Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 051141
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
641 AM CDT MON OCT 5 2015
...Update to aviation forecast discussion...
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 314 AM CDT MON OCT 5 2015
Mid level southwest flow this morning was pushing a weak vorticity
lobe across OK into southern KS. This was generating scattered
showers, most of it appears to not be reaching the ground per obs.
Meanwhile at the surface, the dry ridge axis held in place with
mostly cloudy skies and temps falling near 50 degrees by sunrise.
For today, recent runs from the HRRR and RUC carry this wave and
scattered light showers towards central and east central KS through
the afternoon. Moisture profiles suggest a low level cloud deck
around 3 kft may slowly scatter out by late afternoon while the mid
level clouds linger through the evening. I added a chance for
sprinkles as oppose to showers due to the very shallow low level
cloud deck and much of the forcing associated with moisture at 12
kft. In addition, there remains pockets of dry air in between these
two layers. Highs today were lowered a few degrees given the above
mentioned factors with readings in the upper 60s.
Tonight, skies remain mostly cloudy to overcast while ridging aloft
results in dry conditions. Insulation from cloud cover will keep
lows warmer compared to previous mornings in the lower 50s.
.LONG TERM...(Tuesday THROUGH Sunday)
ISSUED AT 314 AM CDT MON OCT 5 2015
Tuesday through Wednesday, a closed upper low over extreme western
AZ will dig southeast into northern Mexico. An upper level trough
embedded within the northern stream of the upper jet will move
onshore across the pacific northwest on Tuesday and dig east-
southeast into the northern high plains. Low-level CAA across the
northern plains will cause a surface front to push southward into
western NE through the day Wednesday. Scattered showers and
thunderstorms will develop along the front during the afternoon
hours across northeast CO and western NE. The best rain chances will
be west and northwest of the CWA Wednesday afternoon. Southerly
winds to the east of the lee surface trough across the central and
southern high plains will allow high temperatures to warm into the
mid to upper 70s on Tuesday with highs around 80 degrees on
Wednesday night through Thursday night, the ECMWF and GFS differ on
the amplitude of the H5 trough digging southeast across the northern
plains into the mid MS river valley. The GFS is more amplified with
the H5 trough allowing for stronger ascent across the CWA and a
better chance for showers and thunderstorms along the surface cold
front late Wednesday night into Thursday evening. The ECMWF is not
as amplified with the northern plains trough, as it digs into the
mid MS river valley. The ECMWF does not show much in the way of QPF
across the CWA, except for the southeast counties late Thursday
afternoon ahead of the surface cold front. At this time I`ll keep
slight chance pops in the forecast for Wednesday night and chance
pops Thursday into Thursday night. However if the GFS solution
converges towards the less amplified ECMWF, then POPs may have to be
lowered on Thursday. Once the front pushes south of the area late
Thursday night the showers should end across the southeast counties.
Highs Thursday will be around 80 degrees ahead of the front with mid
70s across north central KS behind the surface front.
Friday, there will be a brief cool down as a surface ridge builds
south-southwest from the upper midwest into eastern KS. Highs will
only reach the mid to upper 60s.
Saturday through Monday, highs will warm into the mid 70s on
Saturday with upper 70s to lower 80s Sunday and Monday as a southern
stream upper level ridge amplifies across the southern plains, due
to the retrogression of the upper low over northeast Mexico,
westward towards the Baja CA region.
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z Tuesday MORNING)
ISSUED AT 632 AM CDT MON OCT 5 2015
IFR cigs this morning will be difficult to lift based on the weak
winds within the boundary layer. Guidance somewhat varies on when
conditions will lift to MVFR during the afternoon or early
evening period. There is a possibility the cigs may remain at MVFR
overnight if they can dissipate before sunset.