Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 301020
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
520 AM CDT Mon Mar 30 2020

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 335 AM CDT Mon Mar 30 2020

08Z water vapor imagery showed a shortwave over the four corners
region while a couple closed upper lows were noted over the GReat
Lakes and off the British Columbia Coast. Water vapor also
indicated that the southern stream and subtropical moisture from
the Pacific was set up mainly over OK and TX. At the surface, weak
high pressure remains over the eastern Great Plains while some
subtle pressure falls were noted in the lee of the central and
southern Rockies. This kept the higher dewpoint temps generally
south of the Red River.

&&

.SHORT TERM...(Today and tonight)
Issued at 335 AM CDT Mon Mar 30 2020

The shortwave currently over the four corners should move across
OK and southern KS tonight. However models have continued the
subtle southward trend with the track of the overall system and
now track the surface low either along or south of the Red River.
Because of this, model progs keep the best dynamics over OK and
southern KS. And some of the solutions struggle to develop and QPF
across northern KS. So have tended to lower POPs across the
northern Portions of the forecast area, and continue with
categorical POPs for east central KS. Although QPF amounts are
only a quarter to a half of an inch. Forecast soundings continue
to show some modest elevated instability initially, but as the
event unfolds and the column saturates lapse rates become more
moist adiabatic. So continue with only some slight chances of
thunder. The other adjustment to the forecast was to delay the
onset of precip until late in the day since models have been
slightly slower with the upper wave. This is expected to allow
some insolation with only some mid and high clouds moving in from
the west. With no real change in airmass, think we will see
similar highs as yesterday with upper 60s and around 70. Cloud
cover overnight and a lack of cold air advection is expected to
keep min temps in the mid 40s tonight.

.LONG TERM...(Tuesday through Sunday)
Issued at 335 AM CDT Mon Mar 30 2020

For Tuesday through Friday, models continue to show a closed
upper low developing over western Canada with little movement
through the end of the week. Energy rotating around this upper low
is progged to move through the northern plains and bring a cold
front through the area Thursday night and early Friday. Model
progs of synoptic scale forcing appear to be rather weak or
disorganized with some west southwesterly upper flow and low
amplitude perturbations within the flow. Because of this think the
better chances for precip should be coincident with the frontal
passage. So have some 50 to 60 percent POPs for Thursday night and
Friday. The GFS wants to develop some QPF Wednesday night and
Thursday within a warm and moist airmass returning north. Am a
little skeptical of the GFS as it seems to over do the warm air
advection precip at times. And the GFS even suggests any elevated
boundaries to focus precip are likely to be north of the forecast
area with an inversion over the boundary layer. Nevertheless
increasing moisture and isentropic upglide make it unwise to
discount the GFS altogether. So have some chance POPs late
Wednesday night and Thursday. Have been a little more aggressive
in removing POPs Friday night and Saturday than the national blend
of models would have. All of the operational runs bring surface
ridging into the central plains through the night Friday night
with dry air likely bringing an end to precip chances.

Saturday should be dry with cooler temps thanks to the expected
surface ridge moving through the area. A return flow pattern
redevelops by Sunday as the surface ridge weakens and moves east.
Once again the GFS wants to develop QPF within the warm air
advection pattern. Any forcing appears to be rather subtle. So only
have some slight chance POPs for Sunday.

Temps look to remain mild trough Wednesday and possibly Thursday
since the front isn`t forecast to move through until Thursday night.
A decent pressure gradient looks to develop for Wednesday. South
winds and deeper mixing should help highs once again be around 70
and southerly winds are likely to become breezy. The breezy winds
could persist into Thursday but have not been as aggressive with
them in case timing of the front changes. Friday looks to be the
coolest day with north winds advecting cooler south south and mostly
cloudy skies limiting sunshine.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 520 AM CDT Mon Mar 30 2020

Think VFR conditions will prevail into the evening until the
better forcing and moisture advection moves through. The main
question is whether precip will make it as far northeast as TOP
and FOE with some of the CAMs showing dry air holding on. Even
some of the models struggle to bring lower CIGS into TOP and FOE.
Since the overall trend has been to decrease chances the last
couple days, will error on the optimistic side and keep TOP and
FOE VFR tonight and bring MVFR CiGS into MHK.

&&

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

$$

SYNOPSIS...Wolters
SHORT TERM...Wolters
LONG TERM...Wolters
AVIATION...Wolters



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