Area forecast discussion
National Weather Service Lincoln Illinois
330 am CDT Thursday may 23 2013
Discussion...
issued 330 am CDT Thursday may 23 2013
Short term...today through Friday night
560 dm 500 mb low near the Iowa/WI/IL border and associated upper
level trough to pull eastward across Illinois this morning and over in/Ohio
this afternoon. Broken to overcast low clouds have been spreading
southeast toward I-70 early this morning along with isolated to scattered
light rain showers over northern Illinois mainly north of I-80 so far.
These light showers are north of a frontal trough extending from
1004 mb low pressure over southeast Ontario through Southern Lower Michigan
into northern Illinois near I-80 and into southern Iowa. As upper level
trough and surface trough swing southeast through central Illinois this morning
expect a few light rain showers to occur...then diminish from northwest
to southeast during the afternoon as low clouds clear over the Illinois River
valley later this afternoon and over eastern Illinois during this
evening. Cool today for late may with highs in the low to middle 60s
over central Illinois and 65 to 70f in southeast Illinois from I-70 southeast. North-northwest breezes
to make it feel even cooler today.
1034 mb Canadian high pressure over northern Manitoba and ridging
southward into the central/northern plains to settle into WI and
NE Illinois as 1031 mb high pressure overnight bringing a cool night to
central Illinois as skies clear and winds become light with lows in the
upper 30s and lower 40s. High pressure ridge stays over Lake Michigan
and eastern Illinois Friday providing sunny skies and NE winds less than 10
miles per hour and highs in the middle to upper 60s. Dry weather should continue
across central/southeast Illinois through Friday evening with surface ridge
nearby.
Long term...Saturday through Thursday
Upper level ridge sets up over the Great Plains by this Memorial
Day weekend with upper level low/trough moving into New England by
Sat. This puts Illinois in a northwest upper level flow and models continue to
show upper level disturbances riding southeast along thermal gradient
near central Illinois this Holiday weekend. Have 20-30% chance of
showers and isolated thunderstorms northwest of I-55 after midnight
Friday night. Then spread a 30-50% chance of showers and
thunderstorms eastward across central and western Illinois Sat (slight
chance over eastern/southeast Illinois Sat afternoon) and into eastern Illinois by
Sat night. Looks like 30-40% chance of showers and thunderstorms
continues Monday and Tuesday over much of area with the lower probability of precipitation
near the Wabash River. Surface high pressure over the Great Lakes
and into the central/eastern Ohio Valley to also keep areas NE of
central Illinois drier this Holiday weekend. Upper level ridge shifts
east into the Ohio Valley by middle of next week and shifts
chances of convection north of central Illinois. Temperatures and
humidity levels to gradually increase also from sun-Wednesday with highs
in the upper 60s and lower 70s Sunday and climbing to around 80f
Tuesday and low to middle 80s Wednesday.
07
&&
Aviation...
issued 1105 PM CDT Wednesday may 22 2013
Little change in thinking from previous discussion...timing of
lower ceilings into our area late tonight the main forecast challenge.
MVFR ceilings were located over extreme eastern Iowa and parts of
northwest Illinois late this evening and were tracking slowly southeast along
a weak surface boundary. We should start to see the ceilings lower to
MVFR at all sites starting aftr 06z at kpia and by 09z over at kcmi.
Once they lower to MVFR...the ceilings should remain there through Thursday
afternoon before we see a gradual improvement to VFR Thursday evening.
May see some tempo IFR ceilings at pia and bmi late tonight...more
likely aftr 10z...which would continue through the middle morning hours.
Regional radar loop continues to show quite a bit of rain along and
north of the surface trough which will shift into our area around 12z in
pia and points further east by 15z Thursday. Will continue to indicate
vcsh at the taf sites for now. Look for winds to remain from a westerly
direction ahead of the surface trough axis tonight at speeds of 10 kts or
less...and then switch into the northwest and then north on Thursday
with winds increasing to between 12 and 17 kts by afternoon...with gusts
up to 25kts at times in the afternoon before they slow begin to decrease
after dark Thursday evening.
Smith
&&
Ilx watches/warnings/advisories...
none.
&&
$$
