National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KIND 200058
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
858 PM EDT Fri Apr 19 2024

.KEY MESSAGES...

- Partly Cloudy Tonight and Saturday; Cooler

- Some frost potential Sunday morning, more widespread frost
  possible Monday morning.

- Increasing rain chances next Tuesday, chance for PM thunderstorms

- Temperatures generally near seasonal next week, but brief cooldown
  is possible Wednesday into Thursday

&&

.FORECAST UPDATE...
Issued at 858 PM EDT Fri Apr 19 2024

Fast zonal flow around the base of a northern Ontario vortex will
continue to result in patches of mid and high clouds across central
Indiana through the overnight. Meanwhile, surface high pressure,
centered over the Canadian Rockies will result in a fetch of cold
northwesterly flow. Despite very dry low levels, there will be
enough of a surface gradient gradient to keep winds above 5 knots
and combined with the cloud cover keep temperatures just warm enough
to rule out a frost concern. Overnight lows in the upper 30s and
lower 40s continue to look reasonable.

&&

.SHORT TERM (This evening through Saturday)...
Issued at 230 PM EDT Fri Apr 19 2024

Synopsis:

Surface analysis this afternoon shows Low pressure north of Lake
Ontario, with a cold front that extended southwest across eastern OH
and eastern KY to Northern AL.  Strong high pressure was found over
the Dakotas, with a surface ridge axis extending southeast across
NB, northern MO and into Central IL. GOES16 shows the back edge of
clouds associated with the cold front just about to exit southeast
Indiana. Higher clouds were found upstream over MO and IL, streaming
toward Central Indiana. Cool northerly surface flow was in place
across Central Indiana due to the arriving area of high pressure.
Aloft a deep upper low pressure system was found over northern
Ontario. This system was providing mainly a westerly flow aloft over
the plains and Ohio Valley, with a stream of Pacific moisture in
place.

Tonight...

Quiet, and cold weather is expected tonight. Cold north/northwest
surface flow is expected to continue overnight as the surface high
pressure system will remain over the northwest plains. This will
continue to allow cool, continental air to spill into the Ohio
Valley from Canada. Meanwhile aloft, little overall change is
expected as the upper low is expected to pivot northeast and the
westerly flow with little to no forcing in place will remain in
place. Given upstream satellite and the quick flow aloft, periodic
mid and high clouds will be expected to pass through the night.
Forecast soundings agree to this, showing dry lower levels through
the night given  the cool and dry lower level flow, but saturation
appears aloft from time to time, suggesting passing mid and high
clouds. Thus partly cloudy should work fine.

Cold air advection will remain in play overnight. However the
ongoing pressure gradient across the area should help to keep winds
between 5-10 mph. This along with passing high clouds should be
favorable for the prevention of frost. Expect lows in the middle to
upper 30s north and central, and near 40 south.

Saturday...

Little overall change is expected in the weather on Saturday. The
upper flow remains westerly with Pacific moisture flowing aloft.
Models suggest the lower levels will remain dry with cool, northerly
or northwest flow spilling into Indiana as the surface high remains
strongly in place over the high plains. Forecast soundings again
show dry lower levels with a steep inversion in place within the mid
levels, limiting any cloud development. Upper levels show dry air
aloft with subsidence in place. Thus only a few stray passing high
clouds will be expected from that high, limited, Pacific moisture
aloft. 850Mb temps are expected to linger around -3C, thus a cool
day will be in store. Look for highs only in the lower to middle 50s.

&&

.LONG TERM (Saturday night through Friday)...
Issued at 230 PM EDT Fri Apr 19 2024

Saturday night through Monday...

Quiet weather conditions are expected as surface high pressure
remains dominant over the region. Aloft, guidance shows an
impulse traversing the region which could help to increase cloud
cover late Saturday into early Sunday. Expect the cooler pattern
today to continue over the weekend due to cold air advection. Lows
dropping into the 30s both Sunday and Monday morning combined
with relatively light winds supports the potential for frost.
There is higher confidence in frost Sunday night into Monday
morning at this time since guidance shows mostly clear skies.
Greater cloud cover from the aforementioned upper level impulse
Saturday night into Sunday morning leads to greater uncertainty in
terms of coverage. Highs in the mid 50s to near 60F Sunday should
warm well into the 60s to start the work week due to return flow.

Monday night onward...

Rain chances return towards daybreak Tuesday as a shortwave trough
and associated low pressure system move across the Great Lakes
Region. Return flow ahead of the approaching system should allow for
temperatures to continue moderating. Sufficient moisture return
combined with increasing dynamics supports likely POPs on Tuesday.
The system is likely going to move out Tuesday night.

Cold air advection and surface high pressure building in behind the
departing low will allow for quiet weather conditions to return
briefly before another system approaches late next week. Models
begin to diverge significantly by this point which limits forecast
confidence, but there is a general signal for an active pattern
heading into next weekend. Temperatures likely falling into the 30s
Thursday morning leads to some frost concern though it appears winds
may remain elevated enough to limit this potential. This will be
worth monitoring as blended guidance can sometimes overestimate the
magnitude of nocturnal winds when surface high pressure is building
in.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 617 PM EDT Fri Apr 19 2024

Impacts:

- None

Discussion:

Surface high pressure will build in from the Plains. That combined
with low dew points and models showing very dry low levels will
result in VFR flying conditions through the TAF period. Will only
see some mid and high clouds, especially tonight and at KLAF.

Winds will be northwest less than 10 knots tonight and around 10
tonight Saturday afternoon. Mild gusts are also possible Saturday
afternoon.


&&

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

$$

UPDATE...MK
SHORT TERM...Puma
LONG TERM...Melo
AVIATION...MK