Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/22/18
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
609 PM MDT Fri Sep 21 2018
00Z TAF CYCLE
Rich low level moisture is in place across central and eastern areas
thanks to persistent easterly flow behind a back door cold front that
arrived early this morning. This will allow low clouds with MVFR
and IFR conditions to linger into the early evening across the east
central and southeast plains. Areas of low clouds with IFR conditions
will probably also develop along the east slopes of the central
mountain chain early this evening, and perhaps even at KSAF.
However, models depict drier air settling into the far eastern plains
by late evening, and some downslope flow developing along the east
slopes of the central mountain chain by then. This should cause areas
of low clouds to decrease in coverage and become patchier across the
plains through the late night hours. Fair weather is expected
.PREV DISCUSSION...227 PM MDT Fri Sep 21 2018...
Cool and breezy conditions with a few showers across southeastern
New Mexico will continue through tonight then dissipate after sunrise
Saturday. Patchy fog is possible Saturday morning along the east
slopes of the central mountain chain. High pressure will build over
the state over the weekend and bring delightful weather with mild and
sunny afternoons and cool nights. Temperatures will warm closer to
normal Monday with increasing westerly winds. A back door cold front
is on target to move through the eastern half of New Mexico Tuesday
as a trough of low pressure passes to our north. Showers and storms
may return to the area Tuesday night and Wednesday along with cooler
The back door cold front that moved through eastern NM this morning
has brought cool and breezy conditions to the plains. Low cigs in
its wake are slowly dissipating but will likely redevelop along the
east slopes tonight. The latest RAP visibility product shows fog in a
few areas along the east slopes of the central mt chain. An area of
low cigs are also possible around the Cont Dvd where low level
convergence exists behind the cold front. Temperatures tonight will
be a few degrees warmer than last night with weaker inversions.
Saturday through Monday will offer delightful September weather as
dry upper level high pressure crests over the area. Winds will be
relatively light with temperatures modifying close to or slightly
above normal through Monday. Overnight low temps will be cooler with
efficient radiational cooling leading to strong inversions. Patchy
fog cannot be ruled out within mountain valleys and the eastern
plains on any night as soils are rather moist across the area.
Tuesday will feature another back door cold front across the eastern
plains as an upper level trough shifts east through the central
Rockies. This front is shown with very good model agreement to
advance west into the Rio Grande Valley late Tuesday and set the
stage for showers and storms along and east of the central mt chain
High pressure aloft will continue building in from the west tonight
and Saturday. Temperatures will trend up to slightly above average
over the weekend and into early next week underneath the above
mentioned upper high. A relatively strong backdoor cold front will
drop into eastern New Mexico Tuesday, pushing west of the central
mountain chain Tuesday night. Models are trending wetter with this
feature, developing showers and storms along and near the front as
it moves through eastern and central portions of the state
Wednesday. A drier backdoor front is forecast to slide in from the
northeast Thursday night.
Widespread fair to poor ventilation rates are forecast over northern
and central New Mexico Saturday. Improving rates are forecast for
Sunday through Tuesday with a downtrend in rates Wednesday.
Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Fri Sep 21 2018
.SHORT TERM...(This evening through Saturday)
Issued at 245 PM CDT Fri Sep 21 2018
The upper trough over the northern Great Lakes will continue to
progress eastward this evening/overnight with high pressure
building in from the west. Winds will rapidly decouple/subside by
sunset as the high builds in with skies clearing from the north
and west by early evening. With light winds/clear skies
overnight, temps should cool into the 30s to low 40s over the
region. The favored cool spots across central and north-central
Wisconsin look most susceptible to frost with lows expected into
the low to mid 30s. Will issue a Frost Advisory for these areas
for early Saturday. In addition, some river valley fog may form
early with light flow under the surface high.
Seasonably cool weather will be the rule for the weekend with dry
conditions as the surface high migrates eastward across the Great
Lakes. Highs on Saturday will generally be in the 60s on Saturday
with some modest recovery into the low 70s in spots on Sunday as
southerly flow develops ahead of low pressure developing across
the high plains.
.LONG TERM...(Saturday night through Friday)
Issued at 245 PM CDT Fri Sep 21 2018
A relatively cool period is expected for much of the coming work
week. Temps on Monday will rise back into the 70s ahead of an
upper trough and associated cold front that is forecast to slide
through Monday night. Instability looks fairly unimpressive, but
chances for showers and storms will increase late Monday into
Monday night with the front.
Behind the front, low-level cold advection/breezy northwest winds
are expected Tuesday with some lingering clouds or possibly a few
showers under cyclonic flow aloft with the passing upper trough.
Surface high pressure briefly is expected to build over the area
under zonal flow aloft ahead of another upper trough and
associated cold front dropping out of the northern plains by
around Thursday. This will bring rain chances back to the region.
Highs will generally be in the 60s following the cold front
Monday night, with perhaps even cooler air invading following the
late week cold front
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1100 PM CDT Fri Sep 21 2018
Cigs/vsby/WX: clouds have shifted south this evening - and expect
mostly skc/sct VFR conditions through the weekend.
The one caveat to this is the potential for valley fog and/or bkn
low stratus at KLSE Sat morning. Winds off the deck blowing +10 kts,
but progged via RAP Bufkit soundings to lighten and deepen
overnight. More suggestive of a sct-bkn003 potential at KLSE with
any fog holding over the river channel. Will keep BCFG sct003 for
now. River valley fog will continue to be monitored Sun/Mon mornings
with high pressure in the vicinity. Again, low level winds look to
be a tad too high to allow for dense fog at KLSE - at least for now.
Winds: light vrb overnight. Should become southerly early Sat,
holding around or just below 10 kts through the afternoon.
WI...Frost Advisory from midnight tonight to 8 AM CDT Saturday for
Area Forecast Discussion
National Weather Service Columbia SC
1025 PM EDT Fri Sep 21 2018
A large dome of high pressure aloft will ensure fair weather through
at least Saturday. The high will shift to our east Sunday through
early next week, while a slow moving front approaches and stalls,
and moisture increases from a low-level flow off the Atlantic.
Another front will move into the region mid to late week but may
stall. These factors will lead to increasing precipitation
chances next week.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Surface pressure ridge will remain centered along the New
England coast with ridging extending into the forecast area.
Moisture remains shallow and a strong mid-level cap is in place
which will keep conditions dry overnight. Low temperatures will
range from the mid 60s to around 70 degrees under mainly clear
skies. Most of the models are indicating at least patchy late
night fog given shallow but ample low-level moisture combined
with dry air aloft.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Large dome of high pressure aloft will remain overhead Saturday,
while considerably dry air aloft remains in place. This will ensure
fair weather and continued above normal temps Saturday. Gradual
increases in lo-level moisture may provide some late
night/early morning fog/stratus potential. By Sunday, upper high
to shift to our east. A front will move into the Mid Atlantic
States then back door down towards our region Sunday. Current
indications are that the weak wedge will remain just to our
north Sunday but may be able to progress south into our northern
forecast area (FA) Sunday night. Slight increases in moisture
may provide slight chance POPs Sunday mainly to our north near
the front and near the coast.
.LONG TERM /MONDAY THROUGH FRIDAY/...
Limited confidence Monday on how far south the wedge will get.
GFS more aggressive with it than other guidance. Will expect weak
wedge to be in or near our northern FA early Monday with some
expectation of gradual erosion during the day Monday, though
some uncertainty exists. Upper high to remain to our east while
upper troughiness develops into the central CONUS. Upper
disturbance and area of low pressure offshore to move towards
the SE Coast in clockwise flow around the upper high. Latest
guidance indicates the system weakening as it approaches the
coast. A series of fronts expected to approach our region mid to
late week. Gradual moistening of the atmosphere expected to
lead to increasing POPs. Some questions as to whether the
frontal boundaries will stall near our region or be able to move
through late in the forecast period. Went with model consensus.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected during the 24-hour TAF period
outside of early morning fog or stratus.
Dry high pressure will continue to dominate. There may be enough
low-level moisture combined with nocturnal cooling to help
cause stratus and fog during the early morning hours. Little
boundary layer wind favored fog over stratus. Low-level
moisture was highest in the east and south sections affecting
the AGS, DNL, and OGB terminals. We followed the GFS LAMP and
forecasted a period of IFR fog at these terminals. Forecasted a
period of MVFR farther northwest at the CAE and CUB terminals.
Confidence is low because there was spread in the guidance with
the HRRR and crossover temperatures indicating mainly VFR
conditions. Heating and mixing should dissipate any fog
beginning around 13z. Expect variable but mainly easterly wind
less than 10 knots during the daytime hours.
EXTENDED AVIATION OUTLOOK...An onshore flow should bring
low-level moisture with an increased chance of late night and
early morning stratus and fog. There will be a chance of mainly
afternoon and evening showers and thunderstorms.
Area Forecast Discussion
National Weather Service Grand Junction CO
516 PM MDT Fri Sep 21 2018
.SHORT TERM...(Tonight through Saturday night)
Issued at 348 PM MDT Fri Sep 21 2018
Nice and quiet across eastern Utah and western Colorado this
afternoon as dry southwest flow remains overhead. A few cumulus
clouds have developed across the San Juan Mountains over the last
hour or so with an isolated storm or two possible later on this
evening. Looking at webcam imagery across southeast Utah, patchy
smoke can be seen filtering into the region from the Riggs and
Lonely fires burning in south-central Utah. The experimental
HRRR-smoke shows smoke continuing in this area through this
evening before dispersing to the northeast. Areas of smoke were
also added in and around the eastern Uintas as the HRRR shows
smoke from the Pole Creek Fire moving in from the west late
The upper level gradient will tighten on Saturday as a broad
Pacific trough digs into the northwestern CONUS. Mostly sunny
skies will support mixing during the afternoon hours resulting in
breezy conditions, especially up in northwest Colorado. However,
confidence on the duration and intensity of wind gusts remains
low to moderate, so no changes were made to the Fire Weather Watch
on Saturday. More on that in the Fire Weather discussion below.
Otherwise, weather conditions on Saturday will be very similar to
what was experienced today with slightly warmer temperatures and
isolated storms down south. High level clouds will begin to
increase Sunday night as an upper level jet approaches the region.
.LONG TERM...(Sunday through Friday)
Issued at 348 PM MDT Fri Sep 21 2018
As referenced in the Short Term discussion, an upper level jet
associated with the Pacific trough will dive into the Great Basin
early Sunday. As the jet moves through the forecast area
throughout the day, a surface cold front will also push across the
region. Isolated showers and thunderstorms will develop over the
higher terrain across the northern tier of the area Sunday
afternoon before spreading to the central and southern mountains
Sunday night. Activity will persist into Monday afternoon before
drier air quickly filters into the region from the west-northwest.
Breezy conditions will accompany the passage of the jet and the
cold front, potentially leading to critical fire weather
conditions across far northwest Colorado Sunday afternoon.
Mostly sunny skies will return to the region on Tuesday, though
daytime heating will lead to isolated storms firing over the San
Juan Mountains Tuesday afternoon. Daytime highs will have cooled
to right around seasonal normals on Tuesday, though readings will
rebound back to several degrees above normal by Friday as high
pressure rebuilds over the southwestern CONUS.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 515 PM MDT Fri Sep 21 2018
A few gusty winds up to 30kts are being reported at a few TAF
sites this afternoon. Namely, KRIL AND KEGE while others are
seeing gusts up to 20kts. These winds will die down over the next
few hours giving way to light winds as clear skies continue. More
of the same tomorrow.
Issued at 348 PM MDT Fri Sep 21 2018
Expect southwest winds to increase over northwest Colorado this
weekend ahead of an approaching Pacific trough. Vegetation remains
very dry across the region so gusty southwest winds combined with
above normal temperatures and low relative humidity could result
in critical fire weather conditions. Confidence is increasing for
Sunday afternoon when the ~60 knot upper level jet moves overhead.
As for Saturday, while plenty of sunshine will allow for some
mixing during the afternoon hours, Red Flag criteria looks to be
more borderline. Therefore, the Fire Weather Watches for both
Saturday and Sunday remain in effect.
CO...Fire Weather Watch from Saturday afternoon through Saturday
evening for COZ200.
Fire Weather Watch from Sunday afternoon through Sunday evening
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1028 PM CDT Fri Sep 21 2018
Storms have been firing this evening over NW counties where some
immediate flooding concern exists. Have already issued one
advisory and will continue to monitor there. Expect those cells to
be locked in that area for awhile yet then gradually shift toward
the SE based on latest HRRR runs. Some cells have had some
rotation leading to right movement relative to and opposing to mean
flow...leading to forther slowing of storms and higher local rain
As per previous discussion wet period remains in place for several
days yet. Although most of the focus of convection is farther
north...ingredients are right for locally heavy downpours with
precipitable water values close to 2.5 through Sunday...so will
need to be wary of any training echoes...which might lead to
flash flooding. Most locations more likely to have more of a
localized street or poor drainage flooding threat.
.PREV DISCUSSION... /ISSUED 736 PM CDT Fri Sep 21 2018/
Storms over most of the region have diminished with just some
lingering light stratiform rain. Closer to the coast a narrow band
of showers/thunderstorms moving through the GLS/EFD area with
gusty winds...more storms lining up offshore south of Galveston.
More concerning in the short term is the area of local convergence
around CLL-11R-AUS corridor with the development of thunderstorms.
Have altered the CLL terminal to carry a TEMPO for a few hours
there with TSRA but some of the short term guidance supporting a
threat extending as late as 05z. Some patchy light fog possible
after midnight though the mid/upper cloud deck should help hold
temperatures up tonight.
After 06z except showers to develop in the moist axis over the
coastal waters aimed in general toward the GLS bay area. Expect
scattered showers to stream into the GLS area extending up to
around HOU area with instability on the increase toward morning
will probably see more thunderstorms mixed and the area of
showers/thunderstorms intruding further north into the IAH/CXO
area. By mid morning easily reached convective temperature of 83
should lead to development of more storms inland and a lessening
over the Gulf waters. Area terminals will be plagued with showers
or thunderstorms in the vicinity for hours throughout the day.
Another concern will be the development of a line of storms late
afternoon or evening along the approaching Pacific cold
front/thunderstorm enhanced by outflow boundaries moving through
the Hill Country and nearing the western CWA. The mesoscale
interactions could make for a wet period but it could be just west
of the Metro hubs or it may just reach them. Far from settled
PREV DISCUSSION... /ISSUED 357 PM CDT Fri Sep 21 2018/
Another day today of showers and thunderstorms, and this is a
pattern that does not look to change any time soon as an early
fall front sags towards Southeast Texas. The worst flooding
concerns will be well to our north and northwest, though the
northwestern edge of our area may be close enough to the heavier
rain that we`ll have to keep a close eye on trends and mesoscale
features. Look for daily bouts of showers and storms carry through
next week, with another potential front late next week.
NEAR TERM [Through Tonight]...
For now, radar shows storms are moving quickly enough that,
despite some briefly torrential rainfall, there are not yet any
flood concerns. However, if any type of backbuilding or training
sets up, particularly in places like eastern Harris County where
a round of heavy rain has already fallen.
While water vapor imagery shows a subtle vort max roughly over
the Houston area, expectations are that towards evening, that will
move off to the east, and leave an area of relative subsidence
between this vort max and the vorticity associated with a trough
over Central Texas. That should cause convection to dampen or
even end completely for a brief time. However, any respite will be
short-lived, and towards dawn, convective development looks to
begin again - particularly in the vicinity of Galveston Bay and
its Gulf waters.
SHORT TERM [Saturday Through Sunday Night]...
Saturday and Sunday will again bring us further bouts of showers
and storms, though the character of that rain may change subtly.
Saturday should see trends begin much like recent days, with
nocturnal marine convection transitioning to the coast, and then
spreading inwards. However, at the same time, a boundary will be
dropping into the area from the northwest. Really unsure whether
it`s a true cold front, or some sort of large amalgamated cold
pool boundary, but I suppose in the end it`s really unimportant
precisely what it is. This boundary will serve as the increasingly
dominant focus for convection from Saturday into Sunday as it
Fortunately, the upper trough supporting the front to a high risk
of excessive rainfall in Oklahoma and North Texas today should
begin to flatten and lift to the northeast, starving the boundary
of upper support as it moves southeastward. This should keep the
greatest rainfall threat to the north of our area, though with
ample moisture we may see localized flooding potential from
briefly torrential rainfall. The operative word in that last
sentence, however, is should. Any further deepening of the trough
or failure to eject would combine with the slow moving boundary
and very high moisture levels could create a more significant
rainfall situation. For this, WPC has brought down it`s marginal
risk area for excessive rainfall to the coastline, covering most
of our area.
LONG TERM [Monday Through Friday]...
The string continues early next week, as an inverted trough moves
westward across the Gulf of Mexico. Though it will weaken and
dissipate as it approaches the area, it will keep the subtropical
ridge from building back in and continuing rain potential.
Finally, for the back half of next week, our next upper trough
will move into the area and could bring us our first real taste of
fall...emphasis on "could". The trend in the modeling has been for
a weaker trough, and though it`s only been a subtle trend, it is
enough at this time of year to feel increasingly uncertain about
just how strong its associated front will be. For now, the
forecast does not significantly impact temps and dewpoints for the
late week, but does nudge things down a bit until onshore flow
resumes. What there is more certainty on is continued good
potential for rain, so PoPs still relatively high, especially
given the range of this forecast.
AVIATION [18Z TAF Issuance]...
Scattered shower and thunderstorm activity is expanding across
Southeast Texas and will continue through the afternoon. The
strongest storms will have gusts up to 25-30 mph with brief heavy
rainfall and frequent lightning. Will add TEMPO groups as
necessary through the afternoon hours, but expect periods of
showers and thunderstorms for most of today. Some guidance is more
bullish and keeps the convection around until 02-03Z near the
Houston Metro, but sinking air as a result of the stronger storm
complex over Central Texas will likely dampen these storms closer
With extra moisture from today, cannot rule out patchy fog
development in more rural areas, but a BKN/OVC cirrus deck may
result in no fog development. An additional disturbance and surge
of moisture tomorrow morning will move onshore from the Gulf, so
have started shower development much earlier tomorrow than was
seen today. Isolated thunderstorms are possible early tomorrow
morning, as well. Morning showers will eventually transition to
thunderstorms 16-18Z tomorrow and persist for much of the day.
Light to moderate onshore winds will prevail for the next few days.
Winds may briefly shift to northerly as a weak boundary progresses
southward into the Gulf. The pressure gradient will gradually relax
this weekend as the boundary progresses southward, at which point
winds will follow a typical diurnal pattern. Otherwise, periods of
showers and thunderstorms will continue through the weekend. Expect
locally higher winds and waves in any storms.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 87 72 84 72 / 40 80 60 50 30
Houston (IAH) 77 87 75 86 74 / 60 80 50 70 40
Galveston (GLS) 80 86 78 84 78 / 70 80 60 60 60
Area Forecast Discussion
National Weather Service Louisville KY
950 PM EDT Fri Sep 21 2018
Issued at 945 PM EDT Fri Sep 21 2018
Weakening showers continue to push east over east-central KY. These
showers originated along the surface cold front earlier this
evening. This front has been a little slower than model forecasts on
its movement SE into central KY. The front is very close but still
has not cleared SDF or LOU. A new rain shower recently popped up
again near the Jefferson Co IN-Trimble Co KY line along this front.
Overnight, the front will sag slowly south, but have upped morning
low temps a degree or two in some areas north of the front. Clouds
will stream NE into the lower OH Valley. The next question is precip
potential. With ample moisture available, anywhere south of the
front will have a chance of showers overnight. High resolution short
range models do show development of some showers and perhaps a few
storms over central/south-central KY after midnight. In addition,
current radar shows storms developing over parts of middle and
western TN, which the latest HRRR model lifts NE into south-central
KY late tonight. Thus, have upped POPs some over south-central KY
overnight. Scattered light rain showers may return to parts of north-
central KY by morning.
Issued at 550 PM EDT Fri Sep 21 2018
Radar indicates that a line of showers and thunderstorms continues
to move east into east-central and south-central KY at this time.
Still a few strong cells in the line with gusty winds, but trend
last half hour or so has been for a slight weakening, although still
very heavy rain with the strongest cores. This is along a pre-
frontal trough or convergence line.
The actual surface front is marked by a fine line on radar near the
OH River at this time, and renewed convection that has fired on this
front, even through the pre-frontal convection took a bit of the
energy and instability with it. The frontal storms will sag
southeast, affecting Jefferson, Oldham, and Henry in the immediate
term, with scattered other cells expected over north-central KY as
the front sags south across the OH River.
The front will end precip chances for awhile over the northern part
of the forecast area with some temporary clearing behind it until
more clouds move back into the region from the west and southwest
Grids/forecast has been updated to account for latest radar trends
and expected cloud and precip chances overnight and Saturday.
.Short Term...(This evening through Saturday)
Issued at 310 PM EDT Fri Sep 21 2018
A closed low at the surface located at the southern tip of the
Hudson Bay on the Quebec/Ontario border has a cold front extending
down through the Great Lakes and the Ohio Valley. Several outflow
boundaries ahead of the cold front have produced lines of showers
and storms that are affecting S Indiana and Central Kentucky that
appear to be causing a stabilizing effect on the atmosphere prior to
actual frontal passage this evening, thus reducing the severity of
storm chances associated with frontal passage.
A current line of showers and storms extends from north-central KY
southwestward to SW KY. SPC convective outlook has S Indiana and
central KY is a marginal threat of severe weather. With sufficient
instability (CAPE around 2000 J/kg) and deep layer shear at 30kts,
some of these storms do have potential to be severe. Main threat
would be damaging winds associated with storms (DCAPE between 800
and 1000 J/kg). Another possible hazard would be localized flooding
issues as precipitable water values edge close to 2 inches ahead of
the front. But these storms are moving pretty quickly and training
should not be an issue.
A break in clouds between the outflow line of storms and the actual
cold front could allow enough heating to bolster the line of showers
into storms associated with the cold front as it moves into central
KY this evening. But as the sun begins to set, loss of diurnal
heating should quell any further development and convection should
begin to diminish.
Overnight into tomorrow morning expect a low layer of stratus to
form. Precipitable water values remain high and with another
shortwave pulse moving through the boundary to our south, expect
chances of showers to begin overnight and through tomorrow midday.
A noticeable drop in temperatures should be evident as the front
passes this evening. Highs today rest around the 90 degree mark.
Lows Saturday morning will be around 60 in S Indiana gradually
increasing to mid to upper 60s in southern KY. Highs tomorrow in the
upper 60s in S Indiana and N KY and reaching the upper 70s in south
.Long Term...(Saturday night through Friday)
Issued at 250 PM EDT Fri Sep 21 2018
...UNSETTLED AND WET SEVERAL DAYS...
Behind the initial wave of short-term rains associated with the cold
front, expect continued rain chances Saturday night. With a
departing jet streak aloft, we should have enough lift for a band of
light to moderate rains falling somewhere south of the Ohio River,
even well behind the stalling frontal boundary. We may see a brief
break in the rains Sunday morning as that wave lifts out, but with
the front still close enough and additional waves coming, would not
be surprised to see additional showers form Sunday afternoon.
Models then are fairly uniform in bringing the stalled front back
north as a warm front Sunday night and Monday. A moist airmass comes
with that surge. We could see some low-level jet convergence aiding
storm development early Monday, but otherwise support aloft is weak.
Rain chances Monday night and Tuesday morning will depend in part on
how far north that boundary lifts. A trailing cold front then looks
to sweep across the region some time between Tuesday afternoon and
Wednesday, with model guidance still spread out on timing a little.
Timing more during peak instability would lead to some severe storms
coming through, given stronger winds aloft on forecast soundings.
GFS and Euro both hinting that this front too will stall out,
whereas the GEM pushes it through far enough to pull rain chances
out the rest of the week. Given the GEFS means keeping in solid rain
amounts, have to have at least some rain chances in for the end of
the work week.
As for rainfall totals...we should have some periods with heavier
rain mixed with drier patches. Rainfall totals through Wed are
fairly hefty, with 2-3" along the Ohio River and upwards of 5 inches
over south KY. There`s still some wiggle room here, with regard to
locations and given the longer range of the forecast. Will issue a
Hydrologic Outlook to discuss how area rivers can handle this rain.
Temperatures generally will be below normal this forecast period for
highs and near normal for lows.
.Aviation...(00Z TAF Issuance)
Issued at 750 PM EDT Fri Sep 21 2018
Cold front is nearing SDF and will continue to sag southward through
the evening and overnight. Showers and storms along and ahead of it
have cleared HNB, SDF, and BWG, while LEX should see the threat for
a few storms over the next 1-2 hours. Winds will shift to W and NW
with frontal passage, then become more northerly overnight.
Outside of possible reduced vsbys at LEX with showers in the next
hour or two, conditions should remain VFR into the overnight period.
Toward morning, MVFR cigs may develop at BWG and LEX as additional
low-level moisture begins to move into the area.
Models differ in the timing and amount of the next round of showers
to move into central KY Saturday. TAFs reflect scattered showers (no
thunder) affecting BWG and LEX during the morning with a better
chance in the afternoon under a NE surface breeze and MVFR cigs and
vsbys, possibly IFR cigs at times. SDF should be on the edge of the
rain shield but may see some MVFR conditions later in the day.
Meanwhile, HNB should remain north of the showers, with VFR
Please see the previous forecast discussion for details about this
weekend`s weather and the upcoming warmup next week.
.AVIATION...For the 22/00Z TAFs...VFR will continue for all points
south and east of the Umpqua Divide, with the exception of areas in
the vicinity and downwind of active fires. A cold front approaching
will bring possible showers to the coast and into the Umpqua Basin
later tonight, with cigs likely dropping to IFR along the coast and
MVFR in the Umpqua. Periods of lower vsby are also possible in
.MARINE...Updated 200 PM PDT Friday 21 September 2018...A frontal
system will move through the northern waters by Saturday morning,
bringing some light rain. High pressure will build offshore this
weekend into early next week and a thermal trough will develop along
the coast. Steep seas and gusty north winds may develop south of
Cape Blanco Saturday night. Then, Sunday into Monday, expect a mix
of steep to very steep seas and strong gusty north winds that could
reach gale force south of Cape Blanco. In addition to the possible
gales, steep to very steep waves will be possible across these areas
as fresh swell mixes with the background swell and diminishing wind
waves. North of Cape Blanco, small craft advisory level winds and
seas are possible Sunday evening through Monday. Elevated steep seas
may continue in the waters Tuesday into Wednesday due to a mix of
wind seas and swell. -Schaaf/CC
.FIRE WEATHER...Updated 230 PM PDT Friday, 21 September 2018...
The thermal trough will shift east over the westside valleys today
and will bring warmer afternoon temperatures to most areas. West
winds will increase late afternoon and evening and RHs are low
enough to warrant a headline, particularly over Fire zones 285, 624
and 625, but these areas are not expected to reach critical fire
A weak cold front could bring a few showers mainly north of Cape
Blanco along the coast and from the Umpqua Divide northward and west
facing slopes of the Cascades from about Crater Lake north early
Saturday morning into Saturday afternoon. Models are indicating
slightly higher precipitation amounts, but amounts are still
expected to be less than a tenth of an inch,with the highest amounts
in 617 and the northern Cascades.
Confidence is higher we will be dealing with dry conditions with
gusty northeast winds (another thermal trough pattern) Sunday into
next Wednesday with moderate to poor overnight recoveries possible
starting Sunday night. The models are now showing 925 mb winds
higher and supportive of gusty northeast winds, and the pressure
gradient is tight which also supports gusty winds.
The combination of wind and moderate to poor overnight recoveries
could be cause for concern for the Klondike Fire Sunday night
through Wednesday morning. However, humidity recoveries are too high
for a fire weather watch at this time.
From yesterday`s discussion; "Climatologically, many of our most
robust east winds have occurred during the last week of September
and the first week of October, so this certainly bears some
.PREV DISCUSSION... /Issued 254 PM PDT Fri Sep 21 2018/
DISCUSSION...High clouds continue to stream in from the west this
afternoon on the front side of an upper level trough moving into
the area. More dense cloud cover has reached Florence, and we
expect a continued trend toward increasing and lowering clouds
across the forecast area the remainder of today into Saturday,
greatest and fastest for areas furthest northwest.
Meanwhile, through these high clouds, fire activity appears to
have been slow to pick up. The only discernible area of significant
smoke is currently blowing generally west to east from the north
side of the Klondike Fire from about Glendale south to Merlin.
This is about where the HRRR Smoke Model shows where it should be.
Smoke monitors across the area are not showing increases yet, but
those in Grants Pass and Medford are expected to this evening.
Further south, the predicted increase in smoke from the Delta Fire
in the Mount Shasta area is, thus far, not happening. The reason
all this smoke is being mentioned is because the wind pattern this
afternoon through Saturday evening is expected to be very similar
to what occured last weekend, when some smoke impacts developed
Friday into Saturday. We expect to get a better gage of the smoke
based on what does or does not occur this morning. Thus far, the
situation looks somewhat encouraging in that the fires appear less
active than they were a week ago. However, we`ll see how it looks
later this evening and reassess.
Otherwise, the incoming trough will bring a substantial cool down
to the forecast area between today and tomorrow that is likely to
last through Monday morning. High temperatures are expected to
fall about 10 degrees over today`s for Saturday and Sunday, while
lows stay about the same due to increased cloud cover. We`ll also
need to keep an extra close eye on Monday morning, when drier air
and clearing combine. While not a certainty, it is possible that
some of the colder spots in the west side valleys such as in the
Illinois, Applegate, and Rogue valleys could experience their
first frost of the month/latter half of the growing season Monday
morning. Incidentally, the Autumnal Equinox occurs
tomorrow/Saturday at 654 PM PDT.
Regarding rainfall with the incoming front, while model guidance
has generally trended slower and not as wet as previous model runs
indicated, we do still anticipate some light rainfall along and
near the coast and in the Umpqua Basin late this evening through
Saturday. While isolated locations in northern Coos and northern
Douglas counties could experience a tenth of an inch or more of
precipitation, most areas that get rainfall will see less than
a tenth of an inch. Also of note is that a number of the high
resolution models indicate an area of showers getting going
along/near the Siskiyous Saturday evening. Therefore, a
possibility of evening showers has been added to the forecast for
Sunday through Tuesday dry and drying east winds are expected to
cause temperatures to warm to 10 to as much as 20 degrees above
normal for Tuesday through Thursday. A Rex Block expected to be
present in the eastern Pacific next week does not bode well for
precipitation for our forecast area, so expect that fire season
will continue. -Lutz
Pacific Coastal Waters...Small Craft Advisory from 11 PM Saturday to 5 PM PDT Sunday for
Area Forecast Discussion
National Weather Service Paducah KY
823 PM CDT Fri Sep 21 2018
Issued at 824 PM CDT Fri Sep 21 2018
Made some mid-evening update for the remainder of tonight to
more closely reflect the surge of light precipitation overnight
from the southwest ahead of the mid-level low currently straddling
the central KS/MO border at 00z Saturday (7 pm CDT). Secondary
line of sprinkles and/or light showers will develop northeastward
from southeast Missouri into southern Illinois for the remainder
of the evening, eventually spreading back through west Kentucky by
daybreak Saturday. KPAH VAD Wind Profile shows a more distinct
elevated frontal boundary near 5kft AGL, while the KHPX and
KVWX wind profiles are near 5-7kft AGL.
There is a little more gradient and vertical mixing developing
over south Central Illinois and southwest Indiana early this
evening. This combined with the ageostrophic response to the
approaching low will provide for a slight increase in northerly
winds overnight. Made a slight adjustment (1-2 degrees) on
temperatures overnight to reflect precipitation, cloud cover,
temperature and dewpoint advection behind the front overnight.
The potential for over-running/isentropic lift will persist
overnight from southeast Missouri to points northeast. The 12z
ECMWF, combined with the HRRR, ESRL HRRR, and RAP high resolution
guidance appear to have a good handle on the return of moisture
over the WFO PAH forecast area. Reduced the coverage of any
thunderstorm mention to the evening hours and mainly across
southern sections closer to the frontal boundary, cutting through
the southeast part of the west Kentucky Pennyrile region around
Added a mention of sprinkles from mid-deck cloud cover overnight
and reduced thunderstorm coverage to the southern Pennyrile area
closer to the surface cold front.
UPDATE Issued at 643 PM CDT Fri Sep 21 2018
Updated aviation discussion for 00Z TAFs.
.SHORT TERM...(Tonight through Sunday night)
Issued at 323 PM CDT Fri Sep 21 2018
The outflow from this morning`s convection has passed through the
entire region as of 20Z, and the cold front is difficult to find
in the wind field. It appears to be near the Wabash River to near
Dexter Missouri and is finally getting a push with gusty northwest
winds over southeast Illinois. The outflow boundary thoroughly
messed up the wind fields, but many places were able to warm up
to near 90 degrees with sporadic sunshine. With little forcing
aloft and little convergence on the front, convection will be very
limited if not nonexistent for the remainder of the afternoon. We
will continue to monitor radar/satellite trends, but severe
weather is no longer expected.
This evening will be mostly dry, but a few light showers or
periods of sprinkles will be possible. The 12Z models are not in
the greatest agreement with the onset of the over-running
showers/storms overnight and Saturday. The GFS is wetter and
farther north and east, while the NAM is slower, drier and farther
south. The ECMWF seems to be more like the GFS. Cannot rule out
some thunder mainly over west Kentucky and the Bootheel late
tonight and Saturday, but this will be elevated and weak, so no
severe concerns here. We will maintain likely to categorical PoPs
mainly over the southern half of the region through Saturday.
There should be a lull in the precipitation over most of the
region Saturday night through Sunday, but far southern and
southeastern portions of the region may not be so fortunate. The
consensus of 12Z guidance pushes the warm front back into west
Kentucky overnight Sunday night, so we will see PoPs back into
likely territory. Will also re-introduce thunder in the southeast
at this time.
As for rainfall, far southern portions of the area could see 2
inches through the weekend, but this tapers quickly to under a
tenth of an inch north of I-64. Without the more persistent
convective rates, any flooding issues should be very minor.
However, this may just be setting the stage for issues as we head
into next week.
.LONG TERM...(Monday through Friday)
Issued at 323 PM CDT Fri Sep 21 2018
Confidence in the extended forecast is not that great.
The ECMWF and GFS agree that the warm front will push north of the
area during the day Monday putting our entire area in the warm
sector. They are not in such agreement in the timing of the cold
front, or the general character of the larger-scale upper trough.
The ECMWF has been the most consistent in pushing the cold front
through Tuesday night and then drying us out for the most part for
Wednesday through Friday, while the GFS has a more positively
tilted trough and is slower to move the front into our area and
then kind hangs it up over our area. This will lead to the
potential for heavy rainfall and flooding over the area. The
faster ECMWF would definitely lead to a quicker cessation of the
rain and less of a heavy rain/flooding threat.
Issued at 643 PM CDT Fri Sep 21 2018
VFR conditions are forecast through Saturday. Upper level energy
streaming along and north of a frontal boundary forecast to stall
south of the region will bring the potential for showers into at
least southern portions of the region later tonight into Saturday.
Carried prevailing showers at KCGI and KPAH, with a VCSH mention
at KEVV and KOWB. This may result in a reduction to MVFR ceilings
and visibilities at locations near the Arkansas and Tennessee
borders, but the TAF sites should largely remain VFR. North to
northeast winds around 10 knots will prevail.
Area Forecast Discussion
National Weather Service Shreveport LA
953 PM CDT Fri Sep 21 2018
Flash Flood Watch area and orientation looks good through the
overnight hours as it`s our northwest zones which have received a
bulk of the precipitation thus far. Checking area Mesonet sites
across McCurtain County, Oklahoma, nearly the entire county has
seen rainfall in excess of 2 inches with Idabel having seen 3.33
inches and points north and west of Battiest, Oklahoma have seen
upwards of 5 inches since midnight last night. Likewise, much of
the adjanct counties across Southwest Arkansas in the watch area
has seen 1-3 inches so far as well.
Looking at the lastest radar mosaic, much of our region is
currently in a lull when it comes to precipitation coverage but a
giant slug of precipitation, closer to the orientation of the
upper level trough, is setting up just to our west attm and slowly
moving north and east. Expect this to continue to move eastward
overnight with the area likely to see the greatest potential for
flooding to be in the Flash Flood Watch area, thus no Watch
extendtion in coverage will be made with this forecast.
Did increase rain chances overnight pretty much areawide and also
increased pops through much of our region through the day Saturday
as well based on the latest data coming in from the HRRR and 00z
Many areas currently near or at their overnight lows as of 9 pm
due to earlier rainfall and they should pretty much stay there
Update already sent...13.
.PREV DISCUSSION... /issued 543 PM CDT Fri Sep 21 2018/
Terminal forecast is a big mess through the next 24 hours with a
stagnant upper level trough to our west, continuing to provide
the necessary lift for scattered to numerous convection through
Current thinking is that present convection will begin to
dissipate somewhat in coverage after the 04z hour across all but
our northern and western most terminal locations which would
include the TYR/GGG/TXK. These sites are closer to the above
mentioned lift and could see on and off convection through the
overnight hours. Further to the east, short term progs support a
downward trend in convection later this evening with convection
not developing and/or moving into these terminals until beyond
Sat/14z or so.
For the western terminals, have gone with prevailing VCTS with
TEMPO groups for restrictions associated with TSRA this evening
with additional TEMPO groups needed from midnight through the
predawn hours for continued convection. Went ahead and prevailed
TSRA at the TYR/GGG/TXK/ELD and LFK terminals during the morning
hours on Sat with prevailing TSRA at the SHV/MLU terminals during
the afternoon hours.
Once this convection sets in on Saturday, ceilings will be slow to
improve, if at all so for now, have prevailed MVFR ceilings
through much of the day on Sat.
Look for mostly variable winds through the next 24 hours with
speeds near 6kts or so except for variable winds much stronger and
gusty near thunderstorms.
PREV DISCUSSION... /issued 353 PM CDT Fri Sep 21 2018/
SHORT TERM.../Tonight through Saturday Night/
Enhanced rain chances expected through Saturday across much of
the region with widespread persistent rainfall targeted mainly
across the interstate 30 corridor along a weak and slow moving
frontal boundary. With precipitable water values around 2 inches
areawide, locally heavy rainfall will be possible. As upper-level
trough shifts east across Texas this evening, coverage and
intensity of precipitation is forecast to increase. With latest
RFC flash flood guidance of 3 to 4 inches per hour, and the
potential for 24 hour QPF values approaching 5 inches across
these areas, a flash flood watch will be necessary.
Rainfall axis to shift south across the heart of the ArkLaTex on
Saturday allowing for likely pops areawide with residual
precipitation continuing through Saturday night.
Temperatures tonight to average in the lower 70s. Highs on
Saturday to climb into mid to upper 70s north of I-20 and mid to
upper 80s across deep East Texas and north Louisiana. Cool surface
high pressure building behind the front to bring lows on Saturday
night into the mid 60s to lower 70s areawide.
LONG TERM.../Sunday through Friday Night/
A wet and unsettled weather pattern will continue across the Four
State Region through much of the next work week. On Sunday a shear
axis will exist over the region in between an upper ridge, that
extends along the southeast coast of the US into the Northeast Gulf
of Mexico, and a trough over the Northwest Rocky Mountain States. At
the surface, a surface low will develop along a stationary front
located just north of the Interstate 20 corridor. Showers and
thunderstorms will continue to develop along the boundary through
the beginning of the work week as the sfc low and boundary slowly
move southeast across the region before washing out. By mid week,
rain chances remain in the forecast as another upper trough will
dive towards the region bringing another cold front into the
forecast area and also becoming nearly stationary over parts of East
Texas and Central Louisiana before washing out on Thursday. By
Friday, another cold front will make its way towards the region,
bringing additional showers and thunderstorms through the first part
of the weekend. The prolong period of rainfall this week, will
provide much needed relief to ongoing drought conditions across the
region and cooler temperatures as high temperatues are expected to
remain in the mid to upper 80s.
.PRELIMINARY POINT TEMPS/POPS...
SHV 74 86 71 83 / 50 80 70 50
MLU 73 90 71 85 / 40 70 70 50
DEQ 71 77 66 78 / 100 100 70 50
TXK 72 78 66 77 / 80 90 70 50
ELD 73 83 68 79 / 70 80 70 50
TYR 73 82 70 82 / 80 80 70 50
GGG 74 84 70 82 / 70 80 70 50
LFK 74 87 73 85 / 40 80 60 50
AR...Flash Flood Watch through Saturday afternoon for ARZ050-051-
OK...Flash Flood Watch through Saturday afternoon for OKZ077.
TX...Flash Flood Watch through Saturday afternoon for TXZ096-097-