Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
1252 PM CDT Friday may 22 2015

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

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

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 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 18z tafs through 18z Saturday afternoon)
issued at 1241 PM CDT Friday may 22 2015

VFR conditions will continue through this taf preiod. High level
clouds will gradually overspread the area from the southwest and moisture levels increase on the west side of a
departing high pressure. Light and variable winds will become more
southerly late in the period at about 5-10kts.


Dvn watches/warnings/advisories...


short term...Gibbs
long term...05

National Weather Service Glossary of Abbreviations