Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 190113
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
913 PM EDT Mon Mar 18 2024

.KEY MESSAGES...

- A Hard Freeze Tonight
- Partly Cloudy and Warmer on Tuesday
- Wind gusts near 35 mph on Tuesday
- Elevated fire weather risk on Tuesday
- Rain possible Friday, again early next week.

&&

.FORECAST UPDATE...
Issued at 913 PM EDT Mon Mar 18 2024

Geocolor loop, ob trends and 850 millibar rh progs support slowing
down clear just a bit, otherwise, skies will be clearing late this
evening and early overnight. The clearing along with cold advection
from northwest winds along with dew points in the teens and lower
20s will allow for another hard freeze. Overnight lows near sunrise
in the lower to middle 20s continue to look good.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 253 PM EDT Mon Mar 18 2024

Synopsis:

Surface analysis early this afternoon shows strong high pressure
centered over KS/OK. Low pressure was found near the mouth of the
St. Lawrence River, with a surface trough that extended SW across
Quebec and Ontario to Michigan. Aloft, deep low pressure was found
over Quebec and Hudson Bay, resulting in cyclonic flow aloft over
the eastern half of the CONUS. An upper trough axis associated with
this low, stretched across the eastern Great Lakes, to Western OH,
southern Indiana and western KY. Radar shows scattered snow showers
across northern Indiana in the wake of this feature and isolated
flurries were found over parts of Central Indiana. Cold northwest
flow was in place and cold air advection was ongoing.

Tonight...

Model suggest the upper trough, already to the southeast of Central
Indiana will continue to exit east. This will leave northwest upper
flow still in place with strong ridging in place over the west coast
and shallower but a broader trough in place across the east,
including Indiana. Forecast soundings tonight trend toward a dry
column as subsidence and mid level drying build across the area in
the wake of the trough. Models suggest the lower levels also dry out
considerably by early evening.  Meanwhile at the surface the strong
high pressure system to the west is expected to sink to Texas, while
low pressure settles over Lake Superior. This will set up a strong
transport of dry western air to Indiana and the Ohio Valley. Strong
warm air advection will begin late tonight, but this will not arrive
in time to prevent a fall of temperatures to below freezing.

Overall, decreasing clouds this evening and dry air in place at the
surface will allow for temperatures to fall in to the middle and
perhaps lower 20s. Once again, this may lead to damage to isolated
plant growth that has developed in recent weeks across Central
Indiana. Again, we will issue a SPS to address this.

Tuesday...

Gusty winds and warmer weather is expected on Tuesday.

Models show strong warm air advection in place on Tuesday as strong
high pressure across eastern TX and LA along with low pressure over
the Great Lakes provide an ideal transport of warmer air from the
plains through the day. Models show a nose of warmer air surging
toward Central Indiana by the afternoon with 850mb temps rise to 0C.
Also of note, within the northwest upper flow a strong LLJ near 40-
50 knots is expected to arrive in the morning before passing by the
late afternoon. A dry column is indicated by the forecast soundings
and time heights as the dry and warmer westerly flow persists. This
will allow for good mixing through the day, and also allow for
interaction with the moderate LLJ aloft resulting in gusty winds.
Thus wind gusts around 35 mph will be possible on Tuesday.
Furthermore this should allow temperatures reach the lower and
middle 50s across the area, under mostly sunny skies.

The gusty winds and low relative humidity will lead to an elevated
Fire weather risk on Tuesday. Fuel moisture remains high.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 253 PM EDT Mon Mar 18 2024

Generally quiet weather can be expected early in the long range as
dry northwesterly aloft prevails. At the surface, a cold front will
have recently passed through the state and we will find ourselves
within strong cold air advection. High pressure associated with the
cold continental air mass builds in during the day on Wednesday.
Anticyclonic flow across the region may lead to less cloud cover
compared to today, despite similar magnitude cold air advection.
Therefore, with greater solar insolation high temps should be warmer
than today...likely well into the 40s. However, highs Wednesday and
Thursday likely trend below the climatological average for this time
of year (low 50s). As the surface high settles in late Wednesday,
clear skies and generally light winds may allow for good radiational
cooling. To account for this, we went a bit under guidance for low
temps Thursday morning.

By late week, a cut-off upper low across the Desert Southwest looks
to finally break down and progress eastward. This feature may
partially phase with a wave in the polar jet and bring some
precipitation to Indiana. Overall, with a lack of moisture and
incomplete phasing...am not expecting widespread heavy precipitation.
Rather, amounts should remain on the light side with totals
generally under a quarter of an inch. Trends within guidance will
need to be monitored, in case greater phasing is favored in later
runs. However, recent trends have been towards less phasing between
the two features.

Ensemble guidance is hinting at more significant troughing late in
the weekend and/or early next week. While deterministic models all
differ in how they handle the downstream evolution, the overall
synoptic signal appears in most of them. NAEFS/ECMWF situational
awareness tables likewise show a similar signal starting to appear
around this timeframe. In terms of sensible weather, Indiana looks
to be on the eastern end of a potentially amplified trough which
favors warm moist advection and rain/thunderstorms. It is too early
to determine if there will be severe weather.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 501 PM EDT Mon Mar 18 2024

Impacts:

- The gusty northwest winds will subside to 10 knots or less
  by or just after 00z this evening

- Winds will shift to the southwest and west with gusts to over
  30 knots at times after 13z Tuesday

Discussion:

The upper trough will shift to the southeast of the terminals this
evening. This, a drying column per Hi-Res soundings and sunset
should allow skies to clear overnight with just perhaps some patchy
high clouds.

Loss of mixing at sunset should allow wind gusts to subside after
00z. Winds will be northwest and then west mostly less than 10
knots. However, then a cold front will approach from the northwest
Tuesday. Tightening surface pressure gradient and more mixing will
will in wind gusts to 30+ knots at times during the afternoon.


&&

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

$$

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


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