Area Forecast Discussion
National Weather Service Indianapolis IN
952 AM EST Wed Feb 10 2021
.UPDATE...
The Near Term section has been updated below.
.SYNOPSIS...
Issued at 408 AM EST Wed Feb 10 2021
Today will bring chance for snow across the area with total
accumulations of 1 to 2 inches possible in northern central
Indiana and up to an inch in the south. More chances for snow are
possible this weekend and again early to mid next week. Below
normal temperatures will continue throughout the forecast period
with the start of next week set to be some of the coldest days.
&&
.NEAR TERM /Today/...
Issued at 952 AM EST Wed Feb 10 2021
Going forecast is in fine shape and required only minor adjustment -
regional radar mosaic shows plenty of light returns across the area
but little reaching the ground just yet as dry low level air causes
some evaporation/sublimation of precipitation. Should see returns
expand in coverage and intensity as the day wears on per high res
model solutions, and this is in line with the going forecast.
Previous discussion follows.
Issued at 408 AM EST Wed Feb 10 2021
Radar and surface observations show that scattered light
precipitation is starting to move into southern Indiana as of the
early morning hours. This precip will expand northward through the
morning.
An upper jet over the Ohio Valley will interact with a baroclinic
zone and subtle isentropic lift in the mid to low levels that is
bringing in the precipitation today. Warm moist air from the south
will overrun cold northerly air at the surface. For most of central
Indiana, temperature profiles will remain entirely below freezing
but in the south freezing rain may mix in at times where the warm
nose aloft has a better chance of getting above freezing. The more
significant impacts with this system are slated to stay further
south, for our neighbors in Kentucky. While our souther tier of
counties could see some ice mix in, we are not expecting much in the
way of ice accumulations. Will continue to monitor conditions
through the day, keeping an eye on how far north above freezing
temperatures reach. If they do push further north than currently
forecasted, icing impacts could creep into our forecast area.
Later in the day, a deformation band is expected for form north of I-
70. This band will create an area of enhanced lift and higher QPF
and snowfall totals, of 1 to 2 inches, for the northern half of the
forecast area.
At the surface, temperatures today will range from the low 20s in
the north to the upper 20s in the south.
&&
.SHORT TERM /Tonight through Thursday Night/...
Issued at 408 AM EST Wed Feb 10 2021
The system impacting the region today will start to slowly push
out of the area tonight into Thursday. Light snow will continue to
be possible into Thursday but with minimal moisture, additional
snow accumulation is not really expected beyond tonight. Models
show that the band of moisture will stay to the south in Kentucky
and Tennessee during the short term period as the surface boundary
becomes more stationary across the SE states.
Any lingering precipitation should completely move out by tomorrow
night as the boundary pushes further SE and surface high pressure to
the NW stretches into the area and dries up the atmospheric column.
Below normal temperatures will continue through the period with
highs in the 20s and lows in the teens.
&&
.LONG TERM /Friday through Tuesday/...
Issued at 240 AM EST Wed Feb 10 2021
The main storyline for the extended remains focused on the continued
cold and active pattern for much of the eastern part of the
country...with another surge of bitterly cold air for the weekend
into early next week as a piece of the polar vortex swings across
the Great Lakes along with the potential for additional wintry
mischief into early next week.
A continued blocky and amplified flow pattern aloft will keep the
region stuck in a pattern conducive for continued cold and multiple
opportunities for snow into early next week. The two lobes of the
polar vortex over central Canada late this week will eventually
coalesce then swing south and east across the Great Lakes and
northeast by early next week...carving out a deeper parent trough
across the eastern half of the country and essentially opening the
door for a renewed push of bitterly cold air to advect south
into the region for this weekend and early next week.
At the surface...the Ohio Valley will remain between a large area of
strong high pressure dropping down the east side of the Canadian
Rockies and a stagnant frontal boundary over the Southeast states
early in the period with the high becoming the primary feature
influencing our weather by late Saturday into early next week.
Extended model guidance continues to struggle with the level of
phasing between energy diving south with the PV lobe and just how
much it interacts with the leftover boundary extending from the Gulf
Coast to the Mid Atlantic region. At this point...think potential
certainly exists for some snow at times over the weekend but leaning
towards a less phased setup with lighter snows and accumulation.
A more interesting setup begins to take shape early next week as the
PV lobe kicks out to the northeast and focus turns towards an upper
wave amplifying over the Intermountain West this weekend. As this
feature traverses east into Monday and Tuesday...there does appear
to be a higher ceiling for energy phasing aloft between the polar and
subtropical jets and subsequently...a potential for a deeper surface
wave over the region. With the strong surface high still present
north of the Ohio Valley...there is a threat for a more substantial
winter storm to impact the area with snow and/or ice as plenty of
the remnant arctic airmass from the weekend remains. Another factor
that will likely influence how this plays out is the position of the
southeast ridge and whether it flexes enough to draw warmer air
aloft into the region above a shallow cold airmass. There are a lot
of moving parts here and we remain several days out...but the
potential for a higher impact winter storm does appear to be growing
for early next week.
Temperatures over the weekend will rival the cold blast from this
past weekend with highs bottoming out in the single digits and teens
on Sunday and subzero lows possible in some parts of the forecast
area both Saturday and Sunday nights. Some temperature recovery will
develop by early next week but the overall temperature trend will
remain well below normal for mid February.
