Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 181728
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1228 PM CDT Mon May 18 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 256 AM CDT MON MAY 18 2015

An upper level trough across the upper Midwest will fill as it lifts
northeast across the northern Great Lakes. A southern stream upper
level trough will move east into southern CA Today. The mid and
upper level flow will weaken and become zonal across the central and
southern plains.

Early this morning a cold front was pushing southeast across north
central KS and should move southeast across the remainder of the CWA
by sunrise. Low-level CAA will keep temperatures 10 to 15 degrees
cooler than Sunday`s highs, with afternoon highs only reaching the
mid 60s to lower 70s. Northerly surface winds will increase after
sunrise to 15 to 20 MPH with some gusts to 30 MPH during the late
morning hours. The northerly winds will diminish this afternoon as
the center of a surface ridge builds southward across the central
plains.

Tonight, The surface ridge will move east across the CWA this
evening. After Midnight winds will slowly back to the east towards
sunrise. Deeper moisture will begin to surge northwest across OK
into southwest KS. The resulting isentropic lift and ascent ahead of
the southern stream H5 trough moving into the four corners region
will cause elevated showers and thunderstorms to develop across
western KS late tonight. These elevated showers and storms will
remain west of the CWA through 12Z TUE. Overnight lows will drop
into the 40s.

.LONG TERM...(Tuesday through Sunday)
Issued at 256 AM CDT MON MAY 18 2015

Moisture and forcing for precip is expected to be on the increase
Tuesday into Tuesday evening as the shortwave ridge breaks down
and PVA increases. The magnitude of the forcing is not that
impressive as the shortwave shears out and instability remains
close to nil. Nevertheless the warm air advection pattern and
general vertical motion should lead to widespread showers Tuesday
night. There are even signs of mid level frontogenesis developing
overnight as an inverted trough of low pressure in low levels
moves into southeast KS. About the only question is when will
precip start. The NAM is a little quicker in saturating the column
as a lead shortwave lifts across the area. For now have remained
closer to the consensus in precip occurring mainly during the
night, but do include some low chances across western portions of
the forecast area in the afternoon. With the models remaining
consistent in generating precip Tuesday night have trended POPs up
to 90 percent for the whole forecast area. By Wednesday afternoon,
the warm air advection pattern shifts southeast and ridging build
in. The lose of forcing should cause precip to diminish through
the day. Unfortunately the models hang onto low level saturation
through the day Wednesday, so the forecast anticipates a mostly
cloudy to overcast sky. Highs Wednesday will be cold due to
limited insolation, as well as north winds advecting in cooler
air. At this point, highs in the mid and upper 50s seems
plausible. Tuesday`s temps are not expected to be much warmer as
cloud cover increases from the west. Even with some sunshine
however, models maintain more of an easterly low level flow with
little to no warm air advection. Across north central KS, where
cloud cover is anticipated to be thinking through the day, highs
should be in the upper 50s. Think mid 60s are possible Tuesday
afternoon in eastern KS with a little more insolation.

Wednesday night through Thursday night is shaping up to be dry as
shortwave ridging redevelops over the central plains. With a
modified Canadian airmass over the region, there is not expected
to be much of a warm up on Thursday. Therefore highs are forecast
to be in the lower to mid 60s. Partly to mostly cloudy skies
should help to keep morning lows in the 40s.

For Friday though Sunday, models continue to prog the next wave to
move into the southwest and eventually across the central plains.
There remains some strength and timing issues between the ECMWF
and GFS, specifically a deeper and slightly more progressive
solutions from the GFS. In spite of this, both solutions suggest a
similar pattern and potential for precip. By Friday, the warm air
advection pattern is progged to set up bringing moisture back into
the central plains. With the chance for a weak perturbation within
the southwest flow aloft and only weak inhibition to convection,
the forecast will maintain a chance for precip. Think the better
chances should be Saturday and Saturday night as the main wave
moves into the central Rockies. The persistent warm air advection
pattern through the weekend should allow for temps to moderate
back into the 70s by Sunday. Since models show more clouds than
sunshine through the weekend, they are hesitant to warm temps much
more. Doubt precip will be continuous during the weekend and with
some breaks in the clouds, temps could push 80 by Sunday. Later
shifts can reevaluate this.

&&

.AVIATION...(For the 18Z TAFs through 18Z Tuesday Afternoon)
Issued at 1227 PM CDT MON MAY 18 2015

VFR conditions are expected throughout the entire period.  Gusty
winds will die down by 22Z as high pressure continues to move into
the area.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Gargan
LONG TERM...Wolters
AVIATION...Heller






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