Area forecast discussion
National Weather Service quadrant cities Iowa Illinois
1122 PM CDT Tuesday Jun 18 2013
Update...
issued at 442 PM CDT Tuesday Jun 18 2013
A fairly significant pop/wx/sky/temp/wind/sky update was sent just
prior to 420 PM to reflect a dry forecast except for the far
southwestern County Warning Area. I do not expect strong convection to be
sustained in our County Warning Area...but the this area could see some
dissipating showers as the move from dmx/S County Warning Area. Skies are nearly
clear now in most locations...and will continue to clear. A
perfect night for outdoor activities should greet those who
venture outside tonight.
Ervin
&&
Synopsis...
issued at 221 PM CDT Tuesday Jun 18 2013
Seasonably strong backd0or cold front bringing refreshingly
comfortable air into the forecast area under mostly sunny skies.
Area temperatures at 2 PM are in the middle to upper 70s with dewpoints
on the 50s to lower 60s south on NE winds of 5 to 15 miles per hour. Upstream
analysis shows high now northern Wisconsin to slide into Ohio
Valley by Wednesday evening bringing a warming trend and higher
dewpoints starting late Wednesday afternoon. Upstream analysis
shows typical middle Summer zonal flow with temperatures slightly
above to above normal with a risk of thunderstorms late this week
into next week.
&&
Short term...(this evening through wednesday)
issued at 221 PM CDT Tuesday Jun 18 2013
Tonight...weak high pressure extending from Lake Michigan to allow for
cool mins under a clear to mostly clear sky and light east winds.
Local tools suggest upper 40s in favored low lying locations in NE
1/3 of the area and lower to middle 50s elsewhere. Nice weather
for opening windows.
Wednesday...another nice with fair skies and light east winds becoming
southeast by middle day. Highs a few degrees higher than today
ranging from 77 NE to 83 SW sections.
Nichols
Long term...(wednesday night through next tuesday)
issued at 221 PM CDT Tuesday Jun 18 2013
Wednesday night and Thursday...the mean trends on the latest 12z runs
suggest seasonably strong western Great Lakes anticyclone to start to
weaken and migrate eastward this period...while upper ridging
starts to get squeezed/amplified across the plains in response to
Pacific northwest large upper cyclone/trough complex building inland.
Ridge-undercutting wave energy will utilize some elevated return
flow to produce convection across the central into northern plains/MO
River Valley regions...but Wednesday night should stay dry locally with
just some debris clouds drifting into the western County Warning Area. Lows
in the middle 50s in the northeast...to the lower 60s west. The
plume of elevated return flow/warm air advection should try to adjust
eastward on Thursday...along with low level warm front trying to retreat
northward out of MO and up across the dvn County Warning Area. Although lower level
forcing appears to be not all that great at this time...will keep chance probability of precipitation
going all day. Depending on cloud debris and boundary placement...
high temperatures for Thursday tricky with large variations across the local area
possible. Will lean toward climatology for temperatures for now. Taking medium
range model blend...it appears bulk of nocturnal mesoscale convective system inducing
parameters will set up across the MO River Valley into western Minnesota Thursday
night...but secondary support zone for an elevated Wing of
convection or even a type of mesoscale convective system may try to develop across north
central Iowa and into the dvn County Warning Area late Thursday night. The latest run 12z
European model (ecmwf) continues to be the most bullish model with this idea...while
the 12z run GFS with it/S high amplification of the upper ridge
shunts everything well to the north and northwest...keep the dvn
County Warning Area dry into Friday morning. Will have to keep chance probability of precipitation going especially
in the northwestern half of the dvn County Warning Area closer to elevated thta-
transport Wing.
Friday and Saturday...so starts the period of what happens the day or
period before will greatly impact the next day. The European model (ecmwf) suggests
that morning mesoscale convective system remnants will decay diurnally and enhance a
west-to-east boundary in place across the dvn County Warning Area or very close...
making a Focal Point for more late day and night convection to fire
on. Again if this occurs...it appears will be a secondary convective
zone with main forcing in southwesterly wave train across the northern
plains. Ring of fire pattern establishing across the northern
plains/upper Midwest into the Great Lakes...but how far north or south
the prime mesoscale convective system axis lays out still uncertain at this time. The GFS
maintains high amplitude northerly bias with the dvn County Warning Area mainly dry
Friday night through Sunday morning...while mesoscale convective system/S rage across the
Dakotas...Minnesota into WI and the u.P. Of Michigan. The GFS also builds a high
cape airmass/pool locally with highs in the low to middle 90s and dewpoints
in the 70s. But the European model (ecmwf) and Gem are more ominous with a lower
amplitude upper ridge and further south low level baroclinicity/storm
track. These models would put US on the fringe or under the direct
path of one or more mesoscale convective system/S Friday night and again Sat night. Each one
would have the capability of producing heavy rainfall and possibly
some severe weather...especially the Sat evening/night complex if it
materializes close enough to impact the local area and feed on a high
cape airmass. Needless to say with the potential shown by the European model (ecmwf)
and Gem...will have to keep decent chance probability of precipitation going through the weekend
especially the north half. Will go in between the GFS and European model (ecmwf) high
temperature potential for Sat with upper 80s to near 90 with building heat
indices if dewpoints can get into at least the lower 70s. GFS middle 70 surface
dewpoints for Sat appear overdone and produce 5k+ j/kg sbcapes by late Sat
afternoon.
Sunday through next Tuesday...longer range indications suggest the
dvn County Warning Area to lie very close to ongoing ring of fire pattern across the
upper Midwest with almost daily chances for storms to fire in the
local area or possibly bleed into the County Warning Area from the west or northwest
late at night. Suppose a low chance that most of the activity maintains
to the north across the Dakotas/Minnesota and WI while we remain hot and
capped through Tuesday...but odds are a storm complex will at least
glance the County Warning Area sometime in this extended period...possibly a
significant cape eating storm complex if 18 to 23 c 850 mb mb temperature
gradient can sag through the region. Climatically normal/typical middle
summertime pattern looks to be in store. ..12..
&&
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1121 PM CDT Tuesday Jun 18 2013
Nearly ideal flying weather is expected over eastern Iowa and
northern Illinois through the next 24 hours. Clear skies will last
through 06z/20. Winds will be light easterly...but will remain
well under 10 kts at all times. Visibility should be unlimited
through the period.
&&
Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&
$$
Update...Ervin
synopsis...Nichols
short term...Nichols
long term...12
aviation...Ervin
