IWX issues Area Forecast Discussion (AFD) at Jan 20, 2:46 AM EST169
FXUS63 KIWX 200746
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
246 AM EST Mon Jan 20 2025
.KEY MESSAGES...
- The Cold Weather Advisory remains in effect until 10 AM EST Wednesday
area-wide. Wind chills as low as 25 below zero will be
possible.
- Additional lake effect snow accumulations of up to 4 inches
are expected in southwest Lower Michigan. The Winter Weather
Advisory for Berrien and Cass counties remains in effect until
7 AM EST Monday. The morning and evening commutes may be
hazardous.
- Mainly dry with temperatures returning to near normal by the end
of the week.
&&
.DISCUSSION...
Issued at 244 AM EST Mon Jan 20 2025
Clearing skies overnight have set the stage for a bitterly cold
morning to start the new work week. Expect lows this morning to be
right around 0 degrees, with wind chills 15 to 20 below zero. Highs
only reach between 5 to 10 degrees later this afternoon as a large
area of high pressure dominates over the central CONUS. This area of
high pressure is bringing in cold air all the way from Siberia,
although the airmass should moderate as it makes its way towards our
forecast area. Thanks to snowmelt earlier in the week, air
temperatures and wind chills will likely be a bit 'warmer' than what
models had previously forecasted several days ago as the lack of
snow on the ground allows for more heat to be transfered between the
ground and the air. Nevertheless, 850 mb temperatures will be
between 20 to 25 below zero, with a brief period as low as 30 below
zero on Tuesday. At the surface, this translates to air temperatures
only as high as the single digits during the day and below zero at
night. An area-wide Cold Weather Advisory remains in effect through
10 AM EST Wednesday for wind chills as low as 25 below zero at
times. Clearing skies overnight will again allow for lows in the
single digits below zero tonight and Monday night (except for closer
to Lake Michigan where lake effect snow and clouds act as a blanket
to keep colder wind chills at bay). As the area of high pressure
expands and moves east, it will centered over our forecast area by
early Wednesday morning. Regardless of what the wind chills end up
being (as there's not much difference between -15 and -25), this
dangerous cold will be brutal. Several days of prolonged bitter cold
will take a toll on anyone outdoors, with frostbite possible in as
little as 30 minutes! Limit exposure outdoors and dress in several
layers to stay warm.
Current radar imagery shows lake effect snow showers across
southwest Lower Michigan and north of the Toll Road in St Joseph and
Elkhart counties. Low level winds are converging, with a few
dominant bands of heavier lake effect snow, especially across
southern Berrien County. Decent lapse rates and moisture, as well as
inversion heights around 6-7 kft should allow for lake effect snow
to persist today, although subtle shifts in the bands may allow for
accumulations to vary widely over southwest Lower Michigan. The
Winter Weather Advisory remains in effect for Berrien and Cass
counties in Michigan where up to 4 inches of additional snow
accumulation is expected through Tuesday morning. In southwest Lower
Michigan, reduced visibilities are expected and travel will be
hazardous today, especially along the I-94 corridor. Gusty west
winds of 20 to 25 mph will also lead to some blowing snow. Hi res
model guidance depicts that as the winds shift to become more west-
southwest and a ridge builds to the southeast of our forecast area,
the lake effect snow bands will finally shift out of our area by
Tuesday. The only change made to the Winter Weather Advisory was to
extend it until 7 AM EST Tuesday to account for a longer duration of
lake effect snow. The Advisory may need to be extended further
into Tuesday in the next forecast update.
Temperatures will begin to warm up back towards seasonable levels
(but still below freezing) by mid to late next week. As the Arctic
air and high pressure system exit to the east, it could be windy at
times on Wednesday and Thursday with a strong pressure gradient
across our forecast area. Have kept slight chance PoPs in for
Thursday with models suggesting a clipper-type system could sweep
through the area. The latest long range guidance favors near normal
temperatures and a mostly dry pattern for the end of next week and
into next weekend. It is possible highs get to above freezing on
Sunday and next Monday.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1255 AM EST Mon Jan 20 2025
LIFR/IFR vsbys will continue to be possible at KSBN through
around 09Z. After 09Z, expecting gradual diminishment in the
intensity of the lake effect snow as winds take some subtle
backing to the west which will reduce the fetch over Lake
Michigan. Low level dry air entrainment will also become more
important as this subtle wind shift occurs. Otherwise, gusty
winds from the west-northwest to 20 to 25 knots expected through
this period at both terminals, with VFR conditions expected to
persist at KFWA. A synoptic wave moving into the area late this
afternoon and tonight will provide some weak mid level lift but
likely nothing in terms of sensible weather effects due to dry
nature of mid level airmass. A lull in snow showers is possible
at KSBN after daybreak and through most of the day, but snow
showers could briefly return tonight in wake of the
aforementioned short wave trough passage.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Cold Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
OH...Cold Weather Advisory until 10 AM EST Wednesday for OHZ001-002-
004-005-015-016-024-025.
MI...Cold Weather Advisory until 10 AM EST Wednesday for MIZ078>081-
177-277.
Winter Weather Advisory until 7 AM EST Tuesday for MIZ078-177-
277.
MARINE...Small Craft Advisory until 5 PM EST Tuesday for LMZ043-046.
Heavy Freezing Spray Warning until 5 PM EST Tuesday for LMZ043-
046.
&&
$$
DISCUSSION...Johnson
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Jan 20, 2:46 AM EST---------------
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