Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/05/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
557 PM MDT Mon Sep 4 2017
.AVIATION...
00Z TAF CYCLE
Isol SH and TS will impact western and northern areas through at
least the eve hrs. Gusts to near 40 kt will be the main concern
through 03/04z. Then gust potential should lower some. FMN/GUP/SAF
are likely candidates to receive impacts. LVS will be possible later
in the eve but didn`t show it in the latest terminal forecast. Will
update accordingly. Gusty east canyon wind expected at ABQ Tue
morning with gusts near 35 kt. AWW is possible although not indicated
in the latest fcst.
50
&&
.PREV DISCUSSION...300 PM MDT Mon Sep 4 2017...
.SYNOPSIS...
High pressure aloft will dominate northern and central New Mexico
this week however the center of circulation will wobble around the
Great Basin and southern Rockies, resulting in subtle day to day
variations in areal coverage and movement of showers and storms. A
cold front is still forecast to move into northeast and north
central New Mexico later tonight, then advance south and westward to
the Continental Divide Tuesday and Tuesday night on gusty northeast
to east winds, which would focus showers and storms from the central
mountain chain westward. Highs Tuesday will be 5 to nearly 20
degrees cooler central and east, and just a little cooler west.
Thereafter, isolated to scattered showers and storms will be
featured over mainly the northern and western high terrain. High
temperatures over the east will rebound by Thursday and overall will
be slightly above average to end the week.
&&
.DISCUSSION...
Little bigger crop of afternoon showers and storms compared to
Sunday, but located mainly along and west of the Contdvd, with just
a few along the central mt chain. Movement is to the south and
southwest, although models suggest that will transition to more
westerly this evening. This activity will tend to be a bit drier
similar to Sunday with gusty winds and lightning and not so much
rain, thanks in part to dew points having mixed out into the 30s
again this afternoon over much of the central and west.
The cold front is progged to make it`s entrance into ne NM late this
evening or around midnight, but winds may shift to north prior if
precipitation develops along the ne NM/se CO border earlier in the
evening, per the HRRR and RAP13. An easterly wind will blow into the
RGV Tuesday and continue Tuesday night courtesy of the front and mid
level winds. Convection Tuesday and Tuesday night would be most
likely over the western third to half of the forecast area, but the
NAM12 and GFS generate very little over the region, in fact the GFS
paints more over the north central and east. Consequently didn`t
make wholesale changes to the pop grids for this period although
Wednesday may be more active than Tuesday if the models are correct.
There could be some potential for smoke observed over ern CO today
to be transported by the front into ern NM but vent rates in the
fair to good category over the east central and southeast Tuesday.
Temperatures Tuesday over the central and east will be about 5 to
nearly 20 degrees cooler than today`s, with only slight cooling in
the west. Expect highs to rebound in the east by Thursday and
overall to be near to above average for the rest of the week. Models
still kicking around the idea of an incoming trough late this week,
and developing a closed low to our west, which shifts the upper high
center over or even southeast of NM. Given the wishy-washy nature,
generic pops over the west and north still good for late this week.
There could be another vigorous cold front early next week, but that
depends on the variably forecast upper air pattern.
&&
.FIRE WEATHER...
After above normal temperatures today, a back door cold front will
enter from the northeast tonight and push all the way to the
continental divide by mid day Tuesday. High temperatures will fall a
few to 10 degrees central and west on Tuesday, and up to 19 degrees
across the east. Scattered to isolated showers and thunderstorms
will favor central and western areas on Tuesday with the best precip
chances in the northern mountains. Humidities will also climb a few
to 20 degrees with the front, so wetting footprints will grow. With
the broad upper high centered over the Great Basin, these storms
will move southward and southwestward off the high terrain while
lingering into Tuesday evening. Most of the area from the spine of
the Sangre De Cristo Mountains eastward can expect poor ventilation
on Tuesday. Haines Indices will decrease with the front and remain
moderate for the remainder of the week.
The high pressure system aloft will weaken and migrate southeastward
over southern NM Wednesday and Thursday, before tracking further
southeastward over extreme southeast NM and/or west TX over the
weekend. Clockwise flow around the high pressure system will cause
the track of showers and thunderstorms to shift more out of the
south and west. After trending gradually drier during the latter
half of the work week, humidities should be able to climb some this
weekend. Daily rounds of scattered to isolated showers and
thunderstorms will favor central and western areas Wednesday and
Thursday, before focusing more exclusively on western and northern
areas this weekend. Poor ventilation will cover much of the east on
Wednesday while spreading to include the middle and upper Rio Grande
Valley. vent rates will improve during the latter half of the work
week, although some poors will linger across northeast areas into
Thursday.
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
50
Area Forecast Discussion
National Weather Service Denver/Boulder CO
936 PM MDT Mon Sep 4 2017
.UPDATE...
Issued at 925 PM MDT Mon Sep 4 2017
Minimal cloudiness over the CWA at this time. No precipitation.
Northeasterly low level winds continue over the plains and
foothills. As far as updates go, I`m still not sure where the
cloud deck at 700 mb is supposed to materialize from on the
models later tonight. Left some clouds in, not not total
coverage. No pops overnight. Temperatures are in pretty good
shape.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 242 PM MDT Mon Sep 4 2017
Leading push of cold front has moved through Denver metro area,
but little cooling with this one. Main front was now pushing
through Greeley and Fort Collins, and will move through Denver
and the rest of the plains late this afternoon. Surface
observations show smoke is eroding from the northeast, so
improvement will continue to occur behind the front through the
evening. Latest HRRR Near-Surface Smoke represents this nicely so
have largely adopted this field for smoke forecast tonight. While
the plains largely scour out of the near surface smoke, we do
anticipate the smoke plume aloft to keep hazy conditions in place
on the plains, and some smoke in the high country.
With regard to thunderstorms, frontal surge this afternoon should
push any convection farther to the south and across the Palmer
Divide. Any convection will only be isolated in coverage.
Overnight, we should eventually see some high based stratus
development. Maybe a couple sprinkles from that otherwise dry
conditions will persist through Tuesday.
Highs on Tuesday will be considerably cooler in post frontal
airmass. Most of the plains should see highs closer to 70F.
.LONG TERM...(Tuesday night through Monday)
Issued at 242 PM MDT Mon Sep 4 2017
Tuesday night a large upper level ridge of high pressure will
stretch from British Colombia south into northern Mexico...with a
deep upper level trough of low pressure covering much of the central
and eastern United States. Colorado is stuck between these two
systems under the influence of a dry northwesterly flow aloft. The
combination of the dry and cool airmass in the wake of Monday`s
strong cold front and mostly clear skies will lead to cool
temperatures across the plains Wednesday morning. Most locations
across northeastern Colorado should see low temperatures in the 40s.
A gradual warming trend is expected through the end of the work week
as the upper ridge remains entrenched over the western half of the
United States.
By Friday...the upper ridge breaks down somewhat and shifts eastward
over the Rocky Mountain Region. This is in response to an upper
level trough of low pressure deepening along the west coast of the
United States. This pattern should allow some subtropical moisture
to flow into Colorado from the south and southwest...resulting in
increasing precipitation chances...mainly across the high country.
Models show moisture continuing to increase over the weekend which
may result in better chances for afternoon and evening showers and
storms across the plains and Palmer Divide. The GFS...ECMWF and GEM
Models are are showing another cold front moving across northeastern
Colorado on Monday which could result in another cool and cloudy
day. Since this is all the way out in day 8...have decided only to
lower high temperatures only a few degrees at this time.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 925 PM MDT Mon Sep 4 2017
Models keep the easterly component to the low level winds all
night and Tuesday. No drainage winds! Models keep showing a
pretty decent cloud deck to develop after 06Z. If that does occur,
the deck will be above BKN060, but not much higher. We`ll see.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......RJK
SHORT TERM...Barjenbruch
LONG TERM....Kalina
AVIATION.....RJK
Area Forecast Discussion
National Weather Service Columbia SC
1047 PM EDT Mon Sep 4 2017
.SYNOPSIS...
Fair weather will continue tonight across our forecast area.
Moisture will begin to increase ahead of an approaching cold
front Tuesday. The front will be in the area Wednesday. There
will be an increased chance of showers and thunderstorms
especially Wednesday. It will be cooler and drier behind the
front for Thursday into Saturday. Hurricane Irma will continue
to be monitored into early next week.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Weak surface high pressure over the Southeast will slowly move
offshore tonight. Atmospheric moisture will be slowly increasing
with deeper southwesterly flow developing ahead of an approaching
upper trough. Regional radar as of 0245Z showing weak shower
activity over eastern Georgia which could potentially reach the
southern CSRA before dissipating. A weak shortwave appears to be
maintaining this activity, but moisture remains limited. Added a
slight chance of rain showers to the southern CSRA based on
current radar trends for the next hour or two. Overnight lows
tonight will moderate a bit compared to the past couple of
nights, ranging from the middle 60s north to around 70 south.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A cold front will be approaching the region from the northwest
through the day Tuesday, and expect moisture to be on the
increase through the day in advance of the front. There will be
a weak cap through the day, with weak to moderate instability
possible. Scattered showers and thunderstorms should develop by
the afternoon lasting into the evening hours over the area. The
main cold front will not move into the cwa until late Tuesday
night into Wednesday morning. The front will be slow to move
through the cwa during the day Wednesday, which will bring an
additional chance for showers and thunderstorms throughout the
daytime hours. Rain chances should begin to diminish Wednesday
night as the front finally pushes east towards the coast and
drier air begins to move into the region from the west.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Dry conditions should occur with dry high pressure over the
region Thursday through Saturday night. After that, an onshore
flow pattern may return to the region late in the weekend,
bringing increasing chances for rainfall into early next week.
We will continue to monitor the intensity and forecast tracks
for Hurricane Irma through the longer term periods for possible
impacts on the region early next week.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Expect mainly VFR conditions during the TAF period but there may be
areas of stratus and fog during the early morning hours and
thunderstorms are possible in the afternoon.
Moisture will be on the increase in the southerly flow between
offshore high pressure and an approaching cold front. However, based
on the initial dryness and weak moisture advection believe stratus
and fog will be limited during the early morning hours. The GFS and
NAM MOS plus SREF and HRRR indicate mainly VFR conditions.
However, included a period of MVFR fog at AGS and OGB because
of increased moisture and cooling at these river valley
terminals. The chance was too low to include restrictions at
the remaining terminals. The moisture is expected to remain
somewhat shallow through Tuesday afternoon. Main frontal forcing
should remain west of the area. Therefore, expect limited
thunderstorm coverage with the chance too low to include in the
terminal forecasts at this time. Wind will be light and variable
tonight with an inversion and weak pressure gradient. The MAV
and MET MOS support wind southwest near 10 knots during the day
Tuesday. The NAM and GFS Bufkit suggest peak gusts about 15
knots.
EXTENDED AVIATION OUTLOOK...Thunderstorms may become more
widespread Tuesday night and especially Wednesday associated
with a cold front moving into the area.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
1046 PM EDT Mon Sep 4 2017
.SYNOPSIS...
A cold front will move into the northwest part of the state
tonight, then progress very slowly to the east during the day
Tuesday. A deepening upper level trough will march east across
the commonwealth Wednesday leading to cooler than normal
temperatures and scattered showers. Hurricane Irma is around a
week away from the U.S. mainland.
&&
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Line of storms moving steadily across LE now, and some rain
should reach Warren Co by 1030 PM. There is one very strong-
looking bow echo over the water which, on it`s curent track,
would strafe the PA-NY border, but stay mainly to the north of
PA. It still bears watching, but the HRRR and RAP runs from the
last several hours have been insistent on decreasing the
coverage of the showers/storms as they move into C PA. The CAPE
is definately lower over McKean Co than Warren Co. Deep-layer
shear is still respectable, though. Have adjusted the POPs and
timing slightly for the near term, and kept the idea of
decreasing coverage and intensity. But, the SPC continues with a
SLGT risk into Warren Co and MRGL risk a few Cos deeper into C
PA. So, will continue on with the enhanced wording for tstms in
the wx grid. But, the trend seems to be for weakening as the
HRRR and RAP indicate.
Prev...
Quiet start to the evening with partly cloudy skies and seasonal
temperatures. Band of showers and thunderstorms will approach
NW zones later in the evening and weaken as the push SE into
central PA. Before they weaken, across the NW zones, the
strongest storms could have gusty winds and frequent lightning
with them.
&&
.SHORT TERM /7 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The focus for thunderstorms on Tuesday will be along the slow
moving frontal boundary which will shift to the Susq Valley.
The best llvl SW winds and larger scale forcing will pass across
the region mainly east of a KMDT to KELM line, thus limiting
the chc for gusty winds and hail acrs the region near and to the
south of a KTHV to KAVP line.
The upper flow gradually backs from the west to the southwest
on Wednesday helping to slow the cold front to a crawl with an
area of anafrontal rain blossoming and moving NE across the
southeast part of the region Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Cold front moves into the area later Tuesday and slows down as
a longwave trough drops over the Great Lakes and becomes
stationary. This will bring a period of wet weather Tue into Wed
night with potential QPF amounts of 0.75-1.25. Clouds and rain
showers will keep temps below normal during this period.
Would expect most of the showers and storms to be out of the
area Thursday, but still some chance of a shower across the
north into Friday morning as the upper level trough finally
swings across.
Large high builds into the area for next weekend. Weather looks
to be dry but temps will remain on the cool side.
After that, heading into early next week, interaction between
the departing high pressure area and Hurricane Irma will
determine the track it will take as it approaches the U.S East
Coast. Still quite a wide variation of solutions forecast by
longer term guidance after it slides by the northern Bahamas, so
stay tuned for now.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Cold front dropping across the Great Lakes will track across
Pennsylvania later tonight and Tuesday. Ahead of the front,
extending along the southern and eastern shore of Lake Erie at
02z, is a broken line of strong to severe thunderstorms. This
line will impact the NW mtns over the next several hours, though
it should weaken fiarly rapidly as it pushes further into the
CWA.
So, at 02z, MVFR cigs popping up along the higher terrain of
the west as core of 40kt low level WW jet swings through.
Remainder of region will remain VFR through much of the
overnight. KBFD will see biggest tstm impacts from the line,
while showers and possibly a weakening tstm will approach
central mountain terminals after 06z.
Toward sunrise, ceiling reductions encompass much of NW half of
CWA. These spread into central and SE portions on Tue as
numerous showers and scattered potentially strong thunderstorms
impact those regions as the front stalls nearby.
.Outlook...
Wed...Reductions poss in SHRA - mainly NW mtns and east of Susq
River.
Thu/Fri...Widespread MVFR north. VFR elsewhere. Sct showers
mainly north.
Sat...No sig wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Ross
NEAR TERM...Ross/Dangelo
SHORT TERM...Ross/Lambert
LONG TERM...Lambert/Gartner
AVIATION...RXR
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
316 PM PDT Mon Sep 4 2017
.SYNOPSIS...Temperatures will gradually cool over the next couple
of days with highs falling back to near normal by Wednesday.
Smoke should also begin to move to the north and northeast toward
the middle of the week. Chances for showers and thunderstorms will
return for Tuesday and Wednesday as a low pressure system moves
into the region and taps into some tropical moisture.
&&
.DISCUSSION...Short Term (Tonight through Thursday Night)
Main issues for the CWA center around dreadful smoke conditions
for both the coast and interior zones. Wildfire activity was
strong again today especially the fires over Siskiyou County
and Trinity County where large plumes were evident. Given the
Southeast flow aloft all that smoke is being carried to the north
coast and impacting Crescent City and all other coastal
communities. Same of course can be said for all interior
communities where smoke is trapped overnight. An Air Quality Alert
(North Coast Air Quality Management District) is in effect for
most of northwest CA and given the current and short term weather
pattern expect that to continue for at least another 24-48 hours.
The good news is that the pattern should see a significant change
by Thursday so much of the smoke should be shunted off to the
north and northeast. As far as the weather goes...the hot and dry
conditions experienced over the weekend will give way to cooler
temperatures as a low pressure system currently over the Pacific
slowly migrates toward the North Coast. This system will bring
bring much cooler daytime temperatures through Thursday but also
a threat of more thunderstorms...and yes more lightning induced
fires. At this time best chance for thunderstorm activity will be
tomorrow and Wednesday affecting the usual places ..interior
Humboldt County...Trinity County and easter Mendocino counties.
But given the latest gfs 18z run the low/trough remains over the
coast into Saturday maintaining slightly below normal
temperatures and at least a continued threat of thunderstorms into
the weekend...and perhaps much less smoke.
Long Term (Friday through Monday)
The broad upper level trough that absorbed the remnant energy of
Tropical Storm Lidia will bring the chance for shower and
thunderstorm activity across interior portions of Del Norte,
Trinity, and extreme northeastern Mendocino counties on Friday.
Convective parameters seem to be split as to whether or not
thunderstorms will actually develop thus confidence isn`t high
enough to place them in the forecast with this package. The chance
for precipitation will come to an end late Friday night into early
Saturday morning as an upper ridge noses its way into the area.
Expect above normal temperatures and dry weather starting this
weekend and into early next week.
&&
.AVIATION...Smoke intrusion has had some impact on area
airports/airfields in the last couple of days. This is due to
numerous wildfires pumping smoke throughout the region. At the
coast, fog development has been inhibited. Although clouds
themselves have been clear, a smoke layer continued to measure
"cigs" anywhere from 015-040 feet average. AS the inversion broke
today, smoke was able to mix down and reduce visibilities into IFR
at the coast. Also breezy winds developed along sections of the
coast...especially EKA-ACV. Inland areas including UKI continued
to experience smoke advection with the more concentrated amounts
being in the Northern areas. Throughout the forecast period, no
significants changes are expected except for an influx of mid-high
cloudiness, the remnants of Hurricane Lidia. For the interior,
possible flight hazard or two due to the threat of isolated
thunderstorms in the next couple of days.
&&
.MARINE...The buoys are flirting with Small Craft Advisory level
winds this afternoon, but this is expected to be short lived as they
will gradually be turning to the south. Directional spectrum plots
show that the 4 or 5 feet at 15 seconds are from the south while
locally driven wind waves slowly subside due to the change in wind
direction. Overall, mariners and other ocean dwellers can look for
light winds and seas to continue for the next couple of days with
locally higher winds being possible around Cape Mendocino.
&&
.FIRE WEATHER...As high pressure weakens and moves east...focus
now changes from hot and dry to thunderstorm potential for Tuesday
and Wednesday as a pacific low approaches from the west. A weak
closed upper low circulation will slowly move northward up the
coast entraining some mid and high level moisture into northwest
CA. This feature will also destabilize the airmass as it weakens
on Wednesday and moves across the coast and then northward into
western Oregon. Best chances for thunderstorm activity looks to be
Wednesday as the strongest vort lobe moves over the region while
timing is ripe during afternoon heating. However can`t rule out
Tuesday either given the favorable southeasterly flow and decent
amounts of available moisture. Axis of instability on Tuesday
appears to be over southern Trinity Co. and Yolla Bolly area then
shifting slightly westward for Wednesday. Did also add a slight
chance of showers/tstorms for tonight as well as total totals
close to 53ish and HRRR showing some returns later this evening.
Potential storms don`t look especially wet but not convinced there
will be a ton of lighting either. For now will go with a headline
for interior zones for isolated storms with limited rainfall. The
good news is that by Thursday smoke transport should be toward the
northeast so improving sky conditions may be on their way.
tonkin
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...None.
&&
$$
Visit us at http://www.weather.gov/eureka
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http://www.facebook.com/NWSEureka
http://www.twitter.com/nwseureka
For forecast zone information
see the forecast zone map online:
http://www.weather.gov/eureka/zonemap.png
Area Forecast Discussion
National Weather Service Flagstaff AZ
903 PM MST Mon Sep 4 2017
.SYNOPSIS...Expect a slow increase in shower and thunderstorm
activity for the remainder of the week, as high pressure weakens
and southerly flow develops. High temperatures will decrease to
near average over the next several days.
&&
.DISCUSSION...
A busy evening across northern Gila and southern Yavapai counties
looks to be coming to an end. The potential for isolated showers
will persist into the overnight hours.
&&
.PREV DISCUSSION /318 PM MST/...Significantly more active day than
yesterday in terms of convective development with isolated to
scattered showers ongoing across a large portion of the area.
The last few runs of the HRRR have been persistent in developing a
cluster of storms over northern Gila and tracking this to the
west across southern Yavapai County early to mid evening. Based on
current radar trends, this seems like a plausible scenario. Shower
and thunderstorm activity will diminish greatly from late evening
onward.
The remainder of the week will see a shift in the pattern with the
ridge over the Great Basin weakening and shifting to the east.
We will also see the development of low pressure off the southern
California coast. This will lead to southerly flow and increasing
moisture over the region. Therefore, expect increased shower and
thunderstorm chances over the next several days. Along with the
increased convective threat, temperatures will cool to more normal
levels for early September.
&&
.AVIATION...For the 06Z package...Predominantly VFR will persist
across northern Arizona. Storm coverage will likely increase
Tuesday afternoon from KFLG to KRQE southward. Stronger cells
will produce moderate rain with potential for MVFR visibility and
gusty winds up to 45 kts. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Moisture will gradually increase through the week
leading to an increase in daily shower and thunderstorm activity.
Daytime temperatures will trend down closer to early September
averages. Outside of storms, winds will remain light with a slight
increase in southerly wind by late in the week.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...KD/TPS
AVIATION...KD
FIRE WEATHER...KD/MCT
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
544 PM MDT Mon Sep 4 2017
.SHORT TERM...(Tonight through Tuesday night)
Issued at 150 PM MDT Mon Sep 4 2017
Early this afternoon surface observations show the Canadian cool
front draped near the WY/CO border and then southeast through
eastern CO. There will continue to be a southward push into
northwest CO and northeast UT this evening, but it appears with
the main thrust of the digging upper level trough well east of the
Rockies, the cool surface air will be too shallow to make it over
the Tavaputs and Roan Cliffs. Although all mountain ridges have
diurnal convection occurring this afternoon, the southern
mountain areas are favored for greatest coverage of storms, with
some drifting off over areas south of the San Juan mtns.
Upper level high pressure stretched from eastern OR to NM will
slowly ease its grip on the region Tuesday, but southern mountain areas
will again have enough moisture for another round of afternoon
and evening isolated/scattered storms. With the slightly lower
heights and modest cooling aloft, Tuesday will be a few of
degrees cooler than today.
It looks like Tuesday night will bring the coldest temperatures of
the week to the high valleys and Northwest Plateau of Colorado
thanks to some cooler air filtering westward from the cool
Canadian airmass plunging south east of the Divide Tuesday. We
will continue to monitor these areas for the potential for frost,
but at this time it appears temperatures will remain just warm
enough to preclude a serious frost threat.
Smoke/haze emanating from the wildfires over MT and the Pac NW
states is readily seen in our GOES-16 preliminary/non-operational
imagery behind the cool front. HRRR model smoke concentration
forecasts show the higher concentrations of smoke moving south
over especially northern CO and UT over the next 24 hours. While
we have noticed hazy conditions the past few days, expect
visibility to be noticeably reduced a little more through Tuesday
and possibly beyond.
.LONG TERM...(Wednesday through Monday)
Issued at 150 PM MDT Mon Sep 4 2017
The northwest center of a double-barreled upper level high
pressure ridge extending from the upper Great Basin to New Mexico
will weaken and give way to the southeastern center near the Four
Corners by Thursday. Until then, eastern UT and western CO will be
under relatively stronger subsidence and drier air. That will not
completely preclude afternoon convection from developing over
mainly the San Juan region each day where available moisture will
be slightly higher. By late Thursday, the axis of the ridge will
either be directly overhead or just to the east. Either way, the
upper level flow turns out of the south to southwest, and enhanced
by a developing trough or closed low off the California coast.
This will increase precipitable water values over much of the
region to between 0.75 and a little over 1.00 inch. While these
values are not alarming, it will increase chances and coverage of
showers and thunderstorms for late Thursday thru Monday. With the
weakening upper level high pressure and then increased cloud cover
and moisture for the end of the week, expect high temperatures to
lower further for the last half of the week. then level off for
the weekend. However, temperatures will remain above normal
through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 544 PM MDT Mon Sep 4 2017
VFR conditions will prevail through this evening across the area.
Isolated to scattered showers and thunderstorms, currently located
south of I-70 and favoring the southern mountains and valleys,
will continue through 03Z. Storms will be capable of producing
gusty outflow winds to 35 kts. Hazy skies early this evening will
turn smokey with reduced visibilities overnight into Tuesday as a
cold front helps push this smoke further south and west across
much of Colorado and eastern Utah. The northern and central areas
of the state will have the best potential to see reduced
visibilities in smoke.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...BM
LONG TERM...BM
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Houston/Galveston TX
924 PM CDT Mon Sep 4 2017
.DISCUSSION...
Surface high pressure was ridging into Southeast Texas this
evening. Isolated showers were moving around the ridge over the
offshore waters in the Gulf. Since sunset the showers have
pretty much dissipated; although, a few still were forming about
60 nm offshore of Matagorda. The 01Z run of the HRRR shows the
potential for isolated shower development off of the coast
through the remainder of tonight.
40
&&
.PREV DISCUSSION... /ISSUED 630 PM CDT Mon Sep 4 2017/
AVIATION...
Generally light south to southeast winds are expected for the
remainder of the evening. Some patchy IFR to MVFR fog will likely
set in again tonight/early tomorrow morning before dissipating
after sunrise, very similar to what has been occuring the past
few mornings. A stray shower or two may be possible along the
seabreeze tomorrow afternoon. Otherwise, VFR conditions are
expected throughout the taf period.
11
PREV DISCUSSION... /ISSUED 346 PM CDT Mon Sep 4 2017/
DISCUSSION...
Moisture from a disorganized low in the Bay of Campeche is moving
north into the upper Gulf Coast with isolated showers now being
seen on radar approaching Matagorda. Rain chances will increase
along the coast and nearshore waters through tomorrow morning as
this moisture continues northward though convection should remain
isolated to widely scattered. The main threat will be isolated
cells producing gusty winds affecting marine interests.
A cold front currently entering the Texas Panhandle will move
south over the next 24 hours and enter our northern CWA around
midnight tomorrow night. Lift along the front is forecast to
weaken as the front moves south and so a solid line of convection
in North Texas is expected to develop gaps as it enters southeast
Texas. Showers with moderate rainfall rates will be moving at a
decent pace so QPF amounts should generally be less than a quarter
of an inch. A surface high building south behind the front will
advect cooler and drier air with dewpoints dropping into the 50s
and lows in the 60s Thursday morning. The high will remain in
place and slowly weaken so a gradual warming trend is expected
Friday into the weekend.
Hennig
MARINE...
Light onshore winds and low seas will continue through Tuesday,
before increasing and becoming offshore Wednesday morning as a cold
front clears the upper Texas coast. Expect winds to increase into
the 15-20 knot range behind the front with stronger gusts; these
elevated winds will result in seas building into the 3-5 feet range
nearshore and 4-6 feet range offshore. Caution or advisory flags
will likely be needed at times Wednesday through Friday before
conditions begin improving over the weekend.
Huffman
TROPICAL...
An area of low pressure in the Bay of Campeche is currently being
monitored for potential tropical cyclone development over the next 5
days. Regardless of development, Wednesday`s cold front appears to
make enough southward progress to keep any potential system well
south of Southeast Texas as it pushes the area of low pressure into
Mexico.
Hurricane Irma also continues to churn east of the Leeward
Islands this afternoon and is forecast to intensify further as it
moves west to west-northwest towards Florida over the next several
days. Hurricane Irma`s track beyond that point becomes a little less
certain, but medium range deterministic guidance is in fairly good
agreement that Irma is lifted northward before entering the Gulf of
Mexico as an upper trough reaches the East Coast. Changes in the
depth or trajectory of this trough would influence the ultimate
track of Irma. Additional radiosonde observations will be taken
across a few CONUS sites over the next few days to diagnose the
upper air pattern better. As this data is incorporated to later
model guidance, expect confidence in Irma`s forecast to increase.
Regardless, impacts are not expected in Southeast Texas from Irma
at this time but Irma`s forecast should still continue to be
monitored over the next few days.
Huffman
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 72 93 69 84 61 / 0 20 40 20 0
Houston (IAH) 73 92 70 86 63 / 10 20 40 30 0
Galveston (GLS) 80 88 77 87 73 / 20 30 30 40 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...40
Aviation/Marine...11
AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
519 PM PDT Mon Sep 4 2017
.SYNOPSIS...
Expect low clouds to deepen to coastal slopes by this evening and
a slight chance of thunderstorms over the mountains and interior
locations will be possible. High temperatures will be much cooler
than the past several days, but still a bit above average through
this week. Night through morning low clouds and patchy fog are
forecast through much of this week.
&&
.SHORT TERM...(TDY-THU)
Widespread cooling was occurring today across the forecast area.
Most areas were down over 20 degrees compared to this time
yesterday. Although high humidity continues to make it feel pretty
sticky out there, some relief from the high temperatures is a
welcome relief. The center core of Post Tropical Depression Lidia
was located around 400 NM miles W of Los Angeles around noon
today. Most of the shower activity is now located over the
coastal waters. The last of the lighter showers have exited SLO
county. Latest GOES 16 Vis imagery indicated plenty of cloud
coverage across coastal areas with cloud streets visible over LA
County due to fairly strong SE flow aloft. There is enough low
level moisture that stratus was already starting to kick in across
the LA Coast and San Gabriel Valley. Expecting low clouds to
continue to deepen into this evening.
Looking at the latest high res RAP and NAM soundings
over the area, they were showing a fairly unstable atmosphere
across the LA/VTU Mtns and southern portion of the SBA County Mtns
this afternoon, but less there is much less in the way of
available moisture between 600 to 700 MB. Convective parameters
such as CAPE were around 1440 j/kg and LIs were around -7. PW
values also still relatively high around 1.5" this afternoon based
on GOES Sounder Imagery. Although high res models were not
picking up on any precip across the region today, it`s hard not to
discount at least a slight chance for all interior areas today
from LA to SLO counties later this afternoon. If storms do
initiate, they will be fast moving from SE to NW which should keep
most convective activity over the mountains and interior areas
such as Cuyama Valley and SLO interior valleys. Not anticipating
any widespread thunderstorms like yesterday, but if storms do
develop, there could be some training of thunderstorms and some
localized flooding or flash flooding can`t be ruled out.
For tonight, there will be plenty of low lingering moisture across
coast and valleys. NAM-WRF cross sections were indicating the
moist layer or marine layer to be around 3000 ft tonight into Tue
morning. Have increased low cloud coverage to all areas W of the
coastal slopes. Patchy drizzle is a possibility along the Central
Coast and the San Gabriel Foothill communities of La Canada and
La Crescenta late tonight into Tue morning. High temps for Tue
will continue to trend lower with best cooling across coastal
areas anywhere from 3 to 7 degrees cooler. Otherwise most inland
areas will be about the same as today within a couple degrees.
There will be some afternoon cu buildups over the LA/VTU County
Mtns but for now, not anticipating any thunderstorms to develop as
soundings were more stable and lack of mid level moisture.
Wednesday should see a few degrees of warming as thickness and
boundary layer temps trend up slightly. the marine layer should
shrink down as well by Wed morning but still affecting coastal
valleys. High Temps should around normal to a few degrees above
normal for inland areas.
.LONG TERM...(FRI-MON)
Both the EC and GFS continue stay in agreement with large scale
features through the extended period. AN upper trough out the PAC
NW will begin to drop south in between a 592 DM high to the SW of
SoCal and a 591 DM High centered over N. Mexico and extending west
towards AZ and NV. The upper trough will deepen further over much
of California by Thursday night and Fri. H5 and thickness lvls do
lower a bit and there should be a few degrees of cooling and the
marine layer should deepen both Fri and Sat. Best cooling will be
for areas N of Point Conception. as the upper low cuts off just
off the Central Coast. High temps should be around normal for this
time of year, and night through morning low clouds are expected
to continue through next weekend. Risk for mountain thunderstorms
seems limited late this week.
&&
.AVIATION...05/0015Z.
At 00Z, the marine layer depth was around 2600 feet deep at KLAX.
The top of the weak inversion was up to around 3300 feet with a
temperature near 21 degrees Celsius.
Low confidence in the current forecast. MVFR conditions should
spread into most terminals through 05Z, possibly lowering to IFR
north of Point Conception between 07Z and 16Z.
KLAX AND KBUR...MVFR conditions will likely linger throughout
tonight and into Tuesday morning. There is a 30 percent chance
that VFR conditions could redevelop later tonight. Otherwise,
stratus could scatter out +/- two hours than the current
forecast.
&&
.MARINE...04/900 AM.
Former Tropical Storm Lidia will bring a chance of showers and
thunderstorms to the coastal waters today. Winds and seas will
remain below Small Craft Advisory criteria through Wednesday
afternoon. However erratic and strong gusty winds... lightning...
and choppy seas are likely near any showers or thunderstorms.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK...(THU-MON)
No significant hazards expected.
&&
$$
PUBLIC...Kaplan
AVIATION...Hall
MARINE...Sweet
SYNOPSIS...B
weather.gov/losangeles
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
929 PM CDT Mon Sep 4 2017
.UPDATE...
Issued at 926 PM CDT Mon Sep 4 2017
Scattered thunderstorms will continue to move southeast across the
southern part of the CWA through the late evening hours. These
storms are occurring ahead of cold front that has now reached a
KSLO-KCPS-KVIH line. This front will move south of the CWA by
midnight. There are still some post frontal showers and
thunderstorms, but still expect most of the rain to move south of
the CWA by late tonight. Cooler air is moving in behind the front,
and lows still look like they will fall into the upper 50s and low
60s.
Britt
&&
.SHORT TERM... (Through Late Tuesday Afternoon)
Issued at 330 PM CDT Mon Sep 4 2017
Cold front currently extends from northern Illinois into west
central Missouri. The RAP shows it moving through the CWA by late
this evening. Latest GOES-16 imagery is showing an enhanced CU
field developing ahead of the front from central Illinois into
central Missouri. This is in the same area where the latest SPC
mesoanalysis shows MLCAPES between 2000-3000+ J/kg. Would expect
thunderstorms to develop in the next 1-2 hours as mid level ascent
increases slightly on the tail end of a mid level trough that will
move through the Great Lakes. Still expect that there will be a
threat for a few severe thunderstorms given that deep layer shear
will increase into the 30-40kt range this evening. Main threat
should be damaging winds given the inverted-V profiles seen on the
RAP soundings, but large hail will also be possible. Showers and
thunderstorms will linger over southeast Missouri behind the front
mid-late evening before finally ending by midnight.
Expect a dry day on Tuesday as the front moves well south of the
area, and the atmosphere becomes dry through a deep layer. Winds
will become gusty as forecast soundings showing mixing up to 750mb.
Highs will still be below normal despite the deep mixing.
Britt
.LONG TERM... (Tuesday Night through Next Monday)
Issued at 330 PM CDT Mon Sep 4 2017
Period of well below normal temperatures with dry, tranquil
conditions is expected through early next week. Main focus will be
on temperatures, particularly at night. Coolest conditions still
appear to be on Tuesday and Wednesday night before some slight
modification in the airmass takes place. Continued to lean aob
coolest guidance, and may still not be cold enough especially in
favored valleys of east-central and southeastern Missouri. Lows in
these locations may dip into the upper 30s on Wednesday night.
While lows will be unseasonably cool for early September, it does
not look like any records will be broken, though readings both
Wednesday and Thursday morning at KUIN may get with a couple of
degrees.
Some moderation in the well below normal temperatures appears
probable by early this weekend, but models diverge with respect to a
backdoor cold front across the mid-Mississippi Valley. The ECMWF
drops this front through the area whereas the GFS does not.
Consequently, the ECMWF is several degrees cooler compared to the
GFS. Regardless, at least slightly below normal temperatures along
with a continued run of dry weather looks like to continue
through this upcoming weekend and into early next week.
Gosselin
&&
.AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1217 PM CDT Mon Sep 4 2017
Thunderstorms will develop along a cold front that will move
southeast across the forecast area late this afternoon and this
evening. Thunderstorms will affect the St. Louis area terminals
and KCOU between 23-03Z and could cause MVFR/possible IFR
conditions along with gusty winds. There will be a shift in winds
from southwest to north behind the front. There could be some
lingering showers behind the front through mid evening before dry
and VFR conditions are expected the rest of forecast period.
SPECIFICS FOR KSTL: Thunderstorms will be possible ahead of a cold
front at the terminals between 00-02Z. Any thunderstorms could
cause MVFR/possible IFR conditions along with gusty winds. There
could be some lingering showers behind the front through mid
evening before dry and VFR conditions are expected the rest of
forecast period. There will be some additional gusty northwest
winds on Tuesday afternoon.
Britt
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Omaha/Valley NE
633 PM CDT Mon Sep 4 2017
.SHORT TERM...(Tonight through Thursday)
Issued at 201 PM CDT Mon Sep 4 2017
Much cooler temperatures are heading our direction as a longwave
trough deepens from the Hudson Bay into the Mississippi River
valley region. This leaves our region under strong
north/northwesterly flow as a strong ridge of high pressure
over the western states continues to build north into Canada.
This will allow continued cool advection through the next couple
of days. As was noted today, smoke from fires across the
northwestern states will continue to create hazy skies as smoke
should remain aloft. HRRR vertically integrated smoke field does
take a good portion of the smoke to our south through the
overnight hours. Brisk northerly winds are also expected the next
couple of days, as high pressure pushes out of the Dakotas. Strong
downward momentum should push gusts into the 30mph range,
especially Tuesday.
Cool advection will continue into Wednesday with surface high
pressure moving overhead by Wednesday afternoon. High temperatures
both Tuesday and Wednesday should be in the low 70s with lows in
the 40s across the entire CWA.
.LONG TERM...(Thursday night through Monday)
Issued at 201 PM CDT Mon Sep 4 2017
Warmer return flow will move into the Central Plains by Friday
while a weak shortwave trough moves southeast through
deamplifying northwest flow aloft. We do have a small chance of
showers and thunderstorms in warm air advection regime Friday
night into Saturday. Weak ridging will move overhead into the
weekend which should push temperatures back into the 80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 629 PM CDT Mon Sep 4 2017
VFR conditions through the TAF period. Hazy conditions with smoke
and some mid and high level cloudiness this evening. HRRR
vertically integrated smoke forecasts push this to the south of
the TAF sites by around 08z. North winds 7-12kts to decrease to
around 6kts early in the TAF period...then increase again above
12kts 14-16Z and above 15kts and gusty 15-19Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Kern
LONG TERM...Kern
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Norman OK
654 PM CDT Mon Sep 4 2017
.AVIATION...
TAFS 0500/0524...
A cold front, which extends from just north of Enid to near
Woodward, will move southward this evening and overnight. A
breezy north and northeast wind can be expected behind the front.
Otherwise, VFR conditions will prevail.
&&
.PREV DISCUSSION... /issued 247 PM CDT Mon Sep 4 2017/
DISCUSSION...
The main forecast challenges are determining rain chances late
tonight into Tuesday as well as dealing with near record cool
temperatures Wednesday morning and Thursday morning.
As of 230 pm today, Freedom (101) and Buffalo (100) have reached
the century mark temperature wise according to the Oklahoma
Mesonet. Additional locations in northern Oklahoma will likely
exceed 100 degrees as well.
Tonight, a rather strong cold front will move south and through
at least the northern two thirds of Oklahoma. Sufficient capping
will limit rain/storm potential. Kept 20% for storms after
midnight in far northern Oklahoma, north of a Buffalo to Enid to
Stillwater line where some of the latest models including HRRR
depicted isolated storm activity. If storms form in these
locations, they could be strong with hail and gusty winds due to
sufficient MUCAPE 1500-2000 J/kg as well as 20-35 kt 0-6 km bulk
shear. North to northeast surface winds will increase behind the
frontal passage and should keep overnight lows higher than
previous nights.
On Tuesday, cooler and breezy/windy conditions can be expected.
Rain chances remain uncertain due to the lack of significant
moisture. However, there appears to be enough of a QPF signal from
latest models, sufficient mid level moisture 600-800 mb, some mid
level isentropic lift, and MUCAPE 100-1200 J/kg to allow for
isolated showers and thunderstorm development across much of
Oklahoma and north Texas through the day. Thus, kept 20% chance
across the area. Any rainfall would be brief and light. Not many
locations should get wet. Severe potential remains very low,
though gusty winds could occur with any shower/storm. Surface wind
gusts 30-40 mph will be possible across western Oklahoma and
western north Texas during the daytime hours.
Tuesday night into Wednesday morning, clearing conditions and
decreasing surface winds will allow for cool night. Generally,
went near the cool side of guidance lows, mainly in the 50s. Some
locations, especially rural ones in northern Oklahoma, will likely
fall into the 40s. Readings Wednesday morning will be near
record lows in some areas.
Wednesday, sunny conditions with very low humidity and light
surface winds are forecast. Highs will generally be 5-10F below
average.
Wednesday night into Thursday morning, additional near record low
temperatures will be possible as light surface winds and clear
skies will allow for excellent radiational cooling. The coolest
readings likely in the 40s may be over rural areas across the
eastern half of Oklahoma closer to the surface ridge axis.
Thursday through Monday, a slow warming trend can be expected
along with generally dry conditions. Some latest models have been
hinting at light QPF/rainfall mainly during the nighttime and
early morning hours across western Oklahoma due to possible
isentropic lift in northwest mid/upper flow. As a result, added
low rain chances to account for this. Any rainfall will likely
remain rather light and spotty. Temperatures may rebound to near
average levels by next weekend.
MBS
CLIMATE...
Record low temperatures Wednesday morning and Thursday morning
may be in jeopardy across parts of Oklahoma and north Texas. Here
are the records for Oklahoma City and Wichita Falls.
Wednesday September 6
Oklahoma City...51 degrees...set in 1974
Wichita Falls...52 degrees...set in 1968
Thursday September 7
Oklahoma City...49 degrees...set in 1898
Wichita Falls...52 degrees...set in 1974
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 69 81 52 80 / 0 20 10 0
Hobart OK 69 83 53 82 / 0 20 10 0
Wichita Falls TX 71 88 61 83 / 0 20 10 0
Gage OK 65 77 46 81 / 10 20 10 0
Ponca City OK 67 78 47 79 / 20 20 10 0
Durant OK 71 87 62 81 / 0 20 20 0
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
Area Forecast Discussion
National Weather Service Paducah KY
636 PM CDT Mon Sep 4 2017
.UPDATE...
Issued at 636 PM CDT Mon Sep 4 2017
The AVIATION section has been updated for the 00Z TAF issuance.
&&
.SHORT TERM...(Tonight through Wednesday night)
Issued at 250 PM CDT Mon Sep 4 2017
A fairly strong cold front will move toward the area this evening
and then cross the region overnight. Scattered thunderstorms will
accompany the front with much cooler air to follow as we head
through the short term period. There remains a slight risk of
severe thunderstorms for tonight, mainly along and north of the
I-64 corridor. There is some offset of upper level wind dynamics
and the surface cold front (better dynamics lag frontal
convergence and instability) and we will be losing a good chunk of
instability between 9 PM and midnight.
Best guess for timing remains an onset of thunderstorms this
evening with a 7-10 pm start time looking reasonable for the I-64
corridor of our region then progressing southward through the late
evening and overnight. By tomorrow morning, showers/thunderstorms
will be limited to mainly the quarter of the forecast area,
ending across all of the region during the afternoon.
A large 500 mb trough will pivot SE across the FA through mid
week with surface high pressure building south into our region
from Canada. The much advertised unseasonable cool pattern ushered
in by northerly winds will ensue with max temps only in the mid
to upper 70s Tuesday and the lower 70s on Wednesday with lows
likely reaching the upper 40s in many locations Wednesday night.
.LONG TERM...(Thursday through Monday)
Issued at 250 PM CDT Mon Sep 4 2017
High forecast confidence still remains in place for a dry period
from this Thursday through next Monday across the WFO PAH forecast
area. Below normal temperatures (10-15 degrees) below normal are
expected through the extended period.
Regionally blended model guidance continues to be on the warmer end
of the forecast temperature solutions. Again, weighted temperatures
toward the EKD MOS, as well as the ECMWF/NAM-WRF guidance suite.
temperatures. Given the drier air mass, diurnal temperature ranges
will likely be within a 20 to 28 degree range.
No precipitation expected through extended period. Although the
ECMWF has been running about 5-10 decameters too low in 500 mb
heights recently, it still remain much closer in height fields
versus most of the numerical guidance suite. The ECMWF along with
the RAP model guidance were the closest to the raw upper air
observations at 12z and 18z Monday. Only the UKMET (which has
historically been the case) is more accurate with height fields and
low/high pressure centers in a global sense. Sensitivity of model
fields at 500 mb versus observations is a good benchmark for model
reliability.
Will be interested to see how collaborated NHC/WPC forecasts handle
Irma`s track later this week. There still remains some varied
solutions from the Canadian, GFS, and ECMWF for the next several
days. Depending on the final track of Irma, could see some
interaction with the synoptic scale features near the WFO PAH
forecast area around the middle of September.
&&
.AVIATION...
Issued at 636 PM CDT Mon Sep 4 2017
A broken line of thunderstorms has developed along the cold front
from just north of KSTL to near KDEC in central Illinois. There is
a strong signal in the latest short term guidance that a portion
of this will be progressive, pushing eastward through KEVV and
KOWB after 04Z, while the western portions will develop more
slowly southward for awhile this evening and then mostly
dissipate around 06Z. Left the VCSH at all sites except KPAH where
it may remain dry. An outflow or enhanced frontal passage can be
expected at KEVV and KOWB 04Z-07Z. VFR conditions are forecast,
but lower conditions can be expected if a bonafide thunderstorm
reaches any of the sites tonight. A few northwesterly gusts into
the teens will be possible throughout the area Tuesday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...DRS
SHORT TERM...GM
LONG TERM...Smith
AVIATION...DRS
Area Forecast Discussion
National Weather Service Tucson AZ
200 PM MST Mon Sep 4 2017
.SYNOPSIS...We`ll have enough moisture around this week for
isolated to scattered afternoon and evening thunderstorms.
Temperatures will run several degrees above average the first
half of the week.
&&
.DISCUSSION...Scattered showers and thunderstorms were occurring
across portions of the White Mountains northeast of Safford at this
time. Otherwise, mostly clear skies to partly cloudy skies prevailed
across southeast Arizona early this afternoon. The cumuloform clouds
were most prevalent near the mountains as well as south-to-southeast
of Tucson.
The high resolution models (i.e. 04/12Z Univ of AZ WRF-NAM and WRF-
GFS as well as several HRRR solutions) were in general agreement
with depicting scattered showers/tstms to continue to develop across
portions of the area during the next few hours. These models
generally agree that the favored areas for showers/tstms appear to
be north of Tucson and south of Tucson, with showers/tstms to move
westward into the western deserts this evening before dissipating by
midnight.
The disagreements amongst these solutions are for the Tucson metro
area. The WRF-NAM and WRF-GFS were quite similar with depicting at
least some showers/tstms to occur in vicinity of the metro area, and
especially the northern portion (e.g. Catalina Mountains, Oro
Valley, etc.) of the area. However, a few recent HRRR solutions have
trended downward on precip potential for the Tucson metro area
versus earlier HRRR solutions.
At any rate, have made only very minor adjustment to the inherited
gridded data PoPs based on these differing solutions. Thus, the
offical forecast continues with isolated to scattered showers/tstms
generally west of a Hannagan Meadow-Mt. Graham-Sierra Vista line.
Gusty outflows may produce patchy blowing dust restricting
visibility to less than one mile late this afternoon and early
evening. The expectation is for showers/tstms to end by midnight.
A similar forecast scenario is on tap Tuesday afternoon/evening.
However, the Univ of AZ WRF-NAM and WRF-GFS suggests less coverage
of showers/tstms may occur Tuesday afternoon/evening, as these
solutions depict measurable rainfall to be west of Tucson. The
official forecast continues with isolated showers/tstms across much
of the area Wednesday afternoon/evening.
Strong high pressure aloft presently centered over Utah is progged
to become centered over southeast New Mexico/far west Texas area on
Thursday. Meanwhile, a trough of low pressure will encroach upon the
West Coast. The 04/12Z GFS/ECMWF/CMC and ensembles then depict an
upper low to become centered near the central California coast
Saturday as high pressure aloft remains over far west Texas. The
southerly mid-level flow regime appears to be increasingly favorable
for more widespread coverage of showers/tstms.
The official forecast has isolated coverage of showers/tstms
Thursday afternoon/evening and again Saturday. Somewhat greater
coverage of showers/tstms appears to favor Friday afternoon/evening,
at least based on these solutions. Although the upper low remains
quasi-stationary just west of Los Angeles next Sunday and Monday,
high pressure aloft is progged to build over this forecast area.
Thus, have limited afternoon and evening showers/tstms to mainly
near mountains northeast of Tucson to the White Mountains next
Sunday and Monday with dry conditions elsewhere.
High temperatures at least through Wednesday, and perhaps into
Thursday, will average at least a few degrees above normal. Daytime
temperatures Friday into Sunday will trend quite close to seasonal
normals.
&&
.AVIATION...Valid thru 06/00Z.
Scattered -TSRA/-SHRA mainly west of a KSAD-KFHU line into this
evening and Tuesday afternoon. Otherwise, VFR conditions into
Tuesday afternoon. Surface wind variable in direction mainly less
than 12 kts except gusts to 40 kts near stronger TSRA. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to scattered afternoon and evening
thunderstorms into Saturday, then isolated thunderstorms mainly near
the mountains northeast of Tucson to the White Mountains Sunday and
next Monday. 20-foot winds Tuesday through Friday will generally be
from the east to southeast at 5-15 mph with occasional gusts to 25
mph. Expect terrain driven surface winds next weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Francis
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
327 PM PDT Mon Sep 4 2017
.SYNOPSIS...Isolated to scattered showers and thunderstorms are
expected again this afternoon. The focus of the activity will be
concentrated in Mohave and northern Lincoln counties as well as
along the higher terrain. A ridge of high pressure will move over
the area today and tomorrow increasing temperatures before an
upper-level low digs into the western CONUS later this week.
Moisture will remain trapped under the ridge keeping slight
chances across most of the region each afternoon, primarily over
the higher terrain. &&
.SHORT TERM...Today through Wednesday.
Early morning cloud cover fizzled quickly this morning across much
of the region as the moisture began to mix out. Though, fairly low-
grade low-level moisture remains across most of our CWA this
afternoon, with the 50 dewpoint line stretching from the Colorado
River Valley-Lincoln County. With sufficient moisture and
instability across the southern Great Basin and Mohave County
today, thunderstorms are likely to continue through the afternoon
and evening for these areas. The convective allowing models and
the experimental HRRR are continually depicting a thunderstorm
complex developing later this afternoon across central Mohave
County. Notably, the RAP does have sufficient shear within Mohave
county to generate a severe thunderstorm or two...Though, the
major concern today continues to be outflow winds. With rather
large DCAPE values and an inverted V profile from this mornings
sounding, any storm could produce strong and gusty outflow winds.
By Tuesday, as the high pressure elongates over much of the western
CONUS, the southeasterly flow shifts further south limiting the bulk
of the moisture to the southeastern CWA. Though, with sufficient low
level moisture across most of the region, slight chances for showers
and thunderstorms exists mainly along the higher terrain and in
southern Mohave county. By Wednesday, a moist airmass ahead of the
upper low will increase chances for showers and thunderstorms in the
afternoon across much of the CWA.
Temperatures will be above normal today and tomorrow before they
approach seasonal normals on Wednesday with that northwestern
airmass cooling temperatures a bit.
.LONG TERM...Thursday through Monday.
A general southerly flow will keep varying amounts of moisture over
our region to fuel isolated to scattered thunderstorms through the
coming weekend and early next week. The medium range models indicate
a mean trough along the west coast and a broad ridge near the Four
Corners Region will generally hold their positions. The hybrid
remnant circulation of what was once Lidia is forecast to lift
inland across northern California and Oregon Thursday ahead of a
shortwave trough swinging down to take its place near the central
California Coast which eventually becomes a closed circulation that
remains nearly stationary Saturday through Monday. The GFS and ECMWF
solutions are fairly close at depicting this though the ECMWF has a
more well defined circulation which would enhance southerly flow and
moisture advection over our area. This pattern will keep at least a
slight chance of thunderstorm development over most zones along with
temperatures trending downward toward normal.
&&
.AVIATION...For McCarran...Typical diurnal winds are expected
through Tuesday. However, isolated thunderstorms will occur mainly
east of the area this afternoon and evening, leading to a slight
possibility of thunderstorm outflow winds producing erratic
conditions for the terminal area this evening, but confidence is too
low to mention in the TAF. Any storm activity should die off later
this evening but will develop again Tuesday afternoon which could
result in thunderstorm outflow winds impacting the terminal. Clouds
in the terminal area should remain above 12 kft.
For the rest of southern Nevada, northwest Arizona and southeast
California...Thunderstorms are possibly through this evening mainly
over Mohave and Lincoln Counties and the Sierra. A little more
thunderstorm coverage is possible Tuesday mainly over higher
terrain. Prevailing winds through Tuesday will mainly follow typical
diurnal trends but could be gusty and erratic near any storms this
afternoon and evening.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures. &&
$$
SHORT TERM...Kryston
LONG TERM...Adair
AVIATION...Harrison
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