Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/30/17
Area Forecast Discussion
National Weather Service Albany NY
1043 PM EDT Tue Aug 29 2017
Low pressure will pass well south and east of the region tonight.
Although it will just be mostly cloudy for most of the area, some
showers may reach into the mid-Hudson Valley, northwestern
Connecticut and western Massachusetts. More sun and slightly warmer
temperatures are expected tomorrow, before a cold front brings some
showers and thunderstorms to the area on Thursday. Cooler and
breezy conditions are expected on Friday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1040 PM EDT, Quick update to the forecast to freshen up
the hourly temps and sky cover. Also adjusted pops across
southern New York to reflect recent radar trends. Sent updates
to NDFD and web servers.
As of 730 PM EDT, Latest GOES-16 visible imagery
shows the center of the coastal storms` circulation off of North
Carolina`s coastline with plenty of mid and high level clouds
engulfing our area. Rain associated with this storm is falling
over Long Island with a few sprinkles making their way into the
the Greater Capital District and Mid-Hudson Valley regions.
Recent observations do not indicate any rainfall but a light
shower cannot be ruled out this evening/overnight as the storm
pushes further east.
In terms of the forecast, no major changes were made. Freshened
up the hourly temps and sky cover to reflect recent trends.
As of 404 PM EDT...Upper level ridging continues to shift
eastward, with the ridge axis now located over far eastern New
England and into Atlantic Canada. At the surface, high pressure
continues to be anchored over Maine.
An upper level disturbance is located over the lower Great
Lakes and Ohio Valley region, but is running into the ridge and
starting to weaken. Strong jet streak aloft, along with
divergent southwest flow aloft ahead of this upper level
feature, and a developing coastal storm offshore eastern North
Carolina are helping to produce plenty of mid and high clouds
over the area.
MRMS imagery does show some light rain showers trying to reach
into far southern areas, but the dry-low levels is causing a
lot of this to dry up before it reaches the surface. Upstream
observations over eastern PA and NJ have been fairly light, with
hourly rates of just a few hundredths of an inch.
The coastal low will continue to track northeast off the
Virgina Capes by early this evening and start to accelerate
northeast into the open Atlantic for tonight . Although it
doesn`t appear that this storm will gain tropical characteristics
(due to increasing shear and no closed low-level center), it
should be strengthening as it travels northeast into the Gulf
3km HRRR and NAM guidance suggest some additional light rain
showers will scrape into our southeastern zones overnight as the
storm heads northeast and whats left of the upper level
disturbance passes over the area . Again, some of this will be
lost to virga due to the dry low-levels, but some additional
light rain showers are possible across the mid-Hudson Valley and
western New England, mainly before 5 AM. Amounts will be fairly
light (generally under a quarter of an inch).
Sky cover is currently mostly cloudy to overcast, with the
densest and thickest clouds across southern areas. These clouds
look to remain in place for this evening and into much of the
overnight hours. These clouds may finally start to decrease
towards daybreak as the coastal storm moves farther away and the
upper level jet streak responsible for a lot of the clouds
shifts eastward as well. If clouds break early enough, there
could be some patchy fog, but not high enough confidence in this
occurring to include in the forecast at this time.
Overnight lows will be in the upper 40s to low 50s. The coolest
spots will be across the higher elevations.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Clouds will be breaking for sunshine on Wednesday as brief
shortwave ridging passes over the area. It looks milder than
Tuesday thanks to more sunshine with highs reaching into the 70s
for most locations. It will continue to be fairly comfortable
with dewpoints in the 50s.
Dry weather will continue for Wednesday evening and most of
Wednesday night, but the next storm system will be approaching
from the upper Great Lakes, with increasing amounts of cloud
This northern stream frontal system will be impacting the region
for Wednesday morning through Wednesday mid-afternoon. Although
the surface front should have a decent temperature gradient
associated with it and strong upper level dynamics, limited
moisture and low amounts of instability will keep any showers or
thunderstorms fairly scattered along the boundary and rather
brief. No threat for any severe storms due to CAPE values under
500 J/kg and dewpoints mainly in the 50s to near 60. The front
should be through the entire area by the late afternoon hours,
with winds switching to the northwest behind the boundary. Ahead
of the front, temps should reach into the 70s across much of the
region. Not everywhere will see a shower or t-storm, and even
locations that do, it will be fairly brief.
Cooler and even drier air will work in behind the front for
Thursday night. Skies will be clearing out and temps should be
falling, along with a brisk wind in place. Overnight lows will
reach into the low to mid 40s for much of the region, with even
some upper 30s across the higher elevations.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
It looks like fall weather has arrived for the beginning of
September as the extended period will feature below normal
temperatures, chances for rain and plenty of cloudiness.
After the passage of a cold front on Thursday, Friday will be cool
and breezy as we remain under the influence of an upper level trof.
High temperatures are only expected in the upper 50s to upper 60s
with gradually clearing skies.
The upper low will shift off to the east Friday night as weak
ridging builds into the region. This will allow for temperatures to
drop into the 40s, with 30s in the higher terrain locations. Patchy
frost will be possible in the high terrain.
On Saturday, an upper level trough will dig southeastward into the
Great Lakes region as remnants from Harvey makes their way
northeastward towards the Mid-Atlantic region. These subtropical
remnants appear to fall apart as they move into southern New England
Saturday night with some solutions phasing it with the upper trof.
Whether or not this phasing occurs, rain is expected as both of
these pieces of energy move towards and through our area late
Saturday afternoon through Sunday. So it looks like it will be a
wet, cool and cloudy Labor Day weekend for our area.
Labor Day might shape up to be a nice day for most across the
forecast area as temperatures warm into the 70s (low 80s for the Mid-
Hudson valley) and partly sunny skies. However, this is a chance for
some scattered showers, mainly north and west of the Capital
District as energy from the upper trof passes by to our north.
A strong cold front will approach our area Tuesday morning as an
upper low and trof digs into the Ohio Valley. There are differences
between the GFS and ECMWF regarding strength of the system and
timing of the cold front passage. But it looks like the front and
its associated precipitation will move through our area late Tuesday
into Tuesday night. This should limit convective potential, however,
the GFS model soundings do show some instability. Decided to forego
mention of thunder in the grids at this time to maintain consistency
and to allow for models to come into better agreement with future
runs. Temperatures on Tuesday should be in the upper 70s to low 80s
before cooling off by mid-week.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected through the TAF period with mainly
mid and high level clouds in place through about 14Z. Cannot
rule out some light rain showers at KPOU tonight. Clouds are
expected to become scattered by mid-morning, allowing for a
mostly sunny day. Winds will generally be out of the northwest
around 5-10 knots through the period.
Will have to monitor satellite trends to see if any breaks in
the clouds occur closer to dawn which would allow for some
radiational fog to develop. However, did not include any fog in
the forecast at this time.
Wednesday Night: Low Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Chance of SHRA...TSRA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: Moderate Operational Impact. Chance of SHRA.
Sunday: Moderate Operational Impact. Chance of SHRA.
A coastal storm will be moving northeast from near the mid-
Atlantic coast this evening to out to sea tonight. Far
southeastern areas may see a few light rain showers, while the
remainder of the region will remain mostly cloudy and dry.
RH values will be near 100 percent tonight with light winds.
With sunshine returning on Wednesday, RH values will fall to 45
to 55 percent on Wednesday afternoon with northwest winds of 5
to 10 mph.
A few scattered showers or thunderstorms are possible with a
cold front on Thursday. RH values look to be 50 to 60 percent on
Thursday. Cooler, breezy and drier weather looks to be in place
No hydrologic problems are anticipated through the weekend.
With a coastal storm exiting off the mid-Atlantic, a few light
rain showers will reach in southeastern parts of the area this
evening into tonight. Amounts will be fairly light, as basin
average amounts will only be a few hundredths of an inch.
Elsewhere, it will just be cloudy and dry.
Dry weather will then be in place for Wednesday into Wednesday
night. A cold front may bring some scattered showers and
thunderstorms on Thursday, but basin average amounts will
generally be fairly light and this should have a limited (if
any) impact on rivers and streams. Dry weather will then return
once again behind the front for Friday and most of Saturday.
Some additional rainfall is possible by Sunday with another
frontal system, but amounts look fairly light with this system
With limited amounts of rainfall expected, river and stream
levels will remain fairly steady through the weekend.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
The KENX radar is expected to be down through at least September
1st for the bull gear to be replaced. Technicians started the work
on the bull gear replacement Saturday August 26.
Area Forecast Discussion
National Weather Service La Crosse WI
605 PM CDT Tue Aug 29 2017
.SHORT TERM...(Tonight thru Wednesday night)
Issued at 226 PM CDT Tue Aug 29 2017
Main short-term fcst concerns this period are valley fog late
tonight/early Wed then SHRA/TSRA chances late Wed/Wed night.
Data analysis at 18z had a ridge of high pressure from Lk Superior
SW to KS/OK. Vis imagery showing as area of persistent strato-cu
from NW WI across the central parts of the fcst area to NE IA, where
fog and overnight clouds/fog were the thickest. This slowly eroding
though, but holding early afternoon temps in the mid/upper 60s.
Elsewhere with at least some sunshine thru bkn cu/strato-cu clouds,
early afternoon temps across MN/IA/WI were in the low-mid 70s.
Model runs of 29.12z initialized well. Solutions quite similar for
weak shortwave ridging slides SE across MN/IA/WI tonight. This ahead
of stronger shortwave energy and falling hgts to drop SE across ONT
Wed. Area then left under increased NW flow aloft Wed night as
ridging builds into the northern plains/south-central Can. Short-
term fcst confidence is good this cycle.
For the short term, favorable set-up tonight for radiational fog
formation in the valleys/low laying areas. Sfc ridge axis remains
over the area for light/variable/decoupled BL winds tonight. This
with a moist BL airmass and under what should be weak anticyclonic
925-850mb flow for clear/mostly clear skies tonight. Clouds and
moist BL much of today, with decreasing/clearing clouds late
(keeping sfc temp-dew point spreads low) also favorable for late
night/early morning valley fog. However, one concern is depth of the
light wind layer late tonight. NAM and RAP increase winds at/above
925mb to 10kts or more after 09z. By this time though, BL should be
well decoupled, and increased fog coverage in MS/WI and tributary
river valleys to areas of or widespread in the 06z-14z timeframe.
The increasing winds at/above 925mb late tonight should help BR/FG
dissipation Wed morning, with it dissipating thru 14-15z.
Once the fog dissipates, a generally mostly sunny day expected, with
some low level warm advection ahead of the cold front being dragged
south by the passing ONT shortwave. Trend of above normal highs Wed
looks good, as mixed 925mb temps ahead of the front supporting highs
in the upper 70s to mid 80s. With the warmth and PW values of around
1 1/3 inch progged to be pooling ahead of the front, afternoon and
early evening SB/MU CAPE values looking to build into the 1K-2K j/kg
range across much of the fcst area. This with modest sfc-850mb FN
convergence to accompany the front and some 850-700mb FN convergence
to be right behind the front. Tight model consensus for the front to
be moving into Taylor Co. around 18z, the models break into 2 camps.
One camp moves the front to near hwy 10/I-94 by 00z (trend of
earlier runs), the other camp moves the front to near a KRST-KOVS-
KMSN line by 00z Thu. With main push of the shortwave trough toward
SE ONT/SW QUE, the slower front solution appears more reasonable.
Consensus of some 20-40% SHRA/TSRA chances over the NE 1/3 of the
fcst area late Wed afternoon, spreading S and SW across the fcst
area with the front Wed night looking good. Deep layered shear
generally on the weak side late Wed/Wed evening. Perhaps a strong
storm or 2 in the 21-01z timeframe but organized severe TSRA not
.LONG TERM...(Thursday through Tuesday)
Issued at 226 PM CDT Tue Aug 29 2017
For Thursday thru Friday night: main fcst concern this period is
the cooler temps behind the late Wed/Wed night cold front.
29.12z models in good agreement on NW flow aloft over MN/IA/WI on
Thu as the remnants of `Harvey` are finally lifted out of eastern
TX/lower MS valley. The mid level ridging is pushed east into the
region Thu night as a shortwave comes across south-central Can, with
some weaker lead energy push thru and flattening the ridging over
the region Fri/Fri night. Fcst confidence in this period is good
Thu thru Fri night continues to trend cooler and dry as Can high
pressure settles across the great lakes thru the period. With the
drier low levels and dry E/NE low level flow out of the high, the
shortwave looking to move across and flatten the shortwave ridging
Fri/Fri looks to do little more than spread some mid/high clouds
across the area later Fri/Fri night. Modest shot of low level cold
advection spreads across the region this period. 925mb temps back in
the 13C to 16C range for Thu afternoon and remaining there thru Fri.
Even under what should be mostly sunny skies, consensus highs both
days mostly in the low-mid 70s, around 5F below normal, looking well
trended. Thu night shaping up to be quite cool, with light winds,
mostly clear skies and a dry BL airmass. Consensus lows mainly in
the mid 40s to near 50 look good and will have to watch for the
potential of a few upper 30s lows in the normally cooler, low laying
area near/NE of I-94 come Fri morning.
For Saturday thru Tuesday (days 4-7)
The 29.12Z GFS and ECMWF are in good agreement with a dry beginning
to this period followed by a cold front and associated shower
chances sliding through Saturday afternoon with upper level
northwest flow persisting thereafter. Model solutions do diverge a
bit Sunday, with the 29.00Z ECMWF bringing a weak surface low and a
few showers through on Sunday, while the 29.12Z GFS keeps the area
dry. The GFS then spins up a relatively strong surface low pressure
system in the Dakotas and moves it and most of the precipitation
just north of the forecast area, but the associated cold front does
slide through on Monday, which could bring some showers once again.
Following these precip chances, models are in good agreement of an
upper level trough sagging through the region. A short wave then
slides through the trough giving yet another chance for precip
Tuesday afternoon/evening, with very cool air moving in along with
the precip. 850 mb temperatures are progged to be in the 5-6 C range
by Tuesday evening, with high temperatures generally in the 60s by
the middle of next week.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 605 PM CDT Tue Aug 29 2017
The main concern during this forecast is whether/how much fog will
develop overnight. Looking at the latest data sets, it does not
appear to be a given that fog will be widespread overnight. The
forecast soundings from all models except the 29.21Z RAP keep some
clouds around through the night, especially under the area of
higher moisture levels where the clouds have been slow to
dissipate today. So despite the low level ridge axis overhead,
areas along and east of the Mississippi River may not totally
clear out. Also, there is concern whether or for how long
saturation will occur at the surface. Again, the RAP is the most
aggressive with this, but it also had clear skies for both sites
by late afternoon, which will not verify. The 29.18Z NAM shows a
very short period of saturation for KLSE but not at KRST. Given
these uncertainties, will maintain KLSE going down to IFR in some
fog, but shorten up the time frame a little bit from the previous
forecast and only show a short period of MVFR visibilities at
KRST. Once the fog dissipates Wednesday morning, VFR conditions
for the rest of the day but look for some diurnal afternoon
cumulus ahead of an approaching cold front for both sites.
Area Forecast Discussion
National Weather Service Gray ME
1156 PM EDT Tue Aug 29 2017
High pressure will remain over the region tonight through
Wednesday while an ocean storm passes well to our south. A cold
front will move southeast through the region Thursday, and
provide a chance of showers, especially in the mountains. Much
cooler Canadian high pressure builds into the region behind the
front Friday and Saturday. Low pressure may affect the region
Sunday before moving out to the east Monday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1155 PM...For this ESTF update I made adjustments to near term
grids to reflect satellite trends as well as the 03z mesonet.
910 PM Update...
Made a few changes to include slight chance and a small area of
chance PoPs over southern NH and parts of SW coastal ME
overnight as the cyclone moves northeast overnight. It is
currently off the Virginia coast and will move northeast,
staying south of Cape Cod as it does so. This will only bring
northern New England a glancing blow through daylight...with
perhaps a hundredths or two of rain falling. Other parameters
were adjusted including temperatures, sky cover, and weather to
include more fog across the valleys.
615 PM Update...
Minor changes to the forecast for sky cover and temperatures.
Rain is impacting Long Island as well as CT and RI at this time.
Keeping most PoPs to our south as this system brushes NH and ME
tonight. HRRR brings some tendrils of convection up in the 2-5
AM time frame and will watch this evolution for a couple hours
before changing the current forecast.
High clouds have overspread southern areas due to the ocean
storm moving east off the Carolina coast. We will remain on the
northern fringe of the storm system tonight with only mid/high
clouds to affect the area. The northern edge of the precipitation
will remain south of the area but can`t rule out a few sprinkles
near the the south or southeast New Hampshire after midnight.
Due to the cloud cover over southern areas temps will not be as
cool and also no valley fog should develop in the CT river
valley as it had the last several nights. Over northern areas
where only a thin high cloud cover, temps will be allowed to
radiate so another cool night expected with readings in the 40s.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
The ocean storm races to the east well south and east of our
area Wednesday so clouds will gradually clear from west to east
during the day as high pressure builds in from the west. The
ridge of high pressure crests over the region Wed night allowing
a mostly clear and calm night with radiational cooling so
another cool night expected. Some fog along the CT river valley
may once again form after midnight. Used a blend of guidance for
temps which were all in general agreement.
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
A cold front will pass through the region Thursday. Which the
front will be pretty strong, it will be very moisture starved.
Therefore we only expect scattered showers, mainly in the
mountains. What this front will do, however, is usher in
anomalously cool air for this time of year. By 12z Friday, 850mb
temps in the northern and central zones should fall to around
0c. This could mean the first few snowflakes of the season for
the summit of Mount Washington if enough upslope moisture can be
squeezed out Friday morning in an otherwise drying air mass.
Friday will be be a breezy, if not windy day across the CWA with
temperatures only in the 50s and 60s. SFC high pressure builds
in Friday night and should allow for good radiational cooling.
As long as it is clear and calm we expect several locations to
see lows in the 30s. Some frost will be possible across our
northwestern zones, if it doesn`t fog in first. Saturday should
be a great day, but the models continue with fairly good run to
run consistency on bringing rain on Sunday with a short wave
trough, possibly infused with moisture from whatever is left
over from Harvey.
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR through Wed night. LIFR conditions possible
Wed night from 06z-12z in any CT river valley fog.
Long Term...A brief period of MVFR possible Thu with showers
associated with cold front. VFR with gusty NW winds Friday. VFR
and light winds Saturday. Lower conditions likely sunday in
Short Term...A SCA for hazardous seas over the outer waters will
be needed from Wed into Thu due to some higher swells arriving that
were generated well offshore from the ocean storm passing well
to our south.
Long Term...SCA seas will subside later Thursday. However, SCA
winds from the northwest in the wake of a cold front are likely
MARINE...Small Craft Advisory for hazardous seas from 5 PM Wednesday to
2 PM EDT Thursday for ANZ150-152.
Small Craft Advisory for hazardous seas from 8 AM Wednesday to
8 PM EDT Thursday for ANZ154.
Area Forecast Discussion
National Weather Service Lincoln IL
908 PM CDT Tue Aug 29 2017
Issued at 908 PM CDT Tue Aug 29 2017
Weak low pressure just east of Illinois has kept some spotty
clouds still lingering across eastern Illinois. Most areas are
clear, with light northerly winds, due to high pressure centered
in western Ontario Canada and extending south through Iowa and
NW Illinois. We expect another night of fog formation, especially
across our northern counties, closer to the surface ridge axis.
The airmass has not changed appreciably since last night, and we
had plenty of dense fog form. There are indications the fog may
not be as bad and widespread as last night, but have added Areas
of Fog to our northern and western counties for now. Patchy fog
was left in place for the remainder of our forecast area. The HRRR
still shows expanding dense fog from the north into PIA, BMI, and
as far south as Lincoln later tonight. Can`t rule out the possible
need for another Dense Fog Advisory after 2 am.
Low temps look to settle out in the upper 50s to low 60s, and
current dewpoints are in the low to mid 60s, so low level
saturation looks likely.
Updated forecast info is already available.
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 249 PM CDT Tue Aug 29 2017
Still in wrap around flow on back side of system, so diurnal cu
and showers have developed across the region. The best chances of
isolated/scattered showers will be along and east of I-57 through
For tonight, mostly clear skies with light north winds. Still
plenty of low level moisture, especially for western half of
forecast area, so kept mention of patchy fog in after 06z Wed.
Lows tonight will be in the upper 50s to low 60s.
On Wednesday, surface ridge builds in with scattered diurnal cu.
With northerly flow, highs will only be in the upper 70s to low
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 249 PM CDT Tue Aug 29 2017
By Wednesday night, remnants of Harvey to be making their way
northeast towards Ohio Valley. In the meantime, a northern stream
shortwave to slide southeast through forecast area undercutting
surface ridge. Not a lot of moisture to deal with so just have
slight chance pops for areas along and north of I-36 Thursday
Beyond that, low level moisture will be on the increase from the
south as remnant low moves into western TN by 12z Friday.
Southeastern portions of forecast area to get clipped by showers
and some thunderstorms beginning around daybreak on Friday and
persist through Saturday. By Saturday night, remnants of Harvey to
get picked up by northern stream shortwave and quickly lift out to
northeastern US, so dry conditions expected through Labor Day.
Next chance for rain will begin Monday night as decent cold front
As for temps, to cool down into 70s on Friday, but then warm back
up a bit, into the 80s for the rest of the forecast period.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM CDT Tue Aug 29 2017
Showers that were affecting NE Illinois later this afternoon have
mostly dissipated as the outflow boundary has reached our N-NE
counties. That trend should continue as the boundary layer
stabilizes with the approach of sunset. Therefore, will not
include any mention of precip for CMI/BMI/PIA.
The main concern for this TAF period will be potential for dense
fog again later tonight. HRRR is depicting an expanding area of
VLIFR conditions from the north, affecting PIA and BMI primarily,
but coming close to SPI. Forecast soundings from GFS/NAM show the
potential for fog for at least our northern terminals, including
at CMI. Have included prevailing fog later tonight, with LIFR fog
at PIA, VLIFR fog at BMI, IFR at CMI, and MVFR at SPI and DEC.
Due to the position of the surface ridge axis nearly across
central Illinois, and little airmass change today, feeling fog
potential is looking good at this point.
The fog should dissipate by 15z tomorrow morning, with scattered
strato-cu during the day on Wednesday.
Winds will remain light, primarily from the north-northeast
throughout this TAF period.
Area Forecast Discussion
National Weather Service Jacksonville FL
911 PM EDT Tue Aug 29 2017
.UPDATE...Evening showers with very infrequent rumbles of thunder lifting
NE across Florida will be briefly enhanced as the east coast sea breeze
enhances lift as it presses westward near Highway 301 this hour. Rainfall
will be generally light to moderate with storm total amounts of generally
0.1 to 0.25 inches, however localized amounts of 1-1.5 inches will be
possible in training and slow moving cells which could cause some
minor temporary flooding issues. Convection will gradually lift
northward as a trough axis between PTC#10 and TS Harvey gradually
lifts northward across NE FL and then across SE GA through the
pre-dawn hours. After midnight a low chance of rainfall will
continue mainly north of the I-10 corridor, with an increase in
precip through sunrise possible along the SE GA coast where
convergence along the trough axis will be strongest. Cloudy skies
will become partly cloudy south of I-10 where recent ground
moisture and very light winds could support some low stratus and
patchy fog development.
Minimum temperatures will trend warmer tonight with lows in the
low/mid 70s inland to upper 70s coast.
.AVIATION...MVFR cigs and light/moderate showers will be possible
through about 03Z across NE FL, then after midnight near SSI. Recent
HRRR and SREF guidance suggested an increased chance of prevailing
IFR ceilings impacting GNV after 03Z with recent obs at the
terminal SCT008. Best chances of rainfall Wed will focus near SSI,
JAX, CRG and VQQ where VCSH was advertised by afternoon. Winds
will become very light onshore along the coast tonight, calm
inland with sea breeze dominant circulations by mid afternoon Wed.
.MARINE...Winds will veer ESE through the night as trough axis
lifts northward over the waters. Sustained winds 10 kts or less
will prevail after midnight with combined seas 3 ft or less.
Rip Currents: Moderate risk expected Wednesday.
.PRELIMINARY POINT TEMPS/POPS...
AMG 72 89 73 93 / 20 60 20 30
SSI 77 85 78 89 / 20 60 20 30
JAX 75 89 75 92 / 40 60 10 40
SGJ 75 88 76 91 / 40 40 10 30
GNV 72 92 73 93 / 40 50 10 30
OCF 73 92 74 94 / 30 30 10 30
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
717 PM PDT Tue Aug 29 2017
A fair amount of lightning has occurred in the red flag warning
area this afternoon and early evening. Very little rainfall was
occurring with the storms as they moved to the northeast around
20-25 mph. In addition, outflow wind gusts in the 35-45 mph
range have been observed. Latest radar trends show an overall
decrease in coverage since 6 pm although additional lightning is
expected overnight into Wednesday. For this evening, isolated-
scattered thunderstorms will continue to affect the Basin and
Range from Mineral County to Pershing and Churchill Counties as
well as near the Oregon border. Elsewhere including fire zones 278
and 273, lightning will be more limited as drier air has pushed
storms east for now. We will leave the warnings out and monitor
trends / new data this evening in order to determine if any areas
can be cleared. Hohmann
.PREVIOUS DISCUSSION... /Issued 143 PM PDT Tue Aug 29 2017/
Thunderstorms are possible this evening through Wednesday for
much of western Nevada and far eastern California, with a threat
for dry thunderstorms and fire starts, especially north of
Interstate 80 tonight and Wednesday morning. Very warm afternoon
temperatures will prevail for the upcoming week, with the best
chance for record highs during the Labor Day Weekend.
An upper level trough will provide chances for fast moving
thunderstorms this afternoon and evening. Steering flow winds over
30 knots and dry lower levels will combine to enhance the threat
for dry lightning strikes from these storms. As such, Red Flag
Warnings remain in effect for portions of western Nevada tonight
and again on Wednesday afternoon. Refer to the fire weather
discussion below for additional details. Overall, the main threats
with these storms will be new fire starts from dry lightning
strikes and gusty outflow winds of 40-50 mph.
Storms could continue overnight and persist into Wednesday as
dynamic forcing from a jet streak aloft helps keep convection
building, particularly across northern Washoe and Pershing
counties. Drier air will also filter in behind the jet axis so the
best potential for additional showers and storm will be across
Pershing, Churchill, and Mineral counties Wednesday afternoon.
Storm motions will remain swift with these storms Wednesday
afternoon so the threat for new fire starts from dry storms will
remain. These storms will dissipate overnight as deeper layer dry
air works its way across the region. Conditions will remain dry on
Thursday as an upper level ridge begins to build across the
region. Highs will remain above average with mid 90s across
western Nevada and mid to upper 80s for Sierra valleys. Fuentes
LONG TERM...Friday into next week...
The main concern over the upcoming Labor Day weekend will be
unseasonable heat with record high temperature likely and a
couple monthly records for September possible. The peak heating
days look to be Saturday and Sunday, but highs will remain hot
into next week with upper 90s to triple digits still possible
across western Nevada along with upper 80s for Sierra valleys. If
you have outdoor plans over the holiday weekend keep heat related
impacts in mind particularly for any strenuous activity.
The upper level ridge will slowly drift eastward and will allow
some moisture to return along the western periphery of the ridge
by next week Monday. This will provide the next round of showers
and thunderstorms to the Sierra, with chances expanding eastward
as the high pressure ridge moves off to the east. Fuentes
An upper low will provide generally less than a 10% chances for
thunderstorms for KRNO, KCXP, KTRK, KTVL through this evening.
Better chances are expected farther south and east for KMMH,
KNFL, KLOL where thunderstorms chances will be in the 25-30% range
through Wednesday afternoon. Thunderstorms will be fast moving so
the main threat will be lightning strikes and gusty outflow winds
of 40-45 kts possible near any storms. Fuentes
The forecast remains on track with a jet streak nosing into the
region this afternoon and tonight. Early afternoon convection
remains predominantly virga showers, but as of 1pm thunderstorms are
beginning to develop over Mono and Pershing Counties. Expect this
coverage to expand as surface instability increases and as
convergence increases along the afternoon zephyr. Storm motions will
increase upwards of 30 kts as the jet increases flow aloft later
today into the overnight hours. With these cell motions, storms will
become increasingly drier as the night progresses.
Global models and HRRR still favor another period of thunderstorms
overnight with GFS being the most consistent model and having the
highest extent of thunderstorm coverage. This somewhat matches the
conceptual model of added forcing along and ahead of an approaching
jet streak. However, models are not overly bullish on thunderstorm
formation in the favored jet quadrant over eastern Lassen County and
northern Washoe/Eastern Modoc counties. We`ll keep the forecast
angled more towards the conceptual model expecting thunderstorms
from eastern Lassen arcing through northern Washoe/eastern Modoc
counties into the Basin and Range into Mono County. Westerly flow
should be strong enough to keep thunderstorm development along and
east of the Pine Nuts/Virginia ranges.
The bottom line is that there will likely be isolated to scattered
coverage of dry lightning overnight mainly north of Interstate 80
for northern Washoe, eastern Lassen/Modoc counties, and north of
Highway 50 in the Basin and Range. Drier variety thunderstorms
continue in the Basin and Range Wednesday.
The final concern will be slightly elevated wind speeds for northern
Washoe and eastern Lassen/Modoc counties Wednesday afternoon as a
trough swings through. Valley wind speeds will be marginal, but
upper mid slopes and ridges will possibly see a period of critical
fire weather conditions. Any new fire starts will likely be carried
easily in the slightly breezier than average conditions. Otherwise,
winds drop off Thursday as the ridge begins to build back into the
region. High temperatures will increase back towards record highs
and the 100 degree mark by the end of the week into the weekend.
NV...Red Flag Warning until noon PDT Wednesday NVZ458.
Red Flag Warning until 11 PM PDT this evening NVZ459.
Red Flag Warning until 8 PM PDT Wednesday NVZ453.
CA...Red Flag Warning until noon PDT Wednesday CAZ270-278.
Red Flag Warning until 11 PM PDT this evening CAZ273.
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