Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lincoln Illinois
1130 PM CDT Wednesday Jul 1 2015
issued at 856 PM CDT Wednesday Jul 1 2015
Weak frontal boundary/wind shift the produced The Funnel clouds
this afternoon has shifted into our southeast counties early
this evening. This is where storms have increased in areal
coverage and intensity over the past hour as they track southeast.
A larger complex of storms over west central Missouri was also
pushing southeast into a more unstable air mass over parts of
south central Missouri. It still looks like the bulk of the
heavier rainfall associated with the larger complex of storms
will shift south of our area overnight...with lighter shower
activity to the north. Current forecast has this covered well
and have already sent out an update earlier this evening to
tweak the wording for the rest of the evening. No additional
update needed at this time.
issued at 251 PM CDT Wednesday Jul 1 2015
19z/2pm surface analysis shows a stationary frontal boundary
extending from near Quincy to just south of Paris. Scattered
showers are beginning to develop along this boundary and will become
more numerous as the afternoon progresses. 19z laps data shows
SBCAPE values of 1000 to 1500j/kg along/south of the front. Given
only modest instability...think areal coverage of convection will
remain scattered. Have therefore gone with chance probability of precipitation for the late
afternoon into the evening across the southern two-thirds of the
kilx County Warning Area...with only slight chance along/north of I-74. Low
pressure currently over Kansas will track slowly eastward into
Missouri tonight...providing the focus for additional shower and
thunderstorm development. While most model solutions suggest the
most widespread precipitation will remain south of the area...have
increased probability of precipitation to likely along/south of a Jacksonville to Paris line
from late evening through the overnight hours. Further north...only
widely scattered showers will be noted across the northern County Warning Area. As
the front sags further southward...cooler/drier air will gradually
filter in from the north overnight. As a result...low temperatures
will drop into the upper 50s along/north of I-74...but remain in the
middle to upper 60s south of I-70.
Long term...(thursday through wednesday)
issued at 251 PM CDT Wednesday Jul 1 2015
Broad upper trough to be prevalent across the eastern U.S. Into the
4th of July Holiday. This will keep temperatures cooler than normal
for early July...although a general warming trend will begin on
Sunday as the western ridge flattens and a sizable upper trough
swings through the Canadian prairies.
Models in reasonable agreement through much of the period. Highest
rain chances will be tomorrow morning across the southeast County Warning Area...as
the overnight convective complex drops into the lower Ohio Valley.
Northeast flow will continue to establish itself through the day
and shift the frontal boundary and associated rainfall to our
south. However...have maintained some lower chance pop's in the
15-30% range across mainly the southern County Warning Area into the weekend...as
a series of upper waves tracks through the general trough pattern.
Longer range models continue to feature a cold front approaching
from our northwest...associated with the trough in Canada...with the
period from Monday afternoon into especially Tuesday most favorable
for showers and thunderstorms. The latest GFS is more progressive
with this feature and clears things out by Wednesday morning...while
the European model (ecmwf) lingers the front over central Illinois as it starts to
parallel the upper flow. Will maintain some chance pop's for the
central and southern County Warning Area into Wednesday at this point.
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1125 PM CDT Wednesday Jul 1 2015
Main area of convection will remain south of the taf sites but we
will see scattered showers affect all areas excpt pia and bmi
overnight as a wave of low pressure travels well to our south.
As the area of low pressure tracks southeast of the area on
Thursday...a northeast flow will draw down some drier air in
the low levels and should begin to push the low VFR/MVFR ceilings that
look to be affecting most of the taf locations excpt for pia to
the south by afternoon with VFR conditions expected in all areas
by middle afternoon and on. Surface winds will be out of the
northeast at 10 to 15 kts through the period.