Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 012055
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
355 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 18z TAFs through 18z Saturday Afternoon)
Issued at 1242 PM CDT Fri May 1 2015

Several weak shortwaves will pass over the region during the next
24 hours. However, low level moisture will be non-existent thanks
to surface ridge maintaining its firm grip over the mid-
Mississippi Valley, so impacts of the shortwave energy will be
limited to occasional bands of mid level cloudiness (with bases
aoa 8kft). Any threat of rain will remain very low. Surface winds
will also remain quite light.

Specifics for KSTL: VFR conditions will continue into the start of
the weekend, with the clear skies of this afternoon giving way to
a bit of mid level cloudiness (bases aoa 8kft) tonight and into
Saturday. Winds will remain quite light...generally aob
6 kts...into Saturday morning.

Truett

&&

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

$$

WFO LSX






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