Scientific Forecaster Discussion
Zczc indwrkafd 300401
ttaa00 kind ddhhmm
Area forecast discussion
National Weather Service Indianapolis in
1220 am EDT Thursday Jul 30 2015
the aviation section has been updated below.
issued at 1000 PM EDT Wednesday Jul 29 2015
High pressure is expected to build in the wake of the front
tonight. This will keep dry weather in place across central
Indiana tonight through Friday...along with seasonable
A weak cold front may pass on Friday night...bringing rain chances
back to central Indiana then...followed by a third front on Monday
night into Tuesday. Look for temperatures to remain close to
seasonable normals over the next seven days.
Near term /rest of tonight/...
Issued at 1020 PM EDT Wednesday Jul 29 2015
Brief update...added a 20 percent and isolated shower wording to the
northeast counties to cover shower near Muncie and any others that
may pop up from the outflow boundary in that area over the next 2
hours. After that moves out dry weather should be the rule.
Previous discussion follows...
High pressure...subsidence and less humid air is expected to
arrive in the wake of the cold front. Forecast soundings by 00z
show good middle level warming near 700mb...providing a capping
effect. By 06z a much drier air mass arrives as dew points within
the column drop off dramatically. Thus will trend toward a dry pop
by 03z across much of the forecast area as heating and any forcing
should be lost by then. As for temperatures...will use a blend of the
mavmos and metmos.
Short term /Thursday through Saturday/...
Issued at 1244 PM EDT Wednesday Jul 29 2015
GFS and NAM suggest surface high pressure will build through the
Ohio Valley on Thursday and maintain it/S control through at
least Friday evening. Forecast soundings show a very dry column as
surface dew points drop into the 50s.Convective temperatures on Thursday
appear unreachable...and may briefly be touched on Friday. Thus as
the flow aloft is expected to become more northwesterly over the
next few day...will mainly look for just some passing cirrus from time
to time. Thus mostly sunny days and mostly clear nights are
expected. Through Friday. Will use a blend on mavmos and metmos
temperatures for highs and lows.
On Friday night the GFS hints at a weak cold front pushing across
central Indiana late. Diurnal timing with this system is bad...and
at this time forcing aloft appears minimal. Forecast soundings
remain rather dry and at the surface Gulf moisture remains cut
off. Thus confidence in this quick hitting front is low. For now
will include low chance probability of precipitation mainly across the north where surface
convergence appears to be best. Will trend temperatures on Friday night
warmer than mavmos given the expected cloud with this system.
Another surface ridge is expected to build across central Indiana
in the wake of the quick moving cold front on late Friday night.
Gulf moisture remains cut off amid the northwest flow as forecast
soundings show unreachable convective temperatures amid a dry column.
Will trend toward mostly sunny then with highs slightly cooler
Long term /Saturday night through Wednesday/...
Issued at 222 PM EDT Wednesday Jul 29 2015
Saturday night starts the period dry but another surface trough
settles into the area from the north beginning Sunday and remains
in the area into middle week. Associated weak upper waves will return
a daily chance of storms to most areas from Sunday Onward with
best chances Tuesday when front is across the area.
Without the hot dome upper ridge able to build back in...more
seasonal temperatures are expected ranging from low/middle 80s north
sections to middle/upper 80s south. Relatively comfortable lower 60
dewpoints at the start of the period will creep back towards a
humid 70 degrees early and midweek.
Aviation /discussion for 300600z taf issuance/...
issued at 1220 am EDT Thursday Jul 30 2015
VFR through the period with some leftover cirrus blowoff overnight.
Much drier air has filtered in at the lower levels of the atmosphere
as displayed in dew point which are now in the upper 50s and lower
60s. This should keep for or low stratus from forming overnight.
Calm or light northwest winds will increase to 8 to 12 knots this
afternoon. Not expecting any clouds after sunrise as relative humidity time
sections are very dry and high pressure will build in from the west.