Scientific Forecaster Discussion
fxus63 kind 201354
Area forecast discussion
National Weather Service Indianapolis in
954 am EDT Thu Jun 20 2019
the near term section has been updated below.
issued at 203 am EDT Thu Jun 20 2019
Low pressure over Illinois is expected to cross and exit Indiana
today. This will bring showers and isolated thunderstorms to much
of central Indiana today before ending this afternoon.
High pressure will quickly build across the region tonight and
exit the area on Friday...giving US some dry weather and reprieve
from the recent rains.
A set of upper level weather disturbances are expected to pass
across the area on Friday night and again on Saturday and then
again on Sunday. Although all day soaking rains are not
expected...these quick moving systems will keep chance for rain in
the forecast all weekend.
Wet weather looks to continue into next week.
Near term /rest of today/...
issued at 950 am EDT Thu Jun 20 2019
Cold front currently moving through the local area, with shower
activity along and ahead of the front. Short term model data
suggest this front will pass off into Ohio by the early afternoon
hours, although the upper trough may lag behind the front a bit.
Will keep the higher pops over the northeast zones into the early
afternoon hours, tapering them down farther southwest. Decided to
keep some pops going well into the afternoon hours after the
frontal passage, due to the lagging upper trough.
Will be trimming back the Flash Flood Watch for areas west of the
current frontal position.
Will also lower the highs today a few degrees, given decent cold
advection and cloud cover upstream.
Previous discussion follows.
Surface analysis early this morning shows an area of low pressure
over Illinois and Indiana. Radar shows a band of thunderstorms and rain over
ind....with wrap around moisture in place across Northwest Indiana and
northern Illinois. A warm and humid air mass remained in place across
Indiana with dew point temps in the mid 60s.
GFS and NAM show a short wave over Indiana pushing east through
the day. GFS and NAM show the surface low quickly moving across
Indiana this morning before exiting this afternoon. Lower level
flow looks to remain cyclonic this afternoon as time heights
continue to show plentiful lower level moisture through the
afternoon. Forecast soundings show reachable convective
temperatures and with some cold air advection arriving in the
wake of the low...some instability showers in the wrap around
flow cannot be ruled out. Will trend pops lower as the morning
progresses...but trend back upward this afternoon due to possible
afternoon convection. As for temps will trend highs at or below
Given our ongoing rain...will continue Flash Flood Watch for now.
Short term /tonight through Saturday night/...
Issued at 203 am EDT Thu Jun 20 2019
GFS and NAM show a quick moving area of high pressure moving
through the area tonight and Friday as ridging aloft builds across
the area. Forecast soundings dry out tonight and Friday with
unreachable convective temperatures on Friday. This should lead
to dry weather through Friday morning. Will trend partly cloudy
at that time and stick to the blend on temps.
On Friday afternoon and Saturday afternoon the GFS hints at a pair
of short wave riding the ridge and pushing across central Indiana.
A warm front is approaching from the southwest at the surface but
overall the set-up for rain is much less favorable than it has
been. A warm and humid air mass really doesn't arrive until
Saturday and forecast soundings fail to show deep saturation. Thus
these systems are just not well organized...but chance pops will
be warranted each afternoon as these features pass. Again will
stick close to the blends on temps.
Long term /Sunday through Wednesday/...
issued at 254 am EDT Thu Jun 20 2019
The 00z GFS and European model (ecmwf) and ensembles in good agreement that an upper
ridge will move to the east of the area on Saturday. As it does, a
surface front will lift northeast over central Indiana, leaving the
area in the warm sector. In addition, a pair of upper waves will
move though Sunday and early next week, in the wake of the ridge.
This will keep the threat for thunderstorms around through at least
next Tuesday. More heavy rain and flooding are possible at times.
National blend normal to slightly above normal temperatures in the
lower to middle 80s seem reasonable as convection and cloud cover
battle it out with the warm, moist and unstable airmass.
Aviation /discussion for the 20/12z taf issuance/...
issued at 700 am EDT Thu Jun 20 2019
The GFS lamp and sref both support IFR ceilings through 14z-16z.
Then, good confidence that ceilings will improve to MVFR and
possible VFR after 20z away from thunderstorms. Enough on radar for
vcsh to start off and then with better coverage possible this
Winds will shift from southwest to northwest 5 to 11 knots.
Flash Flood Watch until 8 PM EDT this evening for inz031-038>042-