Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 151141
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
641 AM CDT Tue Apr 15 2014
.SHORT TERM: (Through Late This Afternoon)
Issued at 314 AM CDT Tue Apr 15 2014
Ongoing Freeze Warning still looks on track to expire at 9am.
Despite the cold start, temperatures should climb into the 40s and
50s today. Initially NW winds expected to briefly become lgt/var
today with the passage of a surface ridge, then turn southerly
around the back side of the high.
.LONG TERM: (Tonight through Monday)
Issued at 314 AM CDT Tue Apr 15 2014
Next forecast issue to consider is whether new frost/freeze
headlines are needed for tonight. The surface high will be located
east of the area and wind speeds will be increasing after 06-09z
due to the tightening pressure gradient ahead of a developing
surface low over NE/SD. This means that ideal radiational cooling
conditions will not be present over most of the area. Overnight
lows should be a few degrees warmer than last night (approximately
in the low to mid 30s) with dew points in the low to mid 20s.
Since low-lying areas in the southeastern CWA will probably
decouple early in the evening (under lingering influence of the
departing surface high) and not experience the increased wind
speeds after 06-09z that would interfere with frost formation, a
Frost Advisory looks appropriate for those parts of the
southeastern CWA tonight.
Look for warm and breezy conditions on Wed due to the tightening
pressure gradient ahead of a developing surface low over SD/NE.
Models do not show as much of a secondary low over the OK/TX
panhandles compared to solutions from 24hrs ago, which produces a
different set of solutions for the movement of frontal boundaries
across the central CONUS for Thu-Sat. This variability leads to
continued low confidence in the forecast for Thu-Sat.
Precipitation is possible on Thu night into Fri as a vort max
moves across the region and interacts with moisture being drawn
northward, however one area of model disagreement is exactly how
many vorticity maxima might move across the region during this
time. Models depict another system which could bring precipitation
to the area on Sunday/Sunday night.
.AVIATION: (For the 12z TAFs through 12z Wednesday Morning)
Issued at 608 AM CDT Tue Apr 15 2014
VFR conditions are expected throughout the period as N-S surface
ridge...currently centered from mid MO valley to southern
Plains...pushes east into the Ohio Valley by 06z tonight. Expect a
bit of fairly weather CU to form by mid morning in this
unseasonably cool AMS, but with lack of cyclonic curvature in the
low level flow believe this cloud deck will remain scattered in
coverage...with bases AOA 3kft. These clouds will dissipate
heading into the late afternoon and early evening hours, with
surface winds gradually swinging around to the southeast with the
passage of the surface ridge. Although not included in this TAF
issuance, will need to keep an eye on LLWS potential in the 06-12z
time frame at UIN and COU as low level jet intensifies in
response to deepening low over the plains.
Specifics for KSTL: VFR condtions are expected throughout the
period, with cloudiness limited to a bit of scattered fair
weather CU with bases aoa 3kft from mid morning into mid
afternoon. NW surface winds 7-12kts will become light this
evening and then swing around to the SE in the 5-10 kt range after
midnight with the passage of the surface ridge. Looking ahead to
the outlook period...intensifying low pressure over the Plains
should mean a rapid increase in southerly low level winds,
with sustained winds pushing 20kts by midday Wed.
RECORD LOWS FOR 4/15:
STL - 27 IN 1928
COU - 25 IN 1928
UIN - 24 IN 1928
FAM - 24 IN 1928
MO...FROST ADVISORY from 1 AM to 9 AM CDT Wednesday FOR Crawford MO-
Iron MO-Jefferson MO-Madison MO-Reynolds MO-St. Francois MO-
Ste. Genevieve MO-Washington MO.
FREEZE WARNING until 9 AM CDT this morning FOR Audrain MO-Boone
MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
MO-Ralls MO-Reynolds MO-Shelby MO-St. Charles MO-St.
Francois MO-St. Louis City MO-St. Louis MO-Ste. Genevieve
MO-Warren MO-Washington MO.
IL...FROST ADVISORY from 1 AM to 9 AM CDT Wednesday FOR Clinton IL-
Marion IL-Monroe IL-Randolph IL-St. Clair IL-Washington IL.
FREEZE WARNING until 9 AM CDT this morning FOR Adams IL-Bond IL-
Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
Pike IL-Randolph IL-St. Clair IL-Washington IL.