Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Indianapolis in
415 am EDT Monday Jul 28 2014
the aviation section has been updated below.
issued at 200 am EDT Monday Jul 28 2014
Persistent cyclonic flow aloft will result in below normal
temperatures through the week with thunderstorms possible from
time to time.
Near term /today/...
Issued at 200 am EDT Monday Jul 28 2014
Main challenge today will be cloud cover...temperatures and whether
or not to include probability of precipitation.
Water vapor imagery was showing upper trough near Detroit and
pivoting east towards Lake Erie around the base of vortex just east
of James Bay. Meanwhile...an associated cold front was dropping
southeast across eastern Kentucky. Models are similar and have the
upper trough moving into the Appalachians this afternoon with
northwest cyclonic flow across the Great Lakes and Ohio Valley.
Model time sections were showing decent lingering moisture 800
millibars and below across northeastern parts of the forecast area
but drier across southwestern sections. Models were also showing
some modest afternoon cape. However...with subsidence...will leave
probability of precipitation out. Diurnal cumulus forecasts are suggesting scattered to broken cumulus.
With 850 millibar temperatures only 8 to 10 degrees celsius this
afternoon...will side with the cool side of 00z MOS with well below
normal highs in the 70s.
Short term /tonight through Wednesday night/...
Issued at 200 am EDT Monday Jul 28 2014
Short focus will be on temperatures as well as probability of precipitation as models
suggest deepening moisture and persistent cyclonic flow may
produce thunderstorms from time to time.
Models and particularly the 00z MOS are all hinting at fairly
widespread showers and thunderstorms beginning on Tuesday.
However...despite somewhat deeper moisture...no significant waves
are advertised to move through in the northwest flow aloft...so am
inclined to go with only small afternoon and early evening probability of precipitation
Tuesday and Wednesday all but the southwestern counties. Models do
have some instability forecasted with the lingering low level
moisture and cold air aloft. So...will also stick with thunderstorms
as opposed to just showers despite the well below normal
850 millibar temperature forecasting suggests going cooler than 00z
MOS with afternoon highs in the middle to upper 70s except around 80
southwest on Wednesday...where there should be more sunshine.
Long term /Thursday through Sunday night/...
Issued at 339 am EDT Monday Jul 28 2014
Diurnal showers and thunderstorms will be present each day during
the extended period as a broad low pressure system resides over
eastern Canada. Weak short waves will rotate around that low
throughout the period enhancing shower/thunderstorm development at
times. A secondary low will form late in the period over the Ohio
Valley...keeping precipitation chances in the forecast through the
weekend. Below normal temperatures will persist for duration of
the long term period with highs in the upper 70s/low 80s and lows
in the low 60s.
Aviation /discussion for the 28/0900z taf update/...
Issued at 414 am EDT Monday Jul 28 2014
MVFR ceilings possible very late tonight and Monday morning.
Low pressure was over the eastern Great Lakes...while high pressure
was build southeast from the northern plains. These systems will
keep US under a moderate northwest flow through the period.
Areas of MVFR ceilings were occurring extreme Northwest Indiana and
near Lake Michigan. Models indicate these ceilings may spread south
southeast at least into the klaf and kind by 09z-10z. Not sure about
khuf and kbmg and will only mention tempo MVFR ceilings there.
With daytime heating ceilings should lift and become VFR by late
morning. Models indicate drier air will spread in from the west
Monday afternoon and evening and mostly clear conditions will be the
rule by end of the forecast period.
Winds will be from the northwest 8 to 10 knots overnight and
northwest 10 to 20 knots Monday. Winds Monday night will be 8 knots
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