000
FXUS63 KTOP 151745
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1245 PM CDT Sat Mar 15 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 400 AM CDT SAT MAR 15 2014

08Z water vapor shows an active pattern over the country with a
couple shortwaves within a general northwest flow. One shortwave was
moving into west TX while another digs southeast through the
northern Rockies. Surface pressure has been falling across the
central high plains in response to the shortwave digging southeast.
Surface obs show higher dewpoint temps across south TX poised to
move north today.

Models continue to show a complicated pattern as the shortwave
digging southeast tries to phase with the energy moving into west TX
by this evening. It appears the trend has been for the northern wave
to dig further west of the forecast area into west TX kicking the
wave already there out across OK and AR. This tends to keep the
better pressure falls to the south and there is a concern that the
low level moisture return could be muted because of this. Have not
made any significant changes to the previous forecast and continue
to show increasing chances for precip through this evening as there
should be some QG forcing and frontogenesis affect the area
overnight. The NAM and GFS continue to show some weak instability
developing over east central KS, but this will be entirely dependent
on whether the low level moisture advects in from the south.
Additionally deep layer shear does not look all that impressive over
east central KS so concerns for severe weather are low. The larger
concern will be the winds overnight as the models deepen the surface
low over the southern plains. This should cause the pressure
gradient to really tighten up over eastern KS as the front pushes
south. Models indicate pressure rises behind the front will be on
the order of 6MB per 3 hrs. This is typically strong enough for
sustained winds of 30 MPH with gusts around 45 MPH. Because of this
have decided to issue a wind advisory beginning this evening and
going through the morning Sunday. As for precip behind the front,
consensus is for the column to cool enough for any precip to chance
over to snow. Of course there could be a transition period where a
mix of rain, sleet and snow occurs. There remains some uncertainty
in actual snowfall amounts as the NAM hangs onto a stronger
deformation zone aloft over northeast KS longer than any other
solutions. This causes a band of moderate snowfall somewhere over
the area. However with other guidance favoring the deeper moisture
and forcing south and east of the forecast area, will not completely
buy into the NAM at this point. For now have generally a half inch
of snow possible through 12Z Sunday.

Went warmer with highs today since forecast soundings mix the
boundary layer to 800 MB. Think we will see decent insolation into
the early afternoon which should help temps reach the lower and
middle 70s. Strong cold air advection behind the front is expected
to push temps below freezing with mid 20s along the NEB state line
to the lower 30s in east central KS.

.LONG TERM...(Sunday through Friday)
Issued at 400 AM CDT SAT MAR 15 2014

Very strong winds continue Sunday morning into the early afternoon.
Sustained northerly winds between 25 and 35 mph should persist on
the northwest flank of the deepening surface low through noon when
the Wind Advisory is set to expire. However, strong north winds
between 15 and 25 mph continue through early Sunday evening as the
surface pressure gradient weakens with incoming high pressure from
the northwest. Light and variable winds can be expected overnight
Sunday into Monday. Strong cold advection in the wake of the
closed low will transition all precipitation to snow by 12Z
Sunday. The GFS/NAM show a weak warm nose at h85 hovering just
above freezing across locations mainly south of Interstate 35.
Could perhaps see a mix of snow and sleet before the profile cools
to allow all snow mid-morning. Precip chances come to an end from
northwest to southeast as the system exits Sunday late afternoon.
The latest NAM appears to be the outlier with higher snowfall
accumulations than consensus guidance. Do not see strong enough
forcing for a heavier snow band to develop while temperatures
hover at or just above the freezing mark. Warm ground temperatures
also suggest little to no impact for accumulating snowfall on
surfaces and roadways. Overall believe total snow accumulations of
an inch or less seems reasonable by Sunday afternoon. Short term
guidance continues to trend Sunday highs cooler than previous
forecast as overcast skies, wintry precip, and cold advection
result in readings from the low 40s in north central Kansas to the
middle and upper 30s elsewhere.

The exiting upper trough becomes elongated over the southern and
southeast CONUS while another upper trough digs southeast over the
Pacific Northwest. A deepening surface low over the western high
plains increases winds from the southwest, bringing an end to the
temporary chill as h85 temps from 8-15C advects northward. Highs are
progged in the low 60s for east central areas, to the upper 60s in
north central. If we get stronger mixing from the h85 thermal ridge,
temperatures may be even warmer. The approaching upper trough
deepens over the northern plains Monday evening into Tuesday keeping
the profile mixed with speeds from 15 to 25 mph. While ample forcing
exists aloft between the GFS and ECMWF, there is still a large
discrepancy in moisture profiles. Will leave mention of rain out on
Tuesday afternoon with a slight chance of light rain mixed with snow
Tuesday evening as the system lifts northeast. Strong warm advection
and compressional warming with the approaching cold front Tuesday
afternoon lead to raising highs in the afternoon to the low and mid
60s, which may continue to trend warmer.

Quiet and cooler conditions anticipated for Wednesday with large
area of high pressure in control. Highs in the 50s Wednesday warm to
the 60s Thursday and Friday with the next developing surface trough.
Another cold front will impact the area Friday, but still great
uncertainty for possible precipitation between the GFS and ECMWF.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1236 PM CDT SAT MAR 15 2014

Expect VFR conditions through the early evening hours. A strong
cold front will move southward across the terminals between 2Z and
4Z SUN. North winds will increase to 20 to 26 KTS with gusts of 28
to 35 KTS possible after 4Z. Periods of light rain will mix with
snow and sleet after midnight and last through the mid morning
hours of Sunday. Stratus ceilings will decrease to MVFR levels
with some periods of IFR ceilings. Visibilities will drop to 2 to
4 miles with some lower visibilities in areas of sleet and snow.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY from 7 PM this evening to 7 AM CDT Sunday FOR
KSZ008>012-020>024-034.

WIND ADVISORY from 10 PM this evening to Noon CDT Sunday FOR
KSZ026-035>040-054>056-058-059.

&&

$$

SHORT TERM...Wolters
LONG TERM...Bowen
AVIATION...Gargan