Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
426 am EDT Sat Aug 23 2014

issued at 401 am EDT Sat Aug 23 2014

Warm and humid conditions will persist for one more day before a
brief break in the sticky conditions arrives tonight into Sunday
as high pressure builds in from the northeast. Showers and
thunderstorms will be possible this afternoon and evening with
chances diminishing tonight. Dry conditions are expected until
Tuesday when a cold front begins to approach the area. Highs will
be in the 80s with lows in the 60s the next couple of days.


Short term...(today and tonight)
issued at 401 am EDT Sat Aug 23 2014

Several smaller items to try to sort out for the forecast. First off
will be combination of moist low level air mass and mostly clear
skies allowing for stratus/fog development across the area.
Observations have been showing this already taking place...with
issues expected to persist through at least 10 am before sufficient
mixing occurs to help break things up.

Next up will be attempt to advect in somewhat drier air from the NE
against the persistent but weak SW flow across much of the western
Great Lakes. A subtle boundary was located from S Lake Michigan to
vicinity of feet Wayne. This feature...combined with what appears to
be a middle level disturbance or series of Gravity waves...helped spark
small areas of slow moving showers and storms that have since
dissipated. Locations along and SW of this boundary will see a
chance for hit or miss showers/storms this afternoon/evening if
sufficient heating can take place. Warm and humid conditions will
remain until the NE flow can strengthen slightly as ridge influence
briefly relaxes with dewpoints dropping into the middle 60s (low 60s
ne). A few runs of the RUC try to bring this drier air a bit faster
in NE sections that currently depicted. Given weak nature of
slow...think slower is better at this point until degree of mixing
can be determined. As a result...highs should reach the middle 80s with
heat indices near or just into the 90s.

NE flow will push axis of best precipitation potential to the SW of
the region during the evening hours...leading to what should be a
pleasantly dry night as lows drop into the middle 60s to near 70. Have
kept a lingering slight chance of showers in far SW areas early evening
but then removed all mention of precipitation after 3z.


Long term...(sunday through friday)
issued at 401 am EDT Sat Aug 23 2014

Strong shortwave moving through northern Nevada this morning expected to lift
slowly NE through the northern High Plains Sunday with downstream ridge
moving east across our County Warning Area. Lack of forcing and a little drier air
advecting into our area in the h925-850 mb layer due to easterly flow
around strengthening anticyclone over the lower Great Lakes suggests dry
conditions across our area. Good deal of sunshine should allow
mixing up to near h850 which would result in highs in the M-u80s.

Northern plains shortwave expected to move east to Ontario on Monday. Ridge
over the upper Great Lakes will flatten out in response but should hold
strong in our area keeping conditions dry. Temperatures expected to
continue slow warming trend as winds veer more southerly with highs
in the u80s/l90s.

Ontario shortwave expected to shear out and lift east-northeast into Quebec Tuesday
with trailing cold front sinking slowly south into or close to northern
portion of our County Warning Area by Wednesday morning. Thunderstorms should develop along the
front and may propagate southeast into unstable airmass over our area...
but capping inversion makes this scenario doubtful... so just continued
with low chance probability of precipitation. Temperatures should remain well above normal with highs
around 90 and lows near 70.

Model solutions diverge significantly late week with European model (ecmwf)/Gem
suggesting next strong shortwave to move into mean western trough will
cut-off over The Rockies and then move slowly east... while GFS
suggests a more progressive scenario. In either case... low probability of precipitation
still warranted for Wed-Thu... while GFS indicates cooler/drier
conditions will overspread the area by Friday. This solution in
better agreement with going forecast and given excessive uncertainty
with large model differences... stayed close to previous forecast.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1209 am EDT Sat Aug 23 2014

Stratus and fog will pose a concern into Saturday morning at both
sites as moist boundary layer remains in place from recent
rainfall and abundant moisture in the area. A boundary was located
in the vicinity of both sites but was most active in and around
kfwa where a small area of showers/storms was persisting. This
should drift southeast over the next half hour to hour with
additional activity upstream that could drift southeast towards the
Airport again. Will monitor for amendments.

Otherwise no significant changes planned to tafs into Saturday
night as overall pattern will change little.


Iwx watches/warnings/advisories...


short term...Fisher
long term...jt

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

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

National Weather Service Glossary of Abbreviations