IWX issues Area Forecast Discussion (AFD) at Nov 9, 6:46 PM EST722
FXUS63 KIWX 092346
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
646 PM EST Sat Nov 9 2024
.KEY MESSAGES...
- Sprinkles or light rain will become more widespread overnight
into Sunday morning.
- Drier conditions return for Monday and Tuesday before another
system brings a chance for showers.
- Temperatures should be near or above normal through the period.
&&
.DISCUSSION...
Issued at 300 PM EST Sat Nov 9 2024
Feature of interest for the next 24 hours or so is a well defined
closed upper low in SW Nebraska that will move NE reaching central
WI by 18Z Sun. Increasing isentropic lift ahead of the warm front
was generating pockets of light rain and rain showers from SE Iowa
into NE Illinois. Initial returns having to work rather hard to
overcome a very dry layer as noted on 12Z KILX sounding, but are
occasionally reaching the ground as sprinkles or brief light rain,
which is barely measuring. The degree of lift and lowering CPDs
(Condensation Pressure Deficits) will increase after 00Z from SW to
NE with the most pronounced push happening between 6Z and 15Z Sun.
Mixing ratios of 8 G/KG and PWATS of 1.5" or greater, combined with
some fairly stout flow at times perpendicular to isentropic surfaces
point towards at least a window of numerous showers late tonight
into Sunday, with challenges being faster movement of the showers
and the overall system as well as degree/location of elevated
instability. Overnight, some models are suggesting pockets of higher
QPF, maybe in the 0.50" or more range where some of the stronger
convective elements possibly materialize. However, forecasted QPF
will not capture these finer details and more than likely most areas
will see closer to 0.25" to maybe 0.33". Regardless of how much, any
rainfall is welcome. A few rumbles of thunder cannot be ruled out
with showalter values dropping below zero by 9Z Sun in SW areas
spreading east and leaving by 14Z. Severe weather is not expected
despite favorable shear profiles.
A weak cold front (more of a subtle wind shift and lowering of
dewpoints) will occur from west to east during the afternoon,
bringing any precipitation to an end. Prior to the arrival of the
front, temperatures will likely climb into the 60s, but leave just
as quick as it arrives as modest CAA starts behind the front into
Sunday night and Monday. Another decent northern stream wave will
pass by to the north with its only contribution to our forecast
being another cold front dropping through late Monday into Monday
night to bring colder air that will send our temps to slightly below
normal levels (Highs Tuesday in the upr 40s to low 50s).
A strong upper low, located over the Gulf of Alaska will drop SE to
start the work week, with increasing upper level ridging commencing
for the area starting Tuesday. The low will initially open and
become more progressive, while attempting to phase with a weak upper
low over the Baja of California. Previous model runs suggested this
merger and also increasing upper level winds would cause the upper
trough to close off again, but 00Z and even 12Z Sat runs leaning
against that. This appears to be having some influence on the amount
of moisture to be advected in Wed into Wed night with PWATs more
subdued (maybe touching 1"). Conservative approach on pops remains
warranted for this period limiting to chc for now. In addition, the
wrap around precip that was suggested to linger Thu/Thu night looks
less impressive as well, but will maintain some slgt chc pops.
An elongated trough will set up from California to NE North Dakota
for the remainder of the period, with our region returning to a more
southerly flow and temperatures making a run well into the 50s and
probably near 60. Some pops have been populated by the model blends,
but given the stronger features will remain to the west and south,
suspect these will be removed over time.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 646 PM EST Sat Nov 9 2024
Ejecting upper low will bring a period of rain and at least IFR
conditions late tonight into Sunday morning. Light rain may
begin earlier but ceilings will not drop until roughly 08-09Z.
Brief LLWS is possible 09-12Z, especially at KFWA which will
briefly be in the warm sector. Latest guidance continues to be
relatively consistent with potential for brief LIFR roughly
12-15Z Sun morning but will hold with just a PROB30 for one more
cycle before introducing it as the prevailing conditions.
Conditions also improve rapidly behind the cold front Sun
afternoon with VFR expected.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 1 PM Sunday to 7 AM EST Tuesday for
LMZ043.
Small Craft Advisory from 1 PM Sunday to 1 AM EST Monday for
LMZ046.
&&
$$
DISCUSSION...Fisher
AVIATION...AGD
Source:
IWX issues Area Forecast Discussion (AFD) at Nov 9, 6:46 PM EST---------------
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