Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/22/23
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
615 PM MDT Thu Sep 21 2023
...New AVIATION...
.SYNOPSIS...
Issued at 230 PM MDT Thu Sep 21 2023
A few severe storms in eastern New Mexico could produce damaging
outflow wind gusts and small hail this afternoon and early evening.
Breezy to locally windy west winds tomorrow may create a few hours
of localized critical fire weather conditions in northeastern New
Mexico. A few showers are possible in northern NM on Saturday night
and early Sunday morning before dry weather returns early next week.
A few showers and storms are possible Tuesday and Wednesday in the
eastern half of the state.
&&
.SHORT TERM...
(This evening through Friday night)
Issued at 230 PM MDT Thu Sep 21 2023
Drier southwest to westerly flow aloft combined with surface low
pressure over southeast Colorado/northeast New Mexico was resulting
locally breezy to windy conditions over northern and eastern New
Mexico this afternoon. Humidities were decreasing over the northwest
third of the state as well, but higher dewpoints remain entrenched
especially from the Middle Rio Grande Valley east and southward.
There remains a good deal of uncertainty exactly where over eastern
New Mexico a strong to severe storm may impact, with the HRRR
indicating only a few discrete cells over the region. There is
potential for some gusty buildups around the Albuquerque metro also
before sunset. Most of the convection should diminish by 9 pm or so.
Tonight will be cooler over most of the forecast area with Friday
slightly warmer. Friday and Friday night will be dry although an
increase in mid to high level moisture may lead to a few sprinkles
over the northwest late Friday night. The boundary layer will need a
little time to moisten though so the chance for measurable rain is
rather low. Breezy to locally windy conditions are likely along and
north of I-40 on Friday, and suspect winds may be a little too low
in the grids over the southern portion of the CWA.
&&
.LONG TERM...
(Saturday through Wednesday)
Issued at 230 PM MDT Thu Sep 21 2023
Clouds will increase in coverage across the northwest Saturday
afternoon as upper-level moisture from a portion of the remnants of
Tropical Storm Kenneth move inland. A few sprinkles and light
showers are possible in the northwest as a shortwave comes through
Saturday night into Sunday, but little wetting rain is expected. The
GFS is quicker with this feature and has it moving in as early as
Saturday evening while the EC has doesn`t have it arriving in the
state until early Sunday morning. Cloud coverage from the uptick in
moisture could also prevent the upper RGV from experiencing its
first freeze of the season.
Dry, westerly flow dominates on Sunday as shortwave ridging quickly
builds into place over the Four Corners region. This will allow low-
level moisture to return to eastern NM Sunday night and keep
temperatures down a few degrees. A few showers may begin to develop
along and east of the central mountain chain as early as Monday
afternoon as the ridge starts to slide eastward and amplify. By
Thursday, dry, northwest flow will begin to scour out any low-level
moisture.
Cluster analysis suggests there is a high likelihood that a Pacific
trough will begin to deepen over the West Coast late next week. This
will be something to watch moving forward as it could eventually
bring high winds and/or precipitation to the area during the first
few days of October. Furthermore, the updated CPC outlook shows an
increased probability of above average precipitation for the state
during the month of October.
&&
.AVIATION...
(00Z TAFS)
Issued at 553 PM MDT Thu Sep 21 2023
Scattered to isolated showers and thunderstorms over central and
eastern areas will decrease in coverage with sunset, then diminish
by midnight. High clouds will increase tonight, then thicken and
lower to the mid level of the atmosphere Friday into Friday
night. Dry weather is forecast on Friday, but southwest winds will
be gusty.
&&
.FIRE WEATHER...
Issued at 230 PM MDT Thu Sep 21 2023
Drier southwest to westerly flow is spreading into western NM this
afternoon and this drier air aloft will progress eastward tonight
and Friday. Some localized critical conditions may be achieved over
northwest and west central late this afternoon with minimum
humidities near 15 percent. Wetting showers and storms, a few of
which may be strong to severe with hail and damaging winds, are
possible over eastern NM this evening but areal coverage looks to be
spotty at best and confidence is low in any one locale receiving
precipitation.
Drier conditions expand on Friday while southwest to west winds
remain breezy. Elevated to localized near critical conditions are
possible Friday north of I-40.
A stream of mid to high level moisture will pass over northern NM
Saturday which could lead to a few showers over the northwest.
Sunday will likely be drier again, as well as Monday, at least west
of the central mountain chain. Low level moisture may slosh in and
out of the east next week, with low confidence for wetting rain.
There doesn`t appear to be any significant storms headed our way
next week though, but forecast models have not been very consistent
from run to run.
&&
.PRELIMINARY POINT TEMPS/POPS...
Farmington...................... 45 79 49 74 / 0 0 0 0
Dulce........................... 38 75 39 72 / 0 0 0 0
Cuba............................ 42 76 44 70 / 0 0 0 5
Gallup.......................... 38 80 45 73 / 0 0 5 10
El Morro........................ 39 75 44 72 / 0 0 5 10
Grants.......................... 37 79 45 76 / 0 0 0 10
Quemado......................... 44 78 46 75 / 0 0 0 5
Magdalena....................... 51 81 53 80 / 5 0 0 0
Datil........................... 46 77 48 75 / 0 0 0 0
Reserve......................... 48 81 49 82 / 0 0 0 0
Glenwood........................ 56 85 57 85 / 0 0 0 0
Chama........................... 36 70 37 66 / 0 0 0 5
Los Alamos...................... 51 76 52 72 / 10 0 0 5
Pecos........................... 48 77 48 74 / 20 0 0 0
Cerro/Questa.................... 36 74 38 70 / 5 0 0 0
Red River....................... 36 67 37 64 / 5 0 0 0
Angel Fire...................... 32 69 35 65 / 10 0 0 0
Taos............................ 38 77 42 72 / 5 0 0 0
Mora............................ 43 76 44 72 / 10 0 0 0
Espanola........................ 42 81 46 79 / 20 0 0 0
Santa Fe........................ 47 78 50 74 / 10 0 0 0
Santa Fe Airport................ 46 81 49 77 / 10 0 0 0
Albuquerque Foothills........... 53 82 56 80 / 10 0 0 0
Albuquerque Heights............. 57 85 57 81 / 10 0 0 0
Albuquerque Valley.............. 50 86 52 84 / 10 0 0 0
Albuquerque West Mesa........... 55 84 56 81 / 10 0 0 0
Belen........................... 55 88 57 86 / 10 0 0 0
Bernalillo...................... 52 85 53 82 / 10 0 0 0
Bosque Farms.................... 52 86 54 84 / 10 0 0 0
Corrales........................ 53 85 54 82 / 10 0 0 0
Los Lunas....................... 53 86 56 85 / 10 0 0 0
Placitas........................ 51 81 53 79 / 10 0 0 0
Rio Rancho...................... 54 84 55 82 / 10 0 0 0
Socorro......................... 57 90 58 88 / 10 0 0 0
Sandia Park/Cedar Crest......... 49 76 51 73 / 10 0 0 0
Tijeras......................... 50 79 52 76 / 10 0 0 0
Edgewood........................ 47 79 49 77 / 10 0 0 0
Moriarty/Estancia............... 42 81 45 78 / 10 0 0 0
Clines Corners.................. 49 79 49 76 / 30 0 0 0
Mountainair..................... 50 80 51 78 / 10 0 0 0
Gran Quivira.................... 52 81 52 79 / 20 0 0 0
Carrizozo....................... 60 84 59 84 / 20 0 0 0
Ruidoso......................... 55 77 56 78 / 30 0 0 0
Capulin......................... 46 79 49 76 / 5 0 0 0
Raton........................... 45 82 47 79 / 5 0 0 0
Springer........................ 47 82 47 81 / 10 0 0 0
Las Vegas....................... 47 80 48 78 / 20 0 0 0
Clayton......................... 55 89 56 83 / 10 0 0 0
Roy............................. 52 85 52 82 / 20 0 0 0
Conchas......................... 55 88 57 89 / 30 0 0 0
Santa Rosa...................... 58 88 59 85 / 20 0 0 0
Tucumcari....................... 61 93 59 89 / 30 0 0 0
Clovis.......................... 60 91 60 90 / 20 0 0 0
Portales........................ 61 92 60 91 / 30 5 0 0
Fort Sumner..................... 60 93 61 89 / 20 0 0 0
Roswell......................... 63 97 63 97 / 20 0 0 0
Picacho......................... 61 90 61 90 / 20 0 0 0
Elk............................. 58 85 59 87 / 20 0 0 0
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...99
LONG TERM....16
AVIATION...44
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
314 PM AKDT Thu Sep 21 2023
.SYNOPSIS...
A long wave trough that has brought showery, unsettled weather
over the last few days makes a slow exit to the Alcan border
through tomorrow, allowing high pressure to build across the state
and drier conditions to prevail heading into the weekend.
Accompanying high pressure will be an Arctic airmass however so
temperatures will still run near to below through the weekend.
High pressure keeps weather fairly quiet, although a couple areas
of low pressure along its periphery keep chances for showers
mainly across the northeast near the Arctic Coast as well as
toward the Yukon Delta region.
&&
.DISCUSSION...
Upper levels and analysis...
Current RAP analysis this afternoon shows a vertically stacked
Arctic low positioned north of Nuiqsut, with a longwave trough
axis connecting it to a more complex pair of upper level lows
tracking through the Gulf of Alaska tonight. At the surface,
ceilings are lifting and winds are turning northwesterly through
the central and eastern interior behind a cold front tracking east
with the trough axis. Meanwhile further north and west, an Arctic
front has pushed through much of the North Slope and continues to
bring in more cool and dry air... except across the Arctic coast
where it`s more cool and damp due to moisture from the open ocean.
As a result many of the interior valley locations are seeing more
sunshine than in recent days, although the higher terrain remains
cloudy with upslope and coastal locations are experiencing either
stratus from the Arctic or stratocumulus off the Bering Strait.
Looking through the next few days, high pressure over the Bering Sea
is forecast to build northward into the Strait and shift east
through the interior with more in the way of fair weather. This will
likely allow river valley fog to develop especially overnight, and
especially over the interior, when/where winds are likely to
diminish most efficiently. As the ridge shifts north and east, the
storm track through the Bering Sea shifts toward the Yukon Delta
region for the weekend, though significant winds and precipitation
are likely to remain south of the forecast area. Low pressure off
the Arctic coast will be slower to exit with snow showers persisting
through the Brooks Range and along the Arctic Coast through the
start of the weekend.
Model Discussion...
Major model suites are in good agreement on the depth and
progress of the upper air pattern through the next couple of days
as a ridge builds north and shifts east through Alaska. The
outlier remains the GFS/GEFS, which has tended to cut off and
weaken the ridge through the weekend, bringing the Bering Sea
storm track into better phase with low pressure west of Vancouver
Island. Overall the impact to sensible weather is minimal,
although this scenario would shift the ridge more poleward and
potentially lead to stronger easterly flow along the Arctic Coast
by early next week.
Have continued to highlight stronger-than-forecast wind gusts
along the Arctic coast due to stronger mixing in cold advection.
Central and Eastern Interior...
High pressure moves overhead through the interior over the next
couple of days with shower activity and breezy westerly flow in
cold advection today waning as the Arctic front crosses overnight.
Subsidence from the high and open, relatively warm rivers...along
with the steep drop off of solar insulation... produce a
favorable set up for overnight/morning fog and stratus development
especially in river valleys. Otherwise, the weather will remain
quiet through the weekend with low to nil precipitation chances
and even some clearing especially by Sunday.
West Coast and Western Interior...
Diminishing northwesterly flow through the Bering Strait marks the
development of high pressure over along the West Coast through
this evening. Cold advection behind the Arctic front tracking east
through the interior continues to produce ocean effect cloud cover
and a few spotty showers mostly for coastal communities, but the
expectation is that deep ridging will cut these chances heading
into tomorrow. As the high drifts east, rain chances return to
the Yukon Delta region as a low cuts across the Bering Sea.
Currently a 980mb low just east of the Kamchatka Peninsula, the
low is forecast to fill and weaken significantly as it approaches
the Alaskan coast... with model consensus suggesting a 1000 mb low
reaching the coast near Nunivak Island Sunday evening. Developing
easterly flow should keep coastal impacts to a minimum, with
primarily rain showers except mixing at elevation above about
2500 ft.
North Slope and Brooks Range...
Weather pattern here is dominated by an Arctic low that is
forecast to spin north of the Coast over the next few days. Arctic
front has cleared central and westerns areas by now with
northwesterly to westerly flow and a blanket of stratocumulus and
snow showers. This same general pattern of cold advection from the
Arctic Ocean into the North Slope will continue these cool and
cloudy conditions through the weekend with flow turning westerly
before diminishing. Occasional snow showers also continue in this
regime with light accumulations of an inch or less, except up to 4
inches in the western Brooks range.
Extended Forecast Days 4-7...
The primary question in the extend is the progression and erosion
of the ridge overhead. Will mainly be monitoring model trends with
the next Pacific low approaching the Bering Sea by the middle of
next week, though its track is unclear with significant model
spread.
Coastal Hazard Potential Days 3 and 4...
Minimal threat of coastal impacts with a general easterly flow
across Alaska for days 3 and 4.
&&
.HYDROLOGY...
Rivers are generally steady or slowly falling. No flooding
expected.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ813.
Small Craft Advisory for PKZ814-860.
Small Craft Advisory for PKZ815-851-861.
Small Craft Advisory for PKZ816.
Small Craft Advisory for PKZ859.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
852 PM MDT Thu Sep 21 2023
.UPDATE...
Issued at 840 PM MDT Thu Sep 21 2023
A couple storms are attempting to move across the CO/NE border
into Logan County this evening. It is more stable in Colorado
compared to Nebraska and any storms that move into Colorado should
be short-lived. The primary forecast concern tonight is whether
low clouds and fog will develop. 60 degree dew points have made
their way into far northeast Colorado on easterly outflow winds. A
general northeast flow will push this moisture farther west and
with the help of upslope flow, it will most likely create fog/low
clouds. The extent of the patchy fog in forecast was extended to
include Denver, Greeley, and Bennett.
&&
.SHORT TERM...(This evening through Friday)
Issued at 145 PM MDT Thu Sep 21 2023
Deep upper level low currently over Oregon will track east into
Wyoming Friday. For Colorado, a strong west-southwest flow aloft
will prevail. For the rest of the afternoon/evening, drier air is
moving in from the southwest resulting in mostly sunny skies. A
few showers or storms can`t be ruled out over far northern
Colorado, next to the border with Wyoming and Nebraska. A surface
low and dry line has set up over eastern Colorado. Far northeast
Colorado, should be on the moist side of the dry line this evening
through mid to late Friday morning. HRRR model shows the dry line
is pushed westward over northern Colorado by thunderstorm outflow
from storms over Nebraska. Chances it makes as far west as the
foothills is low, but not none. Cloudy skies and possibly fog are
expect on the moist side of the dry line.
For Friday the surface low and dry line shift east of Colorado.
Behind it gusty west-southwest winds will prevail. The higher
terrain could see gusts to 45 mph with gusts to 35 mph across the
plains. Mostly sunny skies and downslope winds will push highs
into the 80s across northeast Colorado. Models indicate surface
pressure lowers and a new low possibly forms across the Urban
Corridor or near by plains Friday afternoon. This may cause the
winds to weaken mid to late afternoon.
.LONG TERM...(Friday night through Thursday)
Issued at 145 PM MDT Thu Sep 21 2023
Friday night into Saturday, a closed upper low will track across
Wyoming into the Dakotas with a strong westerly flow aloft over
Northern Colorado. This pattern will result in breezy to windy
conditions over the mountains and plains. Models are showing quite
a bit of QG ascent with this system due to a 100KT+ upper jet
over the forecast area. Despite this, precipitation chances
Saturday evening into early Sunday morning are expected to remain
near zero due to limited moisture. The exception may be a few
showers or storms over the Northern Mountains and far northeastern
plains.
Slightly cooler temperatures are expected over the weekend behind
the passage of a cool front with winds gradually decreasing by
Sunday as upper level high pressure builds into Colorado from the
west. Dry and warmer weather is expected early to mid next week as
upper level high pressure dominates the Rocky Mountain Region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 551 PM MDT Thu Sep 21 2023
Light northeast winds will continue until a weak cold front moves
through later this evening. Northwest winds will develop behind
the front and they could gust up to 20 knots briefly. The concern
tonight will be the possibility of fog. There is much better
moisture with dew points in the 60s in Nebraska and this moisture
will move into Colorado tonight. With weak upslope flow, it seems
more likely than not that fog or low clouds will develop at DEN around
8-9Z and last into the morning hours. A TEMPO group for fog/mist
was added. If fog does develop, it may bring visibility down to
around a half mile. The fog or low clouds will clear out tomorrow
morning and then gusty westerly winds will develop in the
afternoon.
&&
.FIRE WEATHER...
Issued at 145 PM MDT Thu Sep 21 2023
Strong westerly flow aloft will bring elevated fire weather
conditions for Friday. Windy conditions are expected over the
higher terrain with gusts to 45 mph. Gusty west winds will spread
onto parts of the Urban Corridor and near by plains with gusts to
35 mph possible here. It will also be mild and dry with relative
humidity falling into 10-20 percent range. Will hold off from
issuing a Red Flag Warning due to marginally dry fuels in addition
to the strongest winds and lowest relative humidities not
coinciding.
Warm and breezy conditions are expected to continue over the
weekend with some improvement to fire weather conditions due to an
increase in the humidity and slightly cooler temperatures.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Danielson
SHORT TERM...Meier
LONG TERM...jk
AVIATION...Danielson
FIRE WEATHER...Meier/jk
Area Forecast Discussion
National Weather Service Cheyenne WY
601 PM MDT Thu Sep 21 2023
.SHORT TERM...(This evening through Friday)
Issued at 345 PM MDT Thu Sep 21 2023
A surface trough draped over the eastern half of the CWA with
elevated instability led to scattered showers and thunderstorms this
morning. Early this afternoon, storms dissipated and pushed
northward out of the CWA. Hi-Res guidance, the HRRR in particular,
develops another round of stronger storms off the high terrain mid
this afternoon and pushes them eastward. The HRRR does have almost
2000 J/kg of SBCAPE making it into parts of the Nebraska panhandle
later this afternoon. This could support an isolated strong storm or
two with hail and gusty winds. Cannot rule out a severe storm later
this afternoon/evening in this setup, especially with a Marginal
Risk for severe weather across most of the panhandle. Other Hi-Res
are less aggressive this afternoon and evening, still showing a
decent capping inversion which will limit convective potential.
Heading into Friday morning, a stationary front and surface low
continues to linger over the Pine Ridge. With some leftover
instability from today`s storms also lingering in the vicinity of
the Pine Ridge, another round of morning showers and thunderstorms
looks possible across the northern Nebraska panhandle counties and
Converse and Niobrara Counties in east-central Wyoming. Beyond
this, the afternoon looks relatively dry for most locations based
off of Hi-Res guidance. A few isolated storms, potentially strong
to severe, may pop in the aforementioned areas as instability
increases throughout the afternoon. Again, there is another
Marginal Risk for severe storms across much of the panhandle and
into our northern Wyoming forecast zones. Currently, Chadron is
even in a Slight Risk for severe storms. Will continue to monitor
this for updates, however the best chance for severe storms looks
northeast of the CWA.
Friday night, a strong cold front pushes through the CWA. There
could be some precipitation associated with the FROPA, however the
bigger concern will be high winds across the usual southeast Wyoming
wind prones. The cold front will increase gradients rapidly across
the Laramie Range and westward. 700 mb height gradients also rapidly
steepen, peaking above 70 meters by Saturday morning. Winds aloft
will greatly strengthen Saturday morning over the wind prones, with
60 to 70 kt 750 mb winds. Strong downward omegas should easily mix
these winds down to the surface. As a result, issued a High Wind
Watch for the usual wind prones, Arlington/Elk Mountain, the south
Laramie Range and adjacent foothills, Bordeaux, and even for
central Laramie County including the city of Cheyenne. Winds
should ease Saturday afternoon as gradients ease behind the front
and an upper- level ridge builds behind it.
.LONG TERM...(Friday night through Thursday)
Issued at 300 PM MDT Thu Sep 21 2023
Key Impact Messages:
1) After an initial High Wind and breezy period, winds will decrease
Sunday but elevated to near critical fire weather conditions will
remain.
2) Elevated to near-critical fire weather conditions continue Monday
into Tuesday. A Fire Weather Watch might be needed Sunday into
Tuesday for particular fire weather zones.
3) Overall temperatures will be at to slightly above normal with dry
conditions expected through next Thursday.
Weather Discussion: Late Saturday into Sunday pattern will feature a
tight closed H5 low over South Dakota with NW H5 flow as additional
subsidence kicks in over SE WY and the West NE Panhandle. While
Saturday will be the main wind event period, height gradients Sunday
will be enough to support elevated winds during peak afternoon
mixing for fire weather concerns. A Fire Weather Watch could be
needed Sunday and potentially into Monday and Tuesday. Internal AI
guidance highlights that 20 to 30 mph gusts and minimum humidity
values falling into the teens each afternoon appear likely. How
these components align with the fire weather forecast zones that
have drier 1/10-hour fuels could necessitate Fire Weather Watches.
Winds will become more marginal Monday into Tuesday as an H7-H5
ridge develops over WY. H7 temperatures will slowly warm through
early next week from 5C Saturday upwards to 10C to pushing 12C by
mid-week across the GEFS ensemble quartile spread. This will help
support above normal high and low temperatures but not close to any
records. Likewise, the suppressing ridge will keep precipitation
chances below 5-10% if that high, Sunday to Wednesday per the NBM
ensemble spread. Moreso, precipitation chances don`t rise above 20%
through into the beginning of October. Minimum relative humidity
values should increase slightly into mid to late week but still
dropping into the low teens to low 20 percentiles per NBM ensembles.
Pattern confidence decreases slightly into late next week but
overall west to southwest flow appears likely with the approach of a
stronger trough over MT. However, most the the dynamic lifting
remaining farther north with the potential for a surface front nearing
the region per ensemble potential and a few deterministic runs. Next
best chance of precipitation could be next Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 547 PM MDT Thu Sep 21 2023
The terminal forecast over the next 12-24 hours will be an active
scenario for most sites. VCTS and VCSH are expected to slowly move
from southwest to northeast between 0z-6z, with KCDR seeing the
longest window of precipitation into the overnight hours. KLAR and
KRWL will remain VFR overnight, and winds gusts picking up by
tomorrow morning to 25-35 knots. KCYS will see the potential for
VCTS to wind down early this evening, and weak upslope flow will
create low CIGS overnight, ultimately in the form of IFR/LIFR
through approximately 15z Friday.
The NE Panhandle terminals will also be impacted by the low CIGs
this evening and overnight. Flight conditions will transition from
MVFR to IFR/LIFR between 6z-15z, and the potential for reduction
in VIS also will become apparent close to the 12z-15z timeframe
for these terminals. Additionally, once the VCSH and VCTS push
northeast, VRB winds with gusts to less than 12 knots will be
expected.
&&
.FIRE WEATHER...
Issued at 300 PM MDT Thu Sep 21 2023
Fire weather concerns will be minimal Friday and Saturday as a cold
front will bring increase moisture and cooler temperatures. Although
RHs will be above 15 percent, very strong winds will accompany this
front. On Friday, areas west of the Laramie Range could see gusts up
to 35 MPH. Even stronger winds are likely across the southeast
Wyoming winds prones early Saturday morning into Saturday afternoon
with gusts up to 65 MPH possible. Fire weather concerns return
Sunday with minimum RHs falling below 15 percent in much of
southeast Wyoming with wind gusts up to 30 MPH. Fire weather
concerns increase into next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from late Friday night through Saturday
afternoon for WYZ106-110-116>118.
NE...None.
&&
$$
SHORT TERM...SF
LONG TERM...JSA
AVIATION...BW
FIRE WEATHER...SF
Area Forecast Discussion
National Weather Service Des Moines IA
638 PM CDT Thu Sep 21 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Thursday/
Issued at 249 PM CDT Thu Sep 21 2023
Take Home Points:
* Confidence still shaky on showers/storms through Sat AM.
* Increasing confidence in strong to severe storm potential Sat PM
* Precip chances next week remain, but variable solutions remain
Discussion:
Another day, another win for the FV3 cores compared to the
operational CAMs. At least for the most part. Morning MCS over
eastern Nebraska tended to be depicted best in the FV3 cores, namely
the experimental RRFS, slowly dragging it eastward and weakening
along/east of the Missouri River this afternoon. Comparatively, the
HRRR continued to persistently dissipate the complex too soon. With
that in mind, have continued to at least blend in the RRFS/FV3 cores
into operational CAM guidance over the next 24+ hours. In this
regard, the primary difference results in a potential complex of
storms tracking across Iowa Friday, remnants of nocturnal convection
from KS/NE areas, which is notably missing in most operational CAM
guidance. That said, recent HRRR runs have begun to pick up a bit
more on this potential. Given expected air mass and timing, non-
severe showers/storms are the expectation through the day Friday
should this materialize.
Friday night may see additional scattered convection as WAA/LLJ
increases from developing Lee cyclogenesis over the Front Range
area. Confidence in coverage is somewhat low though with the range
of guidance, operational CAMs/FV3 cores/etc all showing
scattered/bubbling activity vs any upscale growth/MCS type
development. Air mass will be more unstable with the increasing low
level flow, but best opportunity for severe storms should remain
west of the area into portions of Kansas and Nebraska. While 1000-
2000+ J/kg of elevated CAPE appears likely west of I-35, wind
profiles remain unsupportive of organization. Do not expect much
more than small hail and sub-severe wind potential with pulsey
nature.
Potential for some scattered convection within the building warm
sector ahead of the surface/upper lows will continue during the day
Saturday, as depicted in various longer range CAM guidance. This
could be a sneaky window of opportunity for a strong to severe storm
or two with CAPE and wind fields through the column increasing.
However, expected cap appears more likely to keep early daytime
convection elevated, limiting the severe potential. Something to
keep a casual eye on.
Synoptic and longer range CAMs remain in some disagreement on
frontal timing Saturday afternoon and evening, but general consensus
suggests status quo to subtle westward movement. Overall, the threat
for severe weather remains unchanged with all modes possible given
sufficient overlap in thermodynamic and wind fields. With expected
track of surface low across South Dakota, best threat for tornadic
activity will be up that direction closer to the triple point.
Further south into Nebraska and Iowa, all modes will remain possible
with any initial organized isolated to clustered activity. Upscale
growth through the evening will likely transition primary threat to
damaging winds, though some isolated hail and potentially QLCS type
tornadic activity cannot be ruled out. At this time, the windows of
opportunity are best categorized as mid afternoon to evening over
the western CWA and evening to overnight for central and eastern
areas of the CWA. Details will continue to come into focus.
Sunday and beyond, synoptic guidance continues to struggle to find a
true consensus in the evolution of the upper level trough,
especially as Tropical Cyclone 16 potentially organizes and comes
ashore along the east coast. Suffice it to say, there will likely be
a couple opportunities for additional precipitation, but is trending
drier than forecast packages the last couple of days. Throughout the
forecast, expect seasonable to seasonably warm temperatures with
highs in the 70s to low 80s and lows in the 60s initially, cooling
into the 50s by next week.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 638 PM CDT Thu Sep 21 2023
VFR conditions begin the period with mainly just some high cloud
over the northern and eastern half of the state. Forecast data
continue to point to the likelihood of at least MVFR CIGS/VSBYS
developing at most terminals 09-15Z. Of less confidence is whether
conditions could drop to IFR. If it is able to, KALO and KOTM are
best positioned closer to the sfc moisture. Otherwise, still
expect some spotty pockets of -SHRA lifting northeast through
central IA mainly early tomorrow morning. At this point,
anticipated coverage remains spotty enough to preclude inclusion
in 00Z TAFs. May need to add if trends hold. VFR conditions are
expected after 15z.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Curtis
AVIATION...Hahn
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
801 PM CDT Thu Sep 21 2023
.SYNOPSIS...
Issued at 801 PM CDT Thu Sep 21 2023
Scattered showers and a few thunderstorms will affect central IL
through tonight, with locally heavy rain possible. Showers will
diminish on Friday, with dry weather forecast for Saturday.
&&
.UPDATE...
Issued at 801 PM CDT Thu Sep 21 2023
Scattered showers and isolated storms continue across central
Illinois with the best coverage between the I-55 and I-57
corridors. While there may be a relative lull in coverage over
the next few hours with loss of daytime heating, latest RAP
continues to show a modest low level jet developing late this
evening. This 30 kt southerly jet will develop between 10 pm and
midnight with a focus across portions of west central into central
Illinois, along and west of I-55. Precip coverage should again
increase and will have to keep an eye out for locally heavy
rainfall. Cloud-bearing layer flow per 00Z KILX sounding was only
11 kt and 1.50 inch PWat is just above the 90th percentile. Slow
moving, efficient storms could produce localized rainfall rates of
1.5 to 2.0 inches. One hour flash flood guidance is around
2.2-2.3 inches while three hour FFG is 2.6-2.8+.
Deubelbeiss
&&
.DISCUSSION...
Issued at 211 PM CDT Thu Sep 21 2023
Key Messages:
1) Showers and a few storms, some with locally heavy rainfall,
through tonight.
2) Showers diminish Friday, then dry Saturday and trending drier
for Sunday.
3) Stretch of nice fall weather next week.
Early afternoon visible satellite imagery and surface map
indicated weak low pressure over southeast IA, and water vapor
imagery showed the mid level shortwave swirling over central IL.
Main concern through early evening will be locally heavy rain and
a few gusty thunderstorms in a broad zone centered on I-55, where
some low level convergence overlaps MLCAPEs building near 1k J/kg,
all beneath broad ascent under the upper wave. HREF max 3-hr QPF
(reasonable worst case scenario) depicts a few pockets of 2.5-3"
rainfall through early evening, and this would be supported by
1.5" PWATs and slow storm motions. Even these outlier cases
shouldn`t offer too much in the way of flooding concerns as 3-hr
FFG values are running 2.5-3.5", though if this falls over an
urban area brief water concerns may develop. An inconsequential
but potential attention grabber is the possibility of a few
funnel clouds this afternoon where the low overcast has given way
to a developing CU field with the background vorticity overhead.
Non-supercell tornado parameter, while weak, is non- zero from
southeast IA into west central IL, so these areas would be most
favored for brief funnels. This evening, the convergent nose of a
southerly 30 kt 925 mb jet focuses of the western and central CWA,
fueling or re-invigorating more scattered storms through late
evening. Still not much of a flood risk unless training results in
very localized much higher rainfall amounts.
The slow moving mid level wave gradually fills later tonight and
Friday as it drifts north, allowing shower and storm coverage to
decrease in intensity and coverage. Highest (likely) PoPs are
focused west of I-55 Friday morning, diminishing to scattered
coverage by afternoon. Trended highs cooler in the upper 70s over
the western CWA Friday given more cloud cover anticipated, while
the southeast CWA should reach into the lower 80s.
This weekend, the main weather players for the eastern half of the
CONUS will be a closed mid level low slowly moving out of the
northern Plains, and a tropical system working north along the
eastern seaboard. Between these two features upper level ridging
is forecast to build north over the Ohio Valley and Midwest,
effectively stalling the eastward advance of the Plains low. We
will maintain a dry forecast for Saturday, and chance PoPs over
the western half of the CWA Sunday on the eastern fringes of
forcing ahead of the upper low. Much of the 12z guidance has
trended drier for Sunday and would expect PoPs to be eliminated in
later forecasts if this trend continues.
The remainder of the forecast through mid-week is looking dry and
cooler as a large area of high pressure over southeast Canada
produces easterly flow across the Midwest.
25
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 625 PM CDT Thu Sep 21 2023
Scattered showers and a few isolated storms will continue across
central Illinois this evening and overnight, though coverage
should gradually become more focused west of I-55 Friday
afternoon. Guidance does indicate some fog potential along and
west of the Illinois River tonight which could impact PIA, but
confidence is low at this time. A modest SE breeze will prevail
through the period.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service North Platte NE
622 PM CDT Thu Sep 21 2023
...Aviation discussion...
.SYNOPSIS...
Issued at 215 PM CDT Thu Sep 21 2023
Key Messages:
Severe potential tonight though Friday night. In addition expect
locally heavy rainfall to occur, with highest chances for this
occurring across northern Nebraska.
A cold front moves through the area Saturday with northwest winds
developing.
Mainly dry weather is expected Sunday into the middle of next week.
Temperatures should mostly be near normal during this time.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 215 PM CDT Thu Sep 21 2023
Potent upper level low pressure is located across across the Pacific
Northwest this afternoon. Diffluent flow aloft coupled with mid-
level WAA has contributed to training/redeveloping convection across
northern NE. Locally heavy rainfall has already occurred with 2-3"
recorded in a few spots. Continued scattered redevelopment is
expected to continue across northern NE well into the evening
tonight...as mid-level WAA continues and upper level forcing
gradually increases.
As far as the severe aspect goes, it is a bit complicated. An
earlier MCS across northeast NE contributed to an outflow boundary
that extends from near Holdrege to North Platte. A surface low is
located across far northeast CO. A dryline/steep low-level lapse
rates have pushed eastward into northwest KS south of the low where
temperatures have warmed to near 90. Consecutive runs of the HRRR
develop convection on the nose of the steeper low-level lapse rates
across northwest KS/far SW Neb. As the convection develops it will
push east-northeastward into moist backed southeast low-level flow.
Any activity that develops should quickly become supercellular. Very
steep mid-level lapse rates will contribute to a large hail threat.
Tornado threat is also there, as the backed southeast low-level flow
will result in curved hodographs and effective SRH locally up to 300
m2/s2. Will have to monitor the location of the stalled outflow
boundary which could locally enhance the tornado threat. Convection
will likely increase further into the mid-evening hours across
portions of the Sandhills central/north central NE as the low-level
jet increases. This activity would be more elevated in nature but
could still pose a hail threat.
Confidence in the overall evolution convection/severe is low on
Friday. Parts of northern into central will likely see an overcast
stratus deck for much of the day. Still mid-level WAA will continue
and elevated convection will certainly be possible amid favorable
forcing aloft. A surface low will remain anchored across far
southwest NE, with steep low-level lapse rates again nosing into
this area. This could certainly be an area for initiation, with an
unstable and highly sheared environment located downstream. A marked
increase in convection is expected Friday evening as the better
dynamics overspread the Northern Plains as the upper low approaches.
Northern NE will be located nearer the better dynamics/forcing and
thus the higher pops will be located across this area...decreasing
to the south.
.LONG TERM...(Saturday through Thursday)
Issued at 215 PM CDT Thu Sep 21 2023
A vertically stacked (weakening) upper low should be located across
SD Saturday. A cold front will swing southeastward across the area
as the surface low migrates across SD. The focus for severe will
shift east of the area along the cold front during afternoon. Breezy
northwest winds should overspread our area of western and north
central Nebraska. The continued weakening upper low will remain
anchored across the SD vicinity though early next week. An isolated
shower could occur across far northern NE during this time, but will
be located in the drier sector of the upper low. Temperatures will
generally average near normal during this timeframe. Upper level
ridging may try to nose into the area mid-week ahead of developing
upper level troughing across the western CONUS.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 617 PM CDT Thu Sep 21 2023
Ongoing convection will continue to affect TAF sites, especially
KLBF, through the first part of the valid period. Expect
stratus/fog will bloom overnight, with some additional shower and
thunderstorm development overnight as the low level jet
amplifies. Fog/stratus will persist into Friday morning before
dissipating by the afternoon. Additional convection will develop
Friday afternoon but with low confidence in location/timing will
not mention so late in the period and allow later guidance a
chance to refine the forecast.
Strong, erratic wind gusts are possible near any thunderstorms.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Taylor
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...MBS
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1015 PM EDT Thu Sep 21 2023
.SYNOPSIS...
Potential Tropical Cyclone 16 develops off the Southeast coast
and moves toward eastern North Carolina through Saturday. The
system will move away from the area Sunday, with improving
conditions.
&&
.NEAR TERM /TONIGHT/...
As of 930 PM Thursday...
The 00z observed MHX sounding this evening shows a significant, and
deep, layer of dry air in the low to mid-levels. This is due to a
dryslot well NW of the developing low pressure off the Southeast US
coastline. For now, this is keeping the area mostly dry.
Meanwhile, based on RAP analysis, satellite imagery, and radar
data, a plume of much deeper moisture resides just off to the
southeast of Eastern NC. That plume of moisture will continue to
shift westward overnight as the low off the coast becomes more
organized. Based on recent guidance, the chance of rain will
begin to increase from east to west after 2 am tonight. Prior to
the arrival of the steadier rain, there will be a band, or
bands, of coastal trough induced scattered showers that will
clip the area as low- level moisture continues to increase. The
going forecast handles the situation well, and I didn`t need to
make any significant changes through the overnight hours.
&&
.SHORT TERM /FRIDAY/...
As of 4 PM Thu...Impacts from what is currently Potential
Tropical Cyclone Sixteen will increase quickly through the day
Friday, with strong winds arriving along the coast, and deep
tropical moisture bringing the potential for heavy rainfall
spreading inland from the coast through the day. Tropical Storm
Warnings have been issued for much of the area mainly along and
east of Hwy 17. Minor to moderate impacts are possible across
much of the area are expected by late day, regardless of whether
or not the storm becomes technically tropical. See the
Hurricane Local Statement for more details.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
As of 4 PM Thu...Impacts from Potential Tropical Cyclone Sixteen
will continue Friday night and much of Saturday, with heavy
rainfall, strong winds, storm surge, and tornadoes all possible,
regardless of the technicalities of tropical classification. See
the Hurricane Local Statement for more details on impacts and
timing from Potential Tropical Cyclone 16.
Sunday into next week...Low departs the area to the N and NE,
after this, forecast remains especially murky. Aloft, area lies
in the shear axis between departing troughing associated with
the coastal low and a weak shortwave approaching from the W
crossing through the area late Monday with more zonal flow aloft
slated for Tuesday. Potential for developing weak upper level
troughing over NECONUS sending a cold front through the area
which could lead to a cooler couple of days midweek.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
SHORT TERM /through Friday/...
As of 745 PM Thursday...
KEY MESSAGES
1) Deteriorating aviation conditions on Friday
FORECAST DETAILS
Low pressure developing over the southwestern Atlantic (ie.
Potential Tropical Cyclone 16) will lift north towards the
coast of North Carolina over the next 24 hours, potentially
taking on tropical or sub-tropical characteristics prior to
moving ashore. Regardless of obtaining tropical characteristics
or not, impacts to aviation will begin late tonight, with
deteriorating conditions expected during the day Friday. CIGs
will gradually lower to IFR from south to north as bands of RA
begin to move into the area, and as the low pressure draws
closer. This will also lead to increasingly gusty E to NE winds
developing, with 30-35kt gusts expected close to the coast, and
25-30kt expected further inland. These gusts will increase as
the low moves closer, but those higher gusts will occur beyond
the current TAF cycle. The risk of TSRA may eventually increase
as well by Friday afternoon, especially near the coast, but
given uncertainties in the track and evolution, I decided to
hold off on introducing TS to the TAFs for now.
LONG TERM /Friday night through Monday/...
As of 4 PM Thursday...Conditions expected to improve Saturday
into Saturday night as drier air fills in behind PTC 16. VFR
then generally prevails Sunday into early next week.
&&
.MARINE...
SHORT TERM /through Saturday night/...
As of 4 PM Thu...Local gradient will tighten tonight into
Saturday as Potential Tropical Cyclone 16 develops off the
Southeast coast and tracks toward eastern NC. Conditions will
rapidly deteriorate over the next 18 hours, with very dangerous
marine conditions prevailing much of Friday through at least
Saturday afternoon. Tropical Storm Warnings are in effect for
the entire marine area. Seas will additionally be very large
and dangerous, peaking at 15-20+ ft Friday night.
LONG TERM /Sunday through Tuesday/...
As of 4 PM Thu...Winds eventually becoming WSWerly early Sunday
as the low departs to the NE. Nerly winds 10-15kt Monday become
NEerly late Mon.
&&
.HYDROLOGY...
As of 4 PM Thu...Potential Tropical Cyclone 16 will impact
eastern NC Fri into the weekend. Widespread rainfall
accumulations of 4-6in are expected E of HWY17 through the
weekend, 2-4in far inland zones, which could lead to flooding in
low lying and poor drainage areas and/or localized flash
flooding. A Flood Watch has been issued for all of eastern North
Carolina accordingly.
&&
.TIDES/COASTAL FLOODING...
As of 4 PM Thu...The combination of strong swell from Potential
Tropical Cyclone Sixteen and distant Hurricane Nigel will bring
very dangerous surf conditions through the weekend. Additional
coastal impacts, such as coastal flooding, ocean overwash, and
beach erosion are expected Friday through Saturday night, with
Storm Surge Watches and Warnings now in effect. See the
Hurricane Local Statement for the latest on coastal impacts from
Potential Tropical Cyclone Sixteen. A High Surf Advisory also
remains in effect for beaches from Cape Lookout north from
Friday morning into Saturday afternoon.
Of important note, we will also have to watch for potential
rapid water rises for the soundside Outer Banks Sat. Oceanside
impacts are also likely, especially north of Cape Lookout, with
potential for coastal flooding, beach erosion and ocean
overwash.
Low water will also be possible across the inland rivers Sat.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Tropical Storm Warning for NCZ029-044>047-079>081-091-092-094-
193>196-198-199-203>205.
Storm Surge Watch for NCZ045>047-195-199-203>205.
Storm Surge Warning for NCZ080-081-094-194-196.
Beach Hazards Statement from 8 AM EDT Friday through Friday
evening for NCZ195-196-199-203>205.
High Surf Advisory from 8 AM Friday to 6 PM EDT Saturday for
NCZ196-203>205.
MARINE...Tropical Storm Warning for AMZ131-135>137-150-152-154-156-158-
230-231.
&&
$$
SYNOPSIS...MHX
NEAR TERM...RM
SHORT TERM...CB
LONG TERM...CEB
AVIATION...RM/CEB
MARINE...CB/CEB
HYDROLOGY...MHX
TIDES/COASTAL FLOODING...MHX
Area Forecast Discussion
National Weather Service Pueblo CO
331 PM MDT Thu Sep 21 2023
.SHORT TERM...(This evening through Friday)
Issued at 312 PM MDT Thu Sep 21 2023
1. Still a low risk of thunderstorms over far sern CO into early
evening.
2. Windy and dry Friday, and Red Flag Warning issued for the I-25
corridor, eastern and central mountains from late morning into
early evening.
Dryline was along the CO/KS border at mid-afternoon, with dewpoints
falling off into the 30s and gusty sw winds at 15 to 25 mph
spreading across most of ern CO. Will hold on to some low pops
for the far ern plains into early evening, where HRRR and a few CAMs
still show some activity (CAPE is in the 500-800 J/KG range), though
confidence in severe is waning given wly winds and falling
dewpoints. If activity forms, it will quickly move east into KS/OK
Panhandle by sunset, as best forcing shifts east. Farther west,
gusty w-sw winds were noted at many locations, though for the most
part, relative humidity has stayed just above 15 percent.
Overnight, winds will diminish/decouple at most locations, though
some gusty sw winds may persist over higher exposed terrain. San
Luis Valley mins could again drop toward freezing, mainly right
around Alamosa where winds will be lightest.
On Friday, upper low slides eastward into the nrn Great Basin,
with strengthening w-sw winds across CO. Overall, synoptic
pattern points to breezy to windy conditions across the entire
area, though rather loose surface pressure gradient and modest
15-25 kt mid level flow suggests gusts on the plains will
generally stay around/below 25 mph. Farther west along I-25 and
over the mountains, deep mixing may tap some higher winds above
700mb, and gusts 25-40 mph appear possible. As a result, upgraded
the Fire Weather Watch to a Red Flag Warning for areas from I-25
westward, while dropping highlights for the plains, where winds
will be too weak, and removed Fremont County, where latest update
to fuels shows non-critical conditions. Maxes Fri will warm a few
degf from Thu readings at many locations as deep mixing and dry
air boost numbers, and a few low 90s may appear on the plains.
.LONG TERM...(Friday night through Thursday)
Issued at 312 PM MDT Thu Sep 21 2023
1) Dry through the period with temperatures running 3 to 5F above
normal.
Overall, a quiet and warm week during this long term forecast
period. Storm track will remain well north of the fcst area during
this period, and the region will be in mid level, dry, southwesterly
flow. This will keep temperatures above normal through the period
with dry conditions. With the lower/mid level height gradient being
relaxed over the region, surface winds will not be all that strong
and no significant fire weather concerns are anticipated during this
period.
If there were to be any showers over the region, it would be over
the southern Sangres as a bit better moisture is fcst to be located
over this region.
Overall expect max temps in the 80s over the plains (75-80F
Springs), with 70s over the larger valleys. As for mins, we may see
the San Luis valley getting to around freezing some of the nights,
but a widespread hard freeze does not appear likely. /Hodanish
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 312 PM MDT Thu Sep 21 2023
VFR at all taf sites the next 24 hrs. S-SW winds will gust 20-25kts
at all terminals into early evening, then diminish overnight. SW
winds will increase again late morning Fri, with gusts to 25 kts
after 18z.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM to 7 PM MDT Friday for COZ220-221-
225>230.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...HODANISH
AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service San Diego CA
840 PM PDT Thu Sep 21 2023
.SYNOPSIS...
High pressure to the south will bring warming for the weekend,
but with high temperatures remaining below average. The marine
layer will become shallower with night and morning coastal low
clouds not extending inland much past the western valleys for the
weekend into next week. Tropical mid and high clouds in southwest
flow aloft could bring some virga or sprinkles in the mountains
around Friday night. Not much change or slight cooling for the
early and middle part of next week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Evening Update...
West winds currently gusting 25-45+ MPH along mountain passes and
desert slopes will slowly subside overnight. Satellite imagery
depicts low clouds building back into areas west of the mountains.
The marine layer will become more disrupted this evening into
Friday morning due to high clouds starting to stream into the
area, so intermittent clearing may occur. High clouds are making
their way from the south this evening. These are associated with
weakening Tropical Storm Kenneth approximately 1,000 miles
southwest of San Diego. This system will continue to bring an
increase in high clouds overnight through much of the day on
Friday. Precipitable water values look to go over one inch
tomorrow for southern areas. As with the previous forecast
discussion, some sprinkles are not out of the question,
especially in San Diego County.
These clouds and a trough to the north will lead to another well
below average day with highs 5-15 degrees below average. Quiet
weather with some slight warming is expected for much of next
week with better clearing near coastal areas.
&&
Previous Discussion (1:44 PM Wednesday)...
A low pressure system will move inland into the Great Basin on
Friday. This will maintain cooler temperatures, increased onshore
flow, and a deeper marine layer into Friday. High temperatures
today will be cooler than Wednesday, as much as 15 to 20 degrees
below average in the mountains and valleys. Coastal and desert
areas will be 5 to 10 degrees below average today.
With the increased onshore flow, southwest to west winds will
become gusty over the desert mountain slopes and through the
passes this afternoon and evening, with gusts generally 35-45 mph.
Stronger gusts to 60 mph are possible through the San Gorgonio
Pass.
Mid and high level moisture and clouds from weakening Tropical
Storm Kenneth will move across the area Friday and Friday night,
decreasing on Saturday. While chances for measurable rainfall are
low, there could be some virga and sprinkles out of the clouds,
with about half of ensemble members of the ECMWF now showing some
light measurable rainfall in the San Bernardino County mountains.
The HRRR smoke model, the latest 48-hour run of which goes
through early Saturday morning, shows some smoke from the fires
in northern California approaching the coast on late Friday
evening. There could be some smoke from those fires for late
Friday night and Saturday across portions of the area.
After the low advances east, high pressure will begin to build in
from the south, weakening the onshore flow and bringing a warming
trend Friday through the weekend. The marine layer will also
become shallower, only extending into portions of the western
valleys each night and morning. Even though temperatures will be
warming up, daily highs will continue to be below average through
at least the middle of next week.
&&
.AVIATION...
220230Z...Coast/Valleys/Foothills...Low clouds increasing in
coverage through 14Z. Bases will be 2000-3000 ft MSL with tops to
3500 ft MSL, obscuring higher terrain with VIS reduced to 1-3 miles
where clouds and terrain intersect. Expect clearing 17Z-19Z.
Mountains/Deserts...SCT-BKN clouds at or abv 15000 ft MSL with
unrestricted VIS into Friday morning. Gusty west to northwest winds
through mountain passes and into deserts, weakening after 08Z. Gusts
of 35-45 knots expected, with peak gusts to 55 knots. Areas of LLWS
and MOD up/downdrafts over and east of the mountains, along with
patchy BLDU reducing VIS to 3-5 miles.
&&
.MARINE...
Breezy northwest winds may create rough boating conditions near the
entrance of the San Diego Bay Saturday afternoon. Northwest winds
with gusts approaching 20 kts in the outer waters are expected each
afternoon early next week.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
EVENING UPDATE/PUBLIC...APR/Connolly
AVIATION/MARINE...PG
Area Forecast Discussion
National Weather Service Shreveport LA
1100 PM CDT Thu Sep 21 2023
...New UPDATE...
.UPDATE...
Issued at 1051 PM CDT Thu Sep 21 2023
A few changes to POPs to account for current and forecasted
trends. Otherwise, the remainder of the forecast remains on track.
Scattered showers and isolated thunderstorms will remain possible
overnight, mainly for areas north of I-30. At this time, believe
the severe threat is over, as instability is not too impressive.
But, an isolated strong thunderstorm can`t be ruled out, as more
convection develops overnight. /20/
&&
.SHORT TERM...
(This evening through Friday Night)
Issued at 255 PM CDT Thu Sep 21 2023
Short range high resolution model guidance continues to exhibit
characteristic spread in terms of solutions for this evening`s
convection. HRRR indicates scattered low-end storms moving into
southeast Oklahoma by 23Z. NAM delays the arrival of storms by a
couple hours, and seems to be resolving more vulnerability to the
drier, sheared airmass prevailing over the ArkLaTex. However, what
storms the NAM holds together look to remain more intense than
those the HRRR resolved. HREF is more aggressive still, and taking
all model output under advisement, the chance of severe
thunderstorms remains present this evening and into the overnight
hours. The area of most likely impacts will be primarily confined
to our northwestern quadrant, roughly defined as areas west of
I-49 and north of I-20. These areas are included in a Marginal
Risk (Level 1/5). The threat increases to the north and west, with
the western portions of McCurtain, Red River and Franklin
counties included in a Slight Risk (Level 2/5). The primary
threats with these storms will be large hail of 2+ inches in
diameter and damaging winds in excess of 60 mph. While the threat
is comparably lower, a spinup tornado or two cannot be ruled out.
This activity will be generated by an upper level shortwave trough
riding along the northern side of a large ridge centered over
Mexico, far to our southwest. As the ridge begins to amplify over
the Plains Friday into the weekend, in concert with the deepening
of a trough and closed low over the eastern seaboard,
northwesterly to even northerly flow aloft will sustain a
reasonably active pattern through this short term forecast period,
expanding from this evening`s storms to near areawide coverage
during the day Friday, making for a mostly dry night with rainfall
aiming to make a return before the sun rises on the coming
weekend.
Temperatures throughout will remain slightly above average tonight,
ranging from the upper 60s north to low to mid 70s south and west.
Highs tomorrow will range from the middle 80s in the rain-cooled
north to the mid 90s along and south of I-20, followed by another
mild night of upper 60s to lower 70s.
/26/
&&
.LONG TERM...
(Saturday through next Wednesday)
Issued at 255 PM CDT Thu Sep 21 2023
Cut pops back for Sat given the establishment of a stout mid-level
ridge axis across the Southern Plains, emanating out of the anchored
ridge across Old Mexico. This feature bisects two vigorous troughs,
one of which will likely be a landfalling Tropical Storm along the
Eastern Seaboard and the other, a closed upper level trough exiting
the Pacific Northwest and entering the Great Plains. Progs have been
consistent from run to run on the development of this subsident
feature across our region for Saturday and its rapid disintegration
Saturday Night through Sunday Night as we enter a wet period across
the entire Four State Region. The NBM has really come in wet during
this late weekend/early next week period which is in good agreement
with the latest operational ECMWF and GFS so we will advertise
likely pops across our northwest half Sat Night, nearly areawide for
Sun into Sun Night and across our southeast half for Monday.
As we begin the upcoming work week, upper level troughing continues
to be firmly established across the Appalachians into New England
with a northward building ridge into the Lee of the Rockies and into
the Great Plains. Our region of the country should be centered in
the southwest flank of the upper trough to our northeast which may
allow for us to dry out some Tue into Wed of next week.
Saturday appears to be the warmest day of the Long Term with daytime
highs near 90 to the middle 90s areawide. Substantial rain chances
will help to cool temperatures down for Sunday through the middle of
next week.
13
&&
.AVIATION...
(00Z TAFS)
Issued at 731 PM CDT Thu Sep 21 2023
Mid to high clouds continue to stream into the region, but VFR
conditions remain. However, a cluster of storms across north Texas
will continue to shift eastward over the next several hours. These
storms could bring some convection at KTXK before midnight. Models
suggest this cluster will diminish. But, additional convection is
expected to move into the region towards the end of the TAF
period, likely bringing additional reduced flight conditions to
most of the TAF sites.
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 75 93 72 96 / 10 50 10 10
MLU 71 91 69 92 / 0 40 10 10
DEQ 69 85 66 90 / 50 60 10 20
TXK 71 88 68 92 / 50 50 10 10
ELD 70 86 66 88 / 20 50 10 10
TYR 73 93 74 95 / 20 30 10 10
GGG 71 92 71 94 / 20 40 10 10
LFK 74 94 71 95 / 10 40 10 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
SHORT TERM...26
LONG TERM....13
AVIATION...20