IND issues Area Forecast Discussion (AFD) at Dec 30, 9:31 AM EST
794
FXUS63 KIND 301431
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
931 AM EST Mon Dec 30 2024
.KEY MESSAGES...
- Rain again tonight into Tuesday, potential for 0.50-1.00 inches
of rainfall north of I-70
- Noticeably colder after mid-week with single digit wind chills
possible towards the weekend as arctic air builds in
- A chance for light snow Thursday night into Friday
- Potential for a significant winter storm in the Midwest Sunday
into Monday
- Bitter arctic cold in the week 2 period
&&
.FORECAST UPDATE...
Issued at 931 AM EST Mon Dec 30 2024
GOES-16 visible loop was showing some breaks in the stratus over
mainly southwestern sections of the forecast area, where some patchy
light fog has developed per recent obs. Elsewhere, Hi-Res soundings
are showing very shallow moisture hanging around in the boundary
layer beneath a strong inversion. This suggests more clearing is
possible but confidence is not low of that happening this time of
year with the low sun angle. Even if the low clouds break up to a
degree, mid and high clouds will be streaming in overtop the
Missouri Valley ridge and ahead of a Rockies and High Plains trough.
A weak surface pressure gradient has resulted in light west to calm
winds this morning. As the surface ridge departs to the southeast
and the trough gets closer, winds will shift to the southwest and
south and slightly increase which should allow for late day
temperatures to reach the middle 40s north to lower 50s south which
is some 10 to 15 degrees above normal.
&&
.SHORT TERM (Today and tonight)...
Issued at 304 AM EST Mon Dec 30 2024
Today...
Modest zonal ridging will attempt to build into central Indiana
today in between a potent system slowly departing over the eastern
Great Lakes and another approaching from the Plains. The reality
will be damp, although mainly rain-free conditions early today.
Patchy fog forming through pre-dawn hours amid a subtle decrease in
wind speeds...may be locally dense, especially across northern zones
that saw upwards of 2 inches of rain yesterday. Expect any fog to
linger through the morning rush hour and perhaps even into mid/late
AM hours with winds failing to increase under subsidence.
While there is still a small chance for partial clearing today, it
appears this would be limited to only a few breaks this afternoon,
and likely contained to northeastern zones if anywhere. Above
normal readings will continue for a couple more days, albeit not as
mild as the recent trend. Expect highs today ranging from the mid-
40s across the region's northern third, to low 50s for Sullivan to
Columbus, and points south.
Monday night and Tuesday...
The next weather system will cross the Midwest tonight into Tuesday
bringing only rain to central Indiana through Tuesday afternoon. Low
pressure already beginning to eject from the Colorado High Plains,
will track eastward and bring at least light showers late this
evening to western counties. Main slug of rain to fall after
midnight tonight (and through morning rush hour at least north of I-
70) as the surface low tracks along I-70 from near St. Louis to over
the Indianapolis Metro. Periods of lighter rain/drizzle to continue
over the local region during midday and afternoon hours Tuesday...as
the main forcing departs to our NE while a trough lingers below
ample mid-level moisture into Tuesday evening.
Storm total rainfall is expected to range from around 0.25 inches
across far southern zones to around a half-inch along the I-70
corridor, to 0.70-0.90 inches over the region's northern third. This
light to moderate rainfall, will combine with already near-saturated
soils to maintain Action Stage levels along several Wabash River
points through later portions of the forecast period...and to a
lesser extent contribute to the potential for Minor Flooding on
lower portions of the White River as early as Tuesday afternoon.
Moderate, mainly southeasterly breezes will prevail through early
Tuesday as the circulation approaches...with more robust,
northwesterly gusts to 20-30 mph expected as showers taper off late
Tuesday. The overall damp conditions will bring a lower diurnal
spread, with lows Monday night around 40-45F and highs Tuesday
(morning) near 45-50F before readings closer to 40F settle in by
late day. The normal max/min at Indianapolis early this week is
37/23.
&&
.LONG TERM (Tuesday through Sunday)...
Issued at 304 AM EST Mon Dec 30 2024
Overview:
A complex, active and much colder weather scenario is expected to
unfold across Central Indiana over the next several days. The long
anticipated significant shift in the upper air pattern will develop
and help usher in the arctic air and wintry precipitation
potential. This cold will likely persist through at least mid to
late month before another shift back to seasonably mild becomes
possible.
New Years Eve Night
Deformation zone behind departing low pressure will move across most
of central Indiana Tuesday evening. Models have bulk of precipitation
exiting rather quickly as thermal profiles cool enough to support
transition to all snow. Low level temperatures also look to stay
above freezing until threat of precipitation ends toward midnight.
Would not be surprised if a brief burst of wet snow occurs with
this deformation area, especially over eastern locations, but with
warm ground temps above freezing will not add any accumulations
at this time but will need watch this period.
New Year Day through Thursday
Winter arrives to begin the New Year as much colder air sweeps into
the area under northwest flow and weak high pressure. However, this
initial shot of cold air will simply bring temperatures down to
near normal values, but given recent mild stretch of weather it
will feel quite cold for any outdoor New Year Day activities.
Apparent temperatures look to be in the teens through the day. It
will remain dry during this period.
Thursday Night through Sunday
A fast moving short wave is now forecast to cross the region
Thursday night into early Friday, aided by left front quadrant of
approaching upper level jet max. Models have struggled with timing
of this weak wave and uncertainty remains high in regards to snow
chances and amounts. What we know is moisture is limited and
thermal profiles support snow. Pops right now are in the low chance
category, a function of the model discrepancies in timing and QPF.
This is reasonable for now until better agreement in models develop.
Second round of cold moves in behind this short wave for the weekend
with even colder air to follow beyond the day 7 period. Highs will
only be in the 20s with lows in the teens and apparent temperatures
into single digits and possibly flirting with sub zero for brief
periods late in period.
Models continue to depict a significant winter storm in the Sunday
to Monday time frame across the Midwest and Ohio Valley. Model
differences continue but the 00z global model runs of the GFS and
EC have come into a little better agreement with synoptic pattern.
Still a long ways out and many changes expected. Right now all pcpn
types would be in play, including ice and sleet. However, as we have
pointed out many times, way too much lead time and uncertainty for
any specific detailed forecasts. Disregard any snow and ice
forecasts at this time but remain aware and stay informed from
reliable meteorologists as the week progresses and details begin to
clear by late this week.
Days 8 to 14
Well below normal temperatures expected with high confidence during
this period. Coldest air of the winter season and we could see highs
struggle to leave the single digits and lows near or below zero. If
significant snowpack develops from the aforementioned winter storm,
even colder temperatures would be on the table in this period. Long
range models due show a piece of the polar vortex breaking off
and sinking into lower Canada, aiding in the development of Hudson
bay low and sustain northwesterly flow aloft driving the cold air
southward. However, models do not show a classic pure meridional,
cross polar flow which is often needed for the extreme, record
breaking cold. However, at this time it does look like a good
January arctic blast that needs to be prepared for by everyone.
Now would be a good time to begin review winter storm and extreme
cold checklists and getting together recommended emergency
supplies in anticipation of very cold temperatures.
$$
&&
.AVIATION (12Z TAF Issuance)...
Issued at 618 AM EST Mon Dec 30 2024
Impacts:
- Low MVFR/possible high IFR ceilings into this afternoon
- Winds under 10KT backing from west to southeast by 21Z today
- Rain later tonight-Tuesday to bring MVFR/IFR CIG...MVFR VIS
Discussion:
A somewhat stagnant pattern today under subsidence between weather
systems will promote continuation of low-MVFR/high-IFR ceilings
through much of today. Hoping low-VFR returns within 18-21Z but
only moderate confidence with this timing...and a chance of MVFR CIG
lasting longer at KLAF into the evening. KIND decks may actually
scatter out later this afternoon near the timing of the return of
VFR, but confidence with this potential partial clearing is low.
Next weather system will bring rain through the second half of the
TAF period...arriving from west to east around 02Z-05Z this evening.
Conditions will deteriorate yet again with CIGs falling to low MVFR
by 08Z, and widespread IFR expected by the end of the TAF period.
Risk of visibility reduction from patchy fog at KHUF/KLAF appears to
be mitigated so far by winds around 4-8KT early this morning. MVFR
VIS is still possible along the Wabash through 15Z but confidence
too low to include in either TAF.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...MK
SHORT TERM...AGM
LONG TERM...Lashley
AVIATION...AGM
Source: IND issues Area Forecast Discussion (AFD) at Dec 30, 9:31 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412301431-KIND-FXUS63-AFDIND)
---------------
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!