Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLSX 281140
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
640 AM CDT Sat Mar 28 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 352 AM CDT Sat Mar 28 2015

Focus this morning will be on the potential for accumulating snow...
primarily across central MO. Widespread cloudiness has moved into
the area overnight in advance of a short wave dropping SE in the NW
flow. Not much sfc reflection to this feature with most of the
forcing coming from the mid levels. Radar not at all impressive at
0345 with just light returns showing up from wrn IA into cntrl MO
with only a few stations even reporting precip. Models indicate that
coverage/intensity should gradually increase 9Z-12Z as the precip
continues to slide SSE. Guidance has shifted the precip axis a
little further west now showing most of the QPF west of the CWA so
have attempted to tighten up the eastern edge of the going PoP fcst.
That being said...I still believe areas along and west of a Columbia
to Jeff City line may still get a few tenths of an inch this morning
before the system rapidly slips south of the area. It appears that
most of the precip will be in EAX and SGF CWAs this mrng with the
system just grazing our common border. Any threat of measurable
precip should be well south of the FA by 18Z. The rest of the day
will feature seasonably cold temps in the 40s which is 10-15
degrees below average.

Miller

.LONG TERM:  (Tonight through Friday)
Issued at 352 AM CDT Sat Mar 28 2015

High pressure retreats to the east of the area tonight resulting in
the onset of low level warm advection. The WAA combined with large
scale ascent associated with a short wave digging through the
northern Plains is expected to produce a band/region of showers in
advance of the next cold front. Present indications are the
precipitation will remain just northwest of the CWA through
daybreak, centered from eastern IA into northwest MO. Developing
southerly flow tonight and increasing clouds will help keep
temperatures warmer than the chilly readings of early this morning.
Strong low level WAA and ascent with the digging short wave will
maintain a decent band/region of prefrontal showers spreading across
the area on Sunday in advance of the front. Current thinking is that
the increasing southerly flow will help push temperatures above
freezing before the onset of rain during the morning from northeast
MO into west central IL.  Precipitation should have exited the CWA
by late afternoon with the cold front progressing across the area
from the afternoon into the early evening. Weak surface high
pressure dominates Sunday night into Monday in the wake of the
front, with backing winds on Monday afternoon allowing temperatures
to warm back towards normal levels. Rather non-descript conditions
exist Tuesday into Wednesday as the flow aloft deamplifies and
another weak boundary flirts with the area. Despite this boundary,
warming low and mid levels should translate into warmer temperatures.

Confidence in forecast details diminishes quite a bit during the
later part of the week and beyond as there are some rather big
differences in the flow aloft in the deterministic models. For
late next week the main issue is the timing of a late week cold
front and associated precipitation chances.

Glass

&&

.AVIATION:  (For the 12z TAFs through 12z Sunday Morning)
Issued at 618 AM CDT Sat Mar 28 2015

Focus continues to be the precip...or there lack of...across
cntrl MO this mrng. It would appear the models were a bit too
ambitious with the precip fcst for this system as most echo on radar
is not reaching the ground. Other than a few isld reports, most of
what is getting reported is VFR. Guidance still indicates that the
coverage and intensity of the precip should increase a bit over the
next few hrs but think that if that does occur, the best forcing
will be past the terminal by that time. With that in mind, I
eliminated the prevailing MVFR and replaced it with an MVFR TEMPO
with a higher VSBY. Other than the weak system this mrng, it is a
quiet fcst with VFR conditions thru the rest of the prd with light
E/SE winds below 10kts.

Specifics for KSTL:

VFR fcst thru the prd. Weak upper lvl system passing to the west
this mrng is throwing mid/high clouds across ern MO and SW IL.
These should shift SE this aftn/evng. E/ESE wind today will become
Srly as sfc high pressure moves from Lake MI to the OH vly today.
Winds will increase and become gusty on Sunday as the pressure
gradient increases in advance of a cold front due in later in the
day.

2%

&&

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

$$

WFO LSX






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.