Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 220449
Area Forecast Discussion
National Weather Service Lincoln IL
1149 PM CDT Mon Apr 21 2014
ISSUED 903 PM CDT Mon Apr 21 2014
Showers continue to move across parts of the area this evening.
Current forecast looks ok, but need to make some adjustments to
location of bulk of light pcpn. In addition, will need to remove
mention of thunder from grids/forecast for rest of the evening.
Line of additional showers/storms to the northwest of the area
earlier this evening is dissipating and don`t believe this will be
a factor once front moves through overnight. Expect update shortly.
ISSUED 1149 PM CDT Mon Apr 21 2014
VFR conditions will continue at all sites next 24hrs. Precip is
well past the sites, but clouds around 4-5kft still lingers over
the area as the front is slow to move across the state tonight.
Based on satellite trends, clouds will clear as the front moves
across the state and TAF sites. Once skies clear overnight,
believe they will remain clear through rest of the TAF period. SPI
has some light fog right now and believe this is from all the rain
they had this morning. Will have a TEMPO group to cover this now
and even for several hours once skies clear. Winds will become
northwest behind the front overnight. Then expecting good mixing
tomorrow and winds gusting to around 20kts from the north to northwest.
Winds will decrease during the early evening hours after 00z and
be out of the north.
ISSUED 256 PM CDT Mon Apr 21 2014
Much as anticipated, scattered showers and isolated thunderstorms
are spreading across central and southeast Illinois today,
associated with the passage of a weak frontal system.
Precipitation chances end later tonight as the system pushes east
of the area. Then, primary forecast concerns turn to precipitation
chances with a stronger system for Thursday, as well as with a
more uncertain weather pattern to start next week.
SHORT TERM...Tonight through Thursday:
Given the current speed of the system, the precipitation threat
across the forecast area should end by shortly after midnight
tonight, with fairly rapid clearing expected in its wake.
The cooler air filtering in behind today`s system will drop
temperatures back closer to normal for Tuesday and Wednesday
(highs in the 60s). Quiet weather is expected for this period as
well as upper/surface ridging build across the area.
A stronger system than today`s is still on track for
Thursday/Thursday night, although the severe weather threat with
this system still does not appear to be very high. Instability is
likely to be rather low (CAPE values AOB 1000 j/kg), but bulk
shear will be better (on the order of 40 kts). Some of the guidance
still suggests we may see precipitation as early as late
Wednesday afternoon/Wednesday night in the pre-system warm
advection regime, but the most favored area for this precipitation
remains north of the forecast area. However, the strong WAA will
boost temperatures will above normal once again, with highs in the
70s in many areas.
LONG TERM...Friday through Monday:
Cooler temperatures begin to spill into the area Friday behind
Thursday`s system, but quiet weather is anticipated. From
Saturday, and especially Sunday, through the end of the period,
the forecast details become especially murky. While there is
general agreement that a Rex block will develop during the period,
the specific placement of the ridge and trofs is problematic at
best. The GFS and Canadian models have consistently kept our area
under the influence of the upper ridge and sprawling/dry surface
high, while the ECMWF has consistently pushed the upper low more
quickly beneath the ridge position. These differences suggest that
either an extended dry period (GFS/Canadian) or extended wet
period (ECMWF) is possible. Obviously, this is not very helpful,
and the considerable ensemble spread within each specific model is
not helpful either. So, given the considerable uncertainty,
keeping pops to the drier side of 50/50 seems to be the best bet.
Hopefully the models will sort out their differences soon with
respect to the expected blocking pattern.