Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/17/23
Area Forecast Discussion
National Weather Service Indianapolis IN
921 PM EST Thu Feb 16 2023
.Forecast Update...
Issued at 921 PM EST Thu Feb 16 2023
Minor adjustments have been made primarily to pops overnight as the
weaker tail end of a snow band associated with the elongated upper
level trough off to our west looks to swing through primarily the
northern half of the area overnight. Some sprinkles/light rain
changing to light snow appears possible, primarily north and
northwest, as the weakening band sweeps into the region. Potential
will continue to exist for flurries later tonight into early
tomorrow, particularly northwest where low level flow will align for
a time to allow some lake enhancement to potentially reach into the
area. Temperatures are tracking well and overnight min forecast is
well in line with latest hourly numerical guidance, so left these
numbers alone.
&&
.Short Term...(This evening through Friday)
Issued at 259 PM EST Thu Feb 16 2023
...SEVERE WEATHER THREAT TO REMAIN SOUTH OF FORECAST AREA TODAY...
.Rest of today and tonight...
Active weather continues across the Ohio Valley this afternoon.
Current surface analysis shows an area of low pressure just SW of
Terre Haute moving ENE along the I-70 corridor. Latest IND and SDF
ACARS soundings continue to show a very stable boundary layer with
an inversion aloft, signifying that the main surface warm front
remains to the south, despite a more southerly wind shift. A sharp
north to south temperature gradient has materialized as forecast with
40s in the north and temperatures just recently rising into the low
60s across South Central Indiana. Due to a stable boundary layer,
showers and thunderstorms developing ahead of the low have all
remained elevated with little to no chance of severe weather in
Central Indiana. Forecast and observed soundings show elevated CAPE
upwards of 300-500 j/kg with strong wind shear aloft supporting the
threat for elevated storms. Chance for storms persists through
around 23z with brief periods of heavy rain and lightning expected.
The area of low pressure pushes of to the east tonight while the
upper trough and surface high pressure move into the region. Main
concerns tonight will be gusty northwest winds and lingering
stratus. Low level jet increases behind the low in an area of cold
air advection and steepening low level lapse rates leading to an
environment conducive for gusty winds to mix down to the ground.
Winds should remain relatively light until after sunset, when the
cold front pushes through and winds abruptly shift to the west then
northwest Expect a gradual increase in wind speeds through the
evening and overnight hours with gusts upwards of 20 to 30 kts. Much
colder air advecting in will result in temperatures to plummet back
to normal values for this time of year in the mid to upper 20s.
Gusty winds will likely make it feel much colder with wind chills
falling into the teens areawide.
Low stratus seen on satellite imagery will advect into the region
behind the departing system and linger through the overnight hours.
Forecast soundings and time height cross sections show abundant low
level moisture through around sunrise. Potential is there for a few
flurries north of I-70, however this should not cause any impacts.
Expect ceilings to gradually rise during the morning hours then
begin to clear.
.Friday...
High pressure centered southwest of the region will result in
continued northerly flow on Friday and much drier air advecting in.
Low level jet will be gradually decreasing after sunrise, so expect
gusty winds in the morning to diminish by the afternoon to around 10-
15 kts. Time height cross sections show low level moisture lifting
and dissipating through the morning and afternoon hours, resulting in
a gradual lifting and clearing trend. Brief troughing moving
overhead and northerly winds will usher in a much colder airmass
with 850 mb temperatures falling from +10 Thursday to -12C Friday!
Highs will struggle to get above freezing across the north and may
only reach the mid 30s across South Central Indiana despite some
afternoon sunshine.
&&
.Long Term...(Friday Night through Thursday)
Issued at 259 PM EST Thu Feb 16 2023
*Dry Moderation, Yet Breezy/Windy Through This Weekend*
*Chances of Rain Next Week, Especially Late Tuesday-Early Thursday*
Friday night through Sunday...
The long term will begin with amplified and chilly high pressure
aligned from Texas to the eastern Great Lakes and over central
Indiana. This ridge will slide to southeast of the region by dawn
Saturday, but not before corresponding subsidence and mainly clear
skies bring low to mid-20s across central Indiana.
The weekend will find the surface ridge advancing to the
southeastern CONUS while an overall zonal upper pattern gradually
transitions from slightly ridged to a broad trough. A moderately
strong low-level jet around the northwestern periphery of the
southeastern CONUS ridge...will set-up over much of the weekend from
the central Plains to the southern Great Lakes, and eventually
follow the ridge in a southeasterly direction and into the Ohio
Valley while diminishing Sunday. Resultant surface winds over the
CWA should gust to around 20-30 mph Saturday and possibly 25-35 mph
Sunday as the LLJ axis crosses the region. Strongest gusts should
be north and northwest of Indianapolis especially on Saturday.
Temperatures are expected to moderate amid this southwesterly flow,
reaching well into the 40s on Saturday and the 50s on Sunday.
Monday through Thursday...
Guidance is continuing to indicate a broad upper trough deepening
into the western United States early in the workweek, along with an
impressive 1048 mb arctic surface high slowly oozing from western
Canada into the northern Plains. Surface low pressure will be found
along the leading edge of this colder air...both in a rather weak
front crossing the Midwest in the early week...and then more intense
cyclogenesis near Colorado by the mid-week. Much of the southern
half of the CONUS should moderate to unseasonably warm levels by the
mid-week courtesy of robust southerly flow around the High Plains`
low around the Tuesday timeframe. The long term should end with
these impressive dynamics progressing eastward, with low pressure
passing near or north of the local CWA.
This should all translate locally to isolated to occasionally
scattered rain while temperatures...after a subtle cool down towards
seasonable levels with the weak front Monday...then moderate through
above normal levels. Recent model trends are even suggesting mainly
dry conditions lasting through about the Monday night timeframe with
the remnant southern high pressure continuing to block Gulf moisture
and any passing forcing keeping an overly positive tilt.
Wednesday/Wednesday night should sport the best shot at rainfall
with the deepening Colorado low`s warm frontal zone near the region,
when the Baja energy is most likely to spin near central Indiana.
The potential for heavy precipitation exists in the very favorable
baroclinic zone along the northern side of the storm system, yet
more likely this targets the southern Great Lakes.
Some uncertainties include how and when energy from a cut-off upper
low off of Baja California will eject into the central US...as well
as how far south any eastern appendage of arctic chill may spread
into the Great Lakes prior to the main cold front`s passage.
Nonetheless still expect air cold enough to produce frozen
precipitation would be delayed until the end of the late week when a
drier regime arrives.
&&
.Aviation...(00Z TAF Issuance)
Issued at 559 PM EST Thu Feb 16 2023
Impacts:
* Winds veering from westerly to northwesterly or
north/northwesterly overnight and strengthening/gusting to 25-30KT.
* Widespread IFR or worse conditions gradually becoming MVFR
overnight before returning to VFR Friday afternoon.
Discussion:
As a fairly potent low pressure system exits central Indiana
overnight, wind directions will begin to rapidly veer from westerly
to northwesterly or even northerly at LAF, while strengthening and
becoming gusty in the wake of the low/cold front. Gusts up to 30KT
are expected at times much of the overnight, with winds slacking up
a bit near daybreak Friday and gusts weakening/dissipating.
Sustained winds will likely remain 10-15KT, however.
Widespread IFR or worse conditions, particularly ceilings, are noted
across the area, and these will persist for at least another few
hours before gradually returning to widespread MVFR and remaining in
that category through the night and into midday Friday. Conditions
will gradually return to VFR during the afternoon hours Friday as
low clouds scatter out and clearing begins.
Some fog and drizzle is currently ongoing associated with proximity
to the low, causing poor visibility at a couple of the sites -
expect this to improve along with ceilings later tonight, with no
obstructions to visibility expected beyond this evening.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Update...Nield
Short Term...CM
Long Term...AGM
Aviation...Nield
Area Forecast Discussion
National Weather Service New Orleans LA
931 PM CST Thu Feb 16 2023
...New UPDATE...
.UPDATE...
Issued at 922 PM CST Thu Feb 16 2023
Cold front currently moving through Slidell and western portions
of the New Orleans Metro area sliding eastward. Any severe weather
threat or widespread heavy rain threat has diminished
considerably, and with the recent ZFP update, any severe weather
or heavy rain mention has been removed.
That being said, there are still occasional lightning strikes well
behind the front with some elevated convection. Significant drop
off in temperatures behind the front. Temperatures at New Orleans
International Airport dropped 10 degrees in 13 minutes with the
cold front. Temperatures were in the upper 60s to mid 70s ahead of
the front, but are already down to 50 degrees at New Roads.
&&
.SHORT TERM...
(This evening through Saturday night)
Issued at 416 PM CST Thu Feb 16 2023
Wilkinson County was removed from the Tornado Watch 38 as winds have
shifted out of the W-NW, marking the fropa and an end to the
threat of surface-based convection and severe weather. Otherwise,
the watch is set to expire at 5 PM for the remaining three of our SW
MS counties at 5 PM but it may be able to be cancelled earlier once
the cold front passes by. Despite relatively strong winds and shear
in the low to mid-levels of the atmosphere and abundant boundary-
layer moisture with dewpoints in the lower 70s, convection has not
been particular robust or organized (i.e., supercell or QLCS) over
our area so far today - likely owing to the best synoptic lift
lagging to our west or passing to our north. Additionally,
convective updrafts have only had to work with skinny CAPE profiles
and have thus struggled to overcome several weak capping inversions
as evident on the 18z KLIX and recent MSY ACARS soundings.
Showers and storms have mainly been confined to from Baton Rouge and
points north and west so far today with only brief/scattered showers
occurring across the rest of the area. The most widespread precip
is occurring along and just behind the front. Accordingly, PoPs will
quickly increase from west to east late this afternoon into this
evening as the front progresses downstream. Updated PoPs to better
reflect this timing. Embedded thunderstorms with this front should
gradually become weaker and more isolated after sunset as daytime
instability wanes.
The other story this afternoon is the breezy southerly winds ahead
of the front. Winds 15 to 20 mph are gusting 25-30 mph across SE LA
(away from the coast where the marine layer has significantly
limited the mixing depth). Winds will quickly become northwesterly
behind the front with strong post-frontal cold-air advection helping
to keep the nocturnal boundary layer mixed. This will allow wind 10-
15 mph to gust 20-25 mph tonight.
Much cooler conditions will move into the region overnight tonight
and Friday. Post-frontal stratocu will keep conditions cloudy
through the night but there looks to be enough subsidence behind the
low-level trough passage to allow for breaks in the cloud cover to
develop during the day Friday. Even with the breaks, it won`t feel
very warm with temperatures struggling to rise much through the
upper 40s and lower 50s during the day. The breezy northwest winds
(15-20 mph with gusts 25-30 mph) will produce wind chills in the
upper 30s across SW MS and low to mid 40s in SE LA, including New
Orleans.
Winds will weaken Friday night in response to high pressure building
into the Lower MS River Valley and Mid South. This setup will likely
produce a late season freeze across the northern third of the
region. Used the NBM deterministic for min temperatures but tweaked
it based on support (or lack of support) from the NBM probabilistic
guidance. The probabilities of freezing temperatures tomorrow night
are above 60 percent along the I-10/I-12 corridor in coastal MS,
Northshore and Baton Rouge. These probs quickly decrease to the
south and increase to around 100 percent toward McComb.
The center of the high will pass to our northeast on Saturday and
off the Southeast Coast Saturday night. However, the ridge axis
will extend southwestward toward the Central Gulf Coast. This will
allow for winds to weaken during the day. It will also yield a
favorable radiational cooling setup Saturday night under clear
skies and light winds. Accordingly, blended the NBM deterministic
with the 25th percentile for the typical favored drainage basins
north of the lakes that tend to radiate most effectively. Even
with the cooler trend, forecast min temps are still above
freezing.
&&
.LONG TERM...
(Saturday through Wednesday night)
Issued at 416 PM CST Thu Feb 16 2023
Local area will be in zonal flow to the north of an upper ridge over
the Gulf of Mexico for much of the period. If there is going to be a
shortwave that has an impact on local weather, it would be on
Wednesday, when the upper ridge is more centered over Florida than
the Gulf. Even then, it doesn`t appear that there will be a clear
cold frontal passage. Even beyond mid-week, global operational runs
continue to show ridging across much of the Gulf of Mexico through
the following weekend.
With models in relatively good agreement, no major changes from NBM
necessary with either rain chances or temperatures.
&&
.AVIATION...
(00Z TAFS)
Issued at 542 PM CST Thu Feb 16 2023
Cold front at forecast issuance time was just east of KBTR and
KMCB with TSRA just in advance of the front. KHDC likely to see
TSRA in the next hour or two, but confidence in TSRA occurring at
terminals to the south of Interstate 10 is diminishing. In any
case, low end MVFR or high end IFR ceilings are expected to
become widespread overnight behind the front for several hours.
Ceilings should improve to MVFR during the early morning hours,
and current indications are that VFR conditions should become
widespread Friday afternoon. Wind gusts to 25-30 knots will be
likely at most terminals through the overnight hours.
&&
.MARINE...
Issued at 416 PM CST Thu Feb 16 2023
A Gale Watch was converted to a Small Craft Advisory (SCA) for
all of the waters. The SCA goes into effect this evening (except
for the outer coastal waters where a SCA has already been in
effect for this afternoon) and continues through Saturday
morning. The breezy S winds ahead of a cold front will quickly
change out of the NW this evening in wake of the front. Winds will
be solidly in SCA range of 20-30 kt but forecast soundings do not
indicate the potential to mix down winds of 34 kt or higher given
the uniform wind speeds throughout the boundary layer. Therefore,
speeds in the lower 30 kt range seems to be the most likely peak
gust potential behind the front.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 36 49 29 54 / 100 0 0 0
BTR 40 52 33 57 / 90 0 0 0
ASD 45 54 34 59 / 90 0 0 0
MSY 45 54 40 55 / 90 0 0 0
GPT 46 55 35 57 / 80 20 0 0
PQL 46 57 32 59 / 80 60 0 0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until noon CST Saturday for GMZ530-532-534-
536-538-550-552-555-557-570-572-575-577.
MS...None.
GM...Small Craft Advisory until noon CST Saturday for GMZ532-534-536-
538-550-552-555-557-570-572-575-577.
&&
$$
SHORT TERM...JK
LONG TERM....RW
AVIATION...RW
MARINE...JK