IWX issues Area Forecast Discussion (AFD) at Feb 7, 6:18 AM EST278
FXUS63 KIWX 071118
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
618 AM EST Fri Feb 7 2025
.KEY MESSAGES...
-Dry with variable cloud cover today. Highs will be in the
upper 20s and 30s. Lows tonight will be in the 20s.
-A wintry mix of precipitation is expected Saturday morning
into Saturday evening. Areas from US 30 northward have the best
chance of seeing hazardous driving conditions as a combination
of snow, sleet, freezing rain, and rain occurs. Minor travel
impacts are expected.
-There are several chances for accumulating snow through next
week, particularly Tuesday and then Wednesday night into
Thursday. High temperatures will be in the 20s and low to mid
30s. Lows will be in the teens and 20s.
&&
.DISCUSSION...
Issued at 546 AM EST Fri Feb 7 2025
Today will be dry with variable cloud cover as high pressure settles
overhead. High temperatures will climb into the upper 20s and 30s,
with lows tonight falling into the 20s.
Saturday is the focus with a chance for another wintry mix of snow,
sleet, freezing rain, and rain. Confidence is low to medium, with a
fairly decent spread in the model solutions-the NAM being the
outlier from most of the guidance. The system is fairly quick
moving, developing near the panhandle of OK between 9-12z Saturday
morning and lifting northeastward through Saturday night. At the
same time, a shortwave trough swings through from the Dakotas
eastward into Lower MI (some guidance suggests that precipitation
with this wave is confined into northern Lower MI or the Upper
Peninsula, some further south).These two waves phase between 18z Sat-
00z Sun, which makes the forecast very tricky. The NAM12 appears to
keep the forcing with the northern wave more disjointed from the
southern wave (qpf further north), and lags more in timing than the
other guidance, and the southern wave seems to take a slightly more
ENE track, with the best moisture transport shunted further south
and east than the rest of the guidance. The others have the waves
somewhat merging over our CWA/Lower MI by 21z-00z, and a higher QPF
than the NAM. I went with the majority guidance/consensus pops in
general for now, with more confidence in the timing vs. the specific
precipitation type and amounts-particularly further north. A 175
knot straight jet streak in the upper levels builds overhead towards
18-00z, with a broad area of divergence developing at the nose. The
surface low does deepen accordingly and advections increase in the
low-mid levels accordingly as it heads eastward, with the best
forcing just across our E-SE in the late afternoon/evening then
rapidly exiting. The tricky part will be how far north the warm air
can get, and if the strongest forcing comes together at the time
when the LL moisture is available.
Lowered snow totals slightly in the north as much of the guidance
appears to have the warm nose/moisture transport reaching into our
Michigan counties at least briefly before being shunted south by the
northern wave/more ENE track. This solution brings in more of a
snow/sleet/freezing rain mix during the peak forcing-so have around
0.5 to 1.2 inches of snow accumulation north of I 80-90, and less
than 0.5 inch elsewhere. Ice accumulation is even trickier, with dry
air/high pressure in place at the start in the northeast. How well
we saturate the dgz and how far north the warmer air gets will
greatly impact the totals. For now, have ice accumulations the
greatest along US 30--with my confidence greater east of US 31.
There is low confidence in ice accumulation totals at this point-for
planning purposes just focus on the general area of concern at this
point. Hopefully the 12z guidance comes into better agreement
regarding the waves phasing and the saturation/temperature profiles.
Late Saturday night into early Sunday morning we will see some lake
effect cloud cover, and potentially some light snow in NW Wind
favored snowbelts. However, expect limited accumulation given high
pressure builds in rapidly in the wake of the exiting system,
crashing inversion heights. Moisture also dwindles rapidly.
High pressure builds in for Sunday into Monday night, with variable
cloud cover, light winds, and highs in the 30s and lows in the teens
and 20s.
Beyond then, we have a couple of noteworthy chances for snow, the
first on Tuesday into Wednesday morning as another surface low lifts
in from the southwest and skirts our area. Have 30-40 percent
chances for snow at this point, as some of the guidance shunts the
low southeast enough that we may not see any precipitation.
The next system brings 30 to 50 percent chances of snow for
Wednesday afternoon into Thursday, with a decent portion of the
guidance bringing a surface low from TX into the IN/KY/OH/VA area by
6z Thursday. This has us on the backside of the system, with our
area in the deformation zone. Definitely something to watch through
this week. Highs will be in the mid-upper 20s and low 30s, and
overnight lows will fall into the teens and 20s.
&&
.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 618 AM EST Fri Feb 7 2025
Last evening's gusty winds continue to relax as surface high
pressure noses into the area. Mid level cloud decks arrive this
morning and continue into the day, but enough dry air in the low
levels keep flight conditions in VFR through the forecast period.
West northwest winds continue through much of the forecast period,
but will be more easterly by Friday evening.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for LMZ043-
046.
&&
$$
DISCUSSION...MCD
AVIATION...Roller
Source:
IWX issues Area Forecast Discussion (AFD) at Feb 7, 6:18 AM EST---------------
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