Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 151133
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
633 AM CDT Wed Apr 15 2015
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 302 AM CDT WED APR 15 2015
Mid/upper level low currently lifting northeastward over central KS
as it gets absorbed into the flow out ahead of the stronger
shortwave over the Rockies. Weak isentropic lift continues to spread
over eastern KS on the eastern side of the low. Although there is
still a deep dry layer in the lower levels making it difficult for
precip to reach the ground. Also, the lift does not seem to be well
organized or focused in one area. Short terms models still develop
scattered showers in SE KS, and move them northward over the next
few hours. So expect a chance for sprinkles and or light showers
across the eastern half of the forecast area through noon. Otherwise
mostly cloudy today with highs generally in the 60s. As the western
shortwave moves over the Rockies a deepening lee side trough will
cause the southeast winds to increase up to 15 to 20 mph. Tonight
most of the models keep cloud cover around at least through the
majority of the overnight hours, which should keep low temps in the
lower 50s. Dew points increase through out the day and are expect to
reach the lower 50s by sunset. This increasing low level moisture
could contribute to a lowering stratus deck and or fog before and
around sunrise. During the evening hours thunderstorms may form
along the lee trough in far western KS and move eastward overnight.
There is a chance these storms could reach portions of central KS.
These storms could potentially be supported by steepening lapse
rates, increasing low level moisture, and a slightly veering low
level jet. Although they will most likely be weakening overall and
or will move into central NE since the mid/upper low stays out over
.LONG TERM...(Thursday through Tuesday)
Issued at 302 AM CDT WED APR 15 2015
An upper level trough across the northwest conus will dig southeast
into the four corners region by Thursday, then become a cut-off
closed upper low, which will slowly drift east across northern NM
and southern CO Thursday night through 00Z SAT. A northern stream
H5 trough will move east-southeast from western Canada and begin to phase
with the closed low Saturday night. This will kick the upper low
east across the central and southern plains early next week.
Thursday through Thursday Night, most of the the showers and
thunderstorms will develop across western TX, western KS and eastern
CO where the trajectory of deeper moisture will move northwest from
central TX across western OK into western KS. Minor H5 troughs and a
mid and upper level jet max will allow for stronger ascent across
the mid and lower high plains for thunderstorms to develop. If any
thunderstorm complexes develop across western KS
Wednesday evening, they will most likely move more to the north across
western and central NE due to the meridional mid and upper level
flow to the east of the closed upper low in northwest NM. Most of
the CWA will remain dry through the period. Highs will reach into
the lower to mid 70s across much of the area.
Friday through Friday night, the upper low moves a bit farther east
across southern CO. The deeper moisture will advect northward
farther east across eastern KS. A combination of isentropic lift and
ascent ahead of a 45 to 50 KT mid level jet max will provide enough
lift for scattered to numerous showers developing through the day.
There may be some thunderstorms but MUCAPES look to be under 1000
J/KG across the CWA, thus any thunderstorms will not be severe
across the CWA. The increased cloud cover may keep highs a bit
cooler with upper 60s to lower 70s expected.
Saturday and Saturday night, the upper level trough will lift
east-northeast across the central and southern plains as it phases with
a northern stream H5 trough moving east across the northern plains.
The large scale ascent will allow for periods of showers and
thunderstorms. The deeper gulf moisture may not make it northward
into the plains due to a series of thunderstorms complexes across
southern TX. There will be a lack of a good EML, to to
thunderstorms across the source region, thus I don`t think lapse rates
will be steep enough across the the CWA for severe thunderstorms.
The vertical wind shear will increase through the day Saturday but
with marginal instability we may only see a few strong
thunderstorms on Saturday. A surface cold front will push
southeast across the CWA Saturday night. Highs will only reach the
mid 60s to lower 70s with cloud cover and periods of showers and
Sunday through Sunday night, the upper trough axis will move east
across eastern KS into MO. There will be enough ascent for
scattered showers through the day and into the night. Highs will
only reach the lower to mid 60s due to weak CAA behind the front,
cloud cover and scattered showers.
Monday through Tuesday The phased upper level trough will amplify
across the upper Midwest and Great Lakes States. This will keep the
plains under northwesterly flow aloft and low-level CAA at the
surface. Even with insolation, highs will only reach the lower to
mid 60s. There may be a threat for frost early Tuesday morning with
overnight lows possibly falling into the mid to upper 30s in some
locations. I kept a slight chance for showers since the GFS shows
a minor H5 trough digging southeast across the plains. The ECMWF keeps
the CWA dry early next week.
.AVIATION...(For the 12Z TAFs through 12Z Thursday Morning)
Issued at 623 AM CDT WED APR 15 2015
MVFR ceilings have been slow to work into the taf sites this
morning. Most of the guidance is showing MVFR ceilings through the
entire period though. Observations show a majority of these
ceilings down in SE KS, but progressing northward. There is a slight
chance for breaks in the stratus this afternoon for brief periods.
Otherwise tonight the ceilings should lower although timing of
possible IFR is not certain. The better chances for IFR appears to
be at MHK. Also, fog may develop with decreasing dew point
depressions especially late in the period.