Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/25/18
Area Forecast Discussion
National Weather Service Boise ID
826 PM MDT Fri Aug 24 2018
.DISCUSSION...Smoke has decreased and visibility improved as far
south and east as Missoula/MT to Boise to Burns/OR, about as
forecast by HRRR smoke model, although a little later than that
forecast. Further improvement is indicated this evening as far
south as Sun Valley to Rome/OR, but south of there the smoke will
continue. Smoke is forecast to return north Saturday to all but
our northernmost counties, but then retreat south again to at
least the Snake River Saturday evening and possibly even farther
Upper trough over our area will be reinforced Saturday and again
Sunday, each surge bringing cooler air into our area. Monday should
be our coolest day since at least July 3. No updates for now.
.AVIATION...Tonight and Saturday south of a KBNO-KSNT line layers of
wildfire smoke aloft and local MVFR/IFR visibilities at the surface
along the ID-NV border and in the KTWF area. Mainly VFR elsewhere.
Surface winds variable 10 kts or less through Saturday morning
becoming west 10-15 kts Saturday afternoon. Winds aloft near 10k
feet MSL west 15-25 kts.
Sunday outlook...Mainly VFR. Areas of wildfire smoke. Breezy west to
northwest winds in the afternoon. Slight chance of showers over the
mountains of Baker County Oregon and west central Idaho Sunday
SHORT TERM...Tonight through Sunday...Early afternoon satellite
pics showing the back edge of thicker smoke extending from
central Harney county into Valley county. Do expect areas east of
this line to see visibility improve through the evening as
northwest winds and mixing help to thin out smoke near the
surface. However, skies will not completely clear as southwest
winds aloft continue to favor smoke transport from CA/OR fires
into far southeast Oregon and southwest Idaho. Dry and seasonable
conditions persist on Saturday as a trough axis remains positioned
west of the area, keeping the area under southwest flow. A couple
of smaller short waves will cross the region late Sat/Sun,
increasing clouds and bring a slight chance of showers to the
mountains of Baker county and the west-central Idaho Sunday
afternoon. Elsewhere, conditions remain dry, with passage of the
upper trough bringing breezy and cooler conditions for Sunday.
LONG TERM...Sunday night through Friday...Upper level trough
remains in place through the extended period with reinforcing
waves moving through the region. The best chance for any
precipitation looks to be late Sunday into Monday for areas near
and north of a line Baker City to Stanley. Breezy conditions are
also expected with the passing shortwaves. Next deeper trough will
arrive late next week, though the timing on this varies quite a
bit among the models and thus confidence remains low. Temperatures
will remain mild and below normal.
Area Forecast Discussion
National Weather Service Columbia SC
740 PM EDT Fri Aug 24 2018
High pressure centered near the mid-Atlantic Coast will be
shifting farther off the coast over the weekend. Moisture will
gradually increase over the weekend into next week in an onshore
flow circulating around the high. Near normal temperatures will
increase slightly next week as an upper ridge builds over the
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Dry high pressure will ridge into the forecast area from the
north and northeast through tonight. The dry air mass
associated with the ridge will bring low humidities and
slightly below normal temperatures. The temperature guidance was
consistent. Expect lows tonight in the lower and middle 60s. The
NAM and GFS MOS support winds northeast about 10 mph diminishing
to 5 mph or less this evening.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Upper trough northwest of the region will lift northeastward
through Saturday. Upper ridging across the southeast will
remain, although there may be a slight weakness across the area
Saturday night into Sunday. At the surface, high pressure should
remain through the weekend, with main surface front still south
of the cwa. High pressure should still remain strong enough over
the area Saturday though to keep conditions dry and
temperatures below normal. Saturday night will remain dry and
cooler than normal. For Sunday, a return flow may begin to bring
moisture back into the area, along with the possibility of
isolated showers/storms across the southeastern cwa.
Temperatures will begin to warm back up to near normal for
.LONG TERM /MONDAY THROUGH FRIDAY/...
Through the week, upper ridging still expected to remain over
the Southeastern States, with a flat upper flow pattern off to
the north. May be a slight weakening again late in the week as
another shortwave trough moves north of the region. For the most
part, surface high pressure will remain centered over the
western Atlantic for much of the week. This will allow for a
continued southerly return flow of moisture back into the
forecast area. It will also result in a slight increase in
isolated to scattered afternoon and evening convection from
Tuesday onward. Temperatures will climb back to being slightly
above normal, with highs back in the lower and middle 90s and
lows in the lower and middle 70s next week.
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions generally expected through the 24-hr TAF period.
High pressure over the Mid Atlantic states extending into the
area with weak trough offshore. The pressure ridge will be
shifting more offshore during the period. Air mass remains dry
this evening. Some thin high clouds mainly to the west
overnight. The low level east flow will increase a bit toward
morning in the CSRA which may result in an increase in low-level
moisture. The latest Lamp guidance and HRRR still indicate low
threat for fog. Stratus possible in the CSRA with increase low-
level jet toward morning. Will continue forecast for scattered
low-clouds near AGS/DNL otherwise mainly clear overnight.
Scattered cumulus during Saturday afternoon with continued
northeast winds 5 to 10 knots.
EXTENDED AVIATION OUTLOOK...
There will be an onshore flow circulating around offshore high
pressure. Low-level moisture associated with this pattern
combined with nocturnal cooling may result in areas of stratus
and fog during the early morning hours. Upper ridging will limit
the thunderstorm chance.
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1056 PM CDT Fri Aug 24 2018
Issued at 417 PM CDT FRI AUG 24 2018
Tonight`s forecast challenge will be the potential for severe
thunderstorms developing this evening across north central and
northeastern portions of the CWA. Latest convection allowing
models can`t come to agreement on if convection will develop
tonight.There are a few severe parameters coming together after
sunset tonight; southwest low level jet of 45kts redevelops,
plenty of instability with MUCAPE values 2500-3500 J/Kg, and a
weak boundary setting up over the Iowa/Missouri state line. On the
other side of the coin, the strongest upper level support will
remain in Iowa and combined with a decent cap (temp 10c at 700MB)
across Missouri, the threat of severe thunderstorms remains in
question. While the HRRR is not at all impressed with the
possibility of severe weather, the Nested NAM is all in on strong
thunderstorms developing along a weak boundary along the
Iowa/Missouri boarder and then pushing southward into Missouri.
Have opted to go with a compromise. After 02Z, expect
thunderstorms to develop along the state line and march southward
into north central and northwest Missouri. While widespread severe
weather is not expected, isolated severe thunderstorms are still
possible. Additionally, PWAT values will be 2+ inches, which will
provide heavy rainfall in some areas. All convection will weaken
and eventually dissipate through the evening as the line
approaches I-70. Lastly, patchy fog is expected to develop just
before sunrise in low lying area over the northern 1/4 of the CWA.
This weekend, brutal August heat will return. Expect above normal
temperatures with highs in the mid-upper 90s and humid conditions
to produce heat indices approaching 105F. With that said, a Heat
Advisory has been issued for the Kansas City Metro area for
tomorrow and Sunday.Take extra precautions, if you work or spend
time outside this weekend. If possible, reschedule strenuous
activities to early morning or evening.
By late Sunday into Monday morning, a short wave will provide a
slight chance of precipitation for the extreme northwestern
counties in the CWA, but the next decent chance of
showers/thunderstorms should arrive Tuesday into Wednesday as weak
cool front will struggle to push through Missouri.
.Aviation...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1056 PM CDT FRI AUG 24 2018
VFR conditions will persist through the forecast period, except in
low-lying areas across northwest Missouri where some patchy fog
may develop Saturday morning. Otherwise, skies will be mainly
clear and winds will remain out of the southwest.
KS...Heat Advisory from 11 AM Saturday to 7 PM CDT Sunday for
MO...Heat Advisory from 11 AM Saturday to 7 PM CDT Sunday for MOZ020-
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
256 PM PDT Fri Aug 24 2018
.SYNOPSIS...Seasonable temperatures will continue through early
next week as a series of upper-level troughs impact the West Coast.
Smoke will continue to linger around the area through tonight.
.DISCUSSION...Northerly winds will continue to increase through
tonight across the coastal waters. In response to the winds,
coastal stratus has become nearly eradicated along most of the
northwestern California coast. The lone area still lingering is
south of Cape Mendocino.
Smoke from wildfires in southern Oregon is observed in visible
satellite imagery moving southward down the coast, so introduced
this area into the forecast. Additionally, areas of smoke continue
to linger around the forecast area this afternoon. HRRR smoke
guidance shows the smoke moving out of the forecast area tonight.
Otherwise, seasonable, to slightly below normal, temperatures
will continue as a series of upper-level troughs continue to
impact the West Coast. A more potent upper-level trough digging
through the area towards the end of the work week will bring
small chance of rain, but confidence is low.
.AVIATION...The marine layer remained manifested along the North
Coast into afternoon. A "weakish" frontal/trof boundary pushed
across the area today and mostly cleared out much of the expansive
stratus field, allowing clouds to scatter out at CEC by late
morning. Elsewhere, a substantial amount of low clouds continued
over the inner coastal waters. At 1 Pm, ACV ascended from IFR to
MVFR by reporting CIG010 even as VIS Satellite showed BINOVC in
the stratus deck. Satellite and webcam indicators keep scattering
and partial clearing on track through mid-late afternoon at ACV
with low clouds expected to return overnight. Guidance has CEC in
sort of a mixed bag overnight although the patchy cloudy solution
seems more probable at this writing time.
Interior areas: Tops of the marine layer was a tad bit lower this
morning. Therefore, morning IFR low clouds at UKI were the result of
light southerly flow advected from the south. Elsewhere, smoke (FU)
and haze (HZ) from various wildfires continued. /ta
.MARINE...Northerly winds will continue to increase through
tonight. A Small Craft Advisory remains in effect for the outer
waters through Monday afternoon, with Small Craft Advisories
coming into effect this evening across the inner waters. Localized
near gale force gusts are expected near and downwind of Point
Saint George and Cape Mendocino tonight, but the area is too small
in coverage for any additional products at this time. Seas will
begin to trend down early next week as the northerly winds begin
to wane Monday.
.FIRE WEATHER...A brief period of gusty northeast winds will be
possible late tonight over the ridge tops of interior Del Norte
County as a weak upper-level trough passing through the area.
Otherwise, onshore flow will yield normal to slightly below normal
temperatures area-wide for much of the next week.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 6
PM this evening to 6 PM PDT Saturday for PZZ450-455.
Small Craft Advisory until 3 PM PDT Monday for PZZ470-475.
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Area Forecast Discussion
National Weather Service Grand Rapids MI
1158 PM EDT Fri Aug 24 2018
Issued at 257 PM EDT Fri Aug 24 2018
Unsettled and changing weather conditions will continue over the
area through the weekend and into early next week. A round of
light rain/showers over mainly the northern parts of the area
early this evening will move out of the area. More widespread rain
with some embedded thunderstorms move in after midnight tonight.
Showers and low clouds will linger through midday Saturday before
increasing sunshine in the afternoon. For Sunday, a hot and sunny
day is on track with good chances of thunderstorms developing in
the afternoon with more widespread rain possibly continuing
through the Sunday night timeframe. The first half of next week
continues with periodic rain chances each day.
Issued at 822 PM EDT Fri Aug 24 2018
Little question a line of thunderstorms will cross our area during
the pre-dawn hours of Saturday. I increased the risk for
thunderstorms from chance to likely for the storms before sunrise.
We have the right entrance region of upper jet around the closed
upper low helping the cause of deep layered lift. Precipitable
water values rise to near 2.00 inches and we are on the nose of
the 1000/850 moisture transport vectors. The most unstable cape
rises to between 1000 and 1500 j/kg south of I-96 during this
time. Numerous runs of the HRRR and RAP model continue to show
this line of storms in the 4 am to 6 am time frame. So in
increased the risk for thunderstorms overnight. The previous
shift already had 100% chance of rain, so not much change there. I
don`t believe the storms will be anything close to severe but we
more than likely will see rainfall rates over over 4" per hour for
at least a short time in many areas south of I-96.
.SHORT TERM...(This evening through Sunday night)
Issued at 257 PM EDT Fri Aug 24 2018
Another weak upper low moving through the high plains will keep
our weather unsettled for the next few days. A first round of
showers trying to cross the lake this afternoon is encountering
very dry in-place air. As a result, precip is having a hard time
reaching the ground so far in many areas. Even though this first
round of rain will not be too significant, it will help set the
stage for another more widespread round of rain overnight tonight
as the upper low itself moves through to our north. Rainfall
amounts around a half inch are likely across most of the area by
the time things taper off Saturday morning.
With continuing warm and moist air advection Saturday, along with
building high pressure behind the departing low, clouds will be
slow to diminish tomorrow morning, but eventually the sun should
break out and some storms are possible by tomorrow afternoon
mainly east of I-69.
For Sunday, plenty of sunshine to start the day will take
advantage of the warmer airmass to send temperatures into the
upper 80s at most locations. With upper level high pressure well
to our south, the capping inversion likely won`t be strong enough
to hold off convection, so there could be some strong diurnal
thunderstorms that develop Sunday afternoon. Another threat from
the high pressure being fairly far away will be the threat of
overnight MCS development moving into our area Sunday night into
Monday morning. This will be monitored closely over the next 24-36
.LONG TERM...(Monday through Friday)
Issued at 257 PM EDT Fri Aug 24 2018
Unsettled weather stays in the area for next week as fairly zonal
flow will allow numerous embedded shortwaves to move through the
Great Lakes. Depending on the exact timing of these shortwaves, we
could see storms fire off nearly any day. This far in advance, it
is still too uncertain to say with confidence whether any of these
shortwaves will come through at the right time to take advantage
of diurnal heating. Temperature for the first half of the week
will be above-average in the 80s, but should begin to moderate
back to the high 70s for the latter half of the week.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1130 PM EDT Fri Aug 24 2018
Mainly VFR conditions with isolated MVFR/IFR will gradually
deteriorate to MVFR and eventually IFR during the early to mid
morning hours Saturday as lower clouds and rain and thunderstorms
move in from the west. Thunderstorms will gradually exit from west
to east mid to late Saturday morning but conditions will remain
IFR due to lingering low clouds.
Conditions will only slowly improve to predominantly MVFR
Saturday afternoon and evening. A few showers may linger and also
redevelop into Saturday afternoon and evening with an isolated
storm also possible. However there is not enough potential to
warrant mention of those in any of the terminal fcsts at this time
from Saturday afternoon through the evening.
Issued at 257 PM EDT Fri Aug 24 2018
South winds of 15 to 25 knots are creating hazardous conditions
for small craft and swimmers from Holland to Manistee today. Waves
in the 5 to 8 ft range can be expected to slowly diminish after
midnight tonight. These general conditions are expected to only
slowly improve through Saturday afternoon as the winds swing
around to the southwest during the day. At this time it does look
like the winds will remain strong enough to warrant adding in the
remainder of the zones to the small craft advisory for the
daytime tomorrow. By Saturday evening, winds across the area will
drop off significantly, but a renewed push of southwest winds on
Sunday afternoon/evening could cause conditions to again approach
Issued at 257 PM EDT Fri Aug 24 2018
River levels are running around normal for this time of the year,
with no flooding into next week. Rain is expected this afternoon and
evening with another round overnight. Rainfall of up to around a
half inch is possible. Additional rainfall is possible on and off
all of next week. Locally heavy rain is also possible, but flooding
should be limited or nonexistent.
MI...Beach Hazards Statement through Saturday afternoon for MIZ037-
LM...Small Craft Advisory until 5 PM EDT Saturday for LMZ844>849.
Area Forecast Discussion
National Weather Service Lincoln IL
838 PM CDT Fri Aug 24 2018
Issued at 838 PM CDT Fri Aug 24 2018
Minor updates made this evening to account for a slower
progression of thunderstorm chances into areas NW of I-55 through
midnight. Current storm development has been minimal in the region,
although a supercell in north-central IA could be the start of an
MCS forecast by various hi-res models in the eastern half of IA,
set to propagate into central IL in the late evening and overnight
hours. Last few HRRR runs have featured the closest resemblance
to current thunderstorm activity, yet fail to develop any strong
organized MCS and simply move some scattered weaker thunderstorms
into central IL overnight and southeast IL Saturday morning.
Meanwhile, the 18Z NAM nest propagates a strong MCS into western
IL by midnight, although it appears this will be at least
delayed. As far as severe storm potential, an axis of strong
surface based instability is currently analyzed from south-
central into north-central IA, forecast to weaken and advect
eastward while becoming elevated overnight. This, along with 40-50
kt sfc- 6km bulk shear would favor a hail threat for areas west
of I-57, but have minimal wind threat. SPC continues a marginal
risk of severe storms in this area. The severe weather threat will
lessen with eastward extent across central IL as the upper level
trough pushes eastward into a less unstable region, cooled by
extensive cloud cover in an overall cooler air mass. Current
temperatures are already in the mid to upper 60s, but don`t expect
any further cooling as 10-20 mph of south wind and low cloud cover
continue in most areas.
.SHORT TERM...(This evening through Saturday)
ISSUED AT 324 PM CDT Fri Aug 24 2018
Vigorous upper low noted on 20z/3pm water vapor imagery over
Minnesota will be the main weather-maker across central Illinois
over the next 12-24 hours. A surface trough associated with this
feature will interact with a destabilizing airmass to trigger
scattered thunderstorms across central/eastern Iowa this
evening. Latest upstream satellite/radar mosaic is mostly dry
for the time being: however, mesoanalysis shows MLCAPEs of
1000-1500J/kg across central/western Iowa. All CAMs suggest this
will be the area for storm development over the next few hours,
with the storms tracking eastward into the Illinois River Valley
toward midnight...then across the remainder of the KILX CWA
overnight. Have adjusted PoPs to go with dry weather across much
of the area through the evening, with high chance to likely PoPs
along/west of the Illinois River by late evening. Have spread high
chance to likely PoPs across the remainder of the area overnight.
Will see some lingering showers/storms across the E/SE Saturday
morning, followed by dry conditions across the board by afternoon.
With rapidly rising upper heights and increasing amounts of
sunshine, high temperatures will range from the middle 80s near
the Indiana border...to the upper 80s and lower 90s further west.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 324 PM CDT Fri Aug 24 2018
Late summer heatwave will unfold early next week...with high
temperatures expected to top 90 degrees Sunday through Tuesday.
Thanks to the recent rainfall, surface dewpoints will hover in the
lower to middle 70s...producing maximum heat index values in the
100-105 degree range each afternoon. While these numbers are below
advisory criteria, may eventually need to issue a Heat Advisory
for much of the CWA...mainly due to the prolonged nature of the
heat. 12z Aug 24 models continue to show MCS activity along the
northern periphery of the building ridge Sunday night: however, it
appears this activity will remain north of central Illinois across
the Upper Midwest into the Great Lakes.
The next significant chance for rain will hold off until late
Tuesday into Wednesday as a short-wave trough begins to flatten
the prevailing ridge. Models are in fairly good agreement with
this process, with both the GFS and ECMWF suggesting rain chances
increasing across west-central Illinois as early as Tuesday...and
especially Tuesday night and Wednesday. After that, a cold front
will settle southward into the Ohio River Valley by
Thursday...shifting the best rain chances further south. After hot
temperatures in the lower 90s on Tuesday...readings will drop
into the lower to middle 80s behind the frontal boundary by
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Aug 24 2018
A period of thunderstorms is likely overnight as a line or cluster
of thunderstorms develops over southeast Iowa this evening and and
moves southeastward. Timing is still uncertain, but have VCTS
included in TAFs starting 04-07Z and ending 11-12Z, although this
timing may have to be adjusted later as thunderstorms develop and
start their movement. In advance of this feature, MVFR and some
IFR cigs are in place across the region, with some improvement
spreading from south to north. Behind the thunderstorms, a period
of MVFR cigs is possible especially along the I-74 corridor
terminals, gradually thinning in coverage and lifting in height
through the afternoon into the VFR category. Winds S 10-15 kts,
shifting to SW 10-15 kts around 12Z.
Area Forecast Discussion
National Weather Service Louisville KY
1026 PM EDT Fri Aug 24 2018
Issued at 1025 PM EDT Fri Aug 24 2018
Hi-res models are suggesting a little more coverage of showers
overnight. GFS and RAP time-height sections do show some lift in the
saturated mid-level air moving over us now, so have bumped up pops
for late tonight a little. Kept isolated thunder in the north, where
lift is a little more deep...closer to shortwave rotating around the
Midwest. Updated products out shortly.
.Short Term...(This evening through Saturday)
Issued at 350 PM EDT Fri Aug 24 2018
Weakening complex of showers continues to make slow eastward
progress through Indiana and western Kentucky this afternoon. This
low pressure system will continue to rotate eastward over the Upper
Midwest tonight. This afternoon, surface low pressure was analyzed
over western Minnesota with a surface high now over the Mid-Atlantic
coast. The main SW LLJ axis of warm, moist advection was over
Missouri and Illinois this afternoon, but PWATs over central KY and
southern Indiana will steadily increase overnight through Saturday
morning. The ongoing area of showers is expected to eventually
diminish over central KY by 00-03z this evening. Higher rainfall
amounts are still expected along and west of I-65.
Between 06-18z Sat, the 25-30 kt LLJ will take on more of a WSW
orientation across Indiana and northern Kentucky. Between 4-8 AM EDT
Saturday, scattered showers and thunderstorms developing upstream
are forecast to move over southern Indiana and north-central
Kentucky. Rain chances will be lower south of the Western
KY/Bluegrass Pkwy on Saturday, but isolated showers and storms will
still be possible throughout the first half of the day. We`ll see
improving conditions Saturday afternoon as the system pulls off to
the northeast. Until then, mostly cloudy skies are likely tonight
through Saturday morning. Highs on Saturday will reach the low to
.Long Term...(Saturday night through Friday)
Issued at 230 PM EDT Fri Aug 24 2018
By Saturday evening the upper level shortwave trough axis will be
just east of Central KY as it continues NE. But enough moisture and
instability remain for rain shower chances overnight Saturday and
throughout Sunday, mainly north of I64. SREF, GFS and CMC agree with
a wet Sunday. Can`t rule out a stray tstorm during this time frame
as sufficient CAPE and PWATs are accompanied by decent lapse rates.
No severe weather is expected, though a brief period of
isolated heavy rain can`t be ruled out.
By Monday, ridging stretching from coast to coast across the
southern U.S. will allow enough instability for our CWA to
experience diurnal chances of showers and tstorms through
Tuesday.Conditionally unstable lapse rates, moderate buoyancy and
ample moisture suggest some storms could produce heavy rain. Gusty
surface winds around 20kts possible with DCAPE values around 1000
J/kg and 20-25kts below 850mb.
Upstream, another trough over the northern Rockies will makes its
way towards our area. Any chances of organized convection will be
best with this feature on Wednesday and Thursday. GFS suggests
MUCAPE values of 2917 J/kg with PWATs of 1.81 inches. But with
little shear, expect more heavy rain than severe weather at this
As this trough exits, it will leave a weak boundary to our north
susceptible to shortwave propogation to our area on Friday. Another
chance of showers and tstorms possible then.
.Aviation...(00Z TAF Issuance)
Issued at 720 PM EDT Fri Aug 24 2018
Upper low over the upper Midwest earlier induced the system that is
bringing fading light rains to the region now. Those rains should
continue to dissipate, but a weak low-level jet will pick up over
our area, especially north of the Ohio. This should generate
additional showers around daybreak, perhaps also a rumble of
thunder. Best chances, prob30`s all, are in the I-64 corridor
terminals. Conditions should improve in the afternoon, with little
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
835 PM CDT Fri Aug 24 2018
835 PM CDT
A breezy, drizzly evening uncommon for August will continue, with
the likelihood of isolated to scattered showers and storms
overnight. The severe threat is fairly limited, though a couple
elevated hail-producing storms could develop in the CWA. Some
tweaks to timing and forecast coverage of thunderstorms were made,
to mainly slow down and shorten the duration, as well as ease the
This evening finds a surface warm front draped southward across
eastern Iowa and eastern Missouri, branching from a low in
southern Minnesota. Broad warm and moist advection is occurring
over and to the northeast of this feature, including isentropic
ascent in the lowest levels over the CWA resulting in stratus and
patches of drizzle. A more focused 25-30 kt low-level jet is
pointed into northwest Illinois per 00Z soundings and VWP data.
While the 00Z DVN sounding did show moistening and warming of the
layer below the elevated mixed layer (EML) since 18Z, there is
still appreciable CIN to be overcome, with most unstable parcel
CIN of over 100 J/kg. This will likely result in storm coverage
overnight being less than originally expected, and this is also
favored in the lack of a pronounced short wave feature and just
more of general height falls at our latitude. This still should
certainly be enough to spark some storms, and IR imagery indicates
accas clouds streaming over northwest Illinois. The HRRR has
supported isolated to scattered activity developing in or near
north central Illinois and developing east, as opposed to a more
solid convective area moving in from our west.
With the EML present within the hail growth zone and effective
shear in that layer of 40-50 kt, there is a conditional threat of
a couple elevated supercell storms that could becoming hailers.
The marginal risk from SPC for the IL CWA covers that well.
Otherwise, southerly winds will still show sporadic gusts to 25
mph at times through early overnight, and the combination of these
and the clouds will keep temperatures nearly steady the remainder
244 PM CDT
The main forecast highlights tonight focus around the potential
for a round of eastward moving scattered thunderstorms,
particularly from mid evening over north central IL through the
overnight hours across eastern IL and northwestern IN. The main
concern with these storms will be hail and heavy rain.
While some areas across eastern IL are experiencing some breaks
in the cloud cover at this time, it appears that low clouds will
shift back over the area late this afternoon and definitely for
tonight. Thunderstorms appear probable to develop to our west
across portions of IA late this afternoon into early this evening.
This will be in response to a mid-level impulse currently seen in
water vapor imagery shifting eastward into northern IA along the
southern periphery of the parent upper tough in place across the
Upper Midwest. The storms will then shift eastward into northern
IL during the mid to late evening hours, and into eastern IL and
northwest IN later this evening and overnight as this disturbance
and the associated lower-level moisture transport axis shifts into
Expect the possibility for some stronger storms with this
activity tonight, possibly even into the Chicago metro area. Very
steep mid-level lapse rates were sampled in the special 18z DVN
RAOB and this will likely aid in updraft intensity with these
elevated storms tonight. For this reason, hail (some possibly in
excess of 1" diameter) looks to be the primary severe concern
tonight. Heavy downpours are also likely with these storms, as
they are likely to be very efficient rainfall producers. The
storms will shift out of the entire area by daybreak Saturday,
though low clouds and possibly some fog look to linger into
241 PM CDT
Saturday through Friday...
Saturday will begin the significant warming trend with warm/humid
conditions which should persist through the middle of next week.
Some lingering showers and the possibility of some isolated thunder
should linger into Saturday, mainly for the far eastern portions of
the CWA as the upper level trough tracks east into the Central and
Eastern Great Lakes and sswly low level flow sets up persistent/deep
warm/moist advection. For Saturday, temperatures should rebound
into the middle 80s with dewpoints climbing into the low 70s. Have
generally trended to a dry forecast for the area on Saturday, with
the exception of some lingering sct shra/tsra over the far ern
portions of the CWA. However, there is the chance for some sct
shra/tsra through the diurnally favored hours given the increasing
heat and humidity, but weak upper ridging and an elevated warm layer
may inhibit convection. Sunday through Tuesday should be the
warmest days of the period with the highest dewpoints with periods
of dewpoints in the middle 70s. Heat Index values should reach or
slightly exceed 100 F during this period. There should also be
periodic chances for thunderstorms as a series of shortwaves ride
over the apex of the upper ridging. The greatest chance for more
widespread thunder should be Tuesday evening as a cold front crosses
the region. Following the frontal passage, in a cooler/drier air
mass associated with sfc high pressure will building in behind the
front keeping the region dry through at least Thursday.
For the 00Z TAFs...
633 pm...Forecast concerns include cigs through late Saturday
morning...winds this evening and thunderstorm potential late this
evening into early Saturday morning.
Cigs have been steadily lowering late this afternoon with ifr over
much of northwest IL. These ifr cigs will slowly spread across the
rest of the area this evening...aided by light rain/drizzle which
is now developing across parts of the area. This light precip may
continue through mid/late evening but confidence for its duration
is low. Cigs will remain ifr into Saturday morning...possibly
lowering to lifr west of ord/mdw. Cigs will then begin to lift
late Saturday morning and are expected to scatter by mid/late
Saturday afternoon. Ifr visibilities are possible with any showers
or drizzle this evening.
An upper wave is expected to allow scattered thunderstorms to
develop late this evening and overnight...possibly developing over
the terminals as trends currently show. Previous timing of 06z-
10z or so looks ok but as trends emerge may need to include tempo
thunder for the Chicago terminals. These storms may produce heavy
rain and low visibilities. Showers may lingering through sunrise
as the bulk of the thunder potential shifts east of the terminals.
Southerly winds are expected to remain gusty for much of this
evening with a slow diminishing trend. Gusts 20-25kts for the next
few hours are possible with gusts expected to diminish by the
early morning hours when directions will shift more to the south/
southwest. Winds will then shift more southwesterly later Saturday
morning with some gusts possible mid/late morning into early
afternoon. A lake breeze is possible near the shore Saturday
afternoon but is currently not expected to reach ord/mdw. cms
241 PM CDT
Low pressure deepening over the Upper Missouri Valley and high
pressure slowly sliding off the Mid-Atlantic coast is tightening the
pressure gradient over the lake, with 20-25 kt sustained winds and
30 kt gusts. The relatively stable boundary layer should help
prevent the stronger winds aloft from mixing down to the surface,
but occasional Gale Force gusts will be possible through the
remainder of this afternoon and into this evening. Some of the
larger/taller craft may experience Gale Force winds that may not mix
all the way down to the lake surface. Lighter south and southwest
winds will prevail over the weekend as the pressure gradient
relaxes. The next period of strong southwest winds up to 25-30 kt
looks to be Monday night and Tuesday ahead of a cold front. After an
extended period of SSW winds, a sharp shift back to N or NE for
later next week following the frontal passage.
IL...Beach Hazards Statement...ILZ006 until 1 AM Saturday.
LM...Small Craft Advisory...IL nearshore waters until 4 AM Saturday.
Gale Warning...LMZ777-LMZ779 until 9 PM Friday.
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Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
847 PM CDT Fri Aug 24 2018
Issued at 835 PM CDT Fri Aug 24 2018
A strong cap has really hampered any kind of convective
initiation so far this evening across southern Iowa. Upper-air
sounding out of KDVN at 0000 UTC showed a very distinct capping
inversion from 850 to 775 hPa. Given this strong capping across
eastern Iowa and central Illinois, have reduced PoPs into the
chance category. Any activity overnight that does develop
overnight in the presence of broad warm/moist advection would probably
would be very high-based showers/thunderstorms. If this type of
activity were to materialize, marginally severe hail would be a
possibility across portions of west-central Illinois and
.SHORT TERM... (Through Late Saturday Afternoon)
Issued at 335 PM CDT Fri Aug 24 2018
Primary concern for the short term is chance for severe
thunderstorms tonight. Short range guidance, particularly the RAP,
is showing increasing MU and 850mb computed CAPE this evening over
parts of northeast Missouri and west central Illinois. This
increasing instability coincides with the passage of a warm front
which is lifting through eastern Missouri into western Illinois, and
a strengthening low level jet over eastern Missouri and Illinois.
Additionally, an H5 shortwave currently over western Iowa will be
moving east toward the Mississippi River around the base of the
larger mid-upper level circulation centered over Minnesota. GFS,
NAM and RAP develop precipitation this evening over northern
Missouri or southern Iowa as the shortwave moves through and the low
level jet increases moisture convergence and isentropic lift.
However convection allowing models are inconclusive on areal
coverage and location of where the storms will develop. Have
generally followed the model consensus for PoPs tonight with
thunderstorms developing during the evening over northeast Missouri
and west central Illinois and moving southeast overnight. Looks
like instability will be maximized around 850mb and the 850mb
computed CAPE off the RAP is in excess of 2500 J/Kg over northeast
Missouri and west central Illinois. This combined with 30-40kt of 0-
6km shear will be enough to promote organized convection...possibly
rotating discrete storms or line segments with large hail. Not
sure what the wind threat will be as these storms will be elevated
at least initially.
Current thinking is that the storms will move southeast to near the
I-70 corridor before sunrise Saturday morning, and continue into far
southwest Illinois and possibly into parts of southeast Missouri
after sunrise. Storms should be weakening as they move southeast as
they move away from the strongest instability, and any line segments
will probably break up into individual cells as well. Expect any
lingering rain to e ending by late morning. Attention then turns to
the building heat. Southwest flow will bring increasing heat and
humidity to the mid Mississippi Valley on Saturday afternoon. 850mb
temperatures of 20-23C build across the region which mixes down to
low to mid 90s. With dew point temperatures pushing the low to mid
70s, heat index values will be in the 100-104 degree range. This
will be the first of a string of hot days...especially for the heat-
sensitive St. Louis Metro area. Therefore, have coordinated with
the long term forecaster for this afternoon and issued a heat
advisory for the STL Metro.
.LONG TERM... (Saturday Night through Next Friday)
Issued at 335 PM CDT Fri Aug 24 2018
The focus will be oppressive heat and humidity from Sunday through
Tuesday, turning to pops for the rest of the forecast period.
Sunday continues to look like the hottest day of the period as an
upper level ridge moves in from the south and south/southwesterly
surface flow near the surface advects warm, moist air into the CWA.
This will allow temperatures to surpass 90 degrees throughout the
forecast area. With dew points in the 70s, expect heat index values
to reach or exceed 100 in most areas, with the St. Louis Metro
seeing values approach 105. Dew points will back off slightly on
Monday, keeping heat index values just above 100.
Late Monday into Tuesday, the upper level ridge begins to push off
to the east ahead of an approaching trough. This will be associated
with an uptick in pops, mostly across the northwestern portion of
the CWA during the day on Tuesday. The ECMWF is a little faster and
bolder with its precip chances than the GFS, but have gone with a
blend between the two solution and kept lower pops for this time and
area. This will keep the extreme heat at bay over northeastern
portion of the CWA, but for the southeastern two-thirds of the CWA
that will not likely be impacted by rain and associated cloud cover,
heat index values will again rise to around 100. Due to heat index
values reaching 100 or higher Saturday-Tuesday for the St. Louis
Metro and surrounding counties, have gone with a heat advisory for
duration. This may need to be adjusted for intensity over the
Rain chances will increase across the CWA Tuesday evening and
overnight ahead of an approaching cold front. The front will slowly
move south through the CWA on Wednesday, and will mark the end of
the oppressive heat for the remainder of the period, as highs will
fail to get above 90. The front should clear the area Wednesday
evening, but stall and keep lower pops across the CWA for Thursday.
Westerly flow will settle in over the area for Friday, and guidance
has a shortwave embedded in this flow pass through the Midwest. The
GFS and ECMWF solutions differ in the strength and path of this
shortwave, but confidence in either solution this far out in the
period is low, so will stick with blended pops for now.
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 638 PM CDT Fri Aug 24 2018
Main concern for tonight will be on chances of thunderstorms and
low-level wind shear. Lots of uncertainty with respect to how
thunderstorms will develop and evolve overnight tonight. Will be
watching upstream across north-central Missouri and southern Iowa
the next few hours but current expectation is for scattered storms
to develop across this region over the next couple of hours and
head southeastward. Maintained VCTS groups at terminals for now,
starting first at KUIN late this evening, KCOU just after
midnight, and metro terminals around 3-4AM. Threat of storms
should move southeast of the terminals by late Saturday morning.
In addition to the possibility of thunderstorms, other concern is
for LLWS at KCOU/KSUS/KCPS as southerly winds lighten up at the
surface and winds around 1500 feet AGL increase to around 35 knots
out of the WSW.
SPECIFICS FOR KSTL:
Lots of uncertainty with respect to chances of storms affecting
the terminal late tonight. Maintained VCTS group from 0900 to 1400
UTC Saturday for now given uncertainty. Threat for storms should
shift southeast of KSTL by mid morning on Saturday with VFR
conditions and a light southwest wind for the remainder of the
valid TAF period.
MO...Heat Advisory from noon Saturday to 7 PM CDT Tuesday for
Jefferson MO-Lincoln MO-Saint Charles MO-Saint Louis City
MO-Saint Louis MO.
IL...Heat Advisory from noon Saturday to 7 PM CDT Tuesday for Calhoun
IL-Jersey IL-Madison IL-Monroe IL-Saint Clair IL.
Area Forecast Discussion
National Weather Service Medford OR
816 PM PDT Fri Aug 24 2018
No changes to the forecast tonight into tomorrow morning. The
fires remain very active over our region. The Klondike and Watson
Creek Fires developed pyrocumulus clouds this afternoon suggesting
they will remain very active into this weekend. In fact, some of
the smoke from the Klondike fire appears to have made it up to
around 600 to 500 mb as it moving with the 500 mb flow.
Anyways, overnight temperatures will trend cooler compared to
last night. Look for the marine layer to push in along the coast
and make it into the Willamettte valley tonight, but stay out of
the Umpqua valley. See the previous discussion below for more
information beyond tonight and early tomorrow.
.AVIATION...For the 24/18Z TAFs...Along the coast, conditions are
VFR this afternoon. Expect areas of MVFR/IFR cigs to develop this
evening into tonight. This will mainly affect areas from Cape Blanco
north. South of Cape Blanco, offshore NE winds should allow VFR to
prevail. Although, local IFR cigs are possible near KBOK late
tonight into Saturday morning.
Inland, across the Umpqua basin, expect VFR through the TAF period.
Elsewhere, inland, wildfire smoke will continue to produce periods
of MVFR visibilities.
.MARINE...Updated 200 PM PDT Friday 24 August 2018...A thermal
trough will strengthen along the coast this afternoon and evening
then remain in place this weekend. This will result in gusty north
winds and steep seas, especially for the waters from Cape Blanco
south. Additionally, a small area of gales is possible south of
Brookings between 5 and 20 nm from shore late this afternoon into
this evening. North of Cape Blanco, periods of steep seas and winds
gusting to small craft advisory levels are likely this evening and
tonight and again Saturday evening and night. On Sunday, expect seas
to become less steep north of Cape Blanco as winds lower slightly
and northwest fresh swell with a dominant period of around 9 seconds
builds into the waters. South of Cape Blanco, small craft advisory
level winds and seas will continue.
Monday, the thermal trough may strengthen again bringing small craft
advisory winds and seas to most the waters. Winds and seas are
expected to lower Tuesday into Wednesday.
.FIRE WEATHER...Updated 300 PM PDT Friday 24 August 2018...
Temperatures will remain moderate through the weekend, although
Saturday will be warmer and drier followed by a cooler Sunday.
Recoveries will be good, except for some moderate recoveries well
east of the Cascades. The northern portions of zones 615, 616, and
617 may see some light precipitation Saturday night into Sunday
night, but amounts will be very light in areas that get any
A digging trough over the Pacific Northwest will bring gusty
winds to the east side Sunday. This, combined with low relative
humidities, will bring conditions approaching, but not meeting,
Red Flag Warning criteria Sunday afternoon and evening. Modoc
county will see the worst conditions.
.PREV DISCUSSION... /Issued 301 PM PDT Fri Aug 24 2018/
DISCUSSION...A dry cold front moved through last night, and conditions
are cooler than yesterday at this time. Temperatures are about 10
degrees lower than yesterday, and these at or below normal
readings should stick around through Monday. The main impact to
the forecast area continues to be smoke. There has been notable
improvement in air quality across the forecast area, especially
north and west of Medford. The HRRR smoke model has been a little
optimistic in clearing out the smoke in valleys, and the new
Ramsey Fire is bringing new smoke into the Rogue Valley this
afternoon, so improvement has been slow to occur. The big question
is how much smoke will the Ramsey fire create this afternoon, and
where exactly will it go. Current indications are that heavy
smoke pushes south-southwest from the Ramsey fire into the Rogue
Valley this afternoon. Also, Brookings will see some smoke from
the Klondike fire the next several days because of the developing
thermal trough and northeast winds. Curry County has been added to
the DEQ`s Air Quality Advisory as a result.
Switching gears to other weather impacts, as pieces of energy rotate
from the northwest through the forecast area over the next week,
marine cloud duration and coverage at the coast and West Side will
ebb and flow. The clouds that pushed inland to the West Side this
morning will be less significant Saturday morning. Then, a potent
shortwave trough will push through Saturday night and should bring
in another push of marine layer clouds to the coast and West Side
into Sunday morning. Models suggest another push of marine clouds
Sunday night. Then, a warming trend is expected Monday and Tuesday
as the main upper trough pushes to the east and the area is subject
to southwesterly midlevel flow. Both the EC and GFS operational
models suggest showers are a possibility on Wednesday afternoon.
There is some instability as well, but since this is the first
synoptic model run that the GFS has featured negative Lifted Index
values, we haven`t added any thunderstorms to the forecast for now.
An even more significant upper trough arrives Friday, and this
brings with it a better chance for some rainfall. Both the EC and
GFS operational models bring some precipitation into the forecast
area (mainly along and west of the Cascades) on Friday, but GEFS
data shows minimal chance for a tenth of an inch of rain with the
trough late next week. In any case, it will bring another round of
cooler conditions and likely help clear out any smoke that enters
into the picture again between now and then.
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Monday for PZZ356-376.
Small Craft Advisory until 5 AM PDT Sunday for PZZ350-370.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
Issued by National Weather Service Los Angeles/Oxnard CA
805 PM PDT Fri Aug 24 2018
.SYNOPSIS...Mainly dry weather conditions with temperatures at or
slightly below seasonal averages will persist over the region
through next week. Look for night and morning low clouds which
will dissipate over inland areas each afternoon while only partial
clearing is expected near the coast.
.DISCUSSION...as of 8:00 PM PDT Friday...Primary short term
concern continues to be smoke and associated poor air quality
being transported into the region from fires to the north,
especially northern portions of Sonoma and Napa counties.
Satellite imagery also showing low clouds and fog making a quick
return this evening across many coastal areas. 00Z Oakland
sounding showing marine layer has shrunk to around 1400 feet, down
almost 1000 feet from this time yesterday. The Fort Ord profiler also
confirms some reduction of the marine layer this evening. The marine
layer is expected to deepen to at least 2000 feet by Saturday morning,
with low clouds and fog expected to spread well inland, including the
Salinas River Valley.
Overall synoptic pattern changing little through early next week,
as upper level trough will generally prevail across the West
coast. Slight height rises will be felt across the forecast area
over the weekend as some weak ridging builds into Southwest
California. The slightly higher heights and slightly weaker
onshore flow will lead to some reduction of the marine layer
depth this weekend, especially southern portions of the forecast
area. This in turn will lead to slight warming and drying across
interior sections over the weekend, with warmest interior portions
of Monterey and San Benito counties climbing into the 90s.
While temperatures are expected to nudge downward early next week,
a warming and drying trend will be possible by late next week
as high pressure aloft rebuilds over the southwestern states.
.AVIATION...as of 4:30 PM PDT Friday...for 00Z TAFs. Most areas have
cleared out this afternoon, but clouds are expected to return late
this evening. Most areas have seen at least 6 miles of visibility
this afternoon as the smoke was slightly less of a factor than
expected. Tomorrow is expected to be similar with most areas
clearing in the late morning/early afternoon. Smoke is not expected
to be a factor in visibility in most areas tomorrow, although the
North Bay may be an exception to that. The experimental HRRR smoke
model shows some smoke lingering in the North Bay so KSTS may see
some reduced visibilities. The stratus is expected to return once
again Saturday night. MKK
Vicinity of KSFO...MVFR ceilings are expected to return late this
evening as the stratus moves back in. Haze and smoke are not
expected to be a factor this evening, but confidence is low on this.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VIS Sat shows stratus moving towards MRY
quickly this evening bringing MVFR conditions and SNS will likely
follow shortly after that. Tomorrow clearing is expected around
midday again and smoke is not expected to be as much of a impact as
.MARINE...as of 08:00 PM PDT Friday...Moderate northwest winds
will affect the northern outer waters through Monday night. Winds
will also be breezy through the Golden Gate Gap through Saturday
afternoon. Otherwise, generally light winds will prevail through
Wednesday. Light northwest swell around 3 to 6 feet is
anticipated through the forecast period.
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
PUBLIC FORECAST: Gomberg
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Area Forecast Discussion
National Weather Service Spokane WA
437 PM PDT Fri Aug 24 2018
Expect cooler weather for the weekend. It will remain mostly dry
through Saturday with just an isolated mountain shower possible.
Wild fire smoke from British Columbia will cover parts of eastern
Washington and north Idaho. There is a possibility of some much
needed light rain by Sunday into Monday before another stretch of
dry and seasonably warm conditions returns by the middle of the
Tonight through Sunday: Expect cooler temperatures with continued
smoke concerns as an upper level trough remains over the Inland
Northwest. Breezy west to southwest winds will continue through
this evening from the lee of the Cascades and Columbia Basin
before tapering off. A weak shortwave in the flow aloft brushes
along the BC and N Idaho border by this evening and could produce
isolated mountain convection. Any activity would be short lived
and decrease early this evening. As the upper trough settles over
the region, another shortwave rolls along the BC/WA border
Saturday afternoon and brings a small chance of mountain showers.
Instability looks weak and lightning chances look low. Winds will
be lighter, but afternoon and evening westerly gusts are possible.
By Sunday, the next in a series of shortwaves is expected to
carve out the upper trough a little more aggressively and bring an
increased chance of mountain showers to the region. The Cascades
may see light showers, while the mountains of northeast Washington
into north Idaho stand to see a better chance of showers. Expect
more cloud cover and even the potential for light showers from the
valleys of northeast Washington into the Palouse. Breezy westerly
winds will redevelop Sunday afternoon especially in the Cascade
valleys into the Columbia Basin.
The upper trough will also reinforce the north to northwest flow
aloft and send waves of smoke southward from BC. Visible satellite
shows the current smoke deck covering much of eastern Washington,
and since midday today, the surface winds have mixed it to the
surface with degrading visibilities and air quality, especially
along and north of I90. The HRRR smoke model reflects this trend
and shows increasing smoke overnight across north central and
northeast Washington, while the southern Basin, Palouse and LC
Valley should see limited amounts of surface smoke. The smoke
models continue this trend through the weekend. Although increased
precipitation upstream in BC should help with a decreasing trend
of smoke for the region. More noticeable point will be
temperatures, which will feel autumn-like. Expect highs in the 70s
Saturday, and then cooling down to the mid 60s to mid 70s by
Sunday night through Friday: The pattern change should be pretty
much in place at this point in time with large trof over the
northwest Sunday night that gains a positive tilt with its slow exit
to the east/southeast into Monday. The positioning of the exiting
trof will leave a positively tilted ridge up in British Columbia
which will focus a northwest flow into Eastern Washington and North
Idaho Monday that lasts until possibly Tuesday that may morph into
zonal (west to east flow) Wednesday. Still from Tuesday on into
Friday there is enough clutter in terms of synoptic and smaller
scale timing of shortwaves that could result in a more active
pattern resulting in additional frontal passages Thursday and
Friday. Still the overall trend is a general longwave trof lingering
in place through this entire interval supporting a forecast
consisting of below normal temperatures with the warmest portion of
the forecast occurring Wednesday in association with the zonal flow
transitioning to a warmer southwest one ahead of the discussed small
scale clutter of the active pattern depicted in that part of the
workweek. As far as how wet the passage of the synoptic and smaller
scale disturbances will be well the trend has been for "not very"
since moisture doesn`t seem to be in great abundance with the
entrance and departure of the low over this weekend, however a
moisture tap from the pacific extending over and around the Cascades
in place Wednesday night into Friday which could aid in
precipitation production associated with any of the smaller scale
disturbance passages during that time interval. Otherwise the
continued nuisance associated with the northwest flow Sunday night
into Tuesday will be how much wildfire smoke gets transported down
from British Columbia. For now smoke and haze continue to be
00Z TAFS: Winds will be breezy at times this evening across
KGEG/KPUW/KLWS/KEAT. Conditions have been deteriorating this aftn
across KGEG/KSFF/KCOE/KMWH/KEAT and will likely get worse
overnight before things start to improve Sat aftn. MVFR conditions
are expected, but could see some localized IFR vis.
.PRELIMINARY POINT TEMPS/POPS...
Spokane 51 74 50 68 51 71 / 0 10 0 20 40 20
Coeur d`Alene 49 74 49 68 50 70 / 0 10 0 20 50 30
Pullman 46 74 47 66 48 70 / 0 0 0 20 50 40
Lewiston 52 80 55 72 55 76 / 0 0 0 10 40 30
Colville 45 75 44 69 46 75 / 0 10 0 40 50 10
Sandpoint 44 73 45 66 46 68 / 0 10 0 40 50 30
Kellogg 45 71 45 65 46 65 / 0 0 10 40 60 70
Moses Lake 48 76 50 73 52 79 / 0 10 0 10 10 10
Wenatchee 55 77 56 73 54 79 / 0 0 0 10 10 0
Omak 52 78 54 73 52 80 / 0 10 0 20 40 0
Area Forecast Discussion
National Weather Service Reno NV
230 PM PDT Fri Aug 24 2018
Near average temperatures continue, with a few degrees of cooling
for the early part of next week. Dry conditions, with typical
afternoon and evening breezes are expected through Saturday.
Breezy winds and critical fire weather concerns increase for
Sunday, as a trough approaches the region. No precipitation is
expected for the next week.
The pattern over the next week will feature cooler temperatures and
periods of breezy conditions, as a series of troughs move through
the region. With high temperatures only in the 80s for warmer
valleys, these will be the coolest conditions the region has
experienced since the end of June. To put this into perspective,
however, we are still talking temps near to just a couple degrees
Winds are the greatest concern, with Sunday looking to have the
strongest winds, as peak gusts reach 30-40 mph. This will bring
choppy conditions on area lakes, possible turbulence for aviation,
and increased fire danger. Fire Weather Watches remain in effect for
much of the region. Please see the fire section below for additional
details. The other concern will be winds kicking up dust and
impacting the Black Rock Desert, with the worst conditions likely to
be on Sunday.
Smoke from ongoing wildfires in northern California and Oregon has
drifted across portions of northeast California and northern Nevada.
Based on the current satellite image trends and latest HRRR smoke
runs, this smoke is likely to increase for areas from approximately
I-80 northward overnight. It may appear a bit hazy elsewhere,
especially in Alpine and Mono Counties downwind of the Donnell and
Lions Wildfires. -Dawn
Typical southwest to west afternoon and early evening winds can be
expected today and Saturday, with gusts peaking around 20-25 kts.
Stronger winds are anticipated for Sunday, with surface gusts of
25- 35 kts. This may bring turbulence and localized areas of
blowing dust. This is especially true for those flying into the
Black Rock Desert on Sunday, where surface dust may produce a
decent amount of obscuration.
Otherwise, smoke and haze are likely to increase for areas north of
I-80 overnight tonight (possibly including the Black Rock Desert).
This may bring some surface visibility reductions and terrain
obscuration, with further reductions to slantwise visibility.
Farther south, the Donnell and Lions Wildfires do not appear to be
producing quite as much smoke, but some haze and slantwise
visibility reductions are not out of the question for portions of
Alpine and Mono Counties. Elsewhere, light haze is possible
throughout northern CA/NV. -Dawn
No significant changes were made today, with Sunday still
forecast to bring relatively widespread critical fire weather
conditions to the region. The area of greatest confidence is still
in west-central Nevada, where wind gusts of 30-40 mph are
expected to combine with relative humidities in the single digits
to low teens.
A Fire Weather Watch remains in effect for the region on Sunday.
However, at higher elevations, winds and poor recoveries could begin
Saturday night and potentially last through Sunday night.
Next week, winds will be a little breezier then recent weeks as a
trough of low pressure remains over the west coast. It`s possible
that critical fire weather conditions will re-develop midweek, but
it`s a little too early to say which day that might be. -Zach
NV...Fire Weather Watch from Sunday afternoon through Sunday evening
CA...Fire Weather Watch from Sunday afternoon through Sunday evening
For more information from the National Weather Service visit...
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Saturday)
Issued at 333 PM CDT Fri Aug 24 2018
Early afternoon water vapor imagery shows center of upper low over
southern Minnesota dry air following across southwestern Nebraska
and northern Kansas. Very isolated elevated showers continue to move
across the northern counties but as the trough axis exits believe
this will become even less frequent. A weakly-defined modified cold
front was sinking south into northern Kansas with lower to even
middle 70 dewpoints ahead of it, though visible satellite imagery
showing very little cumuliform development ahead of it. Latest RAP
analysis is keeping significant CIN to mix-layer parcels in place
and any model producing convection along over the next few hours is
hard to find. Will continue with very low PoPs along the boundary,
though ML CAPE values of 2000-3000 J/kg and effective shear around
40 knots would supply an environment for an organized storm.
Main convective concerns over the next several periods are via
elevated ascent. The moisture plume over southern Kansas may become
more active again tonight as modest upglide increases again through
the 310 to 315 K layer. Models do vary somewhat on precip potential,
but went ahead with small chances south of Interstate 70 late this
evening into early Saturday morning with guidance struggling with
the early-day activity. Instability aloft is meager in the higher
moisture and should keep any rainfall amounts light. Main other item
of interest tonight is fog potential with light winds and little
cloud cover behind the stalling boundary, though the weakest winds
should be in northeastern areas where precip has been less intense
in recent events. Potential looks too low at this point for
inclusion with still some wind in the boundary layer on latest RAP
forecasts. Highs Saturday should still be able to reach the lower to
middle 90s as south winds return, with somewhat cooler readings more
likely in southern locations where mid and high cloud may persist.
.LONG TERM...(Saturday night through Friday)
Issued at 333 PM CDT Fri Aug 24 2018
id-level isentropic lift returns in mainly western areas Saturday
night as stronger zonal flow resumes over the northern Plains.
Instability remains low here too. Another round or two of elevated
convection is possible Sunday night and Monday night as the next
upper wave digs into the north-central states. 850 mb temps in the
lower to middle 20s Celsius and gusty south to southwest winds still
keep potential for rather warm daytime temps with low to mid 90s
still expected though persistence of any precip into the daytime
hours yields somewhat reserved confidence. The cold front associated
with this wave passes in the Tuesday to Wednesday periods and could
present a surface-based convective threat though many questions
exist on its timing and how previous precipitation will impact its
pre-frontal environment. Another elevated warm/moist-air advection
regime could develop in the Wednesday night to Friday periods for
still more chances for convection. Post-frontal temps should not
fall too far before rising above normal again late in the week.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 608 PM CDT Fri Aug 24 2018
Expect VFR conditions to prevail through the period. The only
potential issue would appear to be patchy fog around TOP after 08Z
with light winds and high humidities. That said, boundary layer
mixing remains present albeit weak overnight so will not include
at this point.
Area Forecast Discussion
National Weather Service Tucson AZ
906 PM MST Fri Aug 24 2018
.SYNOPSIS...Abundant moisture will remain in the area through at
least Saturday with a threat of heavy rain producing thunderstorms
at any point through Saturday evening. Sunday into Monday drier
air will begin to limit thunderstorms and allow for warmer
temperatures. The middle the week should be dry and warm before
moisture tries to return again next weekend.
.DISCUSSION...Scattered showers and thunderstorms were still ongoing
late this evening after several areas received heavy rainfall today.
Most of the Tucson area received some rain this evening, with a few
spots reporting .5 to .75 of an inch. Latest HRRR solution suggested
that most of the rain, mainly light, will remain across Pima county
tonight before dissipating by daybreak. That said, will keep the
Flash Flood Watch going until midnight even though the threat had
diminished across Cochise, Graham and Greenlee counties. Made some
minor adjustments to the POP values east and west of Tucson for the
remainder of tonight. Otherwise, the forecast looked in good shape.
Please refer to the additional sections in this product for more
.AVIATION...Valid through 26/06Z.
SCT-BKN clouds around 8k-12k ft AGL across much of the area,
although cloud bases could drop to 4-5k ft AGL around heavier
convection. Conditions then improve overnight before another round
of SHRA/TSRA develops Saturday afternoon. Surface winds remain
less than 12 kts through the period with the exception of stronger
gusts near TSRA. Aviation discussion not updated for TAF
.FIRE WEATHER...Deep moisture continues to provide favorable
conditions for thunderstorm development into the weekend. Some
storms will be capable of producing very heavy rainfall in a short
period of time. The pattern then shifts next week allowing for
drier conditions with warmer temperatures. Terrain driven 20-ft
winds persist at less than 15 mph, except in and around
thunderstorms where strong outflows may occur.
.PREV DISCUSSION...Saturday we will still have near record amounts
of PW, at least across the eastern half/two thirds of the area and
as usual, if we get enough sunshine it will be an active day with
convection and local heavy rains. We may have a bit less instability
to help out though.
By Sunday, the light SW flow should have eroded a good amount of our
moisture aloft for much lower PW values, actually back down to more
"normal" levels. This would favor scattered convection generally
east of Tucson that afternoon and shutting down after sunset. The
situation will likely be similar on Monday and both days should have
high temperatures near normal again.
The middle of the week into Friday favors dry and warm with the
upper level high in a less favorable position for storms and drier
air aloft. Then next weekend there is a chance that we start
returning to southern flow with some moisture increase once again.
Flash Flood Watch until midnight MST tonight for AZZ502>515.
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