Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/18/24
Area Forecast Discussion
National Weather Service Bismarck ND
952 PM CDT Tue Sep 17 2024
.KEY MESSAGES...
- Isolated to scattered severe thunderstorms are possible across
western into central North Dakota this evening and tonight.
- An active pattern continues through the week, with low to
medium chances for showers and thunderstorms most days.
- A cooling trend is forecast for the end of the work week and
into the weekend, with highs in the 60s by the weekend.
&&
.UPDATE...
Issued at 911 PM CDT Tue Sep 17 2024
Thunderstorms are currently skirting the far northwest corner
of Bowman county. Numerous thunderstorms this evening have been
lifting north across eastern Montana this evening but have
remained west of the forecast area. Going forward, it appears
the potential for s severe thunderstorm watch for western ND is
diminishing. The convection presently skirting far southwest ND
began just south of Harding county, and a 63 mph gust was noted
as the thunderstorm developed. Analyzing the SPC mesoanalysis
page and surface analysis could provide some clues as to why
convection is currently not as abundant. The 850-300 mb mean
wind is pretty much due north, but there is a surface trough
that extends N-S across far western SD, but as you get into
northwest ND, it turns more northwest towards GGW. This may have
provided enough of a low level focusing mechanism for the
activity to cross over into Montana before it reached ND. Also,
the effective and 0-6km shear both indicate small but definite
min in shear right on the MT/ND/SD border. The 00Z HRRR was
about the only CAM that depicted that SD convection and it
definitely pushed it west into MT before reaching ND. The 01Z
HRRR is already too far east with stronger convection over
Harding County, and the next wave of convection will be with the
main shortwave impulse as it lifts into the Northern Plains.
This convection is currently just north of I-90 in western SD
and has quite a bit of dense cirrus to the north. So the
question now becomes, will this convection be severe as it lifts
into ND. There will definitely be strong effective shear as it
lifts into ND. Bufkit HRRR soundings indicate the instability
aloft diminishes quickly between 9 and 11 PM CDT. There is a
temporary bump in southwest environmental winds over the next
few hours over southwest ND and it`s possible that convection
could help force down some stronger gusts, but in general, we
think the threat for organized severe weather continues to
diminish (I hate these strong shortwaves lifting around upper
lows though, as it seems like there`s always some strong wind
gusts somewhere). By the time the next round of convection
pushes in, we may just see some heavier rain showers and
embedded thunder. 00Z HRRR forecast soundings over southwest ND
don`t support severe storms as the next wave moves in after
midnight.
So with all that, we have cut back on the eastern extent of pops
tonight. We used a blend of the latest HRRR and the time lagged
HRRR for the finer details in pops through 12 UTC. We kept the
likely or higher pops confined to the west through around 09Z,
before, extending them eastward late tonight along the warm
front on the International Border. Updated text products will be
transmitted shortly.
UPDATE
Issued at 611 PM CDT Tue Sep 17 2024
No significant changes for the early evening update. Convection
has developed over eastern Montana, near Glendive. Convection is
also moving through Northeast Wyoming at this time. MLCIN has
dissipated over southeast Montana and into far southwest ND but
MLCIN remains just to the east of here. DCAPE of 1000-1200 J/KG
over the MONDAK area so damaging winds would be the greatest
threat over southwest ND. The main question is how far east the
wind threat would extend as activity lifts into southwest ND
this evening.
&&
.DISCUSSION...
Issued at 225 PM CDT Tue Sep 17 2024
At the moment, surface low pressure sits across eastern Montana,
while a deep upper level trough spans much of the western CONUS,
slowly moving northeast throughout the day. Low stratus across the
north continues to slowly dissipate, while winds continue to
increase in speed as daytime heating continues. Temperatures
this afternoon mostly range from the lower to upper 80s, with a
few areas in the west and south central potentially exceeding
90. Some portions of the central and James River Valley regions
could see some rather humid conditions, with minimum relative
humidity values in these areas ranging from 60-70%.
As the surface low slowly moves northeast, a warm front associated
with this low is expected to slowly press north, moving into
southern North Dakota later this evening. Decent height falls
extending into our west along with 0-6 km bulk shear values in the
30 to 40 kt range will help aid in the formation of some showers and
thunderstorms along this front. Instability remains marginal at this
time, with the main corridor of maximum MUCAPE (with values ranging
from 1500 to 2500 J/kg) displaced ahead of the front, across our
northern tiers of counties. The SPC has outlined a Slight Risk
(level 2 of 5) for severe thunderstorms across our far southwest,
with a Marginal Risk (level 1 of 5) extending a bit further east,
covering essentially the western third of the state. This threat is
rather conditional and dependent on two different things: the
evolution of the storms prior to entering the state, and the timing
of the front itself. Our current thinking is that these storms will
mostly be forming and strengthening in South Dakota, as indicated by
the most recent CAMs runs, so if these storms can get going prior to
entering the area, there`s a better chance they`ll remain severe as
they enter. However, the timing of the front also adds another layer
of complexity, as it seems like the most recent high resolution
models have slowed this front down a bit, with some models
suggesting an arrival time closer to midnight, perhaps around 10 or
11 PM. While prefrontal development of showers are certainly
possible, guidance is suggesting that this will be a mostly
nocturnal event, limiting the severe threat as the instability will
begin to decrease prior to the arrival of the storms. The nocturnal
low level jet is forecast to kick in later on in the night, but by
the time this jet is maximized, the line of showers and
thunderstorms will be well displaced from the shear maximum,
stretching across our northern tier of counties. Some late
re-intensification could occur, but it shouldn`t be too much of
a concern. Overall, the threat is certainly there, but remains
heavily conditional. Modest DCAPE along with relatively steep
low level lapse rates leads to the possibility for 60 mph wind
gusts and half dollar sized hail as the main threats. If severe
weather doesn`t occur, some showers and thunderstorms may still
roll through the area from the south (with chances ranging from
40-60%), moving north through the overnight hours.
Precipitation chances will linger across the west and central on
Wednesday, as the surface low continues to slowly move northeast.
The upper level trough will continue to move northeast as well,
helping filter in some cooler air as it does so. As a result, we can
expect to see the beginning of a cooling trend on Wednesday, where
high temperatures are forecast to mostly be in the 70s and lower
80s. With the approach of the surface low, the surface pressure
gradient is forecast to tighten as well, bringing about some breezy
to windy conditions across the entire area. Southerly winds are
forecast to be around 25 mph at times, with gusts up to 30 to 35
mph. Lows overnight into Thursday will stay mostly within the 50s.
Through the end of the work week and into the weekend, we can expect
to see continued cooling temperatures. As the initially mentioned
upper trough moves off to the northeast through the second half of
the week, troughing is forecast to quickly take its place to our
north, continuing to filter in cooler air to the area. At the same
time, another deep upper level low is forecast to drop south across
the west coast, before drifting slowly towards the east, across the
southern Rockies. These features will help keep much of the Northern
Plains under southwesterly flow aloft, which will result in a
somewhat active period of weather. Near daily chances (mostly 15-
30%) for showers and thunderstorms continue through this period,
though the chances for anything severe diminish quite a bit given
the lower temperatures and weaker forcing. For temperatures,
Thursday and Friday will continue to see highs mostly in the 70s,
with perhaps a very slight warmup on Friday as very subtle ridging
nudges its way between the two troughs. However, Saturday and Sunday
will see cooling once again, with temperatures decreasing into
mostly the 60s. Overnight lows may drop into the 40s during this
time as well.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 611 PM CDT Tue Sep 17 2024
VFR conditions to begin the 00Z TAF period. Low stratus remains
around the Turtle Mountains and may expand later this evening
and overnight, but at this time the consensus is that it will
remain north of KMOT. Otherwise mostly high cirrus to begin the
TAF period with scattered thunderstorms lifting south to north
later this evening and overnight. Included a tempo for Thunder
at KXWA, KDIK, KMOT and KBIS but higher probability looks to
remain over western ND. Did also include a VCSH at KJMS. Breezy
to windy conditions through the forecast period. Southeast winds
ahead of the convection shift more southerly behind the
convection. Windy south winds 15 to 30 knot late Wednesday morning
and through the afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...TWH
DISCUSSION...Besson
AVIATION...TWH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
801 PM MDT Tue Sep 17 2024
.KEY MESSAGES...
- Dry Wednesday and Thursday with increasing fire conditions by
Thursday.
- Cooler temperatures this weekend with good chances (30-60%) for
rain, and accumulating snow in the Front Range mountains.
&&
.UPDATE...
Issued at 758 PM MDT Tue Sep 17 2024
Convection has exited the far nern plains early this evening with
no additonal additional activity expected over the CWA overnight.
It will be windy at times over the higher mtns with a few gusts
up to 60 mph overnight.
&&
.SHORT TERM /Through Wednesday/...
Issued at 215 PM MDT Tue Sep 17 2024
Well convection is ongoing, but this also reminds us how tricky
convective development and modeling is in reality. Earlier CAM
(convective allowing model) output showed mostly one organized
line of convection that should be ongoing at the present time. The
NAMNest had the most reality in the earlier 12Z runs suggesting a
split into a couple lines, while the HRRR is now finally getting
a handle on the real situation - with three lines clearly evident
on satellite and radar data. At this point, it appears the first,
or easternmost of these lines now organizing over the Front Range
as of early this afternoon will become the dominant line as it
pushes east across the plains through late afternoon and very
early evening. This first line is where the main threat of high
and potentially damaging winds can be expected, with the secondary
and tertiary lines expected to eventually weaken through late
afternoon. This means that roughly areas from east/southeast side
of Denver metro eastward across the plains will be the most
vulnerable for high and potentially damaging winds late this
afternoon. Ingredients are still all there for high winds with the
storms, including DCAPE >1200 J/kg, strong mid level
environmental flow (35-40 kts at 700 mb), and linear (QLCS-like)
organization. It`s just that organization may be a bit later than
originally anticipated.
Convection will pass to the east and into Nebraska and
Kansas by/before 7 pm. Clearing skies will then occur overnight
with a much drier airmass moving in. It will still be windy
overnight in the northern mountains and highest foothills with
stronger westerly flow aloft there.
Wednesday will feature dry conditions, mostly sunny skies, and
lighter winds. However, it will still be breezy in the northern
mountains and foothills. Temperatures will a few degrees cooler,
but still above normal for this time of year with highs on the
plains reaching the lower 80s.
&&
.LONG TERM /Wednesday night through Tuesday/...
Issued at 215 PM MDT Tue Sep 17 2024
Colorado will be in between storm systems Wednesday night through
Thursday with a moderate and dry southwesterly flow aloft. This
combined with some upper level ridging should result in dry weather
and slightly above normal temperatures across the forecast area. On
Friday, the southwesterly flow aloft increases as a closed upper low
drifts eastward from Southern California into West Central Arizona.
With a dry airmass still in place, precipitation chances across the
CWA will be limited. However, wouldn`t surprised to see a few light
showers across the high country by late in the afternoon due to
increasing QG ascent ahead of the upper low. In addition, gusty
south to southwesterly winds combined with low relative humidity and
very dry fuels may lead to elevated to near critical fire weather
conditons across the Palmer Divide and adjacent plains.
Much cooler unsettled weather is expected over the weekend as the
upper level storm system and associated cold front moves across the
region. The consensus of the models is that the upper low will track
across the Four Corners Region across Central or Southern Colorado.
At this time there is still some uncertainty in QPF amounts due to
run to run inconsistencies and model discrepancies. This can be seen
by looking at the GEFS, EPS and the CMCE ensembles which have a wide
range of QPF amounts in Denver ranging between 0 and 3.5 inches. It
all depends on the speed and exact track of the storm and local
mesoscale effects. The model averages are suggesting precipitation
amounts between 0.25" and 1.25" across the CWA with 4 to 8 inches of
snow across the higher Front Range Mountains. However, there are no
guarantees in this as minor changes in the storm track could make a
big difference in where the heavier band of precipitation sets up.
We will continue to keep a close eye on this system, so stay tuned
for the latest forecast updates.
Dry and warmer weather is expected early next week as the upper
level storm system moves northeast into the Upper Midwest and upper
level high pressure builds over the Western U.S.
&&
.AVIATION /00Z TAFS through 00Z Thursday/...
Issued at 526 PM MDT Tue Sep 17 2024
There is a boundary to the NW of DIA which could briefly switch
winds to a more NW direction between 00z and 0030z if it holds
together. If it washes out then winds will stay south or go
southeast by 02z. Overnight winds should be drainage. On
Wed, winds will be light and variable by late morning and then
transition to light easterly by 21z. VFR conditions will be in
place overnight through Wed.
&&
.FIRE WEATHER...
Issued at 215 PM MDT Tue Sep 17 2024
It will remain breezy to windy over the northern mountains and
foothills overnight, with gusts around 40 mph on some of the
higher slopes including locations in/near the existing Pearl Fire.
Drier air will move in overnight and Wednesday, with only
moderate humidity recovery tonight in/near the foothills, and then
low humidity readings most areas on Wednesday. Fortunately winds
will be lighter Wednesday, but still breezy across the northern
mountains and foothills. Humidity will remain above critical
thresholds there, but nonetheless given dry fuels and what we
think will be mostly limited rainfall this afternoon, pockets of
elevated fire weather conditions can still be expected in the
windier locations.
Near critical fire weather conditions are possible for the Palmer
Divide, Lincoln county, and the urban corridor during the late
afternoon and evening hours Thursday and Friday due to breezy
conditions and low humidity.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RPK
SHORT TERM...Barjenbruch
LONG TERM...Kalina
AVIATION...RPK
FIRE WEATHER...Barjenbruch
Area Forecast Discussion
National Weather Service Cheyenne WY
934 PM MDT Tue Sep 17 2024
.KEY MESSAGES...
- A powerful storm system will move through the area today,
bringing widespread showers and thunderstorms with the
potential for strong and damaging winds.
- Strong winds may continue in the wind prone areas through
Wednesday morning. A High Wind Watch is in effect.
&&
.MESOSCALE...
Issued at 121 PM MDT Tue Sep 17 2024
Latest GOES imagery shows storms developing across western WY/CO
associated with the large scale upper level low centered along the
UT/ID border. As this system continues to take on a negative tilt,
strong mid/upper level flow continues to round the base of the
trough with support for large scale forcing extending into our area.
Instability is rather limited west of the Laramie Range with more
gradual vertical development, however deep unidirectional flow has
led to showers/tstorms with a few wind gust over 50 mph being
reported. Early morning storms across Sweetwater Co have appeared to
be undercut and become outflow dominant as it propagates eastward
with a northerly storm track. Looking farther south, two areas of
convection exist in western CO including 1) scattered showers and
storms aided by diurnal heating over the higher terrain of the
Mt Zirkel Wilderness moving north/northeast, and 2) another line
recently developing closer to the analyzed surface cold front
that will continue to move east/northeast into southwest Carbon
Co over the next hour.
Overall, still looks like storms will continue to develop early this
afternoon with cold pool organization aided by the cold frontal
passage. Storms will look to intensify rapidly from a potentially
broken line of storms crossing the Laramie Range to a possible MCS
by the time precipitation reaches the NE panhandle early this
evening. Strong winds (70+ mph) remain to be the main hazard today
with these storms, especially in western NE where the HREF
probabilities of wind gusts over 55 mph are greatest.
One feature that will continue to be an evolving situation
as storms develop and cold pool organization commences is the
location of the strongest wind with this complex. So far, the slower
eastward progression of the upper level low has led to a slightly
more broad lee trough than previously forecast. This has limited
southerly moisture advection into the NE panhandle into late this
afternoon where surface dew points remain in the mid-40s while
northeast CO sites are reporting pockets of 50+ degree dew points.
If this persists into later this afternoon, instability may be more
limited across the NE panhandle keeping the focus for stronger
storms, cold pool, and associated wind gusts along and south of the
I-80 corridor. Will continue to monitor future observational trends
into this afternoon.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 335 AM MDT Tue Sep 17 2024
Active weather expected over the next 24 to 30 hours with
multiple impacts and concerns. Current IR Satellite loop shows
the potent Pacific storm system lifting northeast across the
Great Basin region and into Idaho early this morning. This storm
system, and the potent midlevel shortwave extending southward
into four corners region, are expected to continue moving east
across Wyoming and Colorado today, and eventually eject east
into the Great Plains tonight. All models show a sharp
negatively tilted mid to upper level trough lifting northeast
across southeast Wyoming and western Nebraska this afternoon.
Synoptic models show strong forcing across the area today with
intense low level frontogenesis and upper level level diffluence
associated with the jet stream over a large area (along and
east of the Laramie Range, including western Nebraska). Not only
is this storm dynamic, but we`re still dealing with favorable
thermodynamic parameters for a substantial convective threat for
mid-late September. Followed the NAM and the HRRR for
convection potential today since boundary layer parameters are
initializing much better compared to the GFS, especially surface
moisture and MLCAPE. Expect thunderstorms to begin developing
across Carbon county over the next few hours as the area of
strong upper level diffluence begins to move into the forecast
area. This cluster of thunderstorms is forecast to eventually
form a squall line as the Pacific storm and associated
negatively tilted short wave trough axis rapidly moves northeast
into the Front Range. This set up is reminiscent of the June
6th 2020 Derecho event where much of the area received wind
gusts between 60 to 80 MPH across southeast Wyoming and western
Nebraska. SPC added far eastern Wyoming and most of the western
Nebraska panhandle in an Enhanced Risk for severe thunderstorms
and highlighted wind gusts in access of 70+ MPH for the region.
All CAMS and high resolution guidance show a solid line of
severe thunderstorms, with additional bowing segments,
developing across Albany county with rapid eastward propagation
into western Nebraska through the afternoon. Brief very heavy
rainfall, hail, frequent lightning, and damaging winds over 70
MPH are possible with this line between noon and 800 PM this
evening. This line should impact the I-25 corridor between the
hours of 300 to 500 PM, and into western Nebraska between 500 PM
and 700 PM. Once the front moves across the area, temperatures
will quickly drop into the 50s and 60s during the afternoon and
early evening hours.
Otherwise, tricky wind forecast (specifically: non-convective
winds) for today with some models showing a lack of a surface
pressure gradient, while others show a strong west to east
surface pressure gradient that persists a few hours even behind
the main line of thunderstorms. This gradient does relax
tonight, but then strengthens again behind the storm system with
cold air advection near the surface through early Wednesday
morning. Kept the High Wind Watch going for the secondary wind
prone areas of southeast Wyoming since we still have at least 24
to 30 hours of lead time for these zones. Upgraded the Watch to
a High Wind Warning for the Arlington and Elk Mountain zone for
several favorable scenarios for strong gusty winds: (1) Late
morning/early afternoon as the line of strong thunderstorms
starts to organize over the area (2) convective showers
lingering behind the main line of thunderstorms late in the
afternoon through the late evening hours. This set up has a
history of producing brief gusts as high as 70 MPH in this area
over the last several months (3) increasing low level pressure
gradients and low-midlevel subsidence late tonight through
Wednesday morning. There is also a good chance for portions of
I-25 from Casper to Bordeaux/Wheatland to see strong wind gusts
as well with some indication of a mountain wave developing on
the lee- side of the Laramie Range late tonight.
Strong winds are expected to gradually weaken by late Wednesday
morning and Wednesday afternoon. It will be cooler on Wednesday
with highs in the 60s to low 70s west of I-25, and in the 70s to
low 80s east of I-25...warmest temperatures will be found in the
lower elevations of western Nebraska.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 230 AM MDT Tue Sep 17 2024
A progressive weather pattern is being advertised for the extended
forecast. Our region will be under the influence of weak upper level
ridging for Thursday and Friday, causing the area to be
approximately 5 degrees above average for the daytime high, but that
will change by this weekend as temperatures transition to
potentially cooler than 10 degrees below normal for the week of the
autumnal equinox. We will have multiple shortwave disturbances
propagating into our region, bringing a much cooler weather regime
to the area. Areas in the high plains, especially the mountain
zones, will see well below normal temperatures making it feel like
fall outdoors. Towards the beginning of next week, we will continue
to see additional opportunities for precipitation and another
potential round of cooler temperatures. Overall, expect a below
average temperature pattern and higher chances for much needed
precipitation. Daytime highs in the higher terrain portions of the
mountain zones from this weekend into early next week will struggle
to reach the 40s, with lower elevations seeing the upper 50s to low
70s. Keep the umbrella handy due to higher chances of rain
showers/thunderstorms, and an extra layer for the cooler
temperatures that are favored in the extended forecast.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 931 PM MDT Tue Sep 17 2024
Southwest flow aloft will continue as a cold front moves across
the terminals tonight. Scattered clouds from 7000 to 10000 feet
will prevail, otherwise skies will be mostly clear. Winds will
gust to 32 knots at Rawlins until 15Z, and to 20 knots at
Scottsbluff and Chadron until 15Z, then to 42 knots at all the
terminals from 15Z to 01Z, and to 30 knots at Laramie, Rawlins
and Chadron after 01Z.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 3 PM MDT Wednesday for WYZ101-103>105.
High Wind Watch through Wednesday morning for WYZ107.
High Wind Warning until noon MDT Wednesday for WYZ110.
NE...None.
&&
$$
MESOSCALE...MB
SHORT TERM...TJT
LONG TERM...BW
AVIATION...RUBIN
Area Forecast Discussion
National Weather Service Pueblo CO
659 PM MDT Tue Sep 17 2024
.KEY MESSAGES...
- Strong to severe storms possible rest of this afternoon and early
evening across the plains.
- Patchy frost/light freeze possible for central San Luis Valley
tonight.
- Dry and breezy on Thursday. Spotty near-critical fire weather
conditions are expected across the area.
- Cooler and wetter conditions this weekend across the area.
Best chance of showers and storms will be on Saturday.
&&
.UPDATE...
Issued at 656 PM MDT Tue Sep 17 2024
Update to allow Severe Thunderstorm Watch to expire as
scheduled over the remainder of the southern and eastern
plains. Strong storms are likely to continue until 8PM across
portions of eastern Las Animas, Bent, Prowers, and Baca
counties, but storms are expected to remain sub-severe through
the remainder of the evening.
&&
.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 308 PM MDT Tue Sep 17 2024
Currently
At 2 pm, A line of broken storms extended from just west of COS S-
sw`d into the southern Sangres. Other additional showers and storms
were noted over the CONTDVD region. Over the plains the atmosphere
was destabilizing and winds aloft were increasing. SPC has already
issued a watch for the region and lasts until early evening.
Rest of today into early evening...
Storms will continue to progress steadily northeastward. Given the
shear, storms will likely move across the region as a broken line.
Dewpts were noted in the U40s to lower 50s, and CAPE values were
around 500-1000 Js, with the better instability generally east of a
line from KLIC to KTAD. Strong forcing was pushing out in advance of
a negatively tilted closed low pushing east-northeast out of Nevada.
Main severe threat continues to be strong winds, as HRRR guidance
continues to show strong gusts with storms, and the environment is
favorable for strong gusts given the well mixed lower atmosphere and
DCAPE values greater than 1000 Js over the far eastern plains.
Overall, activity should move out of the region by early to mid
evening.
Later tonight through tomorrow...
Much drier air will advect in behind this system and dry weather is
expected tonight into tomorrow all areas. Only weather concern will
be the San Luis valley where temps will be in the 32-34 range and
pockets of frost are likely over the central valley floor.
Temps tomorrow will be above normal over the plains, with mid 80 to
around 90F plains and L70s valleys.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 308 PM MDT Tue Sep 17 2024
Thursday...
Dry and warm conditions will persist across the area on Thursday as
we sit in between two upper lows. Breezy southwest flow will have
temperatures remain mostly steady, with highs in the mid-high 80s
over the plains while the high valleys remain in the 70s. With the
dry airmass remaining in place, Rh values will hover around 15-20
percent through most of the afternoon, while surface winds sit
around 10-15 mph. Unless we get more mixing than the models are
expecting, which is possible but not likely, critical fire weather
conditions will be marginal. Otherwise, the day will be relatively
quiet.
Friday Onwards...
Models have reached better agreement on the track of the next
incoming low as we approach this weekend. Friday will largely be a
transition day, with high temperatures about 5 degrees higher than
Thursday, along with slightly increased moisture from the incoming
system.
As we move into Saturday, models have continued trending south with
the evolution of the upper level pattern, now sending a closed low
directly over Colorado. As it moves in, a cold front will push south
across the area late Friday night into early Saturday. Along the
front, localized convergence and a good amount of monsoon moisture
could net us a healthy amount of precipitation. The exact amounts,
as well as what kind of precipitation (convective vs more
stratiform) we may see will largely be dependent on frontal timing
and instability. As of now, the GFS only shows a few hundred J/kg of
CAPE over the plains, and the system is moving relatively quickly,
so amounts may not be all that high. However, there is still time
for these details to become better resolved in the data.
There is still a bit of uncertainty amongst the model guidance with
regards to the speed of the low as well. The GFS has consistently
been one of the faster models, and the Canadian has been largely
tagging along the last few runs. However, the EC is currently
looking slow compared to the other deterministic guidance by several
hours. Additionally, any shift to the N-S extent of the track will
have a big impact on precip amounts. High temperatures will drop
around 10 degrees as well, in mainly in the 70s to low-80s out east.
For Sunday, post-frontal air will cool us off even more, with highs
in the 60s-70s across the CWA. Some isolated-scattered POPS remain,
but at this point models begin to diverge again on the departure of
the low. Most of the better forcing and moisture will be off to our
north and east, though if the low intensifies faster we may get some
more potent wraparound precipitation into the Palmer Divide. Still
plenty of time for those details to be resolved. Models are much
less clear beyond that, though the cooler pattern may possibly
extend into early next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 535 PM MDT Tue Sep 17 2024
VFR conditions are expected at all three TAF sites, KCOS, KPUB, and
KALS, for the next 24 hours. Gusty southerly and southeasterly winds
are likely to persist for the next couple of hours, weakening after
02Z this evening as showers continue to push eastward and away from
the terminals. Sky conditions are expected to improve throughout
this evening, with mostly clear skies persisting through the
remainder of the forecast period. Showers and storms are not
expected tomorrow. There is a slight chance (<30%) of IFR ceilings
and visibilities with stratus and fog at Alamosa tonight through
early Wednesday morning, especially given the rain received there
today, though confidence was too low to mention in the TAF at this
time.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...EHR
SHORT TERM...HODANISH
LONG TERM...GARBEROGLIO
AVIATION...EHR
Area Forecast Discussion
National Weather Service Tallahassee FL
907 PM EDT Tue Sep 17 2024
...New UPDATE...
.UPDATE...
Issued at 900 PM EDT Tue Sep 17 2024
Showers and even a few thunderstorms continue at this hour in the
Florida panhandle and western Big Bend. Extended rain chances
both in time and location to account for this rain and used the
latest HRRR for timing which should continue for the next few
hours possibly towards midnight ET. Also increased the cloud cover
currently and in the predawn hours when low clouds and fog are
anticipated to develop. Kept low temperatures essentially
unchanged with readings falling to the upper 60s to lower 70s.
&&
.NEAR TERM...
(Through Wednesday)
Issued at 151 PM EDT Tue Sep 17 2024
A frontal boundary currently located just inland from the Emerald
Coast will continue to lift northward this evening. Shortwave
energy aloft will act upon this boundary, within an air mass
characterized by GOES Blended Total Precipitable Water of up to
1.9" along the Emerald and Forgotten coasts. Slow eastward storm
motions and training near this boundary will lead to locally
heavy rainfall, mainly in the FL Panhandle and Western Big Bend,
where there is a marginal risk of flash flooding given the current
saturated soils. This activity will diminish after sunset with
patchy fog possible late tonight across much of the region inland
from the Emerald and Forgotten Coasts. The fog should dissipate
between 9 and 10 AM ET on Wednesday.
Wednesday will feature the highest PoPs near the I-10 corridor,
and although the flash flood threat should be lower, localized
poor drainage flooding cannot be ruled out. Lows tonight in the
60s to around 70 and highs on Wednesday in the 80s.
&&
.SHORT TERM...
(Wednesday night through Thursday night)
Issued at 151 PM EDT Tue Sep 17 2024
Upper level trough begins to lift north and east Wednesday night
into Thursday. This will drag a frontal boundary through the
forecast area on Thursday with west and northwest flow expected to
prevail afterwards. We could see isolated showers along the front
on Thursday, but most activity should be fairly sparse, mostly due
to the drier mid-level air beginning to work its way into the
region. Expect temperatures to climb back to near 90 on Thursday,
especially across our Florida counties.
&&
.LONG TERM...
(Friday through Monday)
Issued at 151 PM EDT Tue Sep 17 2024
Upper level ridge is likely to build across the region on Friday
and into the upcoming weekend. This will usher in very dry mid and
upper level air, largely keeping conditions quiet. The quiet
conditions could last into early next week depending on how fast
moisture returns back into the forecast area. Temperatures will be
in the low 90s with the dry and sunny conditions.
Looking further into next week, concerns will then turn to the
tropics. Guidance has begun to jump on to the idea of potential
tropical development next week. However, it should be noted that
any development in this scenario next week would likely be slow,
and if anything does develop any potential paths or intensity are
very uncertain at this time. Folks should continue to monitor
conditions over the next 7 to 14 days, but we caution against
focusing on any particular model run or outcome as things will
likely change over the next week or two. At this time, it can`t
hurt to check in on your tropical plan and prep kit.
&&
.AVIATION...
(00Z TAFS)
Issued at 737 PM EDT Tue Sep 17 2024
Leftover afternoon convection is drifting from west to east while
exhibiting a slow weakening trend, which is reflected in the near
term models and the TAFs. Not much in the way of lightning so
used a combination of VCSH and tempo SHRA for the next few hours
at all but ABY. Heading into the overnight, patchy to areas of fog
will develop north of the coast and north of ECP, encapsulating
the other sites. Have TLH down to MVFR with the other sites at
IFR/LIFR. Most probable timing is 10-14Z. Conditions will become
VFR after 14Z with PROB30 for convection at TLH/VLD after 18Z.
Coverage of afternoon convection should be less than days past.
&&
.MARINE...
Issued at 151 PM EDT Tue Sep 17 2024
Light and variable winds anticipated through much of the week
with rain chances decreasing after Wednesday. East and
northeasterly flow is reestablished by the weekend and this could
lead to cautionary conditions and higher seas, especially during
the overnight hours. Elevated northeast flow likely continues into
early next week with possible advisory level conditions.
&&
.FIRE WEATHER...
Issued at 151 PM EDT Tue Sep 17 2024
Chances of wetting rains on Wednesday highest near the I-10
corridor, with dry weather returning Thursday. The main fire weather
concern will be pockets of low dispersion on Wednesday in Southeast
AL, the FL Panhandle, and west of the Flint River in GA.
&&
.HYDROLOGY...
Issued at 151 PM EDT Tue Sep 17 2024
Dry conditions are likely after today with little to rain expected
from Thursday to early next week. No hydrological concerns are
anticipated.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 69 87 70 89 / 20 50 0 10
Panama City 72 86 73 88 / 30 30 0 0
Dothan 68 87 68 88 / 10 20 0 0
Albany 67 87 68 87 / 10 20 0 0
Valdosta 69 86 70 88 / 20 50 0 10
Cross City 70 89 72 89 / 10 30 0 20
Apalachicola 73 84 73 86 / 20 30 0 10
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...LF
SHORT TERM...Dobbs
LONG TERM....Dobbs
AVIATION...Scholl
MARINE...Dobbs
FIRE WEATHER...LF
HYDROLOGY...Dobbs