Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 012337
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
637 PM CDT Fri May 1 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 349 PM CDT Fri May 1 2015

First in a series of shortwaves will pass across the region
tonight. Band of mid clouds associated with the shortwave
currently stretches from Iowa into northern KS, and these clouds
will be pressing southeast and overspreading our CWA as the
evening progresses. Showers have also been associated with the mid
deck over IA, and these have been weakening as they work SE. I
have continued some slight chance PoPs over our far northern
counties, but given how dry the low levels are over the mid-
Mississippi Valley think that precip...if it does reach our
area...may be little more than sprinkles.

Overnight lows are expected to range from the 40s over southeast
sections of the CWA where the southward pressing surface ridge will
be exerting its greatest influence...to the lower 50s over northwest
parts of the FA.

Truett

.LONG TERM:  (Saturday through Next Friday)
Issued at 349 PM CDT Fri May 1 2015

Overall trends look on track and few substantial changes were
required for this forecast package.

Temperatures will continue warming each day over the next few
days, especially with return southerly flow and rising heights
aloft. Afternoon highs should reach the upper 70s to lower 80s by
Sunday. Similarly warm afternoon highs are expected through the
middle or end of next week. It will take a while for low-level
moisture to work back northward after a surface high pressure
center finally shifts farther east over the weekend, but dew
points will also start to increase late this weekend and into
early next week.

An upper ridge will flatten and shift across the area this
weekend, keeping the CWA beneath quasizonal flow until a low
pressure system moves into the southwestern CONUS and brings more
of a southwest flow pattern to the area by the middle of the week.
Precipitation chances should be limited to the northern CWA on
Saturday and Saturday night because those areas will be closer to
the upper support provided by a weak shortwave moving across
NE/MN/IA and closer to to the southern end of the best H85 LLJ
moisture convergence. An active frontal boundary should be too
far north for any precip to reach the CWA during the day on
Sunday, but once the boundary starts sinking southward,
precipitation chances increase accordingly between Sunday night
and Monday night. SHRA/TSRA chances during the middle of the week
are associated with a low pressure system lifting from the
southwestern CONUS into the plains.

Kanofsky

&&

.AVIATION:  (For the 00z TAFs through 00z Saturday Evening)
Issued at 629 PM CDT Fri May 1 2015

VFR flight conditions with light and variable wind is expected to
prevail tonight. Mid and high clouds AOA 10,000 FT will overspread
the area and there may be a few sprinkles or light showers over
northeast Missouri and West Central Illinois this evening, but
expect there to be little if any operational impact with this very
light precipitation. VFR conditions are expected to continue
Saturday with wind turning to the southwest as high pressure moves
east of the region.

Specifics for KSTL:

VFR flight conditions with light and variable wind is expected to
prevail tonight. Mid and high clouds AOA 10,000 FT will overspread
the terminal through the night. Expect ceilings Saturday to remain
VFR with variable heights from around 8,000 to well above 12,000
at times. Wind will turn to the southwest Saturday morning and
could be nearly a direct crosswind on the main runways for much of
the day, though wind speed looks to stay below 10kts.

Carney

&&

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

$$

WFO LSX





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