Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 161728
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1228 PM CDT Wed Apr 16 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 315 AM CDT Wed Apr 16 2014

Surface temperatures at 08z across the ongoing Freeze Warning
remained in the mid to upper 30s. With increasing winds for the
remainder of the night and only a few hours left until sunrise, it
does not look like temperatures will remain at or below freezing for
any appreciable length of time, therefore the Freeze Warning will be
canceled with the morning package.

Expect warm and dry weather today with highs in the upper 50s to mid
60s, but the tightening pressure gradient ahead of a surface low
over NE/SD will lead to windy conditions, especially during the
afternoon. At this time, the forecast winds do not meet LSX criteria
for a Wind Advisory (sustained winds of 30-39 mph/26-34 kt and/or
gusts of 45-57 mph/39-49 kts), therefore no wind headlines are
planned. If the actual winds today end up being stronger than
currently forecast, then a Wind Advisory may eventually be needed,
especially for parts of central/northern MO where the gradient will
be tightest.

The combination of strong and gusty winds, low RH, and low fuel
moisture values will produce Red Flag Warning conditions across
parts of the area. Please see the fire weather section below for
additional details.

Kanofsky

.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 315 AM CDT Wed Apr 16 2014

Red Flag Warning conditions are expected for parts of central,
eastern, and northeastern MO today with a heightened fire danger
elsewhere. The WFAS forecast of 10hr fuel moisture for this area
is 7-8% for today. Southerly winds will increase during the
morning hours and remain gusty through the afternoon. Expect
sustained winds of around 20 mph gusting to around 30 mph,
possibly higher at times. Minimum afternoon relative humidity
values should fall to 20-30% with the lowest values across parts
of central and northern MO. Since RFW criteria for wind and fuel
moisture will be met nearly everywhere this afternoon, the area
covered by the RFW is based on a forecast of where minimum RH
values are expected to fall below 25%. Depending on dew point and
temperature trends, the RFW might need to be expanded today.

Kanofsky


&&

.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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