IWX issues Area Forecast Discussion (AFD) at Dec 31, 11:02 AM EST574
FXUS63 KIWX 311602
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1102 AM EST Tue Dec 31 2024
.KEY MESSAGES...
-Rain will spread across the area today, mixing with snow at
times for areas north of highway 24. 1-2" of snow is possible
in south-central Michigan with lesser amounts in Indiana and
Ohio.
-Light lake effect snow could add another inch to snowfall
totals in Michigan late tonight into Wednesday.
-Colder air returns for the end of the week. A light dusting of
snow is possible again Thursday night with more light lake
effect snow on Friday.
&&
.UPDATE...
Issued at 1102 AM EST Tue Dec 31 2024
Forecast generally on track so far with widespread rain still
occuring across the area. The NE flow around the deepening low
had allowed a steady fall in temperatures focused from Hillsdale
to Angola to Rochester (in the mid 30s...34 at our office) where
the deformation zone is establishing itself as expected (maybe a
bit earlier than forecasted) .Snow, mixed with rain, is
occurring at our office at this time, under the heavier band
noted on radar (although much of the higher returns are likely
bright banding from the falling freezing levels). Ground
temperatures are still well above freezing with road model data
indicating road sfc temps into the 40s. This all equates to any
snow melting as it falls and not sticking around for the time
being. As we get into the afternoon and air/ground temps
continue to cool, some accumulations may start on grassy areas.
&&
.DISCUSSION...
Issued at 300 AM EST Tue Dec 31 2024
Next Pacific jet streak and attendant PV anomaly currently entering
the Ohio Valley. Initial elevated fgen band brought some light rain
earlier overnight but attention now turns to primary low level fgen
just now entering our SW CWA. Cross-sections still indicate a
healthy band of fgen extending from roughly the surface to 700mb
with specific humidities over 3 g/kg and significantly reduced
stability extending from the top of the frontal slope all the way to
the tropopause. Still expecting around 0.5-0.75" QPF with this event
(highest in our southern half). Question remains how much will be
rain vs. snow. As the low pressure system moves into our region and
strengthens later today, ENE low level flow will increase and advect
slightly cooler and drier boundary layer air into our region.
Forecast soundings suggest that as the deformation zone pivots over
our central CWA around midday there will be just enough cold air
(combined with heavier precip rates) to support primarily snow.
Outside of this main band it is likely to be more rain and there
does remain some uncertainty as to where exactly this sets up. It
will also be moving through the day which is difficult to reflect in
the weather grids. Thermal profiles are right on the edge and any
location that sees moderate precip rates during the middle/latter
part of the day will see snow as the predominate precip type.
Accumulations on the other hand will be difficult. A lot will be
lost to melting given surface temps above 32F and still relatively
warm ground/pavement temps. Outside of our far N/NE (which will
see the coldest temps/longest duration of snow) expect slushy
accumulations of less than an inch. These will mainly be on
grassy/elevated surfaces and will likely melt quickly after
falling. Our far N/NE zones could see 1-2" by the time synoptic
precip ends late this evening. Of course any location that sees
moderate snow will have reduced visibilities that could impact
travel regardless of accumulation.
There will be some lake response later tonight into Wed as 850mb
temps drop to around -12C. Expect a poorly organized multi-band
setup primarily impacting our MI counties. 300 degree fetch is
certainly not ideal with ample dry air upstream keeping profiles
mostly stable. Inversion heights are also around 5 kft at best and
near-surface dry air keeps LCL's at almost 2 kft. Isolated locations
in SW MI may see up to an inch but overall a low impact event
(esp given the holiday). Snow should wind down by Wed evening.
As the flow flips around to northwesterly for the second half of the
week we will see a weak, moisture-starved shortwave cross the region
late Thu. Not much going for it except some slight fgen response.
Expect a few tenths at best and this could remain just south of our
area. This will be followed by another round of light LES as
temps drop further. Similar fetch and instability problems
remain here but we could squeeze out some light accums on Fri in
typical WNW favored areas. Highs Fri and Sat will be in the low
20s.
Keeping an eye on the system for early next week but trends
have been for a weaker system tracking further south. Still
plenty of time for changes six days out though. Increasing
confidence in cold temps for next week. See CPC 6-10 and 8-14
day outlooks for more info.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 601 AM EST Tue Dec 31 2024
Minimal changes needed for the 12Z TAFs as the previous forecast
is on track. An area of low pressure lifting north out of
Missouri will bring rain to the area (moderate to heavy at
times, especially at KFWA) this morning, which will gradually
changeover to rain/snow or all snow as temperatures fall this
afternoon. Precipitation, whether rain or snow or a mix, will
reduce visibilities down to as low as 2 to 3 miles today.
Ceilings are currently on the low end of VFR but are expected
to drop to MVFR in the next few hours, then down to IFR by the
early afternoon. Winds are beginning to pick up out of the east
already; by early to mid morning, winds will shift to the
northeast and be quite gusty throughout the day. Gusts up to
30kts are expected across the area, especially through the
morning and early afternoon hours. Rain may mix with snow or
changeover to all snow by the afternoon, although minimal
accumulation (only 0.5-1" at most) is expected due to warm
ground/pavement temperatures. The heaviest bands of snow will
have MVFR visibilities and brief periods of moderate snow.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 5 AM EST Thursday for LMZ043-046.
&&
$$
UPDATE...Fisher
DISCUSSION...AGD
AVIATION...Johnson
Source:
IWX issues Area Forecast Discussion (AFD) at Dec 31, 11:02 AM EST---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
