Scientific Forecaster Discussion
fxus63 kind 202028
Area forecast discussion
National Weather Service Indianapolis in
428 PM EDT Thu Jun 20 2019
the aviation section has been updated below.
issued at 211 PM EDT Thu Jun 20 2019
Early afternoon surface analysis shows low pressure over southeast
lower Michigan with a cold front that extend south through western Ohio
and eastern Kentucky. Northwest surface flow behind the front has dried
out the air mass over central in this afternoon as dew points have
lowered into the low 60s with upper 50s upstream over Illinois and Iowa.
GOES-16 visible satellite imagery shows clearing for the most part
over west central and southwest in and some more clearing over Illinois.
So, area should see some sun this evening before clouds move back
in ahead of the next storm system on Friday.
Near term /tonight/...
Issued at 324 PM EDT Thu Jun 20 2019
Forecast challenge for this period is the chances for patchy fog
GOES-16 satellite imagery has been showing clearing skies to the
west over Illinois into Iowa along with surface dew points in the upper
50s and, thus temperature/dew point spreads lower than 2 degrees.
Given the clearing and the lighter winds with weak high pressure
and short wave ridging aloft, would expect patchy fog and
visibilities less than a mile especially near waterways and rural
Short term /Friday through Sunday/...
Issued at 324 PM EDT Thu Jun 20 2019
Challenge this forecast period is timing and amount of rain and
thunderstorms during the period.
Models indicate yet another embedded mid level short wave trough
moving out of the MO and mid MS valley Friday afternoon and
through Indiana by Friday night and through early Saturday. Then,
a brief respite before the next in the parade of embedded short
wave troughs on Sunday afternoon. These waves will activate lift
along a quasistationary frontal boundary that will lie northwest
to southeast through central Indiana for rain and thunderstorms
that could be moderate to heavy at times. This is indicated with
precipitable water values between 1.25 and 1.75 inches going into
later Friday night into Saturday morning. Currently, wpc has much
of the area, with the exception of mie and northeast central
Indiana in a slight risk of excessive rainfall. Storm Prediction Center also has the
southwest parts of central in in a slight risk for severe storms
where that boundary will be located northeast of this area where
there will be a bit more instability and shear.
Main risks for this period outside of the severe weather just
mentioned for damaging winds and hail, but more flooding across
parts of central and southern Indiana.
Long term /Sunday night through Thursday/...
issued at 238 PM EDT Thu Jun 20 2019
Ensembles indicate a fairly strong short wave trough for this time
of year will eject northeast through the plains and into the Great
Lakes early next week. The associated surface frontal system is
expected to pass through the local area in the Sunday night to
Monday night time frame. Will go with fairly high pops during
those times. Progged precipitable waters around 2 inches suggests
heavy rainfall may be a threat.
In the wake of this system, ensembles suggest expansive upper
ridging will build across the plains and Midwest. This may serve
to eventually cap off the air mass, depending how strong the ridge
gets. Ensembles overall are not very bullish on convective
threats locally by the middle of next week. May not take out the
pops totally at this time, but will start to trend the pops down
after Monday night.
Aviation /discussion for the 20/21z taf update/...
Issued at 425 PM EDT Thu Jun 20 2019
ceilings expected to gradually improve during the course of the
afternoon as drier air works into the area. However, it may be
towards the evening hours or after sunset before ceilings scatter
Upper trough is progged to pass off to the east by the late afternoon
hours, so there may still be a few showers in the vicinity of the
terminals until that time.
Occasional to frequent surface gusts 18-22 kts from 280-310
degrees this afternoon will tend to diminish by the early evening
hours. Surface winds will become 320-350 degrees at 4-8 kts after
Flash Flood Watch until 8 PM EDT this evening for inz031-038>042-