Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/10/18
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
549 PM MDT Thu Aug 9 2018
00Z TAF CYCLE
A healthy crop of tstms have formed over the northern and western
high terrain. Tstms will generally move south into valley locales
producing one to two hour long periods of MVFR conditions.
Thunderstorms will be capable of producing moderate to large hail,
frequent cloud to ground lightning, and gusty erratic winds. VCTS
can also produce strong gusty erratic winds. The eastern plains are
expected to also get their fair share of tstm activity between now
and 09Z. Areas from KLVS to KSXU to KTCC could see a passing tstm
between 01Z to 04Z, with storm coverage pushing south to KCVN to KROW
03Z to 06Z. Tstm activity is expected to fully diminish by the early
morning hours, with remnant high cirrus over much of the state.
Tomorrow will see another round of afternoon tstms forming over the
higher terrain and potentially along any sfc boundaries over eastern
.PREV DISCUSSION...246 PM MDT Thu Aug 9 2018...
An active end to the work-week is underway, with thunderstorms
developing further west across the state compared to the past few
days. Storms this evening will be capable of producing locally heavy
rainfall and localized flash flooding. More storms are forecast
Friday, with high temperatures below normal thanks to rain-cooling
and additional cloud cover. Look for continued rain chances through
the weekend, though trending down some from Friday. High pressure
will strengthen over the region next week, leading to an uptrend in
temperatures. However, decent chances for storms look to persist for
the foreseeable future.
The upper high is pulling away, as evidenced by the pressure height
falls noted on the 12Z upper air analysis, and was centered over
Nevada at 12Z. PWATs are trending up across central and western New
Mexico and were near 1" on the KABQ upper air sounding this morning.
An increase in storm coverage is expected this afternoon, especially
across central and west central New Mexico where storms have not been
as plentiful that past couple of days. South or southwest steering
flow will take storms off of the central mountain chain over the
Santa Fe and Albuquerque Metros this afternoon/evening. Both the 12Z
and 18Z NAM, and the last several runs of the HRRR show the eastern
highlands, Estancia Valley, the Sandia/Manzano Mountains and perhaps
portions of the south central highlands getting hammered this evening
and these are the areas where we have our highest evening PoPs. The
Flash Flood Watch is still in effect and will be left as-is this
forecast cycle given no compelling evidence for change. Another crop
of storms with scattered to numerous coverage is forecast for
Friday, but instability will be more limited with daytime
temperatures forecast to be 3 to 8 degrees cooler than today`s. Look
for a downturn Saturday, thanks in-part to some drying of the
atmosphere. Sunday may tick back up in terms of storm coverage, with
the upper high over Utah and a weak upper low over the TX Panhandle.
Northerly steering flow on Sunday would once again take storms off
the higher terrain late day over the Santa Fe and Albuquerque Metros.
Both the 12Z operational runs of the ECMWF and GFS show the upper
high building over AZ/NM next week, leading to an uptrend in
temperatures back to above normal most areas by Wednesday or
Thursday. The GFS shows a weaker high, with daily rounds of storms
persisting. Our forecast is closer to the GFS at this time.
Scattered to numerous showers and thunderstorms will be found over
much of the forecast area for the remainder of the day and into
tonight, especially along and east of the central mountain chain.
After receiving wetting rainfall in several locales, tonight`s RH
recovery should be good to excellent across most of the state. A
continued moist southeasterly flow at the surface should keep
sufficient moisture in place for more scattered to numerous storms
on Friday. Temperatures will run a few to several degrees below
average Friday afternoon in all areas except the northwest plateau.
This weekend high pressure aloft will stretch about a southwest to
northeast oriented axis, wrapping dry air into northern NM on
Saturday. A weak upper low will take shape over west TX, keeping
some mid level moisture in far eastern NM, but overall a downtrend
in storm coverage is expected Saturday. Temperatures will not alter
much Saturday, but could gain a degree or two on Sunday. A
disturbance aloft is then expected to enter northern NM Sunday with
additional storms accompanying and eventually spreading into the
western tier of the state through the evening. The weather next week
will be characterized by a gradual exit of the weak low over west TX
while high pressure remains ill-defined, struggling to re-establish
itself over the Great Basin. This will keep daily thunderstorm
chances going with temperatures approaching normalcy.
Flash Flood Watch until 4 AM MDT Friday for the following zones...
Area Forecast Discussion
National Weather Service Amarillo TX
635 PM CDT Thu Aug 9 2018
VFR for all three terminals for the 00Z TAF period. KAMA does have
a PROB30 group for the last six hours of the period, when it may
fall to MVFR if impacted by thunderstorms. Winds will gradually
become light and variable in the beginning of the period until
about 18Z when the winds pick up to 10-15 kts out of the east to
southeast. KDHT and KGUY may be impacted by and isolated
thunderstorm towards the end of the period but confidence is low.
.PREV DISCUSSION... /Issued 357 PM CDT Thu Aug 9 2018/
Convection developing this afternoon along the axis of an east to
west shortwave trough located across the northern and central
Texas Panhandle. Convection expected to continue pushing slowly
south into the evening hours and then dissipate or move out of the
forecast area by 03Z to 06Z Friday. Recent CAMs and latest RAP
continuing to show convection redeveloping after 06Z to 08Z Friday
across the Interstate 40 corridor southward. Focused POPs for
tonight mainly across the southern half or so of the Panhandles.
Upper flow transitions to northerly to northeasterly tonight and
Friday as the upper trough digs south and west across the
Panhandles and an upper high builds northeast across the Great
Basin region and the northern Rockies and northern Plains states.
Closed upper low develops over the southern Plains states this
weekend and moves westward across the Panhandles or in the
vicinity of the forecast area by early and middle of next week.
Weak frontal boundary to push south across the Panhandles Friday
and Friday night and then remains quasi-stationary near or across
portions of the Panhandles over the weekend. Convection chances to
continue tonight through the weekend and into the early and
middle of next week. Confidence low as to timing and location of
where convection will develop, however it appears that the best
chances should be over the central and southern Texas Panhandle
through Saturday night and then shifting to most or all of the
forecast area by early and mid next week.
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
747 PM CDT Thu Aug 9 2018
Scattered showers and storms continue across the Edwards Plateau and
northern Hill Country. Increased PoPs slightly in this area for the
next few hours. Latest runs of the HRRR continue to decrease activity
shortly after sunset. Otherwise, no major changes were needed to the
.PREV DISCUSSION... /ISSUED 648 PM CDT Thu Aug 9 2018/
VFR at all TAF sites this evening and into tonight. A weak boundary
and associated convection across the Hill Country and Edwards Plateau
should remain to the north of TAF sites tonight. The typical
summertime morning stratus is expected again tonight, but with weaker
winds from the southeast, stratus will not likely make it all the
way to KAUS. MVFR conditions are still expected at KSAT/KSSF. KDRT
will remain VFR throughout the TAF period.
PREV DISCUSSION... /ISSUED 321 PM CDT Thu Aug 9 2018/
SHORT TERM (Tonight through Friday Night)...
A weak outflow boundary across northeast Texas that extends to the
southwest into central Texas is forecast to combine with another
boundary coming down from the northwest to develop a convective line
over the Hill Country and Edwards Plateau later this afternoon.
Several HiRes and even some of the regional and medium-range models
agree on this scenario. In addition, the typical seabreeze activity
should increase within this hour and affect parts of the Coastal
Plains and southeast counties. Most HiRes models keep the stronger
activity just to the north of the Hill Country for the evening
period. However, later tonight/overnight period, an organized
mesoscale convective system is forecast to develop and affect the
Hill Country and especially Llano and Burnet Counties. Some storms
could be strong and produce isolated heavy downpours and wind gusts
of 40 to 50 mph.
An upper level trough axis will remain just to the north of the Hill
Country on Friday and will aid for a new round of scattered showers
and isolated thunderstorms mainly across the southern Edwards
Plateau and Rio Grande Plains. Also, the typical seabreeze convection
is once again expected across the Coastal Plains and southeast
LONG TERM (Saturday through Thursday)...
The unsettled weather persists this weekend into Monday of next week
with several rounds of moderate to heavy rainfall episodes mainly
across the Edwards Plateau and Rio Grande Plains. The I-35 corridor
area is expected to get some activity during the period with best
chances on Saturday night into Sunday morning and again Sunday night
into Monday morning. Some shower and storm activity is possible
Monday and Tuesday as an upper level disturbance departs the area.
The upper level disturbance responsible for the extended period of
rain chances finally pushes to the northeast and away from the area
with rain chances coming to end mid-week.
Storm total rainfall amounts across the Edwards Plateau and Rio
Grande could range from 1 to 3 inches with isolated 4 inches. Areas
along and east of Interstate 35 are expected to get one inch or less.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 77 95 75 93 75 / 30 40 40 40 60
Austin Bergstrom Intl Airport 76 95 75 93 74 / 30 30 40 40 60
New Braunfels Muni Airport 75 95 74 93 74 / 20 20 40 40 60
Burnet Muni Airport 74 92 73 90 72 / 60 60 50 50 60
Del Rio Intl Airport 78 99 77 93 75 / 20 20 40 40 60
Georgetown Muni Airport 76 95 74 92 73 / 50 50 50 40 60
Hondo Muni Airport 74 98 74 96 74 / 20 20 30 30 60
San Marcos Muni Airport 75 96 75 93 75 / 20 30 30 40 60
La Grange - Fayette Regional 77 96 76 94 76 / 10 30 20 50 40
San Antonio Intl Airport 77 96 76 94 76 / 10 20 30 30 60
Stinson Muni Airport 76 97 76 95 77 / 10 20 20 30 60
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
753 PM CDT Thu Aug 9 2018
After the initial Denton County storm this afternoon, the bulk of
the convective activity was south of the Metroplex TAF sites
(Arlington the primary exception). However, the dancing outflow
boundaries throughout the TRACON are finding particularly unstable
air, and a few thunderstorms rooted in the mT boundary layer will
occur through nightfall. Despite the chaotic wind field, for ease
of operations, DFW/DAL are in south flow, inbound traffic avoiding
the thunderstorm clusters south of the Metroplex. While storm
impacts at any metro TAF site would be quite brief, some in-flight
slaloming will be required early this evening.
A low-level trough will remain draped across the Metroplex
overnight. This will promote some upglide, but the main corridor
of warm/moist advection will be oriented through Central Texas
into East Texas. Despite being worked over late this afternoon,
this buoyant inflow beneath steep lapse rates aloft will promote
the redevelopment of thunderstorms across Central Texas later this
evening. This will maintain impacts to south departures and
incoming traffic through both Glen Rose and Cedar Creek.
Eventually, showers may develop closer to the Metroplex, but
probably not until the predawn hours, at which point boundary
layer parcels are unlikely to be involved. In addition, with more
widespread convection to the south literally stealing its thunder,
these shallower updrafts across North Central Texas will have
less favorable lapse rates, and the Metroplex TAFs will carry only
VCSH Friday morning.
In the short term, the wind field will continue to be governed by
outflow. With the proximity of surface troughing, light easterly
winds will likely take hold this evening within the Metroplex.
Veering southerly flow will then overwhelm this late tonight and
prevail through Friday.
With a moisture-rich boundary layer still in place on Friday
beneath weak troughing aloft, some redevelopment of thunderstorms
should occur at peak heating. The weak surface wind field will
allow residual boundaries to linger. With much of the forcing on
the mesoscale, initiation will be largely dictated by the location
of these boundaries, which may be determined by the nocturnal
activity that has yet to occur. While the timing of this
convection would be focused during the typical late afternoon peak
heating period, uncertainties about location will preclude any
introduction of Friday afternoon thunder in the TAFs at this time.
.SHORT TERM... /Issued 347 PM CDT Thu Aug 9 2018/
/This Afternoon and Tonight/
The main challenge in the short term forecast period will be the
location and coverage of precipitation. For the rest of this
afternoon, it appears that locations south of I-20 will stand the
best opportunity for showers and thunderstorms. A few storms will
be possible near the Highway 380 corridor this afternoon as well.
Overnight tonight, storm chances will increase quite noticeably
across the Concho Valley and into Central Texas.
This afternoon, there has been a relative lull in convective
activity from about noon through the 3 PM time frame. A broad
surface trough continues to slide southward through the forecast
area with an mesoscale convective vortex or MCV noted across the
Concho Valley. Agitated CU was noted from near a Gatesville to
Athens line and I`ve nudged PoPs into the 50 percent category
here. There will be a risk for strong to near severe downbursts
given large amounts of DCAPE and a very hot and well-mixed
boundary layer. A small thunderstorm cluster was noted just north
of the Highway 380 corridor in response to just daytime heating.
The cessation of this convection will be interesting, but in
general, it should decrease after sunset.
Overnight tonight, showers and thunderstorms should blossom
across Central Texas and the Concho Valley. RAP and NAM guidance
continue to support strong isentropic ascent along the 305K theta
surface. As noted yesterday, the NAM has done a pretty good job of
handling the overnight LLJ and I see no reason to disregard its
output tonight. 925mb winds will climb into the 30 to 35 knot
range and glide atop the surface trough. There may be some
additional assistance from the aformentioned MCV and this should
help fuel widespread to numerous convection across Central Texas.
HREF members concur with this assessment and mean QPF values are
quite aggressive across this area with rain totals in excess of
4". I`m not completely sold on this potential, but given the very
moist regime (characterized by 2" PWATs) and the unseasonably
strong LLJ, it`s not out of the realm of possibility. I`ve
inserted "heavy rain" wording into the western portions of Central
Texas tonight and there could be a low end flood threat,
especially across some of the more flood prone areas in Central
Texas. Elsewhere, there will be a chance for a lower coverage of
showers and thunderstorms. Overnight low temperatures will fall
into the 70s areawide. There may be a low potential for some
patchy fog along the Red River where skies.
.LONG TERM... /Issued 347 PM CDT Thu Aug 9 2018/
/Friday through next Thursday/
Showers and thunderstorms may be ongoing at the start of the long
term period Friday morning, forced by robust isentropic
ascent/warm advection over-topping a diffuse remnant outflow
boundary/wind shift across Central Texas. Recent hi-res guidance
is in decent agreement in depicting fairly high precipitation
coverage across Central Texas and up to about the I-20 corridor
through the morning hours, and this seems reasonable given the
anticipated magnitude of lift and copious amounts of moisture.
We`ve increased PoPs to 70% across a good chunk of our Central
Texas counties Friday morning. PWATs are forecast to push 2" in
spots here, so heavy rainfall will be possible. In addition,
upwind corfidi vectors of less than 5-10 kts or so, becoming
increasingly boundary-parallel portend some risk for
training/backbuilding cells. Relatively high 1 and 3-hour flash
flood guidance across Central Texas reduce our concern for
widespread flash flooding at this juncture, but some localized
hydrological concerns may arise generally south of I-20 through
the morning hours.
This initial round of convection should diminish into the early-
afternoon as the initiating ascent peters out as the low-level
wind field relaxes. Given the anticipated convective coverage
across Central Texas, re-development of showers and storms during
the afternoon is in question, so we`ve reduced PoPs a bit across
the last few rows of counties. Additionally, if this complex
exhausts a robust enough outflow, it could even hamper convective
chances north of I-20 later in the day. High temperatures will
also obviously hinge on the placement of left over cloud cover and
mesoscale boundaries. The warmest conditions should occur near the
Red River, while locales south of I-20 may have a hard time
getting into the 90s.
A similar scenario may unfold Friday night into Saturday morning
as moist upglide gets cranking once again, and so high-end chance
PoPs will be advertised across much of North and Central Texas.
These may need to be increased as confidence in the placement of
pertinent mesoscale features increases. Over the weekend, upper
level troughing will become more established across parts of West
Texas. This will keep a persistent fetch of deep southerly flow
and associated moisture transport going across the western half of
Texas. The brunt of large scale ascent looks like it will remain
just west of our forecast area by the end of the weekend and into
early next week, and a fairly tight PoP gradient has been
introduced from west-to- east starting on Sunday. Both the GFS and
ECMWF show some pretty dry air punching into our southeastern and
eastern counties during this time frame, and today`s mid-range
ensemble guidance is similarly advertising the lowest
precipitation chances east of the I-35 corridor. Assuming this
upper low doesn`t pivot any farther west than currently
advertised, some of our far western counties may benefit from
decent wetting rains Sunday-Tuesday.
By the middle of next week, the persistent upper troughing and
associated broad cyclonic flow overhead may begin to break down as
the southwestern US subtropical ridge attempts to build back
eastward. Temperatures should rebound into the mid and upper 90s
Wednesday and Thursday, and PoPs will quickly trend downward
through this period.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 77 92 73 89 74 / 50 50 50 30 60
Waco 73 93 72 90 74 / 70 70 50 50 60
Paris 73 93 72 89 71 / 20 30 30 30 30
Denton 74 93 70 88 72 / 40 40 50 30 50
McKinney 74 93 72 89 73 / 40 40 40 30 50
Dallas 78 93 75 91 75 / 50 50 50 30 60
Terrell 75 93 73 90 73 / 40 50 50 30 40
Corsicana 75 91 73 90 73 / 50 70 50 50 50
Temple 73 93 74 91 72 / 70 70 50 50 60
Mineral Wells 74 91 70 86 71 / 50 50 50 40 60
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1032 PM CDT Thu Aug 9 2018
Storms have dissipated and cirrus remains over parts of the area.
Storms along the outflow boundary near the cold front have been
weakening steadily and dissipating. Expecting that a few showers
or thunderstorms could develop along the outflow near RYW-ACT-
PSN though weak subsidence could minimize the chances for
development. Will carry slight chances across the northern
counties. Also toward sunrise may see a few showers over the Gulf
and into the coastal counties. Patchy light fog possible near
CXO/LBX near sunrise but probably more a matter of MIFG.
On a different note...After the rains of Friday and Saturday Saharan
dust blowing out of the Caribbean should move into SETX on Sunday
and linger through Tuesday with upper ridging and drying out the
Last but not least is the potential for great Perseid meteor
shower watching this weekend with mostly clear skies after
midnight. Perseids already started tonight and should probably
peak Saturday or Sunday.
.PREV DISCUSSION... /ISSUED 654 PM CDT Thu Aug 9 2018/
Radar imagery shows most of the remaining showers and
thunderstorms continuing to fizzle out across the region. VFR
conditions should prevail through the morning hours with some
sites such as CXO/LBX potentially seeing some patchy fog in the
early morning hours, similar to the last few days. Winds should
stay up for the next few hours at CLL with a tighter pressure
gradient in place over our northwestern zones as the trough axis
moves southward this evening. Some of the short term/global
guidance is hinting at the possibility of some early morning
convection associated with this boundary. At this time, just not
confident enough that the precipitation will make it that far
south so have kept the TAFs dry overnight.
Convection tomorrow should begin a little earlier across the area,
and spread inland by early afternoon. The typical diurnal summer
wind pattern will continue, with winds light and out of the
southwest tonight turning out of the southeast by the afternoon
hours tomorrow. Gusty conditions will be possible beneath stronger
storms in the afternoon.
PREV DISCUSSION... /ISSUED 340 PM CDT Thu Aug 9 2018/
NEAR TERM [Through Tonight]...
Watching thunderstorm development today has been interesting
purely from a visible satellite perspective. GOES 16 VIS around
15-16Z showed two areas of enhanced cumulus that eventually led to
thunderstorm activity. The first was down along the coast and
currently see activity from Wharton to near Sugar Land. Another
cluster exits east of Houston IAH to HOU. Outflow boundaries from
this convection could initiate new storms over the next hour or
two. The second area of enhanced cumulus was from near Columbus
northeast to Conroe and Lufkin. This activity has not been as
strong and with more pulse increases in intensity. HRRR model runs
were not that bad with this evolution and timing so far and based
on that, overall trend should be for convection to decrease in
coverage after 22Z this evening. Near term forecast has been
updated for these trends and the PoP forecast tries to capture
areas of convection with higher PoPs.
Tonight the main issue will be convection that forms north of the
area and then pushes south. Overall model guidance for tonight and
even tomorrow are very different. Overall thinking is for rain
chances to decrease tonight with loss of day time heating and
instability, but forecast will keep some thunderstorm chances for
areas north of Conroe to account for any new storm development.
SHORT TERM [Friday Through Friday Night]...
Friday`s forecast looks to be quite uncertain based on model
guidance so we will need to go off of what we do know from latest
analysis and guidance. None of the WRF model runs have a good
working scenario for Friday since convection will be mesoscale
driven from any outflow boundaries generated from overnight
thunderstorm activity. There is an upper level low over the Ozarks
currently and its trough axis is expected to push into east Texas
as it stretches out with the low moving east. This does lower
heights and may allow for some weak large scale ascent. Models do
show precipitable water values holding around 2 inches so given
some heating and some lift on the synoptic scale, it reasons to
keep some 40 to 60 PoPs in the forecast. The main question is
where those higher rain chances may end up and that`s where we
will have to go with a blend of the best guidance so far.
Generally this looks to be along the coast but then also across
the northern areas from College Station over to Livingston.
Houston will be stuck in the middle but likely have better rain
chances due to mesoscale boundary interaction similar to today.
Short term hazards and impacts remain relatively the same with
brief heavy rainfall with maybe an inch of rain an hour rain
rate, lots of lightning and downburst winds. The severe potential
looks rather low at this time given the pulse nature of the
convection and overall lack of high instability. WPC has a
marginal/slight risk of excessive rainfall basically for the
northern most areas from the Brazos Valley to east Texas. This
basically accounts for any thunderstorm activity that forms north
of the area and moves south. The main issue here will be if
multiple rounds of storms form and move over the same area.
LONG TERM [Saturday Through Thursday]...
The cutoff low remains centered over the Panhandles in the
Southern Plains on Saturday, as ridging remains over the Gulf.
The continued source of lift from the lower heights aloft will
continue the wet trend through the weekend. Showers and
thunderstorms are the most likely in our northeastern counties on
Saturday near where the front stalls. Our risk for excessive
rainfall remains marginal on Saturday, as the main focus for heavy
rain will be beneath the upper level low in Central Texas. Rain
totals over Southeast Texas will be around 1 inch, with locally
higher amounts near 2-3 inches possible in the Piney Woods region.
Ridging gradually builds westward into the northwestern Gulf on
Sunday and will help dampen rain chances early next week. Despite
surface high pressure approaching from the east, a weak to
moderate onshore flow will periodically pull in moisture from the
Gulf, allowing for a slight chance for diurnal showers and
thunderstorms beginning Tuesday. Otherwise, expect temperatures
just above climatological average with highs in the mid 90s and
lows in the upper 70s next week.
Guidance diverges on the pattern for late next week, as the ECMWF
has another trough digging into the Southern Plains while the GFS
is not as aggressive and keeps the trough in the Central Plains.
Kept POPs near 30 for Thursday to account for the uncertainty.
This will be the feature to watch for the next several days.
Light to moderate winds are expected over the next several days
until stronger onshore winds develop Sunday. These stronger
onshore winds will persist into next week with seas of 3 to 5 ft
expected. Caution flags may be needed particularly Sunday night
into Monday for the most western/southwestern coastal zones. Seas
could potentially be higher both in and near showers or
thunderstorms with slight chances into next week.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 76 95 75 93 75 / 20 40 40 60 40
Houston (IAH) 78 93 78 92 77 / 10 60 20 60 30
Galveston (GLS) 82 88 81 88 82 / 10 60 20 50 20
Area Forecast Discussion
National Weather Service Wilmington OH
936 PM EDT Thu Aug 9 2018
High pressure this evening will be pushed to the south as a weak
cold front noses into the region from the north tonight and
Friday. Showers and thunderstorms will occur as this front and
an upper level trough pushes through the region. On Saturday,
high pressure will build over the Upper Midwest and then help
usher in a drier and cooler airmass for Sunday.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Southward-progressing convection over NE Indiana / NW Ohio is
making it a little bit further than previously anticipated,
although the trend toward warmer cloud tops and gusting-out has
been pronounced over the past 30-60 minutes. Nonetheless, some
increases to the PoPs were necessary in the northwestern
sections of the ILN CWA. Recent observations have had peak gusts
generally in the 20-30 knot range, suggesting that no statements
will be necessary unless an unexpected strengthening were to
Otherwise, generally dry conditions should continue overnight.
Temperature trends were updated slightly cooler in the near
term, but min temps still look fairly reasonable, especially
with some cloud debris spilling into the area. Widespread fog
appears unlikely, with HRRR visibility signals generally good,
and less near-surface saturation in various model soundings
compared to last night.
Previous discussion >
Lower level cloud cover will dissipate fairly quickly this
afternoon. Cirrus spilling into the region from the southwest
will affect the southern CWA this evening and overnight. Showers
and thunderstorms will be possible northwest of the CWA tonight
and could nose towards the I-70 corridor before daybreak. It`s
more likely that cloud cover will be more substantial later
overnight, spreading south over the CWA. Lows tonight will once
again be limited to the dewpoints which are running in the mid
to upper 60s. A few cold pool areas could drop lower, and valley
fog will once again be found in river valleys and low-lying
areas. The cloud cover coming in from the north should limit
this fog to the southern half of the CWA overnight.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
A weak cold front will cross south through Ohio and interact
with an upper level trough to create showers and thunderstorms.
The best chance lies in central Ohio but any portion of the CWA
will see a chance for activity, peaking in the afternoon and
A shortwave within the upper trough will be strongest southwest
of metro Cincinnati and east through the Kentucky/Tennessee
border. The rest of the Ohio Valley will see shortwave energy
underneath the trough interact with some daytime heating
everywhere and a surface frontal passage in the east. A very
muddled upper pattern will occur with energy found in pockets
over the region Friday night. Activity should be on the decrease
through the night but some storms will persist and cannot be
definitively ruled out just about anywhere over the CWA at this
moment in time.
Highs Friday will be a little cooler - lower to middle 80s
under cloud cover, with overnight lows from the lower 60s behind
the front in the north to the middle 60s south of the I-70
corridor and upper 60s along and south of the Ohio River.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
For Saturday into Saturday night, a frontal boundary draped
across the region will slowly sag southeast. Meanwhile, as an
upper level ridge amplifies northeast into the northern Plains
and south central Canada, downstream mid level troughing will
develop across the Great Lakes and Ohio Valley. A chance of
showers and thunderstorms will continue Saturday into Saturday
evening, then pcpn should taper off during the overnight period
with the loss of diurnal heating and frontal convergence. Highs
in the lower 80s will drop into the lower to mid 60s.
For the period Sunday into Monday, the biggest change among the
operational models has been the placement of the mid level closed
low center over our region. The latest ECMWF is closing the center
of circulation farther west then the NAM, GFS, and CMC. The ECMWF
solution would favor a greater chance of showers/storms while the
other models would result in a much lower chance or even a dry
solution over some parts of the area. Have made a compromise which
is to keep a slight chance/low chance of showers/storms continuing,
mainly during the afternoon and early evening hours. Will continue
to monitor later model runs should more adjustments be needed. Highs
Sunday and Monday will range from the upper 70s to the lower 80s
with lows Monday morning in the lower to mid 60s.
For Tuesday into Tuesday night, it still appears that the upper
level closed low will get "kicked" to the east from upstream upper
level energy pushing into Ontario as well as the central/southern
Plains. At the surface, high pressure will traverse west to east
across the Ohio Valley. Have gone with a dry forecast for this
period. However, there will likely be increasing clouds Tuesday
night ahead of the central/southern Plains system. Highs in the
lower to mid 80s will drop into the mid and upper 60s by Wednesday
For the remainder of the extended, Wednesday into Thursday,
aforementioned upper level energy will move into the Ohio Valley
along with a frontal boundary. This will bring the next good chance
of showers and thunderstorms to our area. Highs again will range
from the lower to mid 80s with lows in the mid and upper 60s.
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Storms moving into northern Ohio are expected to dissipate
before reaching the TAF sites, so a dry forecast will be
maintained overnight and into tomorrow morning. Some MVFR fog
will be possible at a few of the sites (with LIFR fog at KLUK).
There is also a small chance of stratus development, as occurred
in patches last night, but confidence is currently too low to
include in the forecast.
Clouds will increase tomorrow, with showers and thunderstorms
developing during the afternoon. A VCSH has been included for
all TAF sites, and future issuances will likely need a period of
prevailing showers, once the timing and location forecast is a
little better known.
OUTLOOK...Thunderstorms will remain possible at times through
Monday, with the greatest chances during the afternoon and
Area Forecast Discussion
National Weather Service Indianapolis IN
1040 PM EDT Thu Aug 9 2018
The Aviation Section has been updated below.
Issued at 354 PM EDT Thu Aug 9 2018
A frontal zone will approach the area late tonight into Friday,
bringing chances for storms at times Friday into Saturday. An
upper level trough will follow later in the weekend, which may
produce a few showers and storms before high pressure allows a
brief break at the start of the week.
.NEAR TERM /Rest of Tonight/...
Issued at 1000 PM EDT Thu Aug 9 2018
Based on southeast trajectory and weakening of the southern end of
storms across northern Indiana, still think these cells will stay
just north of the forecast area, and thus no changes being made to
the PoP forecast at this time. Increased cloud cover some across the
northern counties for much of the night and also the southeast
counties near daybreak. Otherwise no other appreciable changes made
as forecast is on track. Previous discussion follows...
Model blend appears to be overdoing extent of convection thus far
today, particularly the GFS, and this has contaminated forecast
builder initialization. Expect that the most vigorous convective
development currently ongoing across southern Wisconsin, along the
axis of strongest instability pooled ahead of the boundary, will
be the main focus for the late afternoon and evening, and HRRR
suggests this activity will largely dissipate before making it
into central Indiana. Will go dry tonight and monitor the progress
of the northern activity.
Temperatures will likely be slightly warmer than last night owing
to more cloud cover, but between blends being a bit too warm
recently, and compared to persistence, felt that consensus numbers
were slightly too warm.
.SHORT TERM /Friday through Sunday/...
Issued at 354 PM EDT Thu Aug 9 2018
The highest chances for storms will come Friday afternoon and
evening with the presence of the surface frontal zone and an upper
level wave pushing through the region. Activity associated with
the boundary and a secondary upper wave may persist into Saturday
and additional chances will be necessary Sunday as the upper wave
drops into the area and potentially closes off. A significant
severe threat is unlikely at this time.
Consensus temperatures appeared a bit warm given numbers today and
expected low level thicknesses through the period, as well as
potential for expansive cloud cover and precipitation. Made
downward adjustments each day.
.LONG TERM /Sunday night through Thursday/...
Issued at 237 PM EDT Thu Aug 9 2018
Ensembles suggest a cutoff upper low over the Ohio Valley will drift
off to the east early next week, followed by a more substantial
trough that may move into the area by the middle of next week.
Could be some diurnally driven shower activity on Monday afternoon,
especially over the eastern zones associated with the cutoff low.
However, ensembles are very bullish on the precipitation threat this
far west. Will leave some chances PoPs for Monday in those areas for
Otherwise, appears a better precipitation threat may arrive by the
middle of next week, as a stronger trough moves along the northern
parts of the country. Will add some PoPs for next Wednesday and
Thursday to cover this potential.
.AVIATION /Discussion for 100300z TAF issuance/...
Issued at 1040 PM EDT Thu Aug 9 2018
Updated current conditions only. Previous discussion follows...
Quiet weather tonight and VFR conditions expected at the sites as
convection should stay well north or south of the sites. A very
slim chance a shower/storm makes it south enough to impact KLAF,
but certainly not enough to include. A front slowly sinking
through the area will bring some chances for storms on Friday, but
the probability is low enough to leave out at this time. Will
include a deck of few to scattered clouds around 2000 to 4000 ft
during the late morning through the afternoon with this front.
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1154 PM EDT Thu Aug 9 2018
Issued at 1154 PM EDT THU AUG 9 2018
The latest scans of the WSR-88D radar shows that much of the
shower activity has now diminished this hour. We are watching some
activity in the Tennessee Valley that will move into portions of
the Lake Cumberland region over the next several hours. The
forecast looks on track and only minor changes were needed to
blend in the latest obs and trends.
UPDATE Issued at 911 PM EDT THU AUG 9 2018
The latest radar trends have shown a weakening of any of the
isolated showers and thunderstorms that developed this evening.
These showers seemed to be tied to some weak boundary interaction
which shows up well on the SPC Meso data. Given the trends will
take thunder out of the grids and HWO through the this evening
into much of the night. The guidance remains in favor of a
disturbance progressing northeast out of the Tennessee Valley
into eastern Kentucky toward dawn. Only minor edits were made
toward the latest trends at this time.
UPDATE Issued at 651 PM EDT THU AUG 9 2018
The latest WSR-88D radar scans are showing a few isolated showers
tracking across portions of the area this evening. However, did
keep the mention of thunder since there has been some signs of ice
when looking at the MRMS VII product. These will subside as we
loose the daytime heating, but more activity remains possible
toward dawn as an upper level disturbance approaches. Overall
these were mostly minor updates to the grids and also made
updates to temperatures, dewpoints, and winds with the latest obs
.SHORT TERM...(This evening through Friday night)
Issued at 304 PM EDT THU AUG 9 2018
Seeing a rather complicated surface pattern this afternoon. There
is a quasi-stationary frontal boundary aligned from the Ohio
Valley down to the Arklatex region. Mid/upper level charts show a
trough over the eastern CONUS and models drop additional energy in
the form of shortwaves southward out of Canada which tend to
maintain this feature through the short term.
In general the HRRR has been handling the less organized
convective activity poorly, but has managed to capture the more
obvious line of showers and thunderstorms crossing Tennessee and
south central Kentucky this morning. HRRR has been consistently
moving this activity eastward but weakens the northern end
considerably as it passes through our southern most zones through
the afternoon. RAP/NAM solutions follow this scenario as well, but
most models show a general redevelopment of rain through the
overnight as as a shortwave trough enters into the lower Ohio
Valley. Reflected surface wave looks quite weak and undefined.
Lower level wind field is also quite weak but there may be a few
hours of upper level support leading up to dawn from the right
entrance region of a jet streak over OH/WV that may help with some
lift aloft. Whats left of the surface front appears to wash out
with time. Most of any rainfall through the short term should be
associated mainly with relatively weak synoptic features
interacting with mesoscale forces and diurnal heating. Thus
convection will be mainly diurnally driven.
PWATs increase considerably through the overnight into Friday
morning and more significantly across our south, up around 1.8 to
1.9 inches. Storm motion drops off to less than 10 kts as well.
Freezing levels remain respectfully high at around 13 kft and
CAPES are favorable for warm rain processes. Suspect there could
be some low centroid heavy rainers as a result towards dawn and
through much of the day Friday. Temperatures will be moderated
through the period as well with cloud cover and an increased
threat of rain keeping overnight lows up and afternoon highs down
.LONG TERM...(Saturday through Thursday)
Issued at 304 PM EDT THU AUG 9 2018
A shortwave trough will slowly push across the area over the
weekend, but lack of significant forcing will yield only
scattered showers and storms each afternoon. The threat on Sunday
will shift exclusively into southern and southeast Kentucky before
pushing south Sunday evening. As we head into early next week,
the period is looking drier, especially on the 12z GFS. The ECMWF
keeps some small chances in the afternoons, but will limit pops to
only slight chances for Monday through Wednesday. A more
organized system may arrive next Thursday, but details are fairly
questionable at this time range. We may warm up nicely into the
middle of next week pending the strength of the late week system.
Highs through next week will stay fairly close to normal in the
low to mid 80s. with overnight lows staying the 60s.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 743 PM EDT THU AUG 9 2018
We are seeing some isolated shower activity this evening, but
these showers are expected subside through the evening. The only
site the could see issues from these at this point would be JKL,
but have left mention out for now given the up and down nature of
this convection. Did keep the mention of lowering CIGs and VIS at
all the sites again tonight, but a little concerned on how this
will evolve at SME/LOZ given the potential for showers toward
dawn. Also, did opt to TEMPO JKL given the potential for valley
fog to creep into the TAF site. Overall have all the sites seeing
at least IFR conditions or lower at times tonight through Friday
morning. We should see some improvement through the day, but a
upper level disturbance will bring the chances for showers and
thunderstorms through the morning and afternoon Friday. For now
left the mention of VCSH from previous forecast cycle. Winds will
remain light through the TAF period.
Area Forecast Discussion
National Weather Service Medford OR
838 PM PDT Thu Aug 9 2018
.DISCUSSION...Smoke continues to be the main feature of concern
across southern Oregon and northern California. Visibilities have
been ranging from three quarters of a mile to a mile and a half
over the past few hours. This poor air quality will continue again
for one more night and morning before a dry cold front comes
through tomorrow evening and makes things a little less hot. The
winds will pick up tomorrow and will help drive the smoke to the
east-- at least briefly.
With the evening update package, my only changes are to expire the
heat advisory and to ponder the necessity for any fire weather
products for tomorrow. Otherwise, the current forecast looks good,
and the previous discussion will provide the details of the
.AVIATION...For the 10/00Z TAFs...Marine stratus mainly along the
coast but beginning to push back inland. Starting first in the
Coos Bay/North Bend area. A bit of a hole around Cape Blanco but
that will fill in over the next few hours. Confidence is high that
the stratus will come back onshore with widespread MVFR ceilings
and visibility and last through the night. A large closed low
offshore will approach the coast overnight. Generally, this
increases the depth of the marine layer which makes for a low
ceiling and drizzle situation rather than for fog. Inland, we do
not expect stratus will penetrate as far inland as Roseburg
tonight, but it should be close and between 5am and 9am Friday
there is fair uncertainty as to possible ceilings near 2000 ft.
Smoke is the contributer to MVFR weather at Medford, Klamath Falls
and much of southwest Oregon. The latest 24-hr forecasts reflect
similar trends as observed yesterday...deteriorating at evening
and remaining MVFR range overnight, then improving some by late
morning Friday. Stavish/JBL
.MARINE...Updated 815 PM PDT Thursday 09 August 2018...Light
winds and seas continue through Friday, then a weak front will
pass through Friday night into Saturday morning. North wind
develops through Saturday afternoon. Small craft advisory winds
are possible south of Cape Blanco Saturday night and these winds
increase through Sunday with a strong thermal trough over the
south Oregon coast. The thermal trough and winds weaken a but
Monday, then even more Tuesday. Stavish.
.PREV DISCUSSION... /Issued 236 PM PDT Thu Aug 9 2018/
SHORT TERM...The high pressure ridge over the area, which is
bringing very hot temperatures to inland areas, will shift
eastward on Friday as an upper trough moves into the Pacific
Northwest coast. Today, one of the main concern is with heat
impacts across inland areas. Temperatures are on track to be
similar or slightly higher than yesterday. A heat advisory
(NPWMFR) remains in effect through this evening for areas in
southern Douglas, Josephine, Jackson, central Siskiyou and Lake
counties where highs are expected to rise into the upper 90s and
low 100s. A second concern today is with breezy winds and dry
conditions. Across portions of Northern California, breezy winds
and dry humidities are expected this afternoon and evening,
bringing increased fire danger. A red flag warning (RFWMFR) is in
effect for these conditions. On Friday, the upper trough will move
into the Pacific Northwest coast bringing slightly less warm
temperatures. Gusty winds and continued dry humidities will bring
additional fire weather concerns, especially to Northern
California and areas east of the Cascades. Models are in good
agreement showing the upper trough continuing to move inland
Saturday then shifting northeast on Sunday.
Overall, models have trended slightly slower with the upper trough
moving inland on Friday with the trough pushing into the coast
late in the day and into the evening. With this trough moving
onshore, expect temperatures to lower about 3 to 6 degrees across
inland areas. Although the forecast trough progression inland is
slower than previously shown, models are still in good agreement
that winds will increase late in the day Friday and into the
evening across inland areas. The strongest winds are expected in
the Shasta Valley and east of the Cascades, where gusty southwest
winds will develop. The combination of gusty winds and very dry daytime
humidities may bring critical fire weather conditions to these
areas. So, fire weather watches remain in effects for portions of
central and eastern Siskiyou, Modoc, Lake and Klamath counties.
Other inland areas from the Cascades west will also see breezy to
gusty west winds late Friday afternoon into Friday evening.
Additionally, transport winds aloft will increase during the day.
The 12z high resolution HRRR model shows smoke decreasing over
the area as it is transported to the east and northeast Friday
afternoon. So expect some improving conditions, including to
areas west of the Cascades. Of note though, local wildfires will
continue to bring some smoke impacts to areas downwind of the
fires. So expect that any improvement in smoke over the area will
be brief. Smoke is expected to increase again Saturday afternoon
and evening as northwest to west surface and transport winds
return. An air quality advisory (AQAMFR) remain in effect due to
the impacts of wildfire smoke for areas in southwest Oregon. Smoke
impacts are also likely into Northern California.
Along the coast, the upper trough passage will bring a deepening
marine layer Friday into Saturday morning. This may result in
isolated showers or light drizzle along with patchy fog near
coastal areas. Also the marine layer is expected to spread inland
and bring clouds into portions of the Umpqua basin Friday night
into Saturday morning, including at Roseburg. Models indicate the
depth of marine layer extending up to around 1500 to 2000 ft
elevation Friday night and Saturday. So, overall, expect the
clouds to stay north of the Umpqua divide. Saturday will likely
be the least hot day for inland areas with temperatures forecast
in the 80s to near 90 for most inland valleys.
On Sunday, the upper trough will lift northeast. Meanwhile,at a
surface, a thermal trough will develop along the coast. This
pattern will bring a warming trend to inland areas. Guidance
indicates temperatures will warm into the lower to mid 90s across
western valleys but depending on smoke levels, these temperatures
may be slightly lower. With the surface thermal trough along the
coast, also expect breezy northeast winds over the coastal
mountains with lighter northeast winds over the inland mountains
Saturday night into Sunday morning. In the afternoon the winds
will change to north to northwest over the area. With a mix of
northeast to northwest winds, expect areas of smoke from nearby
wildfires to continue to bring smoke and air quality impacts to
LONG TERM...Monday through Thursday, an upper ridge will build
over the region early next week then weak shortwaves may move up
from the south to southwest by mid week. As the ridge builds,
expect temperatures to warm up Monday and Tuesday across inland
area with highs warming back into the mid to upper 90s across
western valleys and in the upper 80s to near 90 for valleys east
of the Cascades. By Wednesday, models are indicating some weak
upper shortwaves and mid level moisture moving into the area from
the southwest. There is lower confidence on the details of these
disturbances as models show significant run to run variability.
Also a significant variable is whether any upper and mid level
moisture originating from Tropical Storm John moves up into
northern California and southern Oregon. So, will continue to
monitor this with future model runs.
FIRE WEATHER...Updated 200 PM PDT Thursday, 9 August 2018...
Hot and dry weather will continue for the next couple of days. The
models continue to trend slower with the progression of the upper
low Friday into the weekend. The slower arrival of the upper low
will lessen the gusty winds and low relative humidity threat into
this evening. This is especially the case in the Shasta Valley. Winds
are still expected to increase some later this afternoon into this
evening in the Shasta Valley, but they are not expected to be strong
and thus Red Flag conditions won`t be met. Therefore we decided to
cancel the Red Flag Warning for fire zone 281. The Red Flag Warning
remains in effect for portions of of Fire zone 285, but there`s
increasing evidence it will affect a small area and adjustments were
made to the coverage area. Details on this can be found at RFWMFR.
The upper low will push closer to the Oregon coast Friday. Models
are in pretty good agreement showing 700mb winds increasing Friday
afternoon. This along with surface heating will allow some of the
stronger winds to mix down at the surface. Also with the slower
arrival of the upper low. Temperatures, especially east ofthe
Cascades could be similar to what they are today. At the same time
relative humidity will be low, thus a Fire Weather Watch remains in
effect for Friday afternoon and evening. The coverage area for the
watch has been left unchanged. For details on the watch please see
South to southwest winds will increase further Friday afternoon
ahead of and with a dry cold front. It will likely result in
critical conditions across the east side bringing low RH and strong,
gusty winds. Winds could gust 30 to 40 mph there with RHs around
10%. West side areas will not be quite dry enough to reach warning
criteria, but gusty northwest winds will also be stronger than
normal and are likely to increase fire activity.
The decision was made to keep the watch and not upgrade at this time
due to the models trending slower with the arrival of the upper low.
Heat: The inland warming trend will continue and reach a peak on
Friday. Wildfire smoke has been a hindrance to heating (typically by
around 3 to 5 degrees), but high temperatures will still be about 10
degrees above normal. We`ll have a one day cool down with
temperatures about 10 degrees cooler, before they rebound on Sunday
and then edge up again early next week.
Lightning: Model guidance is generally indicating moisture
sufficient for thunderstorms to be lacking through at at least the
start of next week. By next Tuesday, there may be sufficient mid
level moisture and instability to bring a threat of thunderstorms,
but this is still a long ways out and the details on timing and
locations of storms could change. -Petrucelli
OR...Heat Advisory until 9 PM PDT this evening for ORZ023-024-026.
Fire Weather Watch from Friday afternoon through Friday evening
Heat Advisory until 9 PM PDT this evening for ORZ031.
CA...Fire Weather Watch from Friday afternoon through Friday evening
Heat Advisory until 9 PM PDT this evening for CAZ081.
Fire Weather Watch from Friday afternoon through Friday evening
Red Flag Warning until 9 PM PDT this evening for CAZ285.
Pacific Coastal Waters...None.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
433 PM PDT Thu Aug 9 2018
.SYNOPSIS...High pressure over the west will maintain very warm
to hot conditions across the interior. Meanwhile, cooler
conditions will persist near the coast due to a persistent
shallow marine layer and moderate onshore flow. Slightly cooler
temperatures are expected by this weekend as high pressure
.DISCUSSION...as of 1:44 PM PDT Thursday...Satellite imagery
shows skies have cleared and stratus has retreated to out over the
ocean. Current temperature trends are running warmer than
yesterday at this time by as many as 10 degrees, with readings
ranging from the lower 60s to lower 70s at the coast, the 70s to
mid 80s around the Bay, and the 90s to near 102 inland.
Expect a repeat tonight with a shallow marine layer near the
coast, locally dense fog is expected at the coast Friday morning.
High pressure will keep the warm/hot temperatures through Friday
before gradual and slight cooling arrives over the weekend when
the upper ridge weakens. Air quality should show some improvement
over the weekend as well when onshore winds strengthen and become
more southwest. Although a cooling trend is indicated, highs
across inland areas will still be quite warm with mid to upper 90s
High pressure aloft will then rebuild westward from the desert
southwest early next week for inland highs edging back to over 100
degrees by Thursday or Friday.
.AVIATION...as of 04:33 PM PDT Thursday...For 00z tafs. VFR
conditions will continue through the evening as stratus resides
along the immediate coast. Slantwise visibility issues will
persist due to smoke and haze from multiple wildfires. Latest HRRR
smoke forecast suggests some possible relief overnight in
vertically integrated and near surface smoke across the Bay Area.
Coastal stratus is expected to return tonight in similar fashion
to what was observed last night with only minor differences.
Patchy dense fog and drizzle possible through the early morning
along the coast. Winds will remain generally light through the
period with locally higher winds and gusts in the
afternoon/evening at KSFO.
Vicinity of KSFO...VFR through the period aside from patchy IFR
cigs overnight and into the early morning. Smoke/haze affecting
slantwise vis will continue to be a concern, although HRRR smoke
model suggests some overnight relief. Breezy winds remain a
possibility into the early evening before diminishing overnight.
Onshore winds will increase again tomorrow afternoon.
SFO Bridge Approach...Same as terminal.
Monterey Bay Terminals...Another early return of stratus is
expected. LIFR/VLIFR cigs overnight into tomorrow morning along
with patchy dense fog. Generally light winds through the period.
.MARINE...as of 02:31 PM PDT Thursday...Breezy northwest winds
will prevail with locally stronger gusty winds along the coast,
especially near coastal gaps and north of Point Reyes and south of
Point Sur. A pair of southerly swells generated by tropical
systems to the south will move through the coastal waters through
the coming days.
.Tngt...SCA...SF Bay until 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm
PUBLIC FORECAST: Sims
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Area Forecast Discussion
National Weather Service Nashville TN
832 PM CDT Thu Aug 9 2018
FOR EVENING DISCUSSION.
A few showers and thunderstorms have developed in western areas
tonight ahead of the upper shortwave trough. Short term models
such as the HRRR and NAMNest want to develop a MCV type feature
across the area overnight, mainly for areas north of I-40 and east
of I-65. Went ahead and raised pops slightly to reflect CAM
consensus. Also added in mention of patchy fog as earlier rains
provided more surface moisture and areas may see some fog
development overnight. Other than that, no major changes to the
forecast this evening and overnight.
00Z TAF DISCUSSION.
VCSH/-SHRA to affect all airports this TAF period with scattered
showers this evening at CKV/BNA/MQY. Cannot completely rule out a
VCTS at BNA/MQY but storms should mainly remain south of those
airports. Overnight, models consistent in bringing -SHRA to CSV,
with more VCSH at BNA/MQY/CSV on Friday. Cigs to remain mainly VFR
but periods of MVFR visibility anticipated at CKV/CSV late tonight.
Area Forecast Discussion
National Weather Service Tucson AZ
202 PM MST Thu Aug 9 2018
.SYNOPSIS...Abundant moisture and favorable flow will provide an
active period for thunderstorms with locally heavy rainfall at times
into early next week. Daytime temperatures will also trend near or
below seasonal normals.
.DISCUSSION...The considerable cloudiness this morning and early
this afternoon had delayed the onset of scattered showers and
thunderstorms today. Latest HRRR solution had backed off on the
amount of activity projected for this evening and tonight. The HRRR
model also showed a much later start to the showers and
thunderstorms, with most of the activity occuring across southeast
Arizona after 03Z Friday. Despite this delay, the possibility of
blowing dust in the lower deserts was still not out of the question.
Thus, will keep the Blowing Dust Advisory posted until 10 PM MST
this evening. Otherwise, models keep a favorable flow pattern across
the region for daily showers and thunderstorms through at least
early next week. Thereafter, the high pressure ridge centered north
of the area will shift southward next week with warming aloft
limiting thunderstorm activity a bit. High temperatures will also
return to normal readings.
.AVIATION...Valid through 11/00Z.
Scattered TSRA/SHRA this evening and overnight into Friday.
Otherwise, SCT-BKN cloud bases generally 8k-15k ft AGL. WLY/SWLY SFC
winds this afternoon will remain less than 15 kts, but gusty erratic
outflow winds to 40 kts will be possible in and around stronger
TSRA. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...The weather pattern will remain favorable for daily
showers and thunderstorms into next week. Daytime temperatures will
remain below normal through the weekend, before warming back to
normal Monday through the rest of next week. Terrain driven 20-ft
winds at less than 15 mph, except for in and around thunderstorms
where strong outflows may occur.
Blowing Dust Advisory through 10 PM MST this evening for AZZ501-
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