Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/04/24
Area Forecast Discussion
National Weather Service Louisville KY
828 PM EST Wed Jan 3 2024
.Forecast Update...
Issued at 825 PM EST Wed Jan 3 2024
Current surface mesoanalysis locates the cold front across the Ohio
River while stratus layer has overrun the frontal line and extends
further southward. Moderate cold air advection is taking place
around 925-mb immediately behind the front and has prompted surface
temperatures to steadily fall. Furthermore, light radar echoes have
been noted in central and southern Indiana along with mPing reports
of winter precipitation, mainly freezing drizzle given the saturated
layer depicted below -10 degree Celsius in ACARS soundings from IND
and SDF. On the other hand, pavement temperatures in southern
Indiana and north-central Kentucky are mostly in the low 40s, except
for bridges and overpasses that are close to the freezing point.
Therefore, updated the grids to reflect a slight chance of drizzle
until at least 6Z with less confidence in spotty freezing drizzle in
elevated surfaces and/or roads.
Cold air advection at 850- and 700-mb and better synoptic lifting
will come later tonight associated with the vorticity advection
ahead of a shortwave trough dropping from the Great Lakes. Although
forecast soundings do not show substantial saturation in the DGZ,
there is a chance that either the drizzle lingers through the night
and becomes a potential problem in some areas once surface
temperatures approach the freezing mark or precipitation changes to
frozen hydrometeors. Regardless, coverage/intensity will be limited
and no accumulations are expected; however, drivers should exercise
caution on bridges and overpasses in southern Indiana and northern
Kentucky for the possibility of slick spots.
&&
.Short Term...(This evening through Thursday)
Issued at 234 PM EST Wed Jan 3 2024
A narrow area of clearing between post-frontal stratus to the north
and mid/high level clouds to the south have allowed for much of
southern Indiana and northern Kentucky to enjoy lots of sunshine
today. Temperatures in these areas at this hour have climbed well
into the low and mid 40s, while areas across central and southern
Kentucky socked in with the clouds have struggled to climb into the
upper 30s.
A cold front will begin pushing through our southern Indiana
counties by late afternoon and early evening and eventually clear
southern Kentucky by midnight. Very little moisture is associated
with the frontal boundary, so not expecting any precipitation, and
it will really only be noticeable via a wind shift to the northwest
and post-frontal stratus quickly filling in behind it. Weak cold air
advection behind the front will drop lows tomorrow morning into the
upper 20s, assuming cloud cover remains intact. Should the stratus
break up earlier than predicted, morning lows could be a bit cooler.
Tomorrow morning will likely start off with clouds for most folks,
but drier low level air is expected to push in from the north and
northeast to help gradually scour out the stratus. Model soundings
do show some low level moisture trapped near the top of the boundary
layer, so it`s possible strato-cu could redevelop during the late
morning or afternoon hours, but most guidance points to skies being
more clear vs cloudy by mid to late afternoon. Highs in the wake of
the front will likely only top out in the upper 30s to low 40s.
&&
.Long Term...(Thursday night through Wednesday)
Issued at 315 PM EST Wed Jan 3 2024
=============================================================
Key Messages:
* Slushy Rain/Snow Mix Likely Friday night into Saturday, mainly
northern CWA (around I-64 & north).
* Light snow accumulation possible
* Wet & Gusty Storm System Likely Around Tuesday
===========================================================
Thursday Night - Friday...
Surface high pressure pushes eastward to the mid Atlantic coast to
end the work week. Meanwhile, a transient shortwave ridge aloft will
control our region. This will result in continued dry conditions
through Friday, and will also continue the trend of temps toward
slightly milder. After a chilly start with lows in the 20s on
Thursday night, highs on Friday should reach toward the mid and
upper 40s for most.
Friday Night - Saturday...
Focus shifts upstream to the next weather-making system as we enter
the weekend. Models continue to suggest a steadily intensifying
surface low tracking from the western Gulf Coast states, up through
the Carolinas and the mid Atlantic as some degree of phasing looks
to occur between northern and southern stream impulses. There is
still some uncertainty amongst varying model solutions as to where
and how strong this phase will be, which will ultimately decide just
how much deep moisture and frontogenetical forcing overspreads our
region. The recent (24 hours) trend has been to back off on some of
the more robust solutions among the 03/00z ensemble suites. In
addition, 3/4 deterministic solutions of the GFS/CMC/ECMWF/NAM
suggest a weaker system. However, the 03/12z run of the GFS did come
in more robust, and given the spread still suggested in the
ensembles would be unwise to back off the messaging for accumulating
snow at this point in the game.
Taking a look at the setup, we do expect an intensifying left exit
region of the 150+ knot upper level jet overspreading our region
later Friday night into Saturday, with a nice frontogenetical
component likely developing somewhere over our region. Low level
temperature profiles continue to look tricky, with deterministic
soundings suggesting a transition from all rain to snow somewhere
across our northern half of the CWA. A closer look at the sounding
over LEX on the more aggressive GFS, for example, shows a deeply
saturated column up through the DGZ, with a several thousand foot
thick isothermal layer paralleling the 0C line. This would likely
result in a heavy, wet snow with snow ratios closer to 5:1 than
10:1. However, given the amount of QPF with that system, you could
still get accumulating snow, even with marginal low level temp
profiles.
The more likely scenario at this point is a less organized system,
with less deep moisture to work with. In addition, the
frontogenetical component is not as strong, which results in lesser
snowfall rates, and the column is less conducive to accumulating
snow. We`ve seen a downward trend in LREF probabilities in
accumulating snow over the last 24 hours, with around a 40% chance
of 1" or more at LEX, and only around 15% chance of 1" at BWG.
As a result of the spread, and the wavering trends with run to run
due to complexity of phasing and secondary surface low development,
will continue to have low to medium confidence in accumulating snow
for the time being. Again, the most likely locations for any accums
will be across our N/NE half of the CWA at this time.
Saturday Night - Sunday Night...
The main storm system quickly departs the mid Atlantic heading into
Saturday night, however a secondary shortwave lags behind, and
brings additional light showery precipitation chances to our region
later Saturday through Sunday night. There will likely be a brief
lull in activity later Saturday afternoon into the early evening
between systems.
P-type with this lingering batch of showers could be interesting,
and given steepening low level lapse rates in the post frontal
regime, may see a mix of rain/snow showers. Right now, it looks like
surface temps stay just above freezing until later Sunday night when
moisture will be departing. May advertise some -SHRASN across our
north, but overall this doesn`t look to be too impactful, if at all,
at the moment.
Monday...
Pretty high confidence in a dry Monday as a brief bout of surface
high pressure and upper ridging control the region. Should be able
to get fairly mild under this brief setup with highs in the 45 to 50
degree range for most.
Monday Night - Wednesday...
The strongest storm system of the long term forecast period is
likely set to arrive Monday Night - Tuesday night as a ~980mb
surface low intensifies through the mid Mississippi River Valley, up
through the Wabash River Valley, and into the Great Lakes region.
Given the current surface low track, which has been pretty
consistent, we would see a rainfall event (perhaps a very brief mix
across our NE on the leading edge and then ending as snow showers
Tuesday night), along with gusty winds given the strong pressure
gradient. Forecast soundings show very moist and stable soundings as
a 60-70 knot low level jet carves out a prodigious warm nose in the
850-700 mb layer. Current storm total QPF ranges in the 1 to 2 inch
range, with locally higher amounts not out of the question. This
would do well to put a dent in some of the ongoing drought
conditions across the region.
The bigger story might be the gusty wind potential with the strong
pressure gradient. Right now, it does appear that the stout low
level inversion and overall very moist sounding would protect us
from the strongest winds aloft. However, late clearing with the dry
slot on Tuesday afternoon could introduce the chance to mix a little
deeper and tap into the strong LLJ core off the surface. Time will
tell on just how much wind potential this system will carry, however
it would appear fairly likely that at least a Wind Advisory is on
the table if current data trends hold. Anything stronger than that
would be depending on mixing deeper, and would likely require some
clearing, or to be deeper into the warm sector.
&&
.Aviation...(00Z TAF Issuance)
Issued at 626 PM EST Wed Jan 3 2024
Impacts/Confidence:
- High confidence in MVFR ceilings tonight
- Medium confidence in returning VFR conditions tomorrow morning.
Discussion...Cold front is already pushing through the northern
section of the TAF area at this moment. As expected, NW winds and
MVFR ceilings are reported along and behind the frontal passage.
There will also be a brief period of wind gusts around 15 knots
accompanying the initial frontal push with low probability of
drizzle or reduced visibilities behind it. Therefore, confidence was
low to mention those elements in the TAF. For tonight, winds will
continue veering to the north while cloud bases stay in the MVFR
range. Consulted guidance indicates a clearing trend starting in the
morning hours but confidence is medium, at best, with timing of VFR.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...ALL
Short Term...DM
Long Term...BJS
Aviation...ALL
Area Forecast Discussion
National Weather Service Melbourne FL
1056 PM EST Wed Jan 3 2024
...New UPDATE, MARINE, AVIATION...
.UPDATE...
Issued at 1050 PM EST Wed Jan 3 2024
A cold front gradually approaches central Florida tonight as
scattered rain showers develop out ahead of the front.
Temperatures are in the upper 50s to low 60s as of 10 PM and
southerly surface flow remains light for now. Recent ACARS
soundings from MCO indicate PW around 1.2-1.3", alongside poor
lapse rates and instability. 0-1km shear is increasing a bit, with
nearly 35-40kt of 0-3km shear. Though modest shear exists, the
lack of other primary ingredients for convection has led to the
removal of thunderstorm mention from this forecast update.
Scattered showers will continue overnight, gradually ending from
northwest to southeast around or shortly after daybreak Thursday.
Early morning temperatures are forecast to be in the 50s from
Orlando northward, staying closer to the low 60s south of there.
Cooler, drier air will filter south behind the front during the
day Thursday.
&&
.MARINE...
Issued at 1050 PM EST Wed Jan 3 2024
Tonight...Winds are beginning to increase at Buoy 41009 as a Small
Craft Advisory begins starting at 11 PM for all offshore zones
(20-60nm). A cold front is forecast to move southward across the
local Atlantic overnight into Thursday morning, accompanied by
scattered showers, especially from Sebastian Inlet northward.
Southwest winds increase and veer north with the gradual frontal
passage.
Small craft should exercise caution across nearshore Brevard and
the nearshore Treasure Coast waters for winds of 15-20 kt. Drier
conditions return from north to south through the early morning as
high pressure builds in behind the front.
&&
.AVIATION...
(00Z TAFS)
Issued at 1050 PM EST Wed Jan 3 2024
VFR conditions become MVFR to IFR as VCSH/-SHRA begins to end
after 07-10z. A cold front pushes south, gradually veering winds
from SW to NNW, 12z-16z Thu. Gusts to 20 kt are possible,
especially at coastal terminals. Conditions gradually improve
after 18z-21z from north to south, with CIGs returning to VFR by
the end of the TAF.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 53 61 49 71 / 70 0 0 0
MCO 57 64 49 73 / 60 10 0 0
MLB 59 67 53 73 / 40 20 0 0
VRB 60 71 54 75 / 30 30 0 0
LEE 52 62 46 71 / 70 0 0 0
SFB 55 64 48 73 / 70 0 0 0
ORL 56 64 48 73 / 60 10 0 0
FPR 59 72 55 75 / 20 20 0 0
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 4 PM EST Thursday for AMZ570-572.
Small Craft Advisory until 11 AM EST Thursday for AMZ575.
&&
$$
UPDATE.......Schaper
LONG TERM....Kelly
AVIATION.....Schaper