Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
330 PM EDT Wednesday Sep 17 2014
issued at 330 PM EDT Wednesday Sep 17 2014
High pressure will remain entrenched across the Ohio Valley
through Friday with dry conditions and moderating temperatures.
Lows tonight will be in the low to middle 40s with highs on Thursday
in the upper 60s to around 70.
Short term...(this evening through thursday)
issued at 330 PM EDT Wednesday Sep 17 2014
Another quiet short term forecast today as surface high pressure
remains anchored over the region. A second night of mostly clear
skies and nearly calm winds will lead to good radiational cooling
conditions. Expect values similar to last night but starting temperatures
are a degree or two warmer this afternoon so overnight lows will be
a bit warmer in a few spots. Stuck close to inherited forecast with
low to middle 40s...which was in line with latest mav and met guidance.
Patchy radiational fog will be possible but a lot of moisture is
being mixed out this afternoon and forecast soundings indicate a
very dry near surface environment overnight. Will leave out any fog
mention for now and continue to monitor through the evening. A back
door cold front will push into Michigan tomorrow as a secondary 1024
mb surface high builds into the region. This front will wash out as
it pushes south but could bring a few clouds to our northern
counties tomorrow. Low level flow will gradually become more
northeasterly but thermal profiles look very similar to today and
expect highs once again in the upper 60s to near 70f.
Long term...(thursday night through wednesday)
issued at 327 PM EDT Wednesday Sep 17 2014
Long term will be characterized by a strong short wave and surface
cold front this weekend but tranquil and relatively cool weather
preceding and following this feature.
High pressure at the surface with northwest flow aloft to start the
period but surface high will be drifting east allowing for return
flow to set up and moderating height field. Local model verification
shows a distinct warm bias of 2 to 4 degrees in 48 hour maximum
temperatures over the last two weeks. Keeping this in mind for highs
on Friday and leaning toward better performing consensus blends
within middle of guidance envelope. This still yields highs into the
lower 70s Friday just a few degrees below normal.
Remnant moisture from Pacific Hurricane Odile will be streaming
toward the Midwest ahead of northern stream short wave arriving this
weekend. While models now agree on keeping parent remnant
circulation and deeper tropical moisture southwest of the
area...expect middle level water vapor and Theta-E surge to ride north
along frontal boundary. Models seem to be picking up on this with
good agreement on precipitable water values rising to over 1.5
inches and moisture pooling along frontal boundary. Result should be
another decent area of rain along cold front Saturday night as it
crosses our area. Not usually too keen on likely probability of precipitation in the warm
season this far out but with it already in forecast and support from
latest models and surrounding offices have opted to continue with
the higher probability of precipitation. Timing across the County Warning Area precludes a higher pop in the
southeast with timing issues between Saturday night or Sunday
morning still in question. Cold front will exit the southeast early
Sunday with drying and clearing during the day.
Air initially behind this front not drastically colder so highs on
Sunday still look to rebound into the 70s. Secondary short wave
drops through Sunday night into early Monday bringing secondary
surge of cooler air. Atmosphere looks relatively dry so not going to
add probability of precipitation at this time. However...Delta T values do increase into middle
and upper teens so lake effect rain showers could develop with any
residual or increased moisture in later model runs. 12z gfs40 does
appear to have a little more moisture this run so will be watching
later runs of higher resolution guidance for possible addition of
probability of precipitation.
High pressure then moves back in for remainder of the long term with
high temperatures back into the lower and middle 60s into the middle
of next week and lows back into the lower 40s.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 147 PM EDT Wednesday Sep 17 2014
VFR conditions expected to persist through most of the period.
Enough residual boundary layer moisture for a healthy diurnal
stratocu deck this afternoon but this should dissipate by later
this evening. Clear skies and calm winds could lead to some MVFR
br but surface dewpoints appear too low for inclusion in the taf
at this time. Otherwise...another VFR day expected tomorrow as
high pressure remains parked over the region.
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