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fxus63 klsx 230008 

Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
708 PM CDT Thu Jun 22 2017

Short term... (through late Friday afternoon)
issued at 349 PM CDT Thu Jun 22 2017

Just a few showers are currently moving across southeast Missouri
into south central Illinois. These are occurring on the northern
periphery of Tropical Depression Cindy. Moisture and showers
associated with Cindy will be confined to the southeastern part of
the County Warning Area while an shortwave trough moves across Iowa into Illinois in
the mid-level flow. This will in turn cause the cold front that is
currently over the upper Midwest to drop south across the region
late tonight and on Friday at the same time the remnants from Cindy
moves northeast across Arkansas and Kentucky. Have kept high
chance/low likely pops for showers and thunderstorms late tonight
through early afternoon on Friday before the rain moves southeast of
the area by late in the afternoon.

Agreeable MOS guidance looks good for lows tonight. Highs tomorrow
will be closer to the sref mean MOS temperatures.


Long term... (friday night through next thursday)
issued at 349 PM CDT Thu Jun 22 2017

Much cooler and drier weather will be the rule beginning Friday
night and lasting through the weekend and at least through early
next week.

Longwave trough will carve out across the eastern 2/3 of the Continental U.S.
This weekend and early next week with northwest flow aloft across
the mid-Mississippi Valley. There looks to be at least a few
reinforcing shots of cooler air behind individual shortwave troughs
and associated cold fronts. The end result should be 4 days of well
below normal temperatures along with dry weather. While the
possibility of isolated instability showers cannot totally be
ruled out during the afternoon hours Sunday or Monday, better
chance of this activity will be further to the northeast where
stronger mid/upper level forcing will reside.

Very strong surface high (~1025 hpa) will settle into the bi-state
area early next week. This high will slowly slide to the east
Tuesday into Wednesday. Return flow around this high will bring
warm/moist advection which will bring an increasing threat for
showers and thunderstorms, mainly focused on the Wednesday/Thursday



Aviation... (for the 00z tafs through 00z Friday evening)
issued at 631 PM CDT Thu Jun 22 2017

A cold front over northwest Iowa will move southeast into Missouri
overnight. Meanwhile, moisture from Tropical Depression Cindy will
continue to stream up into the mid Mississippi Valley ahead of the
front. While VFR conditions are expected to prevail across most of
the area through the evening, there are a few showers moving into
southern portions of the area which could produce some MVFR
ceilings/visibilities as the move north. Guidance continues to develop
showers and thunderstorms ahead of the front as it moves
southeast into our area overnight. Additionally, expect MVFR
ceilings to develop along and behind the front as it interacts
with the rich low level moisture overnight. MVFR ceilings will
likely persist through most of, if not all morning but should lift
and scatter during the afternoon as drier air pours into the area
from the northwest.

Specifics for kstl:

Expect VFR conditions to prevail at Lambert this evening and
probably for a good portion of the overnight hours too. However, a
cold front currently over Iowa will move southeast into the
vicinity of the terminal between 10-12z. Expect showers and
thunderstorms to develop along and ahead of the front...along with
MVFR ceilings as the front interacts with rich low level moisture
from Tropical Depression Cindy. Current thinking is that the front
will be through the terminal by 14-15z Friday but MVFR ceilings
will likely persist for a few hours after the front moves
through...probably through the entire morning and for a few hours
of the afternoon. Expect VFR conditions to prevail thereafter as
cooler and drier air filters into the region.



Lsx watches/warnings/advisories...

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