Area forecast discussion
National Weather Service northern Indiana
121 PM EDT Thursday may 23 2013
Synopsis...
issued at 121 PM EDT Thursday may 23 2013
Rain chances will continue through Thursday afternoon as a cold
front pushes south of the area. High pressure will build into the
area from the northwest Thursday evening...which will bring mainly
dry conditions and below normal temperatures through the weekend.
&&
Short term...(today and tonight)
issued at 407 am EDT Thursday may 23 2013
Cut-off upper level low over the middle MS valley continues process of
being absorbed by trough digging S-southeast across the Great Lakes. Surface cold front
associated with this upper trough extended from Southern Lake Huron to just
south of Lake Michigan and then west-northwest across northern Illinois. Areas of fog
occurring near front over Southern Lake Michigan and extending slightly
inland. Flow light enough to keep this from spreading very far
inland and as winds pick up...boundary layer mixing should allow
visibilities to improve near the lake early this morning. A fairly
widespread area of showers behind the front across northern Illinois... WI...
and northwest Michigan. Forcing responsible for these showers may weaken some
today as upper low continues to shear out... but expect digging upper trough
and lift along frontal zone will be sufficient to maintain Post
frontal showers moving southeastward across our area during the day. Some
showers may linger over southeastern portion of the area early this evening
but should be followed by clearing overnight as strong
subsidence/drying overspreads the County Warning Area.
Rather tight pressure gradient behind the front should result in
gusts up to 30mph behind the front today... a little stronger in
vicinity of Lake Michigan where thermal gradient enhanced. Continuing with
Gale Warning for nsh zones and since beach season has begun...
issued a beach hazard statement for the surf zone.
With strong cold front moving across the area today there will be a tight
temperature gradient with highs expected to range from the l50s northwest to the
u60s southeast. Strong cold air advection today/tonight combined with clearing skies
tonight should allow temperatures to fall into the u30s north and l40s
south. With surface high remaining to the west of our area overnight...
northerly gradient expected to be strong enough to maintain some
light wind throughout the night which should prevent a more significant
temperature drop and frost from forming.
&&
Long term...(friday through wednesday)
issued at 407 am EDT Thursday may 23 2013
Remarkably placid conditions to begin this long term period as
blocky high amplitude wave train slowly propagates
eastward...leaving the southern Great Lakes on subsident side of
impressive middle/upper level ridge. 1030mb surface anticyclone will be
firmly in place by Friday...leading to a pleasant...albeit somewhat
cool...day. Will be interesting to see how warm we actually get with
the strong late may sun angle acting on chilly cp airmass. Thermal
trough will be pushing eastward during the day and 850mb temperatures look
to recover to around 5c by the afternoon. This would usually support
highs only in the low 60s but full sun should allow for a good
superadiabatic response at the surface...pushing highs a few degrees
warmer. Went with generally middle 60s...save for the Lakeshore areas
where light northerly winds will allow for decent marine influence.
Good radiational cooling expected Friday night. Surface high will be
directly overhead with calm winds and full boundary layer
decoupling. Could be some increasing cirrus toward daybreak but the
effect should be minimal and expect lows around 40f once again.
Frost is not likely given marginal temperatures and very dry airmass.
Forecast becomes a bit more muddled heading into the Holiday
weekend. Several weak vortices are expected to Cascade down the
longwave ridge and incite a decent warm air advection/fgen response to our west.
Question will be whether or not this forcing can clip our western
County Warning Area. Given the strength of confluence aloft and persistence of
general Ava in slowly progressing large scale pattern...expect
precipitation will remain closely tied to low level Theta-E gradient draped
over the Midwest. Preponderance of dry air and effect of Cold Lakes
this time of year should maintain high pressure and dry northeast
flow locally...as seen in the last few European model (ecmwf) runs. Wouldnt rule out
a few sprinkles over our southwest at times this weekend but
confidence is much too low to include in the forecast. Baroclinic
zone will eventually work its way east as Pacific jet forces
downstream ridge to shift eastward early next week. Large
disagreement in latest models on how and when this will happen
though. Will keep with previous ecwmf preference for now and hold
off on probability of precipitation until midweek. After another cool day on
Saturday...expect a slow moderating trend through early next week as
ridge axis passes overhead. Temperatures should return to at or above
normal by Tuesday.
&&
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 648 am EDT Thursday may 23 2013
Lake enhanced portion of cold front appears to have stalled near
sbn early this morning resulting in occasional IFR conditions varying to
VFR there. Front will resume S-southeast movement across northern Indiana today
as upper level trough moves through. Thus expect tempo IFR will
transition to predominant IFR at sbn and MVFR at FWA by late
morning. MVFR conditions expected across the area this
afternoon... transitioning to VFR and sky clear this evening. -Shra with
considerable coverage continuing upstream at this time so adjusted tempo -shra
to about a 6hr period of predominant -shra today in latest tafs.
&&
Iwx watches/warnings/advisories...
in...beach hazards statement through Friday evening for inz003.
Michigan...Beach hazards statement through Friday evening for miz077.
Ohio...none.
Lm...Gale Warning until 8 PM EDT this evening for lmz043-046.
&&
$$
Synopsis...ng
short term...jt
long term...agd
aviation...jt
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