Scientific Forecaster Discussion
Area forecast discussion...correction
National Weather Service northern Indiana
358 PM EDT Monday Mar 10 2014
issued at 1144 am EDT Monday Mar 10 2014
Above normal temperatures will rule this afternoon into early
Tuesday as southerly flow Ushers in warmer air. A low pressure
system will track through the Ohio Valley late Tuesday into
Wednesday...bringing accumulating snow to the area. Cooler
temperatures will return behind this system on Wednesday and
Short term...(this evening through wednesday)
issued at 358 PM EDT Monday Mar 10 2014
Mild/quiet weather to persist tonight/Tuesday with main focus on
heavy snow potential Tuesday night into Wednesday...
A northern stream pv anomaly tracking east into Quebec will drop an
increasingly diffuse/shallow cold front south into northern zones
tonight...with this feature likely laying out west-east over central
portions of the forecast area Tuesday as it becomes oriented with the mean
flow. Not expecting any precipitation with this boundary through at least
Tuesday afternoon...with the main impact being trend toward slightly
cooler temperatures and potential for some fog/stratus development late
tonight/Tuesday morning given snow melt and boundary layer
convergence/moistening from shallow cold air advection undercut. Frontal
boundary will tighten up later Tuesday afternoon into Tuesday
evening in response to upstream height falls. Expectations are for
a narrow band of precipitation to develop in vicinity of strengthening 800-600 mb
layer fgen response near/north of the Illinois/WI border and spread east
into lower Michigan during this time...potentially clipping our
Michigan zones. Ptype likely begins as rain before slowly
transitioning to a rain/snow/sleet mix here in the evening.
Deep layered trough entering the Pacific northwest as of this
writing will fracture east across The Rockies later tonight..with
one piece emerging into the Central Plains tomorrow. This upper wave
eventually phases with amplifying/digging northern stream energy
Tuesday night-Wednesday. Models impressive with ~200 meter 500 mb
height falls into the Northern Ohio valley...supporting a
deepening surface cyclone track east through southern Indiana/Ohio
later Wednesday am. Very strong/deep fgen signal and ageostrophic
response under merging upper jets expected later Tuesday night.
Moisture advection also impressive per 5 g/kg tap within 40 knot
cross isobaric flow on the 300k surface. Forcing by Wednesday morning
will then shift to a more mature/classic deformation axis. This
prognosticated deep uvm plume and excellent moisture transport has led to
increased confidence for a relatively quick hitting heavy precipitation
event during this time (mainly in the 8-18z window).
As always ptype/snow amounts/impacts will depend on timing/degree of
phasing. 12z model guidance overall trended stronger/more
phased and north with the track of this system bringing ptype
concerns farther north into southern two thirds of the forecast area.
Current expectations (medium confidence) along/south of Highway 24 in
are for precipitation to start as rain Tuesday night before ending as a
period of moderate-heavy snow...for a brief wintry mix changing quickly
over to snow across central zones...and for mainly snow across far
northern zones. Opted for a Winter Storm Watch for western/northern
zones (4-8 inches and blowing snow)...but held off south of Highway 24
in Indiana/Ohio given later changeover to snow (opted for a Special Weather Statement and
3-6" of snow here).
Long term...(wednesday night through monday)
issued at 358 PM EDT Monday Mar 10 2014
Strong ll cold air advection Wing wrapping in behind departing eastern Ohio bomb to start
the period Wednesday night. Position of surface ridge axis and refreshed deep snow
cover will allow temperatures to plummet County Warning Area wide. Per trends seen in MOS
guidance and raw 2m temperature output...will undercut mins substantially.
Otrws shallow Arctic wedge will erode out just as quick going into
Friday ahead of potent northern stream SW disturbance ejecting eastward across the
northern lakes. While extent of thermal ridge ahead of this system has
waned...strong mixing expected southward through the warm sector and as such will
hold close west/prior numbers.
Remainder of the period in flux west/inconsistent model handling of both
western ridge extent and plethora of ridge riding disturbances breaking
southeastward into the eastern US. Near seasonable temperatures to start the weekend
will not last west/general deepening of eastern US troughing. Expect much of
next week to remain unseasonably cold and unsettled.
Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 137 PM EDT Monday Mar 10 2014
Winds will remain gusty at times through the afternoon before
waning this evening and going calm by the early morning hours.
Calm winds...residual moisture from melting snow...and thin or
non-existent cloud cover should provide sufficient radiational
cooling conditions and allow temperatures to drop several degrees
below the crossover temperature. No changes made to previous taf
visibilities...but definite possibility that lower visibilities
may need to be added at a later time.
in...Winter Storm Watch from late Tuesday night through Wednesday
afternoon for inz003>009-012>018-020-022>025.
Michigan...Winter Storm Watch from late Tuesday night through Wednesday
afternoon for miz077>081.
Ohio...Winter Storm Watch from late Tuesday night through Wednesday
afternoon for ohz001-002-004-005-015-016.
Visit US at www.Weather.Gov/iwx (all lower case)
Follow US on facebook...twitter...and youtube at: