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Area forecast discussion 
National Weather Service northern Indiana
702 am EDT Tuesday Sep 2 2014

issued at 700 am EDT Tuesday Sep 2 2014

Drier and cooler air will infiltrate the region as a cold front
pushes south into the Ohio Valley today. Until then some rainfall
associated with a large convective complex will move through the
region...primariy south of Route 24 this morning. As high
pressure continues to build into the area...look for clearing
skies this afternoon...with highs near 80 degrees...except cooler
near Lake Michigan. Lows tonight will dip into the middle to
upper 50s.


Short term...(today and tonight)
issued at 405 am EDT Tuesday Sep 2 2014

Woefully disheartened by poorly mishandled finer res model output
with respect to spastic primary/derived fields this am. Nam12 too
moist in boundary layer and later afternoon instability and
hrrr3km egregiously overly asserts minor middle level convergence
with heavy amounts in a stripe across northwestern/northern County Warning Area this am.
Following less noisy/conceptually favored sref/GFS through near
term. Zone of marked 7-500 mb qg fgen over wcntl Michigan into northestern Illinois to
race east-northeastward into Michigan thumb/southwestern ont by about 15 UTC. Anticipate
little more than light rain showers given leading edge 850-700mb moisture
flux divergence associated with drying sub altocu deck layer.
Meanwhile to south...convective complex associated with well
veered 925-800 mb jetlet near southwestern in/ncntl Kentucky on order of 45-50kts.
Well veered jet focus through remainder of am hours to keep heavy
rafl well south of County Warning Area...with northern edge /primarily stratiform
quality rainshield passing through southern/southeastern County Warning Area with strong pop
gradient. Given ml cape 250 j/kg isopleth to remain along/south
of Interstate 70 was tempted to remove thunderstorms and rain altogether...however
maintained a token isolated/slight chance mention far S/southeastern County Warning Area
through 12 UTC primarily for possible anvil/peripheral mesoscale convective system strike.
Otherwise...gradual infiltration of drier air and progression of
longwave trough leaves little impetus for afternoon convective
development and sided dry/becoming mostly sunny. Ample longwave
radiational cooling conditions by sunset as Central Plains
surface ridging edges eastward into southwest Great Lakes/middle MS
valley. Given clear/mclear skies and 925 mb thermal trough positioning
from Lake Huron SW into eastern third County Warning Area by daybreak...have
favored ongoing cool temperatures/closer to mav guidance. With strong
surface based inversion anticipate possible fog
issue...uncertainty of coverage...though with wetting across
southern County Warning Area this am...have opted to introduce as areas of fog
for now...allowing later shifts to evaluate probability of dense


Long term...(wednesday through monday)
issued at 405 am EDT Tuesday Sep 2 2014

Weak surface high pressure center will work slowly east-southeast toward the
eastern Ohio Valley on Wednesday providing the area with dry/fair
weather and highs into the low-middle 80s given ample insolation and 850
mb temperatures near 15c. Northern stream will remain active/progressive
through the remainder of the period as next middle level trough axis
(soon to drop into the Pacific nw) propagates east-northeast along the US/Canada
border late this week. Theta-E/warm front surge in response to
attendant Central Plains to upper Midwest surface trough development
brings convective chances into question by later Wednesday
night/Thursday morning. With that said continued with inherited
dry/10 pop forecast in light of consistent European model (ecmwf) dry signal with more
pronounced moisture convergence setting up northwest of the forecast area on
nose of low level jet. Thursday afternoon/night should feature mainly
dry/hot/humid conditions with capped warm sector becoming firmly
established. Depending on cloud/convective trends temperatures may make
a run at 90f Thursday in the west as SW flow deepens and 850 mb
temperatures increase to 20-21c.

Models remain in good agreement in sagging a trailing/weakening
cold front into a moist/unstable environment Friday-Friday evening.
Continued to undercut likely consensus blend probability of precipitation for storms
given weak middle level forcing/lapse rates in part to northerly
track of main pv anomaly through Ontario. Locally heavy rainfall
will be possible if convection fires given high moisture
content/pooling...with not much of a severe risk given Post-
frontal lag of stronger middle level flow. Otherwise...this weekend
into early next week will be characterized by dry (except for
very low shower chance southeast Saturday if slower frontal passage
comes to fruition) and much cooler weather in response to
building high pressure in wake of cold front.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 649 am EDT Tuesday Sep 2 2014

Rain shield to continue eastward advance through northwestern Ohio with
little more than light rain with VFR met conditions for kfwa. A
few rain showers nivof ksbn...immediately along frontal boundary/collocated
middle level convergence axis. Again do not anticipate much if any
aviation related concern apart from wet ry/tempo MVFR ceilings...but
maintain optimism above fueling/alternate criteria. Focus then
shifts to potential br/fog development toward daybreak Wednesday.
Wetted ground/higher xover temperature at kfwa suggests greater liklihood
for deteriorating conditons than across northwestern in/vicinity ksbn.
Address potential for IFR vsbsy in tempo period for outlook/planning
purposes at kfwa.


Iwx watches/warnings/advisories...


short term...Murphy
long term...steinwedel

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