Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/14/23
Area Forecast Discussion
National Weather Service Louisville KY
1000 PM EDT Fri Oct 13 2023
.Forecast Update...
Issued at 958 PM EDT Thu Oct 12 2023
Pre-frontal rain shield is working its way through central Kentucky
and southern Indiana as of this moment. Meager instability and lack
of deep moist convergence is only promoting shallow showers with no
lightning associated and mostly light rain as upstream QPE is just a
few hundreds of an inch. Actual frontal boundary is nearing western
Kentucky, so intermittent rain showers are possible the rest of the
night if the dry air noted in ACARS and GOES water vapor does block
vertical growth. Otherwise, a few wind gusts between 15-20 mph could
be noted ahead and along the front with decent CAA during the day.
&&
.Short Term...(Tonight through Saturday evening)
Issued at 332 PM EDT Fri Oct 13 2023
Currently, a stacked low pressure system over western Iowa will
continue eastward towards northern Indiana, where it will arrive
tomorrow morning. This system`s trailing cold front is currently
stretching south through the Ozarks and is headed straight for the
Lower Ohio Valley. Satellite imagery shows that low level cloud
cover, between 3,500 and 7,000 feet, has already expanded over most
of the CWA, and as the front inches closer, southerly winds will
continue advecting warm temperatures into the area. This will limit
cooling this evening as the sun sets.
Early tonight, rain chances begin increase from west to east over
southern Indiana and central Kentucky as a 35-40 knot low level jet
develops just ahead of the cold front. In this area of precipitable
water values in the 1.2-1.4" range, the main axis of precipitation
is expected to drop anywhere from a couple hundredths of an inch up
to around a quarter of in inch of rainfall overnight. Higher values
will be to the northwest with lower values to the south. Soundings
show saturated and stable low levels. A rumble of thunder is
possible, but believe this will be a mostly rain event. Winds ahead
of the front are expected to be around 10 mph, but they will become
gusty with 25-30 mph gusts possible. The north-northeast to south-
southwest oriented cold front should arrive near I-65 around 9-10z.
Behind the front, winds will veer to the west while gusts ease
slightly, to around 15-20 mph.
Tomorrow, as the low pressure system, to our north, passes to the
east, low level moisture will keep clouds blanketing the area. This
low level saturation will likely produce scattered light
rain/drizzle that shouldn`t amount to anything, but it will make the
day feel much cooler as CAA and cloud cover limited high
temperatures to the 60s. Tight pressure gradients around the system
will keep winds gusting to 20-25 mph through the day.
&&
.Long Term...(After midnight Saturday night through Friday)
Issued at 311 PM EDT Fri Oct 13 2023
Synopsis...The compact upper-level low that brought the cold front
to the Ohio Valley will be merging with a broader/stronger upper low
over the Canadian Maritimes which main impact, along with additional
upstream shortwave troughs, will be carving/reinforcing a longwave
trough over the East Coast with potentially an embedded low. On the
other hand, the West Coast will experience an amplifying ridge ahead
of the next strong shortwave energy predicted to move in through the
Pacific Northwest by the middle of next week. As a result, the Ohio
Valley will be experiencing below-normal temperatures the first half
of the period along with intermittent chances of light rain while
milder temps and sunnier conditions are expected for Tuesday and
beyond.
Model Evaluation/Confidence...Relatively high confidence exists in
the mid-level pattern evolution through Tuesday since main
deterministic guidance agrees on the East Coast troughing and
rotating shortwave energy, especially with enhanced mid-level
vorticity maximum crossing the area Sunday night into Morning
morning. Only tweak was to the temperatures as there was decent
model spread during the Sunday-Tuesday timeframe. Overall, model
predictability decreases significantly during the second half of
next week in association with another wave amplification over the
central US. GFS and ECMWF has been consistently showing this
possibility with embedded upper low over the southern Plains;
however, there is still great variability with location of the
trough axis and degree of amplification. The CMC has been more
conservative with amplification as it depicts an open wave. This
ultimately might impact the temperature and precipitation forecast
as well as the northward extent of Gulf moisture return.
Sat Night - Mon Night...Expect dreary weather throughout most of the
weekend as northerly breezy winds favor cold air advection while the
combination of mid-level vorticity and wrap-around moisture provide
the necessary ingredients for persistent cloudiness and intermittent
light rain showers, which is not enough to end the current drought
but reduced evapotranspiration and some rain is always welcomed.
Echoing previous forecasts, wind gusts would be around 15-20 mph
with isolated values around 25-30 mph. Temperature wise, biggest
cool down will be experienced in the afternoon given that highs will
be in the upper 50s Sunday and Monday (negative double-digit
deviations).
Tuesday - Friday...Brief ridging aloft and surface high pressure
moving to the Mid Atlantic will help with warmer temperatures and
less clouds. Winds will ease and shift to the south by Wednesday but
little moisture recovery is expected by the time the next system
approaches from the west, so any chances of strong to severe weather
looks very unlikely at this point. Also, the aforementioned model
disagreement could impact the precipitation onset and duration.
Official forecast starts to ramp up PoPs on Thursday which might be
more in line with the CMC output, while a more delayed and extended
event (Friday night into Saturday ) seems likely following the
latest GFS/ECMWF solution.
&&
.Aviation...(00Z TAF Issuance)
Issued at 722 PM EDT Fri Oct 13 2023
Impacts/Confidence:
- High confidence in MVFR CIGS tonight and Saturday morning.
- High confidence in gusty winds starting late Saturday morning.
Discussion...Current VFR conditions will last for a few more hours
before cold front brings scattered rain and low-level cloud deck to
the region. Consensus has been that rain will not be intense enough
to cause any VIS reduction, but MVFR ceilings will move in from west
to east tonight. There is lower confidence in IFR conditions, so
they were not included in the forecast with this update. There
might be also some isolated gusts along the front tonight but the
main period for more frequent gusts is late Saturday morning and
onwards. Last but not least, there might be a brief period of VFR
conditions early Saturday morning as the front leaves the area;
however, another period of solid MVFR is in store for the rest of
the day.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...ALL
Short Term...KDW
Long Term...ALL
Aviation...ALL
Area Forecast Discussion
National Weather Service Pocatello ID
153 PM MDT Fri Oct 13 2023
.SHORT TERM...Tonight through Saturday night. High pressure
building into East Idaho today though enough moisture remains in
place to allow for widespread cloud development across the region.
A few very light showers may still be possible in the eastern
highlands, but precipitation amounts will struggle to be more than
a sprinkle and most of the region will remain dry. Clearing skies
overnight should allow for patchy valley fog to form. Temperatures
remain the main challenge, and should be very close to freezing
again across much of the Snake Plain. Will have another Frost
Advisory in place tonight, again with the caveat that a few areas
will probably dip below freezing. A widespread hard freeze below
28F is not expected.
A weak shortwave pushes across East Idaho late tonight into
Sunday. Moisture associated with this feature looks to produce mid
and high cloud cover. Although typically not much of a forecast
issue, it may have the impact of obscuring the partial annular
eclipse during the morning daylight hours roughly between 9am and
noon. No precipitation is expected from this feature as it shifts
northeast through the region through midday. Ridge rebuilds
overnight, allowing for one more potential threat of frost
headlines before the growing season official ends for the purpose
of frost/freeze headlines. DMH
.LONG TERM...Sun through next Fri night. Upper level ridge getting
as strong as 5800+ meters, summertime strength on Sun and Mon. On
Mon night, a vigorous shortwave breaks down the ridge-partially. The
trend of shifting this storm`s track farther north pretty much
leaves the southern half of the forecast area in sunshine with
little chance for precipitation, while the ID-MT border region and
central Idaho have a chance for some light precipitation, from late
Mon night through late Tue night. The upper level ridge returns for
Wed, but sets up to the west, putting Idaho on the cold side with
northerly air flow. However, abundant sunshine keeps afternoon highs
at or slightly above climatic normals for this time of year. The
high means wind should stay light, and the forecast is dry with
mostly clear/clear skies for the period starting Wed. The next storm
arrives sometime next weekend or later. Messick
&&
.AVIATION...A day of drying should eliminate most of the stratus and
fog tonight, so do not see a repeat of reduced CIG or VSBY for the
morning at any of the airdromes. Guidance had quite a bit of low
level moisture early on, and had to tone down the cloud coverage.
Not sure 14/11Z or 14/12Z or so when mid-level moisture from a very
weak shortwave slides through during the day, which may affect
viewing of the eclipse. However, no impact from wind, CIG, or VSBY
to aircraft operations. Messick
&&
.FIRE WEATHER...A weak shortwave clips the area on Saturday before
the ridge builds back in for the rest of the weekend and into
Monday. Thanks to the ridging, highs will gradually warm through
Monday with most of us in the 50s and 60s still today, but back into
the 60s and 70s by Sunday and Monday. As temperatures warm, min RHs
will slowly drop with most zones in the 20 to 40 percent range by
Sunday and Monday. The ridge breaks down a bit for Tuesday as a
system moves through just to our north. We`ll catch some of the weak
troughing/zonal flow from that system which brings an increase to
wind gusts near 30 mph through the Snake Plain, increased precip
chances in the higher elevations, and a decrease in our temperatures
with highs in the 50s and 60s Tuesday through Thursday. AMM/JAM
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 3 AM to 9 AM MDT Saturday for IDZ052>054.
&&
$$