Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service quadrant cities Iowa Illinois
642 am CDT Friday may 22 2015

Synopsis...
issued at 317 am CDT Friday may 22 2015

A weak surface trough stretched across the area this morning.
This trough led to some showers and thunderstorms across the
western Great Lakes yesterday evening. In our area...the trough
brought drier air into the area as high pressure began to build in
across the upper Great Lakes. This high pressure resulted in clear
skies this morning along with lows in the 40s across the area.

&&

Short term...(today and tonight)
issued at 317 am CDT Friday may 22 2015

Quiet weather for the short term. The main forecast concern are
the temperatures through the short term. From a sensible weather
Point of View...Friday should be perfect. High clouds will move
into the area late in the day as our pattern turns to a more wet
one.

Models are in good agreement with the momentum fields through the
short term. Ridging across the area today will turn to a more
southwest flow later in the day. Models forecast a wave moving
into the area tonight. This wave will likely lead to middle level
clouds and no precipitation. Low level moisture will begin to return
across the area tonight into Saturday. This will lead to partly
cloudy to mostly cloudy skies for the area tonight. This will help
moderate our temperatures tonight.

As far as temperatures go for today...boi verify shows that bcconsraw has
been the best for high temperatures for the last 30 days or so. Populated
with this and increased temperatures a few degrees. This was also the
case for low temperatures.

Long term...(saturday through thursday)
issued at 317 am CDT Friday may 22 2015

Pattern to become active with periodic bouts of showers and storms through the
period... with the main challenges of timing and impact on temperatures.

Upper level ridge overhead at the start of the Memorial Day weekend will slowly
migrate to the southeast states by the end of the weekend and remain
anchored there for much of next week. This will act as a block to slow the
progression of western Continental U.S. Systems and generally keep our area in active
southwest flow aloft favorable for periodic disturbances. At the same
time... Gulf moisture will be increasing through the weekend into early next
week and will combine with the periodic disturbances for several bouts of
showers and storms. Severe weather is not anticipated into early next week due
to increasing tropospheric moisture /limited dry air/... and low instability.
However... local areas of heavy rain possible as precipitable water values
increase to around 1.5 inches /2+ Standard deviations above normal/ by Sunday
evening.

Best thoughts on timing out rain chances for the Holiday weekend attim is that
Saturday looks to be the best of the weekend in terms of many dry hours. Rain
chances then increase by middle to late Saturday evening west/southwest County Warning Area with
low level jet and attendant warm...moist transport and convergence. Continued
increasing rain chances elsewhere overnight Saturday night with likelihood of
rain on Sunday an overall damp day with veering jet and moist axis lingering.
Some indications that rain may taper off in coverage Sunday night and on Memorial
Day as potential to be in-between upper air disturbances if timing holds... with
generally scattered coverage and several dry hours to be found. Temperatures
look to be near seasonal levels through the Holiday weekend with increasing
humidity.

Tuesday through Friday... if timing holds then potential to see a break from rain
chances or at least lower chances midweek with veering flow and attendant drying
as an upper level shortwave passes from the upper Midwest into the Great Lakes.
But then late week...active pattern looks to become re-established as upper level
ridge amplifies over southeast states and moisture returns with more energy
traversing slowly eastward from western Continental U.S.. temperatures generally look to be around
normal.

&&

Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 620 am CDT Friday may 22 2015

VFR conditions are forecast through the taf period. High pressure
today will give way to moisture returning from the south and west.
This moisture will return as middle level to high level clouds. Have
included a bkn100 overnight to depict this moisture return.
Otherwise winds appear to be light and out of the east.

&&

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

$$

Synopsis...Gibbs
short term...Gibbs
long term...05
aviation...Gibbs

National Weather Service Glossary of Abbreviations