Area forecast discussion
National Weather Service Des Moines Iowa
413 PM CDT Tuesday Jun 18 2013
Short term.../tonight /...
issued at 410 PM CDT Tuesday Jun 18 2013
Weak boundary moving through the eastern County Warning Area...denoted by wind shift
from northwest to northeast/east behind the boundary. This was
associated with a weak upper level disturbance dropping through the
region earlier today. Seeing a few radar echoes go up near the
boundary in area of enhanced cumulus over the east/southeastern County Warning Area.
Latest mesoanalysis suggesting decent cape and some shear across the
far southeastern County Warning Area. Therefore may continue to see a couple
isolated cells through the remainder of the afternoon hours. Expect
any activity to die off with sunset and the current cumulus field to
clear as surface high pressure skirts the area to the east. Upper level
ridging will build in aloft from the west...with return flow setting
up across the western County Warning Area late tonight. Theta-E advection begins
aloft in southwest/westerly flow toward 09-12z. This may result in
some middle level cloud cover developing across the western County Warning Area toward
sunrise Wednesday. Moisture push not all that strong...so stuck with
increasing cloud cover and a dry forecast. May see a little light
fog develop with the clear skies and light winds across the eastern
County Warning Area...but visibilities expected to remain in the 3-5 mile range so
did not mention fog in the grids.
Long term.../Wednesday through Tuesday/...
issued at 410 PM CDT Tuesday Jun 18 2013
Upper level ridge will gradually settle over the Midwest the next
several days as an upper low churns over the Pacific northwest.
Numerous short waves will ripple through the southwest flow and
over top the ridge into the weekend before the upper low lifts
north into Canada and a subtropical high begins to build north
into the nations middle section. The initial short wave arrives over
western Iowa by Wednesday afternoon accompanied by increasing
Theta-E advection into the overnight. A better chance for
convection arrives Thursday as the Theta-E advection continues and
the low level jet becomes more focused into western Iowa. Some
severe weather may accompany each system through a better chance
appears late Thursday into Thursday night. Models suggesting the
potential for a complex to develop over North Dakota then follow
the corfidi vectors down the instability axis and drop south into
the forecast area.
The pattern does not change much until Sunday as the system pulls
northeast into Canada. Temperatures through the period will
gradually warm and should be in the the middle 80s to lower 90s. The
thermal ridge begins to arrive toward the end of the period with
the 700 mb cap of +12c to +16c arriving. This would lead to highs
well into the 90s. Have not gone quite this high yet but have
trended warmer.
&&
Aviation...18/18z
issued at 1245 PM CDT Tuesday Jun 18 2013
Mainly VFR conditions expected through this evening...with
possibility for visibilities to drop to MVFR in some light fog late
tonight. Some instability around this afternoon suggesting
potential for an isolated thunderstorms and rain near kmcw...Kalo...and kotm.
However uncertainty is high as upper level disturbance is exiting
the area...this left out any mention of thunder in the tafs at
this time. Winds to shift around to the east/southeast through the
period...with moisture increasing aloft late tonight. Therefore
expect some low/middle VFR ceilings by early Wednesday morning across the
western taf sites.
&&
Dmx watches/warnings/advisories...none.
&&
$$
Short term...beerends
long term...donavon
aviation...beerends
