Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/16/23
Area Forecast Discussion
National Weather Service Indianapolis IN
1013 PM EST Wed Feb 15 2023
.Forecast Update...
Issued at 1013 PM EST Wed Feb 15 2023
Few significant changes required to the going forecast this evening.
Convection is ongoing across Oklahoma along the warm front just
ahead of the strengthening low that will move through the forecast
area tomorrow. An additional area of storms is ongoing pushing into
western Tennessee along a surface trough extending from the
aforementioned low. Expect a gradual increase in shower and storm
coverage as the low continues to strengthen and moves toward the
area overnight - but precipitation will likely not reach the area
until late.
Severe threat remains an issue for tomorrow, in a background
environment of extremely strong deep layer shear. Question remains
exactly how far the instability axis spreads northward given high
resolution guidance continues to ever so slightly trend southward
with the low track. Suspect that bulk of the threat will remain just
south/southeast of the area, although a few strong to severe storms
sneaking up into the far southern/southeastern forecast area late
morning into mid afternoon tomorrow remains a concern.
&&
.Short Term...(This evening through Thursday)
Issued at 300 PM EST Wed Feb 15 2023
...STRONG TO SEVERE THUNDERSTORMS POSSIBLE IN SOUTHERN AND
SOUTHEASTERN INDIANA TOMORROW...
.This evening and tonight...
Current surface analysis shows broad southwest flow across Indiana
this afternoon as a low pressure system pushes into Ontario with a
trailing front extending southwest toward a developing low in the
Plains. Gusty winds of 30-40mph have been ongoing across the region
late this afternoon, but will gradually diminish towards the evening
hours. Low level jet max has already moved off to the northeast;
however a mixed layer up to 0.5-1 km agl continues to reach into an
area of enhanced winds aloft. 19z IND ACARS soundings shows steep
low level lapse rates under the inversion allowing winds to continue
to mix down to the surface. Expect winds to diminish around or just
after sunset as mixing weakens and strongest low level winds move
out of the region.
The frontal boundary just north of the region will sag south through
Central Indiana tonight as a cold front, resulting in winds becoming
northeasterly overnight. In Addition to the wind shift, expect
temperatures to fall into the 30s across the north, 40s around the I-
70 corridor, and near 50 across Southern Indiana. With the front
expected to stall over or just south of the area, a sharp north to
south temperature gradient is likely to persist tonight into
tomorrow.
Lift increases overnight over the front as a much warmer airmass is
advected northward ahead of the low overnight. Latest short term
guidance has precipitation moving into the area from the south
around 5am-7am. Forecast soundings show a sharp inversion north of
the now warm front, with steep lapse rates and elevated instability
as precipitation moves in, so expect embedded thunder and lightning
within the broad area of rainfall. This is a classic set up north of
a warm front for this time of year.
.Tomorrow...
By Thursday morning, the surface low will be centered over southern
Illinois and will track across the I-70 corridor while gradually
strengthening through the afternoon hours. Latest trends today by
the short term higher-res models have shifted the track of the
surface low a few rows of counties south of the I-70 corridor, which
could have significant impacts on where the sharp temperature
gradient sets up and who could and could not get severe weather
during the afternoon. With this in mind, the best chance for severe
weather is across Southern and Southeastern Indiana, mainly south
and east of the Indianapolis metro area.
Expect rain, thundershowers, and low clouds to be around during the
morning hours tomorrow. As the warm front pushes northeast, a brief
dry period with possible peeks of sun will occur mid morning
through the early afternoon hours mainly south of I-70. A brief
window for strong to severe storms is possible starting initially in
the southwestern counties between 15Z and 18Z and then across the
southeastern counties between 18Z and 21Z. Storm motion will be
quick with speeds of 50-60mph likely.
Guidance today remains in good agreement for the severe potential
with around 50-70kts of effective bulk shear, 400-1000 J/kg of CAPE,
and 150-250 m^2/s^2 of 0-1km helicity. Current thoughts are in the
timeframe that were previously mentioned that isolated to scattered
discrete cells will push through with the potential for damaging
winds as the primary threat as well as a non-zero hail and tornado
threat. South central Indiana will be on the far northern edge of
the severe threat with much more favorable conditions south and east
of the forecast area. Areas north of I-70 will generally be north
of the warm front with a lack of good moisture flow, so only expect
showers and a few rumbles of thunder. Also expect a very sharp
temperature gradient again across the region with highs approaching
70 degrees in Southern Indiana and temperatures struggling to reach
50 across north central Indiana. Gradient winds up to 40 mph are
likely at times as well through the afternoon hours with mixing down
of the LLJ winds aloft. Quiet conditions will then arrive by the
evening hours as the storms push through Ohio.
Very complex forecast across the forecast area tomorrow and any
shift in the track of the low north or south could bring the severe
weather threat and warmer temperatures further north or south as
well. Currently expecting the severe threat to remain south of
Indianapolis with how current model trends have been. Current
thinking is that discrete thunderstorms could initiate over the
southern and eastern counties during the late morning/afternoon
hours. A few could become severe before moving out of the area, but
still think the best chance for severe storms is south and east of
the region.
&&
.Long Term...(Thursday night through Wednesday)
Issued at 300 PM EST Wed Feb 15 2023
**30-35 degree drop Thursday night / Cold, Blustery Friday**
**Windy Saturday, breezy Sunday amid moderating temperatures**
Thursday Night through Friday night...
The end of the workweek will see a quick blast of late winter cold
behind the departing and deepening storm system. Guidance is
continuing to show any rain/storms east of Indiana by 00z Thursday
evening, with a broad frontal zone progged to cross the region
overnight. Strong northwesterly winds gusting at least briefly to
25-35 mph will usher in much colder air, restoring near normal
temperatures in the mid to upper 20s by dawn Friday. Most locations
should see thermometers drop 30-35 degrees...with the current
forecast bringing a 38-degree change in 17 hours to Bloomington.
Lake effect snow showers will be advancing south-southeastward
towards central Indiana`s far northwest and far north-central
counties late Thursday night and early Friday. Suspect mainly
flurries for these zones amid the rather short-lived forcing,
although a thin coating of snow cannot be ruled out between the
Lafayette and Kokomo areas. Seasonably strong and amplified
Canadian high pressure will continue to advance into the region
while the air mass center plunges to Texas by midday Friday.
Blustery, gradually backing northwesterly flow will continue Friday
...with morning 20-25 mph gusts diminishing later in the day under
decreasing clouds as the surface ridge builds in.
Temperatures will only rebounding 5-10 degrees Friday amid the
strong cold air advection regime, with highs in the low to mid-30s,
making for the coldest day in two weeks. Dry conditions will
continue amid broad subsidence. Friday night will be the lone sub-
normal overnight of the long term with low 20s prominent across
Indiana.
Saturday through Sunday...
A western upper ridge will have progressed across the Rockies while
flattening, which will serve to quickly kick/advance the center of
the surface high across the southeastern United States. Broad
return flow will subsequently stream from the Lower Mississippi
Valley into Indiana. There is increasing confidence that a decent
gradient courtesy of weak low pressure across the central Plains...
will bring robust south-southwesterly winds gusting over 25 mph both
afternoons. Latest runs are showing a decent low-level jet setting
up from the central Plains into the Chicagoland area...with a broad
swath of 35-50 kts at the 925 mb level. Suspect the local region
catches at least the edge of any better winds, and especially during
the day Saturday when the jet would be better organized. Therefore
did not deviate from the Blend`s peak gusts of 30-35 mph across the
northern tier Saturday.
Dry conditions are expected with the high pressure`s proximity to
our south blocking any Gulf moisture...with no forcing approaching
from our north/west. A potential isolated weak wave embedded in the
widespread ridging may cross the Ohio Valley, yet suspect only
increased clouds from this feature with precipitable water values
suppressed under 0.50 inches as far south as the Gulf coast. Ample
warm advection should moderate readings through the weekend, with
low 50s expected to return by Sunday afternoon.
Monday through Wednesday...
A broad mid-level trough will prevail over North America early next
week while its southeastern quadrant is expected to become more
zonal over the Ohio Valley/Midwest. This should place the CWA on
the warmer side of a rather strong north-south gradient between very
cold air established over interior Canada...and warm ridging across
the Deep South and Gulf of Mexico.
A passing northern stream cyclone should drag a cold/quasi-
stationary front to near the Ohio Valley around the Monday timeframe.
At least weak overrunning would bring corresponding precipitation
chances...although with any appreciable cold air likely contained to
the Great Lakes and northward...so far appears rain would be the
favored precipitation type. Latest guidance is also indicating a
decreasing trend in QPF, especially towards the northern Midwest.
Energy ejecting eastward from a cut-off upper trough off of Baja
California...should then promote cyclogenesis across the central
CONUS towards the mid-week. An open fetch of increasing deep Gulf
moisture would bring the potential for heavy rain near the Tennessee
Valley...with more moderated rainfall amounts favored near the
Midwest. Less certainty in timing and intensity of this system with
considerable run-to-run model variation in the ejecting southwest US
wave, as well as how it will interact with a broad, deepening
Pacific coast H500 trough. Nonetheless appears greatest confidence
is in rain again being the favored precipitation type with
increasing heights across the middle of the CONUS likely pushing the
freezing line northward into Michigan.
High temperatures from Monday on will follow a slight cooling trend
although daily readings should be overall slightly above normal with
morning lows around the freezing mark. The normal max/min at
Indianapolis through the long term is 42/26.
&&
.Aviation...(00Z TAF Issuance)
Issued at 548 PM EST Wed Feb 15 2023
Impacts:
* Winds shifting from westerly to northerly overnight, then easterly
by daybreak, up to 8-12KT at times.
* Low ceilings, showers, and perhaps thunderstorms moving in late
tonight to around daybreak Thursday.
* Winds becoming gusty late tomorrow afternoon as precipitation
moves out and a cold front passes.
Discussion:
Generally quiet conditions are expected early in the TAF period with
mostly clear skies, winds becoming lighter as gustiness dies down,
and no obstructions to visibility.
Late tonight into Thursday, low pressure out of the southwest will
pass northeast through the area, with widespread showers and some
embedded thunderstorms expected. Will carry VCTS at the southern 3
sites for a time, and hopefully refine later tonight into tomorrow
morning as extent of convective coverage becomes more apparent.
Widespread low ceilings will also overspread the area, with ceilings
rapidly becoming MVFR then widespread IFR late tonight into
Thursday. This will persist through the time frame of precipitation,
with MVFR conditions potentially persisting beyond.
As the low begins to depart late in the period, winds will become
westerly and begin to gust in the 20s to near 30KT range as the cold
front passes.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Update...Nield
Short Term...CM
Long Term...AGM
Aviation...Nield