Scientific Forecaster Discussion
fxus63 kind 231925
Area forecast discussion
National Weather Service Indianapolis in
225 PM EST Fri Feb 23 2018
the long term section has been updated below.
issued at 253 am EST Fri Feb 23 2018
A frontal system will linger in the area through Saturday night,
resulting in unsettled weather. High pressure will build into the
area for the early parts of next week. Another low pressure system
may affect the area towards the middle of the week.
Near term /this afternoon/...
Issued at 949 am EST Fri Feb 23 2018
Radar this morning shows a stream of showers across far southern
Indiana...streaming along the Ohio River and mostly out of the
ind forecast area. A few lingering light showers were found to
the north of the band...exiting the area to the northeast. Water
vapor imagery shows the tropical plume of moisture stretching from
Texas to the Ohio Valley and points northeast...continuing the
reoccurring theme of moisture streaming into the region. Goes16
shows abundant cloud cover across central Indiana...continuing to
feed into the region amid the tropical flow aloft.
Forecast soundings and time heights show some dry air working in
into the column this afternoon. This is primarily due to some weak
subsidence as Indiana will be caught between the departing short
wave and the next approaching wave for tonight. Lower levels still
remain rather saturated...thus little to no sunshine will be
expected on this February day. Hrrr keeps than main precipitation
plume to the south of central Indiana this afternoon. Thus given
these factors have trended toward only slight chances for
rain...mainly this morning...then trending toward a dry forecast
this afternoon as the dry air arrives. Kept expected highs close
to the latest lav guidance which appears to match up well with
the values given by forecast builder.
Short term /tonight through Sunday night/...
issued at 253 am EST Fri Feb 23 2018
Warm advection and organized lift expected to increase late tonight
as a 35-40 kt low level jet begins interacting with a frontal zone
located just south of the Ohio River. Will bring high pops back into
the area by the pre dawn hours of Saturday.
Will keep high pops going through Saturday night as a final upper
level wave kicks out across the western Great Lakes Saturday night.
Models suggest wind fields may become quite strong over the area by
Saturday night, with a low level jet around 60 kts, and mid level
jet around 95 kts. This may result in some high winds associated
with any convection that may develop Saturday night with the cold
front, although lapse rates/instability look rather poor at this
Will cut off the pops after Saturday night as it appears the cold
front will be east of the area by then.
Will keep the Flood Watch headlines as is, given the high
precipitable waters progged over the area through Saturday night.
Still appears best threat will be over the southern half of the
forecast area based on expected position of the low level jet.
The heaviest rain axis may shift north into the northern zones for a
time Saturday as the 850mb front lifts north.
Progged low level thicknesses suggest the GFS MOS highs for Saturday
may be too cool. Will bump up the guidance a category in that
period. The remaining periods look OK for now.
Long term /Monday night through Friday/...
Issued at 225 PM EST Fri Feb 23 2018
European model (ecmwf) suggests a return of the SW flow pattern of warm air
streaming into the Ohio Valley. On Monday night through Tuesday
night...the European model (ecmwf) shows little in the way of upper support.
Meanwhile high pressure remains across Florida...allowing a warm
and moist Gulf flow to push into the area. Thus have trended with
above normal temperatures at that point but a dry forecast.
On Wednesday night through Friday...the European model (ecmwf) suggests several
short wave pushing through the SW flow aloft. The coup de gras of
the pattern in this period coming on Thursday night as low
pressure looks to move again through the Great Lakes and sweep a
cold front across Indiana. This appears reasonable given the warm
southerly Gulf flow in place ahead of the approaching dynamics.
Thus have included several periods of rain showers on Wednesday
and Thursday...with best chances on Thursday as the cold front
Aviation /discussion for the 231800z tafs/...
Issued at 1145 am EST Fri Feb 23 2018
MVFR ceilings are expected to persist this afternoon...before quickly
deteriorating toward IFR and perhaps LIFR this evening and
Tropical plume of moisture across the area will continue to push
through the Ohio Valley this afternoon and tonight.
Forecast soundings and time height sections show saturated lower
levels persisting this afternoon and observations and goes16
imagery suggest MVFR ceilings will persist through the afternoon.
However...as heating and mixing is lost this evening...expect ceilings
to become IFR...similar to the previous night before stronger
forcing arrives overnight.
A strong short wave will push through the area tonight and into
Saturday...providing forcing for precipitation development. Time
height sections show strong Omega and forecast soundings show a
saturated column starting tonight through Saturday. Again this
will result in IFR conditions.
Flood Watch through Sunday morning for inz045>049-051>057-