Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 171131

Area Forecast Discussion
National Weather Service Topeka KS
631 AM CDT Tue Apr 17 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 340 AM CDT Tue Apr 17 2018

Early this morning the mid level ridge was located over the central
Plains while a mid and upper level trough was approaching the Four
Corners. Moisture was increasing across the southern Plains as 50+
dewpoints have moved into south central Oklahoma at 07Z.

Today the upper trough will move east across the Rockies and out
into the western High Plains by late afternoon. A surface low
pressure area will form in the Lee of the Rockies and then move into
western Kansas this afternoon. Models are consistent with moving the
low east northeast across north central and northeast Kansas as the
upper trough moves across Nebraska and South Dakota with the
southern extent into far northern Kansas this evening. The surface
low is forecast to deepen in response to the 100 kt 500 mb jet moves
across eastern Kansas this evening and overnight. This will induce a
moisture flux into northern Kansas, although shallow as 850 mb-700
mb moisture transport vectors suggest deeper moisture will be
advected northeast into Iowa tonight. That said, forecast soundings
show north central and northeast Kansas to remain capped with the
presence of an EML showing up on forecast soundings. This evening
there is elevated instability which depending on the model would
suggest potential for storms to develop across the northern counties
of the cwa this evening. CAMS show storms developing as early as 01Z
along the Nebraska border the moving off to the east. About 60 kts
of shear is forecast in the 2-6km layer and corresponding hodograph
favors mid level rotation. About 500-1000 J/kg of elevated cape is
forecast as well. There is the potential for a few of the storms to
be capable of producing hail tonight, mainly sub-severe given
limited moisture profiles.

Another challenge for today will be how far north the warm front
moves and resulting temperatures. Models also develop some stratus
over the area as well, so could see temperatures range from the 50s
along the Nebraska border to the 70s south of I-70. Winds will
increase later tonight after midnight as the surface low deepens and
pressure gradient increases on the backside of the low from the
north in the 20 to 25 mph range with gusts over 30 mph.

.LONG TERM...(Wednesday through Monday)
Issued at 340 AM CDT Tue Apr 17 2018

The main takeaways for the extended period reside with gusty winds
Wednesday resulting in very high fire danger and rain chances for
the weekend.

By Wednesday morning the upper low and associated surface low will
continue lifting eastward into the mid-Mississippi River valley. A
stout surface pressure gradient -- on the order of 6-7 mb  -- will
remain across the CWA Wednesday morning. H85 winds are progged to
remain between 40-45 kts through much of the day. With BL mixing
heights likely to exceed H85, expect northwesterly winds sustained
between 20-30 kts with gusts up to 40 kts. The northwest winds will
advect drier air into the region for Wednesday afternoon, decreasing
RH values to near 30 percent. This combination of gusty winds and
dry conditions will yield very high fire danger concerns across the
much of the area Wednesday afternoon. High temperatures could
greatly vary Wednesday from far northeast KS to central KS depending
on cloud cover progression. Current progs suggest much the area
should see mostly sunny skies by afternoon and highs in the 60s. The
one exception is far northeast KS where clouds will be last to clear
given the closer proximity to the upper low, yielding highs near 50.
As the surface low progresses into the Ohio Valley Wednesday night
the gradient will greatly decrease, allowing winds to lighten.

A high amplitude upper level ridge will build into the central
Plains by Thursday, ahead of the next upper low. Although minimum RH
percents reach the lower 30s Thursday afternoon, light winds are
expected with the surface ridge overhead, yielding minimal fire
weather concerns at this time.

The surface ridge will progress eastward allowing southerly surface
flow to overspread the region by Friday. WAA will remain weak
however as moisture trajectories from the Gulf orient towards
western OK/TX. A lead shortwave and DCVA will allow lee cyclogenesis
across SE CO to occur Friday night. ECMWF/GFS/Canadian solutions
remain in good agreement with the surface and upper lows moving
along the Red River Saturday into Sunday. As a result the highest
QPF would fall south of the CWA. Any precipitation is expected to
fall as liquid however, given H85 temperatures near 3 to 5C and
surface temperatures in the 40s and 50s. Upper level ridging builds
into the region early next week, yielding drier and warmer


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 631 AM CDT Tue Apr 17 2018

VFR conditions are expected through 07Z Wednesday then becoming
MVFR. East to southeast winds around 12kts with gusts to 22 kts
after 16Z, winds shift to the west northwest in the 07Z-09Z time
period and increase to near 20 kts with higher gusts to near 28kts
near the end of the period. LLWS is possible at TOP and FOE for a
few hours from 05Z to around 08Z-09Z. Precipitation is expected to
remain north of the terminals and have left out for now.


Issued at 340 AM CDT Tue Apr 17 2018

Very high fire danger is expected across much of the area
Wednesday. Minimum RH values are progged to near 30 percent
during the afternoon. That being said, any prescribed burn today
could be reignited tonight as winds shift to the northwest and
increase to 20-30 MPH with gusts up to 40 MPH. Wind speeds will
decrease Wednesday evening as the surface pressure gradient




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