Scientific Forecaster Discussion
fxus63 kind 121637
Area forecast discussion
National Weather Service Indianapolis in
1137 am EST Thu Dec 12 2019
the aviation section has been updated below.
issued at 349 am EST Thu Dec 12 2019
Dry conditions but increasing cloud coverage expected through
Friday midday. Then chances of precipitation are in store for
this weekend and early next week. The early weekend system could
see snow mix in with rain, mainly during overnight hours. Sunday
night through Monday night has a better chance of precip and has a
better chance of snow accumulation. The end of the forecast period
will likely be dry with temperatures slightly below normal.
Near term /rest of today/...
Issued at 933 am EST Thu Dec 12 2019
Upped sky cover some with cirrus moving overhead. May have to up to
mostly cloudy depending on how thick upstream cirrus is. Otherwise
just made some tweaks to the overall forecast.
Previous discussion follows...
Cloud coverage will be increasing from the west throughout the day as
a weak surface trough moves into the area. During this time, the
surface pressure gradients will tighten and winds will be breezy
from mid morning to this evening with gusts up to 28 kts. The
southeasterly air flow will allow for warmer temperatures to
return today... expecting highs in the low to mid 40s.
Short term /tonight through Saturday night/...
Issued at 349 am EST Thu Dec 12 2019
Sky coverage will briefly clear out tonight between systems but
clouds will overspread again throughout Friday. Dry conditions
are expected through midday Friday. A shallow upper level trough
will begin deepening as it approaches the region. This upper
trough in combination with the slowly exiting high pressure system
to the east, will bring moisture from the Gulf of Mexico starting
Friday afternoon in the more southeastern counties. Pops will
then increase through Saturday before diminishing by the overnight
hours. Models still show variability on locations of lift and
precipitation... this system looks to be wavy and not very strong,
leading to a lack of confidence on how things will turn out.
Friday and Saturday nights could see snow either mix in or
completely transition to snow further north. Isolate, minimal snow
accumulations are currently what is expected. Model sounds are
hinting at a warm nose situation Saturday evening and night
meaning that freezing rain could be possible at times. Given that
confidence and pops are somewhat low, have left any freezing rain
out of the forecast for now but will continue to monitor as we get
closer. Temperatures will be near to slightly above normal for
the short term.
Long term /Sunday through Wednesday/...
issued at 235 am EST Thu Dec 12 2019
Models and ensembles are in general agreement that a southern system
will lift northeast over the Ohio or Tennessee valleys next Monday.
The 00z GFS was the furthest north, taking it over central Indiana
and the 00z European model (ecmwf) furthest south, taking it over Tennessee and
southeastern Kentucky. Meanwhile, the ensemble means were a
compromise. The Euro and ensembles means both suggest some snow
accumulation, while the GFS favors a more rain event. The blend
leans more away from the operational GFS, which is preferred at this
Prior to the snow potential, zonal flow and surface high pressure
support dry weather Sunday and Sunday night. Meanwhile, high
pressure will again support dry weather by Tuesday in the wake of
the low pressure system.
With the exact track of the low pressure system up in the air, not
only could the confidence in precipitation type be better but so too
could be the confidence in blend temperatures. Thus, will not make
any changes. Blend afternoon highs are mostly in the 30s
Aviation (discussion for the 121800z taf issuance)...
issued at 1137 am EST Thu Dec 12 2019
VFR conditions are expected through the period.
Mid and high clouds will rule across the taf sites through the taf
period. Winds may gust over 20kt this afternoon at the western
sites, and conditions will be near low level wind shear criteria at
klaf this evening.
Clouds will begin to lower on Friday, especially at kbmg and then
eventually kind as a system develops over the southeastern states.