Area forecast discussion
National Weather Service northern Indiana
739 PM EDT Friday may 24 2013
Synopsis...
issued at 317 PM EDT Thursday may 23 2013
High pressure will continue to build across the Great Lakes
tonight... causing fair weather across the region and unseasonably
cool temperatures. Areas of frost are expected across much of
lower Michigan...northern Indiana and Ohio. Temperatures will
slowly warm through the weekend.
&&
Short term...(this evening through saturday)
issued at 315 PM EDT Friday may 24 2013
Main focus of forecast on overnight lows tonight and frost
potential.
Clear skies dominate conditions across the area. Temperatures have
struggled to climb to previous forecast highs but now trying to
recover somewhat with several spots in the upper 50s to lower 60s.
Dewpoints in the middle to upper 30s were quite common across the
region...setting the stage for yet another cold night. Models all
agree on winds decoupling this evening and temperatures rapidly dropping
with a favorable setup for frost mainly across the northern half.
Guidance also suggests that some high cloud cover may drift in
later tonight from convection upstream expected to develop.
Overall timing of this appears to be more in the 9 to 12z window
or later...increasing concerns for colder temperatures. Guidance all
supports temperatures in the upper 30s across the north with mav running
the coldest...even in favorable drainage areas (with beh at 29).
After extensive coordination...have opted to hoist frost advisory
for generally the northern half of the forecast area.
After a cold start...temperatures should rebound through the day
Saturday...back to the lower 60s. Lake breeze may develop and keep
conditions locally cooler near the Lake Shore areas. Hi res models
indicate convection left over from overnight activity drifting southeast
possible skirting far SW sections. With dry air mass in place
suspect measurable precipitation will remain well west of the area
resulting in a continued dry forecast.
&&
Long term...(saturday night through friday)
issued at 315 PM EDT Friday may 24 2013
Low level ridge axis will gradually shift east of the area Saturday
night into Sunday allowing southeast low level flow to setup.
Primary low level baroclinic zone is expected to stretch from
southern Minnesota into southern Indiana Saturday evening. Veering
low level winds Sunday/Sunday evening will allow for slight
northward displacement of this baroclinic zone and eastward shift to
associated weak low level frontogenesis axis. Middle/upper forcing
mechanism for precipitation not very distinct but enough elevated moisture
advection may allow for scattered showers to affect western portions
of the area late Sunday/Sunday night. Axis of stronger low level
thetae advection should shift from west to east across the area late
Sunday night into Monday and have maintained chance -tsra probability of precipitation west
tapering to slight chance central. Better chance of convection in
the Sunday night/Monday period likely to reside just west of the
area across the corn belt in region of better low level mass
convergence associated with low level jet. Guidance has been
wavering on strength of convectively enhanced vorticity maximum from this
upstream activity moving into the local area Monday. Still suspect
GFS may be overdone with convective feedback issues...but some
larger scale synoptic support also likely in the form of smaller
scale vortices ejecting out of broader western Continental U.S. Negative upper
height anomaly. With better middle/low level moisture in place by
Monday night and some hints of weak middle level wave moving through
Monday night/early Tuesday...have focused Middle Range chance probability of precipitation more
in this period.
Dampening central Continental U.S. Upper ridge and digging western Continental U.S. Trough
will allow for better low level warm frontal northward displacement
by Tuesday with local area still expected to get back into warm
sector Tuesday afternoon. Possible wildcard for temperatures Tuesday is if
any convection can persist across northern portions of the area into
Tuesday that may suppress effective surface warm front until later
Tuesday/Tuesday evening. Have not made many changes to previous
forecast in highs from upper 70s to lower 80s Tuesday...and have
maintained a south to north pop gradient following expected
progression of warm front. Have kept the Wednesday-Thursday period dry with
renewed middle/upper level height rises across the Great Lakes region
as western Continental U.S. Trough approaches The Rockies. This should set up a
few warm and mainly dry days in the warm sector. Have introduced
chance thunderstorms and rain probability of precipitation again toward the end of the period as large scale
trough ejects into the central/northern plains.
&&
Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 728 PM EDT Friday may 24 2013
High pressure will be over the area tonight with light winds
expected. High clouds will stream in late tonight but no impacts
on aviation. Winds will be variable Saturday morning with a
general trend toward northwest in the afternoon but should remain
at or under 10 knots.
&&
Iwx watches/warnings/advisories...
in...frost advisory from 2 am EDT /1 am CDT/ to 9 am EDT /8 am CDT/
Saturday for inz003>009-012-014-016.
Beach hazards statement until 7 PM CDT this evening for inz003.
Michigan...frost advisory from 2 am to 9 am EDT Saturday for miz077>081.
Beach hazards statement until 8 PM EDT this evening for miz077.
Ohio...frost advisory from 2 am to 9 am EDT Saturday for ohz001-002-004-
005.
Lm...Small Craft Advisory until 8 PM EDT this evening for lmz043-046.
&&
$$
Synopsis...Fisher
short term...Fisher
long term...marsili
aviation...Lashley
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