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Area forecast discussion 
National Weather Service northern Indiana
136 PM EDT sun Apr 19 2015

issued at 130 PM EDT sun Apr 19 2015

Low pressure will move north from the Ohio River to the Great
Lakes this afternoon and tonight. Rain will spread north across
the area during the afternoon. Temperatures will fall into the 50s
after the rain begins. Overnight lows will remain in the 50s as
well. The rain should diminish this evening but more rain is
expected Monday.


Short term...(today and tonight)
issued at 348 am EDT sun Apr 19 2015

Morning water vapor shows southwest Continental U.S. Upper low finally
beginning to lift northeast and open as it is absorbed by digging
northern stream trough. Piecemeal ejection of pv anomaly will
bring two main batches of rainfall. The first will arrive this
afternoon with a secondary wave at the beginning of the long term
period. Pushed back and refined timing of precipitation onset this
afternoon based on latest guidance. Slow ejection of midlevel vorticity
maximum and exceptionally dry antecedent airmass (reference current
surface dewpoints over the area and 00z kdtx sounding) suggest
precipitation will probably not fully infiltrate our County Warning Area until late
afternoon. This idea is supported by nearly all of the latest hi-
res guidance which indicates precipitation not arriving in earnest until
around 20z. No doubt we will get a decent rain event by that time
though. Good cva/height falls will support deepening surface
cyclone directly overhead with a healthy slug of 295-300k
isentropic ascent. Most impressive aspect of this event is the
degree of moisture advection. Strong south-southwest subtropical jet will
allow northward expansion of pronounced Gulf moisture plume with
precipitable water values climbing to around 1.4 inches...near the 99th percentile
for this time of year. Heavier rain will not last particularly
long given orientation of forcing is orthogonal to the mean flow
but most locations should pick up around 0.5-0.75 inches. MUCAPE
is virtually nonexistent with moist adiabatic lapse rates
throughout the column. Contemplated pulling thunder mention
altogether but models suggest a few pockets of static instability
may be possible and an isolated embedded thunderstorm cant be
completely ruled out. Therefore held with inherited isolated
thunder mention. No severe threat.

Brief break in steady rain expected later tonight (after midnight)
as our area resides in between midlevel waves. Highs today may still
reach the middle to upper 60s given delayed arrival of low level
moisture plume and associated rainfall. Will still be ample
middle/upper level clouds during the early part of the day but did
adjust maximum temperatures up by a few degrees to be more in line with latest
consensus guidance. Lows tonight should hold around 50f under mostly
cloudy skies.


Long term...(monday through saturday)
issued at 348 am EDT sun Apr 19 2015

Sig scattered remains west/two pronged ejection of southern stream SW energy. Lead
SW will lift up through the southern lakes this afternoon while secondary
follows Monday am...inducing a likely vigorous frontal wave along southwestward
trailing cold front. However details associated/west this development differ
considerably both west/development along the cold front and midlvl deformation
evolution through the day. Broad consensus argues for bumping probability of precipitation
higher both Monday am and Monday afternoon.

Otrws this period and beyond will be dominated by deep northern stream cutoff
as it meanders slowly eastward from the northern lakes on Tuesday to southeast Canada/New
England Sat. Given County Warning Area remains positioned firmly within largely
subsident southwestern flank of upper trough axis again dropped allblend pop
Happy guidance in light of sig drying as modified polar air wraps
southward through the Ohio Valley. Sky forecasts at this range difficult to
ascertain however given the degree of ll cold air advection and building surface ridging
W/time...frost/freeze threat likely to be a major issue west/damage to
emerging fruit trees especially Thursday and Friday nights as ll thermal trough

After Monday...temperatures through the remainder of the period will be well below


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 130 PM EDT sun Apr 19 2015

Radar shows large area of rain gradually moving north and should
begin to reach terminal sites early this afternoon. Dry lower
levels initially keeping ceilings in the VFR range but expect these to
lower as rain persists and area of low pressure moves closer and
intensifies. MVFR conditions followed by IFR expected toward late
afternoon or early evening. Dry slot works in middle to late evening.
Could see brief improvement depending on strength of drying but
for now stayed with solid IFR ceilings overnight. Second wave moves in
Monday morning with next batch of rain showers expected during the


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