Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/17/24
Area Forecast Discussion
National Weather Service Denver/Boulder CO
757 PM MST Fri Feb 16 2024
.KEY MESSAGES...
- Snow continues in the mountains, with the heaviest snowfall
falling this evening and Saturday morning. Snow and blowing snow
will create hazardous travel conditions in the northern
mountains.
- Winter weather advisory for the foothills and I-25 corridor this
evening. Expect snow covered/icy roadways after 5 PM.
- Light mountain snow late Sunday/Sunday night.
- Nice warm up early next week with the next chance of snow late
Wednesday/Thursday
&&
.UPDATE...
Issued at 747 PM MST Fri Feb 16 2024
This evening is mostly going as expected with a band of moderate
to briefly heavy snow across the I-70 mountain corridor and Denver
metro area. There is some slow north-to-south drift of the band
which fits the low level cold advection. This will limit the time
any location is under the band to a few hours. There`s a weaker
secondary band near the northern Colorado border which is also
about as expected. Current snow forecast looks pretty good, with a
less concern about anyone getting much higher amounts. We did add
the freezing drizzle in the shallow saturated air ahead of the
snow band, now limited to Douglas, Elbert, Lincoln counties, that
could put down a couple hundredths of an inch of ice before the
snow arrives. Also raised the PoPs in the northeast corner and
dropped tonight`s lows a couple of degrees since we were getting
close already. If the clearing is fast enough, it could get colder
along the northern border.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 202 PM MST Fri Feb 16 2024
Day Cloud Phase satellite imagery shows a consistent deck of low
clouds socked in across the lower elevations with the exception
with some clearing a little up the hill over the Palmer Divide.
Another perspective from space, mid-level water vapor imagery,
shows the incoming shortwave trough dropping into southern WY.
This will be the system responsible for the snowfall impacts
across northeast Colorado this evening. Mesoanalysis shows the
mid-level front draped across southern WY and seeping into the
northeast CO corner. Radar shows snow showers accompanying this,
gradually dropping southern along the WY-CO border. Snow continues
across the mountains this afternoon.
Let`s talk about the environment first...In the next few hours,
the mid-level front will progress southward. As the front moves through,
NE upslope fills in behind it early this evening eventually
building to 10-15 kts up to 700mb. Pretty decent.The region will
be under sufficient synoptic ascent with additional support from
an upper jet. There are plenty of different dynamics contributing
to an environment favorable for snowfall, specifically more
organized banding. Model soundings this evening reflect this quite
well with a decent depth of saturation in the DGZ couples with
unstable lapse rates. So not only are bands supported, but higher
snow rates will be supported within these bands with rates up to
an 1"/hour. Model guidance has shown a good general consensus on
the banding potential; however, the high res guidance has still
shown wavering in location of these bands from run to run.
Some are highlighting potential for bands to set up over portions
of northern Weld County and around the Denver metro and westward
into the foothills. There is still uncertainty with the exact
location and this will have impacts on where the higher localized
amounts will be.
Across the lower elevations, moisture is currently shallow as
shown by current ACARS soundings. This won`t last long as the
front moves through with deeper upslope flow behind it. Over the
next few hours expect snow to develop across the lower elevations
and continues across the higher elevations. Between 5 and 10 PM
will be the more likely timeframe to see bands develop which will
contain the heavier rates. This unfortunately runs with in the
evening commute period which has resulted in the issuance of a
Winter Weather Advisory for the urban corridor and Palmer Divide
through early tomorrow. Travel may be hazardous this evening with
slick roads and visibility issues. Mountain snow will continue
this evening with potential for a few moderate bands, with Winter
Weather Advisories in place there as well. Snow decreases from
north to south after midnight across northeast Colorado.
As for amounts...Starting with the lower elevations 2-5" is the
more likely range. Localized banding may result in areas with 6
inches or potentially higher. For the mountains, accumulations of
3 to 10 inches total from today into early tomorrow favoring the
higher ranges such as the Park Range.
Early tomorrow morning conditions gradually clear. If it clears
quick enough, there may be some patchy fog development across
areas such as Weld County. Saturday will be dry and cool with
highs in the upper 30s across the plains and teens to 20s for the
high country.
.LONG TERM...(Saturday night through Friday)
Issued at 202 PM MST Fri Feb 16 2024
Clearing skies and lighter winds under the ridge should result in
a cold night in the mountain valleys by Sunday morning, with
Middle Park seeing temperatures 0 to -10 degF, and North/South
Parks in 0 to +10. A short wave trough across the U.S. West Coast
helps build a ridge across Colorado on Sunday, which also ushers
the start of a significant warming trend. During the day on
Sunday, a much stronger trough upstream over the Pacific Ocean
acts to shear apart the Sunday trough as it moves across the
Central Rockies. There is enough moisture associated with the
trough axis, and combined with steep lapse rates and west upslope,
light mountain snow is possible Sunday evening into early Monday.
The overall lift looks less impressive than previous model runs,
and the ensemble systems (especially the Euro) are not excited
about accumulating snow. Suffice to say impacts from any snow that
falls will be minor, for now 0-2" look to be the potential across
the northern and central mountains, and probably next to nothing
for south of I-70 in the mountains. Across the plains, downslope
will keep it dry and warm, with highs in the upper 40s to low 50s.
The mountain valleys will see highs in the 30s.
On Monday and Tuesday ensemble output is in fair agreement that
there will be ridging over Colorado, but by later Tuesday some
moisture may work its way into the mountains of Colorado. The QG
lift remains to our west during this time, and southwest upslope
with poor lapse rates is not favorable for accumulating mountain
snow. Thus, low PoPs (15-40%) for snow seem reasonable late Tue-
Wed with the trough still upstream, with the highest chances
across the Park Range. The southwest flow advects significantly
and progressively warming air from Monday into Tuesday, getting
above 0 degC Monday and then +2 degC on Tuesday. Highs across the
plains will range from the mid to upper 50s on Monday to the low
to mid 60s on Tuesday. It will be quite breezy (gusts 25-35 mph)
across the plains Monday afternoon with strong northwest winds
aloft mixing down to the surface.
The trough across the western U.S. still looks to move across
Colorado sometime late Wednesday or Thursday, but ensemble guidance
has it looking a little disorganized. It seems likely though that there
will be colder air aloft, better west upslope, and enough
moisture for accumulating snow in the mountains. Ensemble spreads
for snowfall in the Thursday timeframe are quite large, pointing
to the high uncertainty in the strength and position of the
trough. All ensemble systems put a high chance of snow across all
of our mountains, with all ensemble members from the GEFS, Euro,
and CMC showing accumulating snow, but the range of outcomes
could be anything from an inch to 10", more or less, at this
point in time. Will keep PoPs high in the mountains during this
period and refine the timing and potential impacts as it gets
closer. The uncertainty is perhaps even greater across the plains
and I-25 corridor. There is reasonable agreement that rain
changing to snow could occur, but wide spreads in QPF. The models
are also showing a pretty strong cold front sweep across the
plains sometime on Thursday which would explain why snow is
generated in the model output. For now will keep Wednesday warm
across the plains with highs around 60 since it is pre-frontal in
all of the guidance, and start the downward trend in temps on
Thursday. The NBM pretty much just shotguns 20-40 PoPs across the
plains and I-25 corridor late Wed through Thu, even though
realistically we should only be looking at a 12 hour window for
snow given the amount and type of forcing. However, this far out
there is no reason to deviate from the NBM.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 747 PM MST Fri Feb 16 2024
LIFR conditions in light to moderate snow are expected in the
Denver area through about 08z, with IFR conditions lingering until
10z-13z. There`s a slight chance (20%) of a slower departure of
the snow or fog redevelopment as skies clear that could continue
IFR conditions as late as 16z. After that, skies will clear with
light winds through the day Saturday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Saturday for COZ031-033-
034.
Winter Weather Advisory until 2 AM MST Saturday for COZ035-036-
038>041-043.
&&
$$
UPDATE...Gimmestad
SHORT TERM...Mensch
LONG TERM...Schlatter
AVIATION...Gimmestad
Area Forecast Discussion
National Weather Service Louisville KY
826 PM EST Fri Feb 16 2024
.KEY MESSAGES...
* Mix of rain and snow this afternoon through tonight. Snow
accumulations possibly reaching 1 to 2 inches, mainly along and
north of Interstate 64.
* Cold start to the weekend with highs 10 to 15 degrees below normal
in the upper 20s/mid 30s.
* Warming temperatures through the first half of the week from the
50s to low 60s by midweek.
* Next system could bring showers and possible thunderstorms by
Thursday.
&&
.UPDATE...
Issued at 826 PM EST Fri Feb 16 2024
The heaviest snow band continues to move eastward with most of its
impacts along and north of I-64. Things are quickly ending north of
the Ohio River, and have the western edge of the main snow band
clearing our CWA between 10 and 11 PM EST. Most locations should
expect between a half an 1 inch of additional snowfall when the main
band passes through. So far amounts have ranged from a dusting to
almost 2" across southern IN.
Still keeping an eye on the band south of I-64 where some snow is
falling, however expect most totals to be less than 1", so feel that
the SPS mentioning a dusting to 1" should have that handled.
Will keep the advisory going for a bit even as snow ends given that
temps should be continuing to fall a couple degrees below freezing.
Some slick spots may remain, so don`t want to end things too
quickly.
Previous Update
The main heavy snow band is now arriving as advertised and will
generally work eastward impacting areas along and north of I-64 over
the next several hours. This feature should be able to produce
snowfall rates of around 1" per hour as it quickly passes through,
and will likely cause deteriorating conditions quickly. Upstream
reports show this band could easily put down a quick 1 to 2" as it
moves through, with local amounts up to 3" not out of the question,
especially across our northern tier where residence time will be a
bit longer.
The surface low is now passing to our south and east quickly this
evening, which will result in cold advection at all levels. This
will erode any of the warm nose remaining, and change p-type to all
snow across the advisory area through the evening. No changes
planned to the current forecast at this time.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 321 PM EST Fri Feb 16 2024
The system we have been watching for days is now arriving. Concerns
from yesterday remain. We warmed into the 40s across central
Kentucky and at least the upper 30s across southern Indiana, but as
rain showers have already moved across many areas in north central
Kentucky, temperatures have dropped back to the upper 30s to low
40s. 2" soil temperatures range from near 40 across southern Indiana
to the mid 40s near the Kentucky parkways. So in short, ground and
air temperatures still need to drop to see impacts from frozen
precipitation. Using aircraft soundings from SDF, profiles below
around 800mb are currently above freezing with a warm nose below
850mb. Models are generally not handling this well.
Looking at the radar, most of the CWA has received some
precipitation, excluding our far southern Kentucky counties and the
greater Lake Cumberland area. The general motion is from the west-
southwest to the east-northeast. There are two slugs of
precipitation. The northern area extends south from central Indiana
into our northern row of southern Indiana counties. This area is
seeing frozen precipitation. No impacts have been reported or
expected yet, but going forward our northern row of Indiana counties
from Dubois to Jefferson have the best chance at seeing accumulating
snow. Overall totals and impacts are expected to be reduced because
of the aforementioned temperature issues. The Winter Weather Advisory
was left in place to cover this threat. Areas farther south could
see some accumulation, but the main concern is farther north. The
southern line of precipitation across central Kentucky has had some
frozen precipitation mixed with rain. It also has a history of
lightning across western Kentucky back to Missouri. This threat will
continue as the line moves east across southern Kentucky. No severe
weather is expected.
Currently, the forecast has a change over to snow in Jasper around 4-
5 PM EST, Louisville around 6-7 PM EST, and Lexington around 7-8 PM
EST. Before these times these areas will likely see some type of
frozen precipitation mixed in. Many areas that see frozen
precipitation will likely see sleet mixed in as well, due to the
warm nose. Sleet will also help reduce snow amounts. Expect
precipitation to quickly come to an end from the northwest to
southeast around 9 PM to 1 AM EST.
Behind the precipitation, skies are expected to begin clearing in
the following hours. Breezy northwest winds will drop Saturday
morning lows into the upper teens to mid 20s, resulting in any
untreated water freezing.
Tomorrow, skies will completely clear and become sunny, but cold air
advection is expected to limit highs to the the upper 20s to mid
30s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 245 PM EST Fri Feb 16 2024
Saturday Night through Wednesday...
Eastern CONUS trofiness will eventually give way to a more zonal
pattern early next week. Expect tranquil weather given a
dry column and most jet energy staying well to our north and east
over the northern Great Lakes.
The latter part of the weekend will be quite chilly, especially
Sunday morning when lows bottom out around 20. Daytime highs in the
40s on Sunday will eventually recover solidly above normal levels,
reaching the 60s by Wednesday.
One caveat in this portion of the forecast period centers around a
weak Clipper, which is progged to drop through the Ohio and
Tennessee Valleys on Tuesday. However, at this point it looks to
be moving too quickly to tap into any moisture, so won`t advertise
any precip at this point.
Wednesday Night through Friday...
Progressive trof axis will push through the Ohio Valley on Thursday,
with some hints of phasing between the northern and southern
streams. Neither is very amplified at this point and the wave
remains positively tilted. Slight model differences in timing and
intensity of this impulse, but a decent soaking rain appears more
likely than not. Could see some embedded thunder, but not confident
enough to mention it beyond south central Kentucky. Should dry out
on Friday but temps will be knocked back below normal.
&&
.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 650 AM EST Fri Feb 16 2024
We`ve seen a mix of p-types at the TAF sites late afternoon into the
early evening, although the heavier snow band just went through HNB
and dropped a quick inch of snow. Elsewhere, SDF/LEX have seen
mainly RASN with a few PL mixed in at times. SDF/LEX are next in
line to get the heavier snow band over the next 1 to 4 hours, and
have that timed accordingly in those forecasts. Could easily dip
around or below 1 SM for a brief period. BWG has remained all rain,
however may end as a brief wintry mix before precipitation exits
later tonight.
Do expect a mix of IFR and MVFR ceilings through the night, before
clearing occurs in the pre-dawn hours to sunrise at BWG/SDF/HNB. LEX
may hang onto some MVFR until midday or so on Saturday.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Weather Advisory until 1 AM EST Saturday for KYZ029>043-
048-049-057.
IN...Winter Weather Advisory until 1 AM EST Saturday for INZ076>079-
083-084-090>092.
&&
$$
UPDATE...BJS
SHORT TERM...KDW
LONG TERM...RAS
AVIATION...BJS