Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 221136
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
536 AM CST Sat Nov 22 2014
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 348 AM CST SAT NOV 22 2014
Early this morning an amplified upper level trough was located
across northern Mexico, NM and far west TX. This H5 trough will
northeast into northern TX tonight. While another H5 trough moves
east-southeast from northern CA into the central high plains by 12Z
Deeper moisture advection at the surface and 850mb will continue
across southern and eastern KS. The advection fog will continue
through the morning hours. Visibilities have improved as southerly
winds have been increasing across the CWA. There may be some patchy
dense fog across the central and western counties of the CWA. I may
keep the dense fog advisory going for the Flint Hills as
visibilities may be reduced to a few hundred feet through 800 AM.
The isentropic lift and WAA will keep a chance for drizzle and
perhaps a light rain shower through the day across portions of east
central KS. Due to the warm start this morning and despite cloud
cover, highs Monday should reach the mid 50s to around 60 degrees.
As the H5 trough across northern CA moves into the central high
plains late tonight an 850mb and surface low will develop across
western OK and western KS. This will surface and 850mb winds to back
a bit more to the south causing deeper moisture to gradually expand
west across the CWA. The drizzle and light rain showers will expand
westward across the CWA. Fog may once again develop across the
northern and western counties as deeper moisture advects northwest
into a slightly cooler airmass.
.LONG TERM...(Sunday through Friday)
Issued at 348 AM CST SAT NOV 22 2014
Models are now trending towards a stronger shortwave trough...now
moving onshore in the Pacific Northwest...to swing southeastward
around the south side of the upper low over the northern Plains and
across the county warning area (cwa) on Sunday. This will likely
increase not only rain chances...but also QPF amounts. Timing
appears to be centered on the cwa around 18z...so will keep the pops
as a 12 hr block for now and let upcoming forecasts fine tune the
west to east progression of the pop trends. In summary...increased
pops across the area and ended precipitation over the eastern cwa a
little faster due to good model consistency with a stronger
subsidence signal with the passage of the stronger shortwave trough.
Will also extend thicker cloudcover longer across the cwa which will
limit highs behind the front to the upper 40s in the north central
counties with the low to mid 50s elsewhere.
Once the forecast goes dry Sunday night after midnight...will keep
the cwa dry through the remainder of the forecast. The only
exception will be the far northeast corner near Hiawatha with the
passage of the next clipper which tries to clip that area with light
snow. Ether way...overall model trend is further northward with the
clipper and the resulting band of snow. Still...the timing of the
front is similar on Wednesday...so after highs in the 40s through
mid week...will lower highs into the 30s for Thanksgiving Day as the
center of the Canadian surface ridge builds southward over the cwa.
The ridge axis does translate eastward by Friday with highs back
into the upper 30s to middle 40s.
.AVIATION...(For the 12Z TAFs through 12Z Sunday Morning)
Issued at 535 AM CST SAT NOV 22 2014
Pessimistic forecast throughout the entire TAF period. Dense fog
throughout the area leaves sites in the IFR/LIFR range, with little
chance for improvement until late morning. At 17Z, have MVFR
ceilings/visbys hanging on the entire day and into the late
evening. Fog is likely tomorrow morning, therefore, have introduced
IFR conditions into the TAF beginning between 06-07Z, although it is
possible conditions will deteriorate to LIFR again tomorrow.
DENSE FOG ADVISORY until 8 AM CST this morning FOR KSZ022-023-