Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/01/23
Area Forecast Discussion
National Weather Service Indianapolis IN
941 PM EDT Thu Aug 31 2023
.Forecast Update...
Issued at 941 PM EDT Thu Aug 31 2023
High pressure was providing a clear and cool evening for the final
evening of August. Clear skies should continue, along with light
winds. Still looks like there could be some patchy ground fog,
mainly north, where proximity to the surface high should bring near
calm winds in spots.
Temperatures have fallen quickly this evening, so adjusted hourly
conditions to reflect this trend. Also nudged down low temperatures
some areas based on these trends.
&&
.Short Term...(This evening through Friday)
Issued at 141 PM EDT Thu Aug 31 2023
* A spectacular end to climatological summer across Central Indiana.
* Warming trend towards above normal temperatures begins tomorrow
.This evening and tonight...
What a way to end climatological summer with temperatures in the
70s, low humidity, and sunny skies! High pressure centered over
Michigan is responsible for these conditions; however as this high
shifts eastward and ridging strengthens overhead, temperatures will
begin to heat up once again.
For the rest of the evening and tonight, expect tranquil weather to
continue across Central Indiana. Latest IND ACARS sounding shows a
shallow mixed layer under 1 km agl working to mix down drier air to
the surface keeping humidity values lower. Winds are gusting to
around 15-20 mph this afternoon as well, but should diminish towards
sunset as mixing wanes and an inversion forms at the surface. Many
areas across North Central Indiana experienced the coolest morning
lows in months earlier today with mid to upper 40s observed from
Kokomo to Muncie. Expect another cool night again with upper 40s
possible in North Central Indiana and low to mid 50s likely further
south. With the center of the high pushing away from the region,
expecting winds to stay slightly elevated overnight leading to lows
a few degrees warmer than last night and less of a fog potential.
Kept patchy fog near sunrise in the forecast for areas that reported
it earlier this morning, mainly from Lafayette to Kokomo to Muncie.
But otherwise, conditions are dry enough and winds may remain just
high enough for widespread fog to not be a concern.
.Friday...
The start of meteorological fall will start out on a warm note as
another extended period of at or above normal temperatures are
expected. Surface high pressure becomes centered over the northeast
tomorrow while upper ridging strengthens and pushes eastward into
the Midwest as well. 500mb heights rise above 591dam tomorrow while
southerly flow and warm air advection in the lower levels all work
to bring a much warmer airmass into the region. Expect highs to
reach the low to mid 80s Friday, about 10 degrees warmer than high
temperatures on Thursday. Southerly flow from the Gulf will result
in rising humidity levels as well, but currently not expecting
humidity to reach the oppressive levels reached a few weeks ago. Low
level subsidence inversion and low mixing heights will likely keep
too much dry air from mixing down to the surface. Additionally with
the lack of any rain lately, dry soil moisture, and low dew points
already in the region, it will take a while for humidity to
increase. Expect dew points to rise into the 50s to low 60s
tomorrow. Overall, a warm, September day is expected Friday before
much hotter conditions arrive for the weekend.
&&
.Long Term...(Friday night through Thursday)
Issued at 141 PM EDT Thu Aug 31 2023
Hot temperatures are the main focus in the long term portion of the
forecast. It still appears heat indices will stay below critical
levels, and likely below 100F, but there are some uncertainties. See
analysis below for details. A low probability of rain emerges by
around the middle of next week, but dry weather will prevail until
then.
Since the pattern is somewhat different with the upcoming period of
heat compared to the previous period of heat, there are model
performance considerations. Questions include: 1. magnitude of
moisture return and 2. model bias with regards to temperatures
(which was an issue for the last period of heat). The previous event
saw anomalous moisture which was deep enough not to mix out and this
impacted temperatures (cooler than modeled). It also contributed to
high heat indices and heat related impacts.
On the synoptic scale, forecast confidence is quite high with
anomalous 500-mb heights. Multi-model ensemble run-to-run
comparisons may show a slightly more amplified/anomalous ridge and
slightly further east position into early next week, but generally
negligible changes sensible weather. It is these minor details with
potential model biases and moisture magnitude to could result in
minor shifts in our forecast over the next few days. We do not see a
path where we would substantially exceed 100F for heat indices,
however, given the synoptic-scale stability in medium range
guidance. So, heat-related illness should be fairly minimal during
this upcoming anomalously warm period.
There is a low probability of some precipitation Tuesday night into
Wednesday. It does appear that on the periphery of eastern surface
high, at least modified moisture return will occur early-mid week.
There is an upper low with low latitude subtropical origins that
will eject northeastward ahead a shortwave trough and potentially
enhance mid-high level moisture. This, in addition to modified low-
level moisture, should push precipitable water values above
climatology. As the aforementioned shortwave trough`s associated
front moves through sometime between Tuesday night and Wednesday
night (there is spread in the medium-range models), interacting with
moisture, this should bring at least sparse coverage of convection
across Indiana.
Looking beyond the 7-day period, there is above confidence in
continued above normal temperatures given the signal in the medium-
range ensemble suite. This should be a mostly dry pattern as well.
&&
.Aviation...(00Z TAF Issuance)
Issued at 627 PM EDT Thu Aug 31 2023
Impacts:
* Low probability of fog at KLAF near 11Z.
Discussion:
High pressure will provide a dry atmosphere, keeping conditions VFR
for the vast majority of the time. Some patchy ground fog is
possible at KLAF around 11Z, so kept the 6SM mention for now.
Winds will diminish some overnight then become more southeast on
Friday at 10kt or less.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...50
Short Term...CM
Long Term...BRB
Aviation...50
Area Forecast Discussion
National Weather Service North Platte NE
637 PM CDT Thu Aug 31 2023
...Aviation discussion...
.SYNOPSIS...
Issued at 332 AM CDT Thu Aug 31 2023
Key Messages:
- Heat will build into the region the next several days.
- Little chance for rainfall as the upper level ridging becomes
established through the weekend.
- Increased fire weather concern with the continued dry and
increasingly hot weather.
- Some relief next week as the upper level ridging is suppressed
to the south.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 255 PM CDT Thu Aug 31 2023
Fire weather concerns are again in the picture as fuels/grasses
across the area continue to dry out. The hot weather and gusty south
winds the next few days will continue to keep concerns elevated, and
even critical across portions of the area. Otherwise hot weather is
expected Friday as many areas approach 100 degrees. A leeward
surface trough will become established across eastern CO and western
NE. A fairly tight pressure gradient will reside across the
Central/Southern Plains to the east of this surface trough. Gusty
south winds will continue as a result, and expect frequent gusts in
the 25-30 mph range.
.LONG TERM...(Saturday through Thursday)
Issued at 255 PM CDT Thu Aug 31 2023
Fire weather concerns will continue this weekend. The pattern as a
whole will remain unchanged. A persistent leeward trough will remain
across the western High Plains with high pressure anchored across
the lower Mississippi Valley region. The surface pressure gradient
between the two will continue to ensure gusty south winds. The heat
and low humidity will remain in place as well, and expected many
areas to reach near critical in terms of fire weather conditions. The
exception will be across the Panhandle, where winds will be lighter
through the weekend nearer the surface trough.
Upper level low pressure which will be located along the Pacific
coastal region this weekend, will begin to migrate eastward the
first of next week. As this occurs expect the upper level ridging to
be suppressed to the south as the troughing shifts northeastward
toward the Northern Plains by Tuesday. A cold front should shift
southward into the area Tuesday as the troughing lifts northeast.
This should bring an end to the hot weather along with at least some
chance for scattered rainfall.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu Aug 31 2023
Expect VFR conditions across central and western Nebraska through
Friday with nothing more than some mid/high clouds expected.
However, winds and wind shear will impact aircraft operations this
TAF period.
Winds will generally diminish through this evening until a robust
southerly/southwesterly low level jet becomes established overnight
into early Friday morning. While much of the night will feature
a laminar flow regime at KVTN and KLBF, expect an occasional gust
will mix down overnight so will indicate this in the TAF. Low level
wind shear can be expected with winds just off the surface around
45kt from about Midnight through daybreak Friday. Onset of diurnal
heating and boundary layer mixing Friday morning will generate some
gusty conditions as the diminishing jet mixes down. Gusty conditions
are then expected to persist with good mixing through the end of the
valid period.
&&
.FIRE WEATHER...
Issued at 255 PM CDT Thu Aug 31 2023
Fuels/grasses have continue to dry across the region, and with
the lack of rainfall and heat expected the next several days,
critical fire weather conditions are expected. Far southwest
Nebraska will be the first location to experience these conditions
Friday afternoon. Frequent south winds gusting over 25 mph will
combine with lowest humidity values around 15% and have issued a
Red Flag for that area.
Fire weather concerns will continue into the weekend. Critical
conditions could materialize, especially for locations along and
east of Highway 83. This would be the area that has the highest
chance of seeing the combination of gusty winds and low humidity.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 7 PM MDT Friday for NEZ210.
&&
$$
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...MBS
FIRE WEATHER...Taylor