Scientific Forecaster Discussion
fxus63 kind 171841
Area forecast discussion
National Weather Service Indianapolis in
141 PM EST Tue Jan 17 2017
the long term section has been updated below.
issued at 217 am EST Tue Jan 17 2017
Unseasonably warm weather is expected the next few days as
southwesterly flow within the atmosphere continues to keep
Arctic...winter air at Bay in Canada. Low pressure over Illinois
will quickly exit Indiana today...allowing high pressure over the
Central Plains to build across the Ohio Valley. Clouds are
expected to linger across the area as the high pressure system
The high will bring cloudy but mainly dry weather to central
Indiana on Wednesday...before the active weather pattern resumes
of the end of the work week and the weekend. At that
time...several strong upper level weather systems will push
through the Ohio Valley bringing more chances for periodic
showers...but above normal temperatures.
Near term /today/...
Issued at 217 am EST Tue Jan 17 2017
Surface analysis early this morning shows low pressure over
Illinois...with cyclonic lower level flow in place across Indiana.
A cold front trailed the low...stretching south across southeast Missouri
into Arkansas. Water vapor imagery showed a dry slot intruding in
to the system across southern Illinois and central Indiana. Water
vapor also shows the highly amplified and unusual pattern fro
January...with a deep trough across the Western Plains and
southwest with southwesterly flow in place across Texas into the
Ohio Valley. Radar shows much of the precipitation exiting central
Indiana...with a thin band ahead of the cold front over central
Indiana. Overall...best forcing appears to have left the area as
dry air on the previously mentioned dry slot begins to intrude in
to the area.
Forecast soundings today show drying within the column as the
surface low is expected to pull farther northeast to the Great
Lakes. Time heights also show the departure of deep moisture...the
the continuation of lingering lower level moisture through the day
and into tonight.
Aloft the GFS shows Indiana caught between one departing short
wave associated with the departing low and and another arriving
wave within the flow aloft. Thus overall...forcing today remains
weak. Given the lower level clouds a sprinkle of drizzle cannot be
ruled out...but will aim for a cloudy day and try to contain pops
to the morning hours with the departure of the low to the north.
As for temps will use a blend and trend to or below given the
expected clouds and slight cold air advection.
Short term /tonight through Thursday night/...
Issued at 250 am EST Tue Jan 17 2017
Time heights and forecast soundings continue to keep ample lower
level moisture lingering across the the region through Wednesday
night. The previously mentioned second short wave looks to pass
across Indiana and the southern Great Lakes tonight...but forecast
soundings fail to show deep moisture. At the surface...high
pressure over the Central Plains looks to be building across the
Ohio Valley. Thus with a few ingredients for precip but not
everything coming together...including anti-cyclonic flow in the
lower levels...will only include a low chc pops for very light
precip. Given the expected clouds will trend lows tonight at or
warmer than a superblend.
GFS and NAM suggest that the large surface high pressure system
will slowly push through the Ohio Valley from Wednesday and
Wednesday night. Forecast soundings and time height sections keep
the all too familiar pattern of trapped lower level
saturation...indicating that plenty of clouds will continue to
linger across the area. Aloft...the previously mentioned second
short wave departs by Wednesday morning...allowing for ridging to
build across central Indiana and the Ohio Valley ahead of the
next strong upper level weather system over the Western Plains.
Thus will continue the mainly mostly cloudy forecast through
Wednesday night. Will stick close to a blend on temps.
Our next weather system will begin to move into the area on
Thursday and Thursday night. The surface high pressure system
will depart to the east allowing a warm front to push toward
central Indiana from the southwest. Aloft...strong forcing arrives by
late Thursday afternoon and Thursday night as the GFS shows a
strong upper low pushing into Missouri and beginning to influence
the Ohio Valley. Thus will begin to ramp pops higher as the day
progresses on Thursday into Thursday night.
Long term /Friday night through Monday night/...
issued at 141 PM EST Tue Jan 17 2017
Well above normal temperatures and period rain showers will be
featured this weekend and early next week. Models are in pretty good
agreement on the overal synoptic features, so regional blend looks
Negatively-tilted upper trough will be over the lower Great Lakes
Friday night, and a trailing upper low will lift north over the
plains, well west of the forecast area. This should result in mostly
dry weather over central Indiana through Saturday. Still, would not
rule out a stray shower or two Saturday with good return flow and
impulses in southwest flow aloft. After that, a strong Southern
Plains upper low will lift northeast across the Ohio Valley on
Monday. This will bring more shower chances to the area starting
Saturday night. Activity will be widespread over some locales by
Sunday and start to decrease in coverage Monday night in the wake of
Aviation /discussion for the 17/1800z taf issuance/...
Issued at 1238 PM EST Tue Jan 17 2017
Rain has subsided across the area, but lingering MVFR/IFR ceilings
will continue for the majority of the taf period. Klaf could also
dip into the LIFR range at times tomorrow morning since it will be
more directly impacted by a short wave moving through the lower
Great Lakes region tonight. Meanwhile, winds will generally be
west/southwesterly at 5 to 11 kts and up to 14 kts at kind this