Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kiwx 230554 

Area forecast discussion
National Weather Service northern Indiana
154 am EDT Wed Oct 23 2019

issued at 153 am EDT Wed Oct 23 2019

Clearing skies are expected overnight, with lows dropping into
the upper 30s inland and the low to mid 40s near Lake Michigan.
Partly sunny, breezy, and a little warmer for Wednesday with
highs in the mid 50s to lower 60s.


Short term...(this evening through wednesday)
issued at 208 PM EDT Tue Oct 22 2019

An upper level low pressure system located north of the Great
Lakes continues to provide energy overhead allowing for
cloud cover into the first portion of tonight. However, low level
moisture begins to push northeast early Wednesday allowing for
clearing skies after midnight. The airmass overhead contains 850mb
ts at or slight below 0c allowing for temperatures to drop into
the 30s for lows tonight despite winds staying above 10 mph.

Wednesday's winds will continue to remain gusty as the pressure
gradient still remains overhead leading to 925mb winds around 30
mph with a mixing height to at least 925mb. In areas south of
US-30, mixing heights reach 850 mb where temps are around 5c
alluding to temps able to reach the low 60s. For Wednesday night,
another shortwave rounds the trough bringing increasing clouds and
another chance for showers within an overrunning regime. The
chance for showers will mainly stay north of US-30 and west of
I-69. Precipitation amounts are expected to remain below 0.10 inch
with the storm's progressive nature, a lack of moisture in the low
levels and only weak low level moisture flux convergence. With
some increased moisture, expect lows to be warmer Wednesday night
bottoming out in the 40s.


Long term...(wednesday night through tuesday)
issued at 208 PM EDT Tue Oct 22 2019

Behind the aforementioned shortwave, height rises help the
precipitation to depart before sunrise Thursday. Then, increasing
f-gen forcing should keep cloud cover around as a front forms
overhead. There is a chance for showers along this front, as
forced by weak energetic waves along the, with the best time
period Thursday evening into the overnight. Weak Theta-E advection
will limit moisture return keeping rainfall totals at a minimum.

And this is where the models diverge in their solutions for Friday
and the weekend. A shortwave rounds the trough down into western
portions of the Southern Plains states Thursday night. A blend of
the Gem/ec allows the vorticity to get strung out across the
Central Plains states forming an upper low across western portions
of the Southern Plains. Meanwhile, the GFS keeps the flow more
progressive limiting precipitation chances for Saturday
night/Sunday across our area. Will side with the ec/Gem and wpc
with this forecast, especially since the gefs does show a few
solutions similar to the Gem/ec. This lean would also increase
sunday's highs to either side of 60, which is around average for
this time of year.

Do expect Friday to have the coolest highs of this work week only reaching
the low 50s as a result of the cold advection behind the forming
front from Thursday.

With the models struggling to handle the weekend system, little
can be gleaned about next week, except that below normal
temperatures are expected to come in mid to late week next week
behind the cold front. Am not yet ready to buy the GFS speed of
the cold air coming in or its magnitude.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 153 am EDT Wed Oct 23 2019

VFR conditions are expected at the taf sites through the period,
with mainly gusty winds/low level wind shear to contend with.
Surface high pressure anchored over the southeastern Continental U.S. Has
expanded northward into our forecast area, forcing much of the lower
ceilings associated with the surface low further north. During the
day, expect southwest winds to gust up to around 25kts. The upper
level trough over our forecast area tonight will shift eastward, and
flow aloft becomes more zonal. A sharpening trough over Minnesota/WI Wed
eve will strength the llj, thus have low level wind shear in for both sites during
that time.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory until 2 PM EDT this afternoon for lmz043-



Synopsis...mesoscale discussion
short term...roller
long term...roller
aviation...mesoscale discussion

Visit US at www.Weather.Gov/iwx

National Weather Service Glossary of Abbreviations