Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 171152
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
652 AM CDT Thu Apr 17 2014

.SHORT TERM:  (Through Tonight)
Issued at 300 AM CDT Thu Apr 17 2014

A weak cold front will move into the area today and could serve as
the focus for scattered light rain showers during the afternoon
and evening. Convergence along the front is not very impressive
and the low levels are somewhat dry, but the combination of
increasing large scale ascent ahead of an approaching vort max
along with the presence of a surface boundary merits slight chance
to chance PoPs.

Kanofsky

.LONG TERM:  (Tomorrow through Wednesday)
Issued at 300 AM CDT Thu Apr 17 2014

For the last 4 nights in a row, no two consecutive 00z runs of the
ECMWF/GFS/GEM have had the same solution for upcoming frontal
systems, and there has also been a fair amount of variability
between models regarding the location of important features such as
upper vorticity maxima and surface boundaries. The latest runs keep
a strong vort max and its surface low up near the US/Canada border
on Fri night and Sat, therefore precipitation is no longer expected
with this system across the LSX CWA. The dominant feature for
Fri-Sat now appears to be ridging. Winds should eventually turn
southerly, bringing warmer air into the region for Sat and
reinforcing a baroclinic zone extending from the US/Canada system
as it starts to occlude. A broad trough moving through the desert
southwest could bring precipitation to the area on Sun/Mon. Chance
PoPs remain an acceptable compromise in light of the model
uncertainty. Confidence remains low in the forecast for this
weekend and beyond.

Kanofsky

&&

.AVIATION:  (For the 12z TAFs through 12z Friday Morning)
Issued at 638 AM CDT Thu Apr 17 2014

Weak cold front currently on the door step of KCOU and KUIN will
drift east today, and not reach the STL metro area until 21-00z
time frame. Post frontal band of MVFR SC with bases 1-2kft has
worked into northern Missouri, and over the last few hours higher
clouds have obscured their movement on satellite imagery. However,
surface ob trends as well as RUC low level RH progs suggest that
this cloud deck will reach KUIN shortly, and then dissipate by
mid-late morning. With this expected trend, cloud deck should
remain n of KCOU, and not threaten STL area. Otherwise, cloud
trends today and into this evening should be dominated by a
thickening mid deck with bases aoa 5kft. We are expecting a few
post frontal showers, but given the hit and miss coverage that is
anticipated have not included in TAFS at this time.

Specifics for KSTL: Weak cold front currently over mid MO not
expected to reach the area until the 21-23z time frame, with winds
shifting slowly to the northwest once fropa occurs. Otherwise,
looking for a gradual increase in mid clouds over the area, with
bases remaining aoa 5kft. A few showers are possible in the
evening, but as mentioned in the primary aviation discussion have
omitted from this TAF set due to the spotty nature of the precip.

Truett

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






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