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Area forecast discussion...updated aviation 
National Weather Service St Louis MO
554 PM CST Mon Jan 26 2015

Short term: (tonight through Friday night)
issued at 349 PM CST Mon Jan 26 2015

Northwest flow is expected to continue thru Tue across the ern Continental U.S. While
a ridge extends along The Rockies. Main flow is across the Pacific
northwest while a cut off low continues to spin off the sthrn California/Baja
Coast. The closed low gets absorbed into the mean flow on Tue and
flattens the ridge Tue night/Wed. Upper heights across the mid-MS
Vly begin rising Tuesday night as a low amplitude ridge builds into
the area for Wed ahead of the energy, which is the remnants of the
closed low, approaches the region late Wed night into Thu mrng. All
this while a separate nthrn stream short wave follows closely behind
for Thu aftn/Thu evng. These two features will effectively reinforce
the East Coast trough towards the end of the wk.

At the sfc, weak low/clipper that produced the light snow across
Illinois today will quickly exit to the southeast this evng. Not much cold air advection
behind this system despite nwrly winds. Temps are in the 50s and
60s in the air behind this system across the plains today. Sfc
ridge passes to the NE of the forecast area overnight allowing winds to
become S/south-southeast by Tue mrng. New surface low dvlps in the Lee side trough
on Tue in response to energy topping the ridge and tracks east-northeast to
near keok by 6z Thu. This puts the County Warning Area in the warm sector on Wed.
The 850 mb thermal ridge noses into the forecast area drng the aftn with
temps ranging 8-12c, though soundings suggest we will not realize
that potential, only mixing to near 925mb. Guidance indicates that
most of the precip will remain north of the low track, so have
just slight chance pops across the nthrn and ern portions of the
County Warning Area for late Wed night into Thu mrng. The low moves into the ern
grt lks Thu with the cold air advection on the backside of the storm returning
temps closer to normal for the end of the wk. Another short wave
comes onshore along the West Coast Wed night/Thu. This system is
expected to be a player in a potential wknd storm system.

There will likely be a significant east/west temp gradient across the County Warning Area
on Tue due to potential cloud cover along and east of the MS r on
Tue and a better thermal profile with deeper mixing across cntrl MO
on Wed. Temp gradient relaxes for Thu and Fri under cold air advection. Used a
blend of MOS guidance along and east of the MS r on Tue due to
expected cloud cover. Didn't use the cooler met guidance exclusively
as it has had a cool bias recently. Went closer to the warmer mav
across cntrl MO on Tue. Went aoa guidance on Wed due the synoptic
set up but didn't get carried away due to the limited mixing.

2%

Long term: (saturday through next monday)
issued at 349 PM CST Mon Jan 26 2015

The trough that moves onshore late in the wk cuts off over the
wknd and slowly drifts south along the Baja Peninsula. Meanwhile,
another short wave drops out of Canada in the mean flow with
height falls continuing into sun until the trough axis passes sun
aftn/evng. GFS and European model (ecmwf) both have precip mvng into the area late
Sat and continuing into sun but differ significantly in the
details. The GFS has a decent sfc low tracking from the nthrn
plains into the grt lks while the European model (ecmwf) has a weaker low mvng from
the sthrn plains into the southeast. Guidance has been anything but
consistent with this system having it one run and then not on the
next so do not have a great deal of confidence in any solution
attm. With colder air in place, the system bears watching.

2%
&&

Aviation: (for the 00z tafs through 00z Tuesday evening)
issued at 554 PM CST Mon Jan 26 2015

Next clipper system moving through forecast area this evening, so
winds to veer to the west then northwest. As for cloud cover, tafs
along Mississippi River to see MVFR cigs move back in around 02z
Tuesday in KUIN and around 05z Tuesday in Metro area. Kcou to
remain mostly clear through forecast period. KUIN to scatter by
mid morning on Tuesday while Metro are will not clear out til
towards 00z Wednesday. In the meantime, surface ridge to build in
and winds will veer to the east towards end of forecast period.

Specifics for kstl:
next clipper system moving through forecast area this evening, so
winds to veer to the west then northwest. As for cloud cover,
Metro area will see MVFR cigs move back in around 05z Tuesday.
Cigs will not clear out til towards 01z Wednesday. In the
meantime, surface ridge to build in and winds will veer to the
east towards end of forecast period.

Byrd
&&

Lsx watches/warnings/advisories:
MO...none.
Illinois...none.
&&

$$

Weather forecast office lsx

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