Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Lincoln Illinois
1105 PM CDT Tue Mar 31 2015

issued at 835 PM CDT Tuesday Mar 31 2015

A quiet weather scene expected to continue for at least the next
24 hours across central Illinois as high pressure shifts off to
our east by Wednesday morning. The combination of light winds and
a clear sky tonight will bring most of the area some rather cool
temps by Wednesday morning. That process is well underway this
evening with temperatures already dropping off quickly across the
area and have made some adjustments to the hourly temperature
grids. Otherwise, the rest of the forecast is on track for the
rest of tonight. No zone forecast product update needed this evening.

Winds will increase out of the south on Wednesday which should
bring afternoon temperatures into the 70s over most of the area.
A slow moving cold front will approach the area early Thursday
morning with shower and thunderstorm chances increasing from
northwest to southeast, especially during the day on Thursday.


Short term...(tonight)
issued at 255 PM CDT Tuesday Mar 31 2015

High pressure currently centered over northern Missouri will drift
eastward across the area this evening, leading to clear skies and
light winds. As the high shifts further east, a light southerly
return flow will develop overnight. Thanks to radiational cooling
of the dry airmass, low temperatures will likely be a few degrees
cooler than numeric guidance suggests. Have therefore undercut both
the met/mav numbers, with lows dropping into the upper 30s and lower


Long term...(wednesday through tuesday)
issued at 255 PM CDT Tuesday Mar 31 2015

Surface high pressure slips off to the east of Illinois into the mid
Atlantic states by 18z Wed with increasing southerly breezes and fair
amount of sunshine boosting highs to 70-75f with mildest readings in
the western counties. 12z models are trending slower with arriving
of showers and thunderstorms Wed night and have went dry across area
Wed evening with chance of showers and thunderstorms after midnight
Wed night over Illinois River valley, mainly NW of Illinois River and slight
chance elsewhere. Strong surface low pressure of 995 mb over Alberta
Canada moving east across southern Canadian prairies and pulls a
cold front toward the Illinois River by 18z Thu and through southeast Illinois
during Thu night. Have increase chance of showers and thunderstorms
Thu and Thursday night. Storm Prediction Center has slight chance of severe storms just
SW of Shelby and Clay counties Thu afternoon and early Thu evening
with marginal risk of 5% se of I-55 for wind and hail. CAPES peak
from 1000-1700 j/kg Thu afternoon between 18z/Thu and 00z/Fri south
of I-72. Still mild Thu with highs mid 60s NW of Illinois River and lower
70s in southeast Illinois.

Surface low pressure ridging NE along frontal boundary near the Ohio
River on Friday to keep high chances of showers Friday with isolated
thunderstorms and heavier rains se of I-70. Total rainfall of 0.70-1
inch from I-55 NW from Thu thru Fri while 1.5-2 inches from I-70 se
where some rivers in southeast Illinois could approach flood stage again.
Flash flood guidance values in southeast Illinois are fairly high, running
around 2 inches per hour. Cooler temps Friday behind the cold front
with highs around 50f in central Illinois and mid to upper 50s in
southeast Illinois. Slight chance of showers over eastern Illinois Fri evening
then dry conditions expected this weekend high pressure settles into
Kentucky/Tennessee by sunset Saturday. Highs Sat in the 50s and climb into the
low to mid 60s Sunday and Monday.

Looks unsettled again next Monday-Wednesday with Illinois getting in a
southwest upper level flow and disturbances tracking near the
region. Chances of showers and a few thunderstorms from Monday
through Wednesday. Milder highs Tue in the upper 60s and lower
70s, then turning cooler again Tue night and Wed as cold front
pushes se through central and southeast Illinois.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1100 PM CDT Tuesday Mar 31 2015

VFR conditions will prevail thru this forecast period (06z thu).
Little change expected across the area through tomorrow morning
as surface high pressure shifts off to our east. As the high
pushes further away Wednesday morning, look for surface winds
to increase out of the south and be rather gusty during the
afternoon and early evening hours. South winds of 12 to 17 kts
can be expected after 16z tomorrow with gusts up to 25 kts psbl
during the afternoon and early evening hours. A cold front will
be well off to our northwest tomorrow and then edge slowly towards
our area by Thursday morning. Showers and thunderstorms along the
frontal boundary will also approach our western taf sites but not
until after this forecast period, more towards the 09z-12z time
frame Thursday morning.


Ilx watches/warnings/advisories...


short term...Barnes
long term...07

National Weather Service Glossary of Abbreviations