Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 131738
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1238 PM CDT Thu Mar 13 2014
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 307 AM CDT THU MAR 13 2014
Main concern for this period is fire weather danger potential
across northeast Kansas.
Quiet conditions observed this morning with a broad area of surface
high pressure across the region. In the mid levels, water vapor imagery
showed a weak shortwave trough over Colorado, with predominant
northwest flow in place.
High pressure skirts east later this morning as a open surface
trough shifts in western Kansas. Winds back from the west to the
southwest, increasing through mid morning into the afternoon between
15 and 25 mph sustained. Gusts around 30 mph are likely during the
late afternoon as the aforementioned wave translates east over
eastern Kansas. The combination of strong mixing in the boundary
layer and drying air aloft result in dewpoint temperatures falling
to the lower and middle 20s by late afternoon. Combined with strong
warm advection from the southwest boosting highs to the low 70s,
confidence is high that uncontrollable fire growth is likely today.
Have issued a Red Flag Warning for much of the area. See the Fire
Weather discussion below for more details. Skies remain clear this
evening as mid level flow becomes zonal ahead of another weak
embedded trough over northern Kansas. A cold front approaches north
central Kansas early Friday morning. Have placed cooler temperatures
for these areas with lows in the in the upper 30s to near 40
degrees. Farther south, high cloud coverage increases, holding
warmer temps in the lower and middle 40s before the front passes
later in the morning.
.LONG TERM...(Friday through Wednesday)
Issued at 307 AM CDT THU MAR 13 2014
Little has changed in the long term forecast over the past few days.
Still expecting periodic short wave troughs and associated cold
fronts. The greatest uncertainty within the forecast is associated
with a trough that will impact the region over the weekend, and the
potential precipitation associated with this system.
One of the aforementioned cold fronts will pass through the area on
Friday, but will not be particularly cold as a well mixed boundary
layer, plenty of sunshine, and a temperature profile a fair amount
warmer than yesterday (Wednesday) suggest that highs will still
climb into the lower to middle 60s. This will be a dry airmass with
low RH expected once again but winds behind the front will struggle
to top 20 mph. Will need to keep an eye on this period for fire
weather concerns should winds be a bit stronger than anticipated.
With the front being so weak and more short wave energy crossing the
Rockies, return flow is expected to begin by Friday night into
Saturday, keeping lows in the mid/upper 30s, and highs on Saturday
in the mid/upper 60s...although there is some potential to go higher.
Late Saturday into Sunday is when the greater uncertainty arises.
Models are having a difficult time in consistently phasing a
combination of northern and southern stream energy. The one
disturbance, in southern California this morning, will drift into
the southern Plains by Saturday. As is often the case with a closed
low (as it currently is), the timing of the system`s eastern
progress varies greatly from model to model. The GFS is on the fast
side of the guidance envelope while the NAM is very slow with the
energy. So, while agreement is at least fair in the timing of the
northern stream energy diving south out of Wyoming on Saturday,
there are substantial differences in how everything evolves beyond
that point. The GFS for instance, is faster with the southern energy
and offers little phasing...sending the initial wave off to the east
while the northern stream trough deepens almost due south along the
front range...resulting in little to no precipitation locally as all
energy is too far displaced south and west. The NAM on the other
hand, slow with the southern trough, allows the two disturbances to
almost fully phase...deepening the upper trough substantially with
increased ridging over the southeastern CONUS. This results in a
further slow down and a northeastward turn to the storm system...
bringing quite a bit of precip into Kansas. The ECMWF offers a
solution somewhere in between the GFS/NAM, has been somewhat
consistent, and oftentimes performs better in handling SW closed low
ejections, so leaned toward the ECMWF rendition. This would bring at
least some chances for precip into the area, although amounts would
probably be on the low end. If precip develops, rain seems most
likely although snow could eventually mix in especially north. The
takeaway point is that while precip chances are low, the forecast
could change quite a bit over the next few days.
Sunday will be cooler with strong cold advection expected but Monday
and Monday night still appear primed to be warmer than most all
guidance with strong warm advection, sunshine, and southwest winds.
Tuesday offers another trough passage with weak precip signals, and
have left the forecast dry at this time and only a bit cooler
.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1234 PM CDT THU MAR 13 2014
Expect VFR conditions through the next 24 hours. Strong low-level
wind-shear will be possible at the terminals, as winds at 1500 feet
above the surface increase to 55 to 65 KTS between 6Z and 12Z FRI,
and surface winds decrease to 10 KTS to 12 KTS after midnight. A
weak front will shift winds to the north-northwest after 12Z FRI.
RED FLAG WARNING until 7 PM CDT this evening FOR KSZ008>012-