Scientific Forecaster Discussion
fxus63 kind 181038
Area forecast discussion
National Weather Service Indianapolis in
638 am EDT Tue Jun 18 2019
the aviation section has been updated below.
issued at 159 am EDT Tue Jun 18 2019
A lingering frontal boundary is expected to remain in place across
southern central Indiana today. An upper level weather disturbance
is expected exit the area this morning...allowing showers and
storms across the southern parts of the forecast area to depart.
However...the warm and humid air mass in place across central
Indiana may result in some scattered showers and thunderstorms
this afternoon and evening.
Another area of low pressure is expected to push toward Indiana on
Wednesday...and pass across the state through Thursday. This will
result in more wet weather with showers and storms on Wednesday
Some dry weather looks possible on Friday before chances for
showers and more storms returns this weekend.
Near term /today/...
issued at 159 am EDT Tue Jun 18 2019
Surface analysis early this morning shows a stalled frontal
boundary stretching from southern Illinois across Indiana to Ohio
and northwest PA. Water vapor shows a plume of tropical moisture surging
northward from Mississippi and Alabama...into the Ohio Valley and
then northeast to PA and wny. Radar mosaics shows showers and
storms within the plume drifting northeast...exiting with current
short wave as the moist flow is expected to shift farther
east...away from Indiana.
Thus a brief change in the upper flow will limit some of the deep
moisture and forcing today...however a warm and humid air mass
remains in place at the surface along with the pesky lingering
frontal boundary. Forecast soundings this afternoon show
attainable convective temperatures...mainly south...with more
limited cape available and pwats have fallen to around 1 inch.
Hrrr suggests diurnal convection during the peak heating hours
this afternoon. Thus will try and trend toward a dry morning
followed by chances for showers and storms across the south this
afternoon and into the evening. Northwest areas...laf and okk will have
the lowest chances due to proximity to the front.
Finally...cameras across the area are showing spots beginning to
fog up. Given our location on the north side of the front...the
plentiful lower level moisture and the limited mixing
overnight...an ideal set-up for fog is in place. Will watch obs
closely and should enough spots get below a quarter mile...will
not hesitate with a dense fog advisory this morning.
Short term /tonight through Thursday night/...
Issued at 159 am EDT Tue Jun 18 2019
After diurnal convection ends across southern parts of the
forecast area this evening...wet weather looks to return to
central Indiana late tonight and continue through Thursday. The
GFS and NAM both suggest another strong upper wave pushing out of
the plains states and pushing across central Indiana on Wednesday
before exiting the state on Thursday. Again...several short waves
ahead of the upper trough will pass on Wednesday before the main
forcing passes on Thursday. Within the lower levels...our pesky
frontal boundary remains...providing a focus for precip. Time
heights are already hinting at deep moisture and excellent
moisture by 18z Wednesday. Forecast soundings shows deep moisture
into Thursday evening as pwats surge over 1.72 inches. Thus with
plentiful ingredients in play once again...will trend pops during
this time at or above the nbm. Given the expected rain...a new
Flash Flood Watch may be needed again soon. As for temps through
the period will trend highs cooler and lows warmer than the nbm.
Long term /Friday through Monday/...
issued at 308 am EDT Tue Jun 18 2019
Good confidence the unsettled weather will continue through much
of the long term.
Models and ensembles similar in bringing an upper ridge over the
area on Saturday. The ridge will force a front to lift northeast as
aa warm front and move across central Indiana Saturday and Saturday
night. After that, several waves will move through the area ahead of
an approaching upper trough. This trough will move through early
next week as it flattens. The result will be more thunderstorms with
the continued potential for heavy rain and flooding.
National blend highs near or slightly above normal look reasonable
by Saturday as the area becomes firmly entrenched in the warm sector.
Aviation /discussion for the 181200z taf issuance/...
issued at 638 am EDT Tue Jun 18 2019
GFS lamp and trends suggest IFR conditions will improve to MVFR and
better after 14z-15z. Could see some showers, except at laf and
especially 17z-02z as the atmosphere destabilizes. Confidence is
good on the trends if not exact timing.
Winds will be light and variable or calm.
Flash Flood Watch through this afternoon for inz037-039-045>049-