tropical development so
far this year.
At any rate, depending on the eventual track and strength of
the low, minor impacts could be felt across Eastern NC, mainly
along the coast. Coastal areas could see gusty winds, rough
surf and an elevated risk of rip currents. More widespread
precip is possible during this time frame, especially along the
coast, but will keep chance PoPs with so much uncertainty still
to be resolved. High temps through the period, generally in the
upper 70s to low 80s, with overnight lows in the mid 60s to low
70s. Gradual warm up expected late week.
Thursday and Friday...High pressure will move in from the north
behind the departing low pressure. Some scattered thunderstorms
will be possible in the afternoon and evening both days, and
temperatures will be in the low to mid 80s for highs and low 70s
to upper 70s for lows.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Short Term /through 00Z Sunday/...
As of 645 PM Friday...No big changes to the TAF with VFR
conditions expected to prevail through the next 24 hours as
deeper moisture lingers along the coast east of the TAF sites.
Winds should remain NE tonight and Saturday with at least 4-7
knots overnight, precluding fog formation, especially given lack
of any precipitation at the TAF sites during the day on Friday.
Long Term /Saturday Night through Wednesday/...
As of 350 PM Fri...VFR conditions expected through Sunday, then
occasional periods of sub-VFR conditions are possible, as
rain showers and isolated thunderstorms move into the airspace
through Wednesday.
&&
.MARINE...
Short Term /Tonight and Saturday/...
As of 940 PM Friday...Marine forecast is decent shape as winds
continue ENE/E at 10-20 knots with seas 3-5 feet. As the
gradient tightens over the waters by early Saturday, between
high pressure over the northeast and low pressure over Florida,
winds will increase along with waves. In general over the
coastal waters winds of 15 to 20 are expected with gusts to 25
kts especially south of Cape Hatteras tomorrow. North of Cape
Hatteras while a few gusts to 25 kts are possible, confidence
for stronger winds and higher waves do not occur until Saturday
night.
Long Term /Saturday through Wednesday/...
As of 350 PM Fri...Strong winds and dangerous seas expected to
develop this weekend and continue into next week, a tropical low
pressure system develops near a stalled frontal boundary along
the Gulf Stream.
Models continue to show the potential for tropical low
development along the stalled frontal boundary off the SE coast
this weekend into early next week. There is still much
uncertainty to be resolved with this feature, given the varying
model solutions and lack of run to run consistency. Winds
initially ENE 15-20 kt Saturday night, will become NE 20-25 kts
overnight, and then 25-30 kts at times Sunday through Monday.
Winds then lessen to 15-20 kts Tuesday and Wednesday. Seas will
be initially 4-6 ft south of Cape Lookout and 3-5 ft to the
north, and will build 5-9 ft south of Cape Lookout Sunday, and
4-7 feet to the north. Seas will then lessen south of Cape
Hatters Monday 4-7 ft, and build to the north 7-11 ft. Seas will
remain elevated Tuesday as well, generally 6-10 ft. Given the
uncertainty on how this system will evolve, mariners should
continue to monitor the forecast over the next several days.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...Small Craft Advisory from 9 PM Saturday to 1 AM EDT Wednesday
for AMZ135.
Small Craft Advisory from 4 AM Saturday to 1 PM EDT Thursday
for AMZ154.
Small Craft Advisory from 4 AM Saturday to 9 AM EDT Wednesday
for AMZ156.
Small Craft Advisory from 4 AM Sunday to 1 PM EDT Thursday for
AMZ150-152.
Small Craft Advisory from 8 AM Saturday to noon EDT Tuesday
for AMZ158.
&&
$$
SYNOPSIS...EH
NEAR TERM...CTC
SHORT TERM...EH
LONG TERM...CQD/SGK
AVIATION...CTC/EH/SGK
MARINE...CTC/EH/SGK
Area Forecast Discussion
National Weather Service Phoenix AZ
815 PM MST Fri Aug 25 2017
.SYNOPSIS...
Quiet, but hot weather will move into the Southwest this weekend. A
modest increase in moisture levels early next week will result in
slight rain chances across southern Arizona, possibly stretching
into southeast California. Temperatures will also cool a few degrees
in response to the moisture return.
&&
.DISCUSSION...
The limited afternoon convection across the state has largely
dissipated this evening though persistent accas indicates a larger
pocket of residual midlevel moisture drifting through the eastern
half of Arizona. Both the GFS and NAM BUFR soundings (in addition to
several high resolution models including the HRRR and 3km NAM)
continue to strongly suggest these clouds advecting into the Phoenix
metro overnight into an environment characterized by steeper lapse
rates and a couple hundred J/kg of MUCape. However without better
ascent fields or gravity wave interactions, as well as a very dry
subcloud layer, virga is the most likely outcome late tonight. Some
sprinkles/brief light showers are certainly possible and have
increased POPs (and cloud cover) very modestly towards sunrise.
&&
.PREVIOUS DISCUSSION...
/149 PM MST Fri Aug 25 2017/
.Tonight through Sunday...
There continues to be very good model consensus that very strong
ridging aloft will build northward into the Great Basin by Sunday as
moisture/energy from Hurricane Harvey helps amplify the downstream
trof dropping southward into the eastern 1/2 of the CONUS. Both the
EURO and the GFS models raise 500mb heights into the 593-595dm range
by Sunday which is around 2SD above the mean. These high heights
combined with light downslope easterly flow through the column looks
like it will be enough to push lower desert highs up into the 111-
114 degree range across SW AZ and SE CA, or 6-8 degrees above
normal. These well-above normal highs combined with lows in the mid-
upper 80s will push HeatRisk levels into the high/very high range
across that region. This continues to support our current Excessive
Heat Watch across those regions.
Slightly higher moisture values (PWATS as high as 1.50 inch) likely
will hold temperatures down a bit across South-Central AZ.
Convective activity is expected to be limited to isolated
shower/storms across the higher terrain well north and east of
Phoenix through early Sunday due to limited moisture in the low
levels (sfc dewpoints mainly aob 60F) and a subsidence inversion in
the mid-levels of the atmosphere. Some increase in convective
activity appears likely by Sunday afternoon as winds turn easterly
through the entire column.
Sunday into Monday, a short wave moves down the eastern periphery of
the anti-cyclone sending a back door front through New Mexico and
into Arizona. This easterly push will be enhanced through the
synoptic interaction/forcing of Harvey. The main impact will be an
increase in mid-level moisture and a slight decrease in
temperatures. This pattern becomes blocked and remains essentially
in place through the work week. We`ll likely see a decent amount of
mountain convection each day though with just marginal instability
they likely won`t get too strong. The showers/storms will want to
push southwestward into the lower elevations but instability there
will still be limited, meaning they will more than likely decay as
the move away from the mountains. Enough mid level moisture spreads
far enough west that convection may be possible over Joshua Tree NP.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Minimal aviation impacts through Saturday afternoon under partly
cloudy skies. Models are insistent that 12K ft accas cigs will
develop overnight producing scattered virga around the metro. While
some sprinkles are possible at the terminal sites, accumulating
rainfall will be unlikely. Otherwise, winds will remain light with
fairly typical wind shift timing.
Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation issues through Saturday afternoon under clear
skies. Winds will generally favor a southerly direction though
periods of variable directions are likely during the morning hours.
Aviation discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Monday through Friday:
Slight rain chances will spread westward all the way into
southeast California early next week. Humidity values will stay
somewhat low each day with minimum values mostly between 12 and 20
percent. Apart from thunderstorms, winds will tend to follow
familiar warm season patterns. Temperatures will be several
degrees above average this weekend, then cool slightly early next
week.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Watch from Sunday morning through Sunday evening
for AZZ530-532-533-536.
CA...Excessive Heat Watch from Sunday morning through Sunday evening
for CAZ561-563-565>570.
&&
$$
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DISCUSSION...MO/Percha/Iniguez
AVIATION...MO
FIRE WEATHER...Iniguez
Area Forecast Discussion
National Weather Service Great Falls MT
806 PM MDT Fri Aug 25 2017
.UPDATE...
Latest RAP analysis in combination with water vapor
imagery suggests that patch of upper-level moisture has
developed/progressed eastward along the predominant zonal flow
aloft across the northern Rockies. This has led to the development
of lee-side mountain clouds along the northern parts of the front
range, especially across Glacier and Pondera Counties. Because of
this, I`ve decided to bump cloud cover a bit in this forecast
update. However, look for these clouds to slowly diminish after
midnight with dry and calm conditions expected areawide through
the morning hours. KLG
&&
.SYNOPSIS...
A westerly flow aloft will reside over the region today, resulting
in a few isolated thunderstorms over Southwest MT. Over the
weekend and into early next week, expect an upper level ridge of
high pressure to redevelop over the region. Expect a return to
very warm afternoon temperatures by Sunday, with dry conditions
expected from Saturday through Monday.
&&
.AVIATION...
Updated 0035z.
Isolated thunderstorms continue to affect portions of southwest
Montana this evening but will dissipate by 04Z. Skies will be mostly
clear to partly cloudy for widespread VFR conditions Through late
Saturday afternoon. Some distant mountains/passes will be obscured
at times by smoke.
&&
.FIRE WEATHER...
Isolated thunderstorms are possible mainly south of a line from
Helena to Lewistown before Midnight. Otherwise expect a
significant warming trend along with low humidity from Saturday
through Monday along with no precipitation. Overall winds will be
light Saturday through Monday. Brusda
&&
.PREV DISCUSSION...
/ISSUED 635 PM MDT Fri Aug 25 2017/
Tonight through Sunday...The westerly flow aloft currently over
the region will transition to an upper level ridge for Saturday
and Sunday. Scattered thunderstorms over Southwest MT this evening
should generally end before Midnight...then a prolonged period of
dry and quiet weather conditions is expected over the region over
the weekend. With no precipitation expected along with mostly
sunny skies...afternoon highs will be a few degrees above normal
Saturday...then close to 10 degrees above normal for Sunday.
Brusda
Sunday night through Friday...Much of the long term will be
controlled by the mentioned large area of high pressure across
the western US. Monday remains mostly dry with highs returning
back into the 90s. Tuesday sees the ridge slightly eastward
bringing some southwest flow with low amounts of moisture. The
result will be continued warm temperatures in the 90s...with
perhaps just enough moisture and instability for isolated showers
and thunderstorms across the southwest. Wednesday through Thursday
a series of weak disturbances will attempt to break the ridge
down. Limited moisture and weak instability from continued warm
temperatures may bring more scattered showers and thunderstorms
each day. Temperatures again look to be in the 80s and 90s. Models
then indicate a weak dry cold front may bring slightly cooler and
dry conditions for Friday...with highs in the mid to upper 80s.
Each day in the long term will have at least elevated fire danger
with low RH forecasted. Winds and dry thunderstorms may even bring
high fire danger on Wednesday through Friday. Anglin
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 51 82 50 90 / 0 0 0 0
CTB 45 81 46 89 / 0 0 0 0
HLN 54 86 52 92 / 0 0 0 0
BZN 50 83 49 90 / 30 0 0 0
WEY 41 77 38 81 / 20 0 0 0
DLN 50 82 47 88 / 20 0 0 0
HVR 51 84 50 92 / 0 0 0 0
LWT 52 80 49 88 / 10 0 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening Eastern Beaverhead
National Forest.
&&
$$
weather.gov/greatfalls