IWX issues Area Forecast Discussion (AFD) at Apr 19, 10:11 PM EDT496
FXUS63 KIWX 200211
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1011 PM EDT Sat Apr 19 2025
.KEY MESSAGES...
- For tonight, expect partly to mostly cloudy skies with lows
in the 40s.
- There are chances for rain with isolated thunderstorms Sunday
afternoon into Monday afternoon. The highest chances will be
Sunday night into Monday morning. Additional low to mid range
rain chances are possible through the work week, with the best
potential on Friday afternoon.
- High temperatures in the 50s and 60s Sunday will rise into the
mid to upper 60s and 70s for Monday and Tuesday. Highs from
the middle to latter portion of the work week will climb as
high as the mid to upper 70s before falling back to around 70
for the weekend.
&&
.DISCUSSION...
Issued at 743 PM EDT Sat Apr 19 2025
A sprawling trough across the western US becomes cutoff across
the southwestern US as the northern stream continues eastward.
This allows a baroclinic zone to set up from TX to arcing
towards the Lower Great Lakes region. What's left of that energy
in the southwestern US moves up towards the Lower Great Lakes
Sunday evening. So, as the cold front that caused this morning
showers and storms slowly shifts southeastward, rain shuts off
for all areas by after midnight tonight. This brief reprieve in
the rain is caused by surface high pressure nudging into the
area. It attempts to shut rain off as mid 30s to mid 40s dew
point air nudges in from the north. Better moisture exists south
of US-30, so am not as sold on rain as far north as the GFS and
ECMWF have. For what it's worth, the NAM doesn't have rain in
the area at all Sunday. This thinking would keep the forecast in
line with the previous shift of having mostly slight chance
PoPs and a pocket of chance PoPs west of IN-15 at times and
other times south of US-30. A warm front attempts to lift
northward Sunday evening and may provide a time period with some
thunderstorms as the NAM indicates some variation of 250 to
1250 J/kg of CAPE coupled with 30 to 40 kts of effective shear
may be around. All of that appears marginally severe, though.
The timeframe with the best moisture appears to be late Sunday
night into early Monday morning as an occluded front swings west
to east through the area, but dry air is quick to fill back in
in the mid levels shutting off heavier rain to either drizzle or
off altogether. Rain should be done Monday afternoon as sfc
high pressure noses in from the south and heights become looser
across the area. Expect gusty winds (25 to 35 mph) Monday
afternoon as a cold front pushes through and CAA takes over.
The aforementioned sfc high pressure area is west of the area later
day Tuesday and this allows WAA to take over Tuesday night into
Wednesday morning. Warmer high temps with 70 degree highs may be
more prevalent Wednesday through the end of the week as a result.
One dampener on that warm of high temps would be that there's some
model consensus around bringing some convection eastward through
Lower MI on a stationary front similar to an MCS type evolution on
the eastern edge of LLJ. Although the resultant location (and if it
even happens) could change in the days to come.
Medium range guidance diverges Wednesday night through the end of
the work week as the GFS is already bringing in the next trough and
allowing for rain Wednesday night with some thunder possible. The
ECMWF does have some connection to the Gulf during this time and it
would only require some forcing to get showers and maybe some storms
started. With the northern stream jet north of the area and the
subtropical jet weakening, more defined areas of forcing will be
harder for models to find and track between Thursday and Friday
allowing quite a bit more uncertainty. Will keep slight to chance
PoPs during the end of next week to indicate the possibility of rain
and thunder, but nailing down a day and time comes with uncertainty
at this time.
Look for drying some time next weekend as high pressure comes in and
cooler/drier air arrives from the north.&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 743 PM EDT Sat Apr 19 2025
Predominantly VFR conditions at the TAF sites through the
period, with MVFR ceilings possible at KFWA this evening and
at both sites after 19z Sunday. Have a tempo for the next couple
hours at KFWA as the lingering low level ceilings lift/move out
of the area, becoming VFR overnight at around 5-10kft. A brief
period of high clouds closer to 15-25kft is possible, but should
fill in towards mid-late morning once again. Light winds out of
the NW should shift N-NE overnight, with KSBN becoming variable
around 3-4 knots for a period. Flow in the morning becomes more
E-SE and strengthens to around 10-13 knots, with gusts up to
around 25 knots becoming more likely towards mid-late afternoon.
There is a lot of disagreement regarding the timing of rain
tomorrow afternoon with the next system, with a more showery
versus persistent look at KFWA. Have VCSH at KSBN starting at
15z and around 19z for KFWA based on a consensus of guidance,
and have prob30 groups to cover more impactful conditions. After
21z, MVFR ceilings around 1500-2500 feet are possible, but
confidence was too low to include as a predominant group. Most
of the guidance has ceilings of around 2500ft for now, with only
the NAM showing one hour of 1500ft around 22-24z at KFWA.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 1006 PM EDT Sat Apr 19 2025
Predominantly VFR conditions at the TAF sites through the
period, with MVFR ceilings possible at KFWA this evening and
at both sites after 19z Sunday. Have a tempo for the next couple
hours at KFWA as the lingering low level ceilings lift/move out
of the area, becoming VFR overnight at around 5-10kft. A brief
period of high clouds closer to 15-25kft is possible, but should
fill in towards mid-late morning once again. Light winds out of
the NW should shift N-NE overnight, with KSBN becoming variable
around 3-4 knots for a period. Flow in the morning becomes more
E-SE and strengthens to around 10-13 knots, with gusts up to
around 25 knots becoming more likely towards mid-late afternoon.
There is a lot of disagreement regarding the timing of rain
tomorrow afternoon with the next system, with a more showery
versus persistent look at KFWA. Have VCSH at KSBN starting at
15z and around 19z for KFWA based on a consensus of guidance,
and have prob30 groups to cover more impactful conditions. After
21z, MVFR ceilings around 1500-2500 feet are possible, but
confidence was too low to include as a predominant group. Most
of the guidance has ceilings of around 2500ft for now, with only
the NAM showing one hour of 1500ft around 22-24z at KFWA.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...MCD
Source:
IWX issues Area Forecast Discussion (AFD) at Apr 19, 10:11 PM EDT---------------
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