Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 161941
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
241 PM CDT Wed Apr 16 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 233 PM CDT Wed Apr 16 2014

A rather tranquil night is on tap for the area. The surface low
currently in extreme northwest Iowa will move northeastward tonight
and into Wisconsin by daybreak, with the attendant cold front
stretching from northeast MO into west central MO at 12Z. As a
result the surface pressure gradient will weaken this evening. This
along with an end to deep mixing around sunset will result in
quickly diminishing southerly surface winds. Surface winds do remain
southerly all night but due to extensive lower tropospheric ridging
well into the GOM, low level moisture return will be nil and limited
to an increase in mid-hi level moisture. The associated cloudiness
and southerly winds will keep temperatures warmer than last night.

Glass

.LONG TERM: (Tonight through Tuesday)
Issued at 315 AM CDT Wed Apr 16 2014

Surface low and upper vort max move through IA into WI tonight,
leaving a trailing cold front stretching from WI into northern MO
and central KS. The wind shift and temperature contrast across the
boundary are not terribly impressive tomorrow, but with a vort max
forecast to approach and move across the area, the boundary could
provide a focus for SHRA during the afternoon and evening.
Instability parameters look weak therefore kept thunder out of the
forecast.

It`s not clear whether the aforementioned boundary washes out in
place or sinks a bit farther south tomorrow night, but a new warm
front should develop somewhere in the region on Fri/Sat as another
surface low develops to the west in response to an approaching
upper vort max. ECMWF/GEM/GFS all show different orientations for
the warm front which extends from a surface low over SD/ND, CO, or
both depending on which model and which run. Over the last couple
of days, the model solutions for Fri-Mon have varied quite a bit
compared to their previous runs (particularly with regards to the
location of surface synoptic systems and the placement of upper
vorts), and tonight`s runs are no exception. Since the models seem
fairly insistent that some kind of low pressure system ought to
affect this part of the country late in the weekend or early next
week, chance PoPs for Sun/Mon look like an acceptable compromise
in light of the model uncertainty.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1219 PM CDT Wed Apr 16 2014

The main element to contend with will be surface winds. Southerly
winds will gust to 25+ kts this afternoon, diminishing around
sunset. The wind will slowly and gradually veer to more south
southwesterly during the late night and early morning hours on
Thursday with a wind shift to the west as a weak cold front slowly
pushes across the region. VFR flight conditions will prevail
through the forecast period. Any chance of showers will be beyond
the valid TAF period - Thursday afternoon and evening.

Specifics for KSTL:

The main element to contend with will be surface winds. Southerly
winds will gust to 25+ kts this afternoon, diminishing around sunset.
The wind will slowly and gradually veer to more south southwesterly
on Thursday morning with a wind shift to the west in the mid-late
afternoon associated with passage of a weak cold front. VFR flight
conditions will prevail through the forecast period. Any chance of
showers will be beyond the valid TAF period - Thursday evening.

Glass

&&

.FIRE WEATHER:
Issued at 233 PM CDT Wed Apr 16 2014

20 foot winds are strong and gusty. 10 hour fuel moisture and
relative humidity thus far this afternoon has remained above
criteria for red flag conditions. There are still 2-3 hours left
of potential and I expect that fuel moisture will fall below 9%
and RH will likewise dip at or below 25% in at least parts of the
warning area. Thus we will keep the Red Flag Warning going through
700 pm as scheduled. Conditions will be improved on Thursday with
lighter winds and slightly more moisture along with a cold frontal
passage.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...RED FLAG WARNING until 7 PM CDT this evening FOR Audrain MO-
     Boone MO-Callaway MO-Cole MO-Franklin MO-Gasconade MO-
     Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-Moniteau
     MO-Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls MO-Shelby
     MO-St. Charles MO-St. Louis City MO-St. Louis MO-Warren MO.

IL...NONE.
&&

$$

WFO LSX






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