IWX issues Area Forecast Discussion (AFD) at Nov 5, 5:54 AM EST815
FXUS63 KIWX 051054
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
554 AM EST Tue Nov 5 2024
.KEY MESSAGES...
- Winds from the south will gust up 40 to 45 mph today with
record warmth expected.
- Light rain over northwest Indiana will shift eastward late
this afternoon and into the overnight with 0.25-0.5 inches
expected for most areas.
- Dry conditions return Wed-Fri but temperatures will remain
above normal.
&&
.DISCUSSION...
Issued at 328 AM EST Tue Nov 5 2024
Challenging forecast today with respect to wind headlines. Upper
level jet core is now finally pulling the upstream trough NE with
associated frontal boundary making slow eastward progress...pushing
through our area during the evening hours today. Low level gradient
continues to tighten today with winds of 50-60 kts in the 900-850mb
layer. The question, as always, is will we actually be able to mix
into that in a stable, WAA regime. Guidance members are displaying
typical biases with GFS and HRRR suggesting much deeper mixing and
stronger gusts than NAM and other hi-res solutions. Past performance
suggests the answer is likely somewhere in the middle which would
point to wind speeds right around 40 kts at the top of the boundary
layer. The issue is that PBL mixing alone is not 100% efficient,
particularly in a regime that favors rising motion. This leads to
isolated/brief pockets of stronger gusts (mainly during the mid-
morning mix out) but not a widespread or long duration of the
stronger gusts. Further complicating matters is degree of clouds and
precip in our western zones. Hi-res models show just SCT showers
scraping our western counties during the day today but this is
enough to doubt deeper mixing that our eastern zones will likely see
given less precip and clouds. And one final note is that typically
the strongest gusts occur with the actual frontal passage and
associated pop of isentropic descent. This front is fairly broad and
diffuse though with a weakening gradient by the time it passes
(mainly after sunset). Still, a few models do show a quick pop of
stronger gusts during the evening hours along/behind the front that
could approach 40 mph. Given the uncertainties noted will simply
stay the course for now with current advisory timing and location.
Day shift can make adjustments as necessary with the benefit of more
observational evidence.
By contrast, the precip forecast is relatively straight-forward.
Precip will continue to clip our W/NW zones through the morning with
isolated thunderstorms as currently observed. This activity is
expected to dwindle somewhat around midday but latest radar and
satellite trends suggest even hi-res models are trying to retrograde
this precip a bit too much and think at least SCT showers will
continue through the day west of US-31. Primary front then passes
west-east roughly 22-06Z with a solid line of showers expected. As
has been discussed, the parent trough will be rapidly weakening by
tonight with a sheared out vort max passing largely to our north.
Associated front is not well-defined but the resident airmass is a
moist one and there appears to be sufficient low level convergence
to support light rain (roughly 0.25 inches) for most locations right
along the front this evening. Continue to leave out any thunder
mention as profiles remain too stable to warrant a mention.
Rest of the week remains quiet weather-wise. Strong jet and attendant
PV anomaly currently digging into the Rockies will form a cutoff low
near the Mexican border by Thu. This causes midlevel ridging to
build over the Upper Midwest through Fri as another trough slides
from Ontario to the North Atlantic. Increasing subsidence and very
strong dry air advection will yield increasing sunshine by Thu and
Fri. Incoming airmass is not cold either and highs will remain
around 60 which is roughly 10 degrees above normal. Upper low will
eventually eject NE this weekend with another round of rain and wind
likely, mainly Sat night and Sunday.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 551 AM EST Tue Nov 5 2024
This morning, VFR to MVFR ceilings are expected at KFWA and
MVFR to IFR ceilings are expected at KSBN. Showers will remain
scattered throughout the morning, gradually diminishing by the
afternoon. Expect a few hours of drytime this afternoon
(especially east of KSBN), before widespread rain arrives along
a cold front by the evening. Additionally, expect strong LLWS
to 40 to 50 knots through 14Z. At the surface, depending on how
much the strongest winds can mix down, southerly wind gusts
will be quite breezy throughout the day. The strongest wind
gusts (up to 40 knots are possible at KSBN and up to 35 knots at
KFWA) will likely occur this morning and afternoon, although
winds will remain elevated through the evening hours as the
front moves through. Rain will be done between 05-08Z Wednesday.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory until 4 PM EST /3 PM CST/ this afternoon for
INZ005-006-008-012>015-017-020-022>024-103-104-116-203-
204-216.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for LMZ043-
046.
Gale Warning until 11 PM EST this evening for LMZ043-046.
&&
$$
DISCUSSION...AGD
AVIATION...Johnson
Source:
IWX issues Area Forecast Discussion (AFD) at Nov 5, 5:54 AM EST---------------
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