Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
301 PM EDT Thursday Oct 23 2014

issued at 135 PM EDT Thursday Oct 23 2014

High pressure will drift east of the region this afternoon and
evening as a weak disturbance approaches from the west. This will
bring just a slight chance for a light shower or sprinkle tonight
but most areas should remain dry. Temperatures tonight will be
warmer than previous nights with lows only falling into the 40s.
Highs on Friday will climb into the lower and middle 60s.


Short term...(this evening through friday)
issued at 259 PM EDT Thursday Oct 23 2014

Short wave expected to move across the region tonight but in a
weakening state. Associated surface boundary to also be in a
decaying state with little to no reflection of it by the time it
reaches our local area. Hires guidance in agreement on decaying band
of showers overnight with only a few hundredths quantitative precipitation forecast being shown at
best and confined to western areas. Stayed with a low chance pop
west and slight chance central while keeping probability of precipitation out of eastern
third of County Warning Area.

Upstream clouds are expected to make their way into
area overnight and latest time height cross sections and soundings
suggest these may hang around through Friday morning and even
through the afternoon. Have trended sky cover up...especially Friday
morning with possibility of moisture becoming trapped once again
underneath remaining frontal inversion.

Temperatures tonight expected to be warmer with lows remaining in the 40s
under increasing clouds. Friday still looks to be near or slightly
above normal with highs reaching the lower 60s most areas with middle
60s south. If clouds persist through the afternoon may see highs remain
in the 50s in some areas.


Long term...(friday night through thursday)
issued at 259 PM EDT Thursday Oct 23 2014

Largely zonal 150+ knots upper level jet will send a decent shortwave
across the northern Great Lakes and Ontario late Friday night into
Saturday. Our County Warning Area will remain on the subsident right exit region of
this jet...limiting precipitation potential...but a cold front will push
through the area on Saturday and usher in some cooler air for the
latter half of the weekend. Thermal trough doesn't fully infiltrate
the County Warning Area until Saturday night so afternoon highs should still reach
the middle to upper 60s for most locations. Expect highs only around
60f on Sunday. Although most synoptic forcing bypasses US to the
north and moisture is limited...did introduce a silent 10 pop for
the Friday night/Saturday period to cover the chance for an isolated
sprinkle along the front.

Temperatures quickly rebound heading into early next week as longwave ridge
axis shifts over the Great Lakes and deep southwest flow develops
ahead of next trough. This will advect a very warm airmass into the
region with 850mb temperatures approaching 16c. May not mix quite that high
given low sun angle and strong subsidence inversion but low 70s
should be easily attainable on Monday and perhaps again on Tuesday.
Cold front will arrive late Tuesday with our next shot of rainfall.
Good height falls/low level convergence and ample moisture ahead of
the front should lead to at least a broken line of showers across
the area. Instability fields still too meager for thunder inclusion
but wouldn't be surprised to see a few isolated lightning strikes.
More seasonable temperatures return for the second half of next week
as middle/upper level flow temporarily deamplifies once again.


Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 135 PM EDT Thursday Oct 23 2014

Middle and high clouds will slowly increase later this afternoon and
this evening ahead of a weak disturbance. Satellite shows area of
clouds upstream approaching. There is an area of MVFR and even IFR
ceilings on the back side of this cloud shield. Approaching wave and
weak surface front will continue to weaken as it moves east. Not
confident the lower ceilings will reach taf sites given expected
frontolysis. However...model soundings do show a moistening in
the lower levels after 06z...especially at ksbn. Trapped ceilings with
remant boundaries are also favored this time of year. Thus have
introduced some MVFR ceilings at ksbn for now but left kfwa VFR. Trends
will be monitored this evening and overnight for more detail in
later taf issuances.


Iwx watches/warnings/advisories...


short term...Lashley
long term...agd

Visit US at www.Weather.Gov/iwx (all lower case)

Follow US on facebook...twitter...and youtube at:

National Weather Service Glossary of Abbreviations