Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
341 PM CDT Wednesday Jun 3 2015

Synopsis...
issued at 340 PM CDT Wednesday Jun 3 2015

Apparently just enough forcing with the upper level trough
approaching from the west to kick off an area of showers this
afternoon in our western County Warning Area and were moving east. Lack of
cape/shear will not mention thunder the remainder of the
afternoon. 3 PM temperatures were in the middle to upper 70s at most
locations.

&&

Short term...(this evening through thursday)
issued at 340 PM CDT Wednesday Jun 3 2015

Forecast focus on a chance of thunderstorms.

Tonight...low confidence on precipitation trends as operational
models are very much in disagreement of timing and coverage of any
showers or storms. Certainly the strongest forcing and shear will
remain well to our west so this is where the bulk of the storms will
exist. Will maintain small probability of precipitation but there may also be plenty of dry
hours. This will be a warmer night with more cloud cover and slowly
increasing low level moisture. Minimum temperatures will be in the
lower 60s at most locations.

Thursday...low confidence again with where the bulk of the storms
will occur with some of the models totally dry. I will only have 30
probability of precipitation due to this lack of confidence. Once again the better forcing
remains well to our west mainly in the plains. Maximum temperatures
will be around 80.

Long term...(thursday night through wednesday)
issued at 340 PM CDT Wednesday Jun 3 2015

Increasing chances for significant rains late Thursday and Friday the
main forecast issue.

Long term forecast assessment...average to below average or fair to
poor with solutions poor ability to initiate convection and then translate
these convective systems main concern Thursday night and Friday. Verification
from last night and today shows convection conceptual models of evolutions
are poorly handled. Persistence supports a moderate strength and maturing
convective system to affect at least southern portions and possibly
more Thursday night into Friday am. This will impact redevelopment Friday
PM and evening with backdoor cool front. Local past events suggest
areas of .5 to locally 1.5 plus inches of rain with low risk of severe
until possibly late Friday PM if have enough heating. Impacts on high
temperatures up to 5 degrees lower a secondary concern for Friday.

Overview...initialization and verification poor to very with convective
systems with hi-res European model (ecmwf) and forcing from UKMET the most adequate.
Run to run variance is large and between convective events in solutions
with a 60/40 mix of hi-res European model (ecmwf) to GFS and 80km NAM-WRF forcing.

Thursday night...forcing from mesoscale convective system generation tool indicates
convective system to arrive near midnight or later with possibly
some strong storms in far south near inflow region. This will have
an impact on mins with heaviest precipitation due to evaporative
cooling suggesting lows may be a few degrees too high in south for
later shifts. Have likely probability of precipitation all but far north.

Friday...lots of clouds and possible training along with backdoor cool
front to make for a challenging forecast. Reliable large scale features
suggests some redevelopment late PM and evening. Non-hydrostatic process
will preclude reliability of any solutions with upper level
diffluence supportive of redevelopment over southeast or far east sections.
High temperatures of 75 to 80 degrees NE to SW with moderate to
high confidence some areas may be too high due to more clouds and
lingering precipitation. Highest precipitation values Thursday
night and Friday are suggested to fall along and especially south
of I-80 corridor into northern Missouri and west central
Illinois. Once again likely probability of precipitation along and south of Highway 30.

Friday night...backdoor cool front suggests low clouds and some evening
showers possible but again timing an issue as mentioned before. Best
chances should be along and south of Highway 34. Clearing late in NE
sections suggested for mins in the middle 50s and possibly a bit
lower.

Saturday...east winds and lower dewpoints for a seasonable day
with some late PM showers and isolated storm in far west toward
evening with next approaching digging short wave.

Saturday night and Sunday...moderate probability of precipitation with likely probability of precipitation suggested
with nocturnal mesoscale convective system that may have potential for heavy rains and isolated
severe for mostly straight line winds. This issue should be better known
in the next 24 to 48 hours. Temperatures again should be impacted with
60 to 65 degrees for lows and 77 to 83 a decent starting point.

Sunday night through Wednesday...precipitation to end Sunday night with
weak northwest uper level flow and surface high for seasonable temperatures...dry
to mostly dry and moderate humidities. Highs upper 70s to lower 80s
and lows in the upper 50s to lower 60s.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 115 PM CDT Wednesday Jun 3 2015

VFR conds through this taf cycle with low confidence in convective
trends. Much of the convection should remain well to our west and
north. South winds 10 to 20 knots this afternoon then becoming
southwest overnight and into Thursday at around 10 knots or less.



&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.

&&

$$

Synopsis...haase
short term...haase
long term...Nichols
aviation...haase

National Weather Service Glossary of Abbreviations