Scientific Forecaster Discussion
fxus63 ktop 242001
Area forecast discussion
National Weather Service Topeka Kansas
301 PM CDT Sat Jun 24 2017
Short term...(this evening through sunday)
issued at 246 PM CDT Sat Jun 24 2017
Conditions were pleasant across the region this afternoon as surface
high pressure moved over the cwa, resulting in light winds and
afternoon high temperatures in the upper 70s to low 80s. This
surface high pressure will remain over the central U.S. Through
Sunday, with an expansive and broad mid-level trough stretched
across much of the north central and northeastern Continental U.S.. with this
mid-level pattern in place, northwesterly flow aloft is expected
tonight through Sunday. Models continue to show a couple of weak
embedded waves developing within this northwesterly flow, with water
vapor imagery showing the first wave over south central NE tracking
into north central Kansas this afternoon. While the regional radar was
showing some light reflectivity returns extending into north central
KS, only some mid-level clouds were developing as there was a large
layer of dry air just above the surface with dewpoints in the 30s.
If saturation increases enough in the mid-levels, the weak lift
present may help to produce some scattered sprinkles late this
afternoon through tonight. As the embedded wave progresses
southeastward across the County Warning Area overnight, these chances for scattered
sprinkles may extend from north central Kansas into central and portions
of east central Kansas. Another weak embedded wave may skim across
central to east central Kansas Sunday afternoon. While lapse rates look
to be nearly moist adiabatic, model soundings show the cap over this
region breaking by mid-afternoon so cannot rule out the potential
for some scattered showers and isolated thunderstorms to develop.
Despite decent 0-6km shear in place (40-50kts), any instability
present should be quite limited to only 100-200 j/kg. Temperatures
will remain cooler than normal with lows tonight in the 50s and
afternoon high temperatures on Sunday in the upper 70s/near 80.
Long term...(sunday night through saturday)
issued at 246 PM CDT Sat Jun 24 2017
Chances for thunderstorms move back into our area late Sunday
night into Monday, as the surface high shifts to the east and the
warm front moves eastward over eastern Kansas, aided by shortwave
energy moving over the front around the base of the longwave
Great Lakes trof. This push from the larger scale trof in turn
pushes the cooler air back southwest for Tuesday, and brings
a short break in rain chances.
Pattern starts to transition out of northwest flow aloft late Tuesday as
zonal flow returns, with next shortwave moving out of the High
Plains overnight Tuesday night into Wednesday. As low and mid
level flow become southerly once again, increased moisture and
instability also start to migrate back northward over the state.
Could be enough especially Wednesday through the late week for
strong storms, but evolution and timing still evolving. The ec is
more progressive with the next longwave moving into the Central
Plains, bringing a front through late Thursday with quieter
conditions Friday and Saturday. The GFS is a little slower and
deeper with the trof, and would suggest stronger overnight
convection in our north Thursday night and a frontal passage on
Friday afternoon with a generously unstable airmass to work with.
Ensemble plots are about an even split as to speed of the
longwave, and forecast is a blend toward the middle at this time.
Highs rise from upper 70s on Monday back into the middle 80s on
Wednesday into possibly the late week until the potential front
gets through for the weekend.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1217 PM CDT Sat Jun 24 2017
For the 18z tafs, VFR conditions are expected through the period
with winds remaining less than 10kts generally from the north