Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/04/23

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 939 PM MDT Sun Sep 3 2023

.UPDATE...
Issued at 933 PM MDT Sun Sep 3 2023

Weak convection continues to move northeastward over the plains
this evening. There is little to no lightning and the rain
falling is all light rain. Models, including the high resolution
versions all have it ended by 06Z. Will make appropriate Grids
updates.

&&

.SHORT TERM...(This evening through Monday)
Issued at 247 PM MDT Sun Sep 3 2023

Decent batch of scattered showers and thunderstorms have already
developed over the mountains and especially over the Front Range
foothills and Douglas county. Embedded wave moving through the
moderate southwest flow while water vapor showing drier air
already moving into southwest Colorado. Expect storms will be
ending fairly quickly in the mountains by early this evening.
Latest ACARS soundings around Denver showing close to an inch of
precipitable water so can expect heavy rain with the storms.
Storm motions are moving at a decent clip of 10 to 20 mph so
prolonged heavy rain appears limited. We are seeing rainfall rates
around a half inch of rain in 30 minutes or less. Expect some of
these storms to move out over the adjacent plains through this
evening.

For Monday, the main upper trof now entering the Great Basin will
weaken and lift rapidly across the Northern Rockies with trailing
trof moving across Northern Colorado during Monday afternoon. The
best chance for storms will be over the northeast plains, especially
along and north of Interstate 76. This is the area with the best upward
forcing and moisture. Further south, the airmass will be drier with
less upward forcing. There will also be drier and more subsident airmass
moving into the mountains as the trof sweeps across the region.

.LONG TERM...(Monday night through Sunday)
Issued at 247 PM MDT Sun Sep 3 2023

Upper level zonal flow begins Monday night into Tuesday. A weak
passing shortwave can be seen across 500mb heights. Mid-level
moisture exist throughout the mountains and valleys. Combining this
moisture with weak MLCAPE between 200-300 J/kg and large DCAPE
values near 1000 J/kg should lead to isolated gusty storms mainly in
the northern foothills and along the Cheyenne Ridge. These storms
should remain sub-severe and likely will only produce gusty winds
and light rain through late Tuesday afternoon. Expect majority of
the region to remain dry. High temperatures trend slightly below
normal as parts of the plains reach the mid 70s to low 80s and parts
of the mountains and valleys reach the mid 60s to low 70s. An upper
level ridge approaches our CWA starting Wednesday morning. This
brings a drying trend for all areas Wednesday and Thursday. Without
much cloud cover, afternoon temperatures increase and parts of the
plains rebound to 90 degree by Thursday afternoon. As this drying
trend occurs, this may increase fire weather concerns across Park
county depending on fuel status. Increasing moisture arrives Friday
through the weekend, thus keeping NBM PoPs in the plains and
mountains during this period. Ensembles keep slightly above normal
temperatures through the weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 933 PM MDT Sun Sep 3 2023

Models have weak drainage winds going at DIA by 05Z-06Z. There
will be no ceiling issues.

&&

.FIRE WEATHER...
Issued at 247 PM MDT Sun Sep 3 2023

There will be near critical fire danger over the Palmer Divide
Monday afternoon, especially over southern Lincoln county. However
duration of conditons looks to only be an hour or so with gusty
southwest winds and lowering humidity levels.

&&

.HYDROLOGY...
Issued at 247 PM MDT Sun Sep 3 2023

Strong scattered showers and thunderstorms will be moving over the
area through this evening with heavy rain with the stronger storms
with a limited threat for flash flooding. Lesser chance of flash
flooding Monday afternoon as a drier airmass and stronger westerly
winds move into the area.

Starting Tuesday through Thursday, the flash flood threat trends low
due to drier air entering the region. Moisture returns this weekend
which may bring isolated showers and storms to the mountains.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE.........RJK
SHORT TERM.....Entrekin
LONG TERM......AD
AVIATION.......RJK
FIRE WEATHER...Entrekin
HYDROLOGY......Entrekin



Area Forecast Discussion

National Weather Service Indianapolis IN

 1011 PM EDT Sun Sep 3 2023

.Forecast Update...
Issued at 1011 PM EDT Sun Sep 3 2023

Little changes made to the forecast with this evening`s update. Main
weather focuses are patchy fog tonight, hot and humid conditions
tomorrow, and a very slight chance for a shower along the IL/IN
border.

Quiet conditions expected in the short term across Central Indiana
as ridging aloft and high pressure continue to be the main weather
influence. High pressure, clear skies, and light winds will once
again create optimal conditions for radiational cooling overnight.
Adding patchy fog in the Wabash River Valley again mainly from 06-
12z as fog has developed in this location the past few nights under
the same conditions. Not expecting anything widespread, but brief
periods of fog are possible in small valleys, sheltered areas, corn
fields, and near water through sunrise.

Simple Water Vapor RGB shows an upper low under the ridge near
Dallas, TX slowly pushing northward into the Plains with a large
axis of moisture streaming up into the mid Mississippi Valley ahead
of it. While hot conditions are expected to persist into tomorrow,
expect increasing moisture advection northward into the area as the
upper low pushes closer and winds in the low and mid levels become
southerly. This may lead to conditions feeling a tad more humid
tomorrow than they did Sunday. Potential is there for an isolated
shower or thunderstorm tomorrow afternoon in far Western and
Southwest Indiana where the best moisture advection is closer to the
upper low. Subsidence under the high and a stubborn cap near 750mb,
evident on IND ACARS soundings, will work against deep convective
development tomorrow; however would not rule out a shower or two.
Therefore, putting 15 PoPs for the counties along the IL/IN border
tomorrow afternoon.

&&

.Short Term...(This evening through Monday)
Issued at 251 PM EDT Sun Sep 3 2023

Broad diurnal cu field remains over all but far southern portions of
the forecast area this afternoon on the back side of an axis of
slightly deeper moisture across the upper Ohio Valley. This had
limited mixing of drier air aloft and as a result dewpoints have
remained a few degrees higher than anticipated in the upper 60s and
lower 70s. 18Z temperatures were mainly in the mid and upper 80s
with a few spots flirting with 90 degrees.

Ridging at the surface and aloft will remain the primary drivers in
the hot and mainly dry pattern continuing into Labor Day. Both
features will however shift southeast slightly as the upper low
over east Texas this afternoon lifts into the Ozarks by MOnday
evening. This will enable a slug of moisture to lift northeast into
the lower Ohio Valley by Monday afternoon which may be sufficient
enough to generate a stray shower or two in the Wabash Valley. More
on that potential below but ultimately...the short term will be
highlighted by hot and humid conditions.

Expect the cu field to gradually diminish in coverage through the
afternoon as slightly drier air advects into the region. Despite the
clouds...temperatures have not really be impeded and expect the
entire forecast area will peak in the upper 80s and lower 90s by
late afternoon. Cu will fully dissipate near or just after sunset
leaving mostly clear skies and light southwest flow overnight. Once
again...localized shallow ground fog will be possible near daybreak
Monday...especially in low lying areas and near bodies of water.

As mentioned above...the ridging at the surface and upper levels
will remain close enough to the area to maintain largely dry
conditions...bu the subtle shift E/SE to both features will enable
moisture to advect northeast between the ridge and the
aforementioned upper low. Forcing aloft is minimal but in tandem
with the increase in low level moisture...potential is there for a
few small showers to develop focused across the Wabash Valley during
the afternoon. The combination of drier air in the mid levels and
overall poor lapse rates should keep any convection from getting
tall enough to generate any lightning and thunder. Most will remain
dry...and any isolated showers will diminish Monday evening. Expect
another healthy cu field for the afternoon but this will also
dissipate towards sunset.

Temps...lows tonight will settle in the mid to upper 60s. Low level
thermals support highs Monday very similar to today...peaking in the
upper 80s and lower 90s.

&&

.Long Term...(Monday night through Sunday)
Issued at 251 PM EDT Sun Sep 3 2023

The rest of the week will include a tandem of regimes...the
continuation of humidity and marginal heat more common in July...
with scattered mid-week showers/t-storms preceding a cold
front...that will bring a seasonable, yet dry late week/weekend.

Monday Night through Thursday...

Recent model trends have see-sawed somewhat on POPs for the first,
weak tropical wave remnants on Tuesday...as despite a moist column
with isolated pockets of 2.00+ inch precipitable water, better
forcing will be hanging back to the west while this small
circulation lifts into the predominant area of surface high pressure
centered just to our southeast.  Most of the scattered showers/few
non-severe TRWs should be diurnally driven.

Wednesday-Wednesday night will bring a more organized batch of
isolated/scattered showers amid this continued mainly dry
pattern...when a H500 wave crossing the north-central CONUS
approaches the Midwest.  However, following a receding upper pattern
over interior Canada, this system will also weaken slightly while
lifting through the Great Lakes.  Yet the potential for showers and
embedded non-severe thunder exists ahead of the trailing cold front,
especially if this boundary`s approach were to time well with
Wednesday`s peak heating.

Thursday should be a day of transition, certainly in lower humidity
as the center of a narrow dry conveyor following the second wave
pushes eastward near the CWA...and H850 temperatures fall closer to
15 Celsius, even if the center of the arriving high pressure is
still positioned well to our north, near Hudson Bay. Any stray
showers from lingering anafrontal lift would be favored south/east
of the Indianapolis Metro, with higher confidence in rain-free
conditions towards the end of the workweek.

Temperatures will average about ten degrees above normal between
generally very warm daytimes and unseasonably high overnight
minimums.  Tuesday`s record high minimum is 75F from 1881...the
current forecast for IND is 73F.

Friday through Sunday...

A familiar scene will return for the late week/weekend with Indiana
positioned between the suppressed subtropical ridge to our
south/west and a pronounced trough slowly crossing eastern Canada.
Broad Canadian high pressure will gradually cross the Great Lakes,
with central Indiana catching the southern side of this dome.  Dry
conditions will once again prevail...both in rain-free weather as
well as lower dewpoints.  Guidance indicates pockets of mid-level
moisture spilling across the top of the flattened western upper
ridge...yet suspect a noticeably drier lower column would prevent
any rain from reaching the surface. Readings will be on the whole
seasonable. The normal max/min at Indianapolis through the long
term is 81/60.

&&

.Aviation...(00Z TAF Issuance)
Issued at 740 PM EDT Sun Sep 3 2023

Impacts:

* Mainly VFR conditions expected tonight and tomorrow
* Slight chance of fog overnight at KLAF, KHUF, and KBMG

Discussion:

Quiet evening across Central Indiana this evening as high pressure
remains the dominant weather influence over the region. Latest
satellite imagery shows decreasing cumulus clouds as the sun begins
to set. Mainly VFR conditions expected through the period other than
a slight chance of fog in the Wabash River Valley. Brief periods of
MVFR to IFR conditions possible at KLAF, KHUF, and KBMG overnight
tonight due to fog, however any fog development is not expected to
be widespread and should quickly dissipate at or around sunrise.

Another relatively quiet day tomorrow with mainly clear skies and
southerly winds around 6-10 kts. Potential for gusts of 15-20 kts at
times 16z-22z tomorrow afternoon due to afternoon mixing. Diurnal cu
will develop by midday Monday with the potential for greater
enhancement and perhaps even an isolated shower by late day at KHUF
and KLAF as an axis of moisture lifts into the area in tandem with
weak forcing aloft. Kept out any mention of showers tomorrow in the
TAFs as coverage of any shower activity will be very low. Will add
mention of SHRA with later TAF issuances tomorrow as timing becomes
clear of any shower threat during the afternoon hours.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Update...CM
Short Term...Ryan
Long Term...AGM
Aviation...CM