Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 090532
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1132 PM CST Fri Dec 8 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 200 PM CST Fri Dec 8 2017

Aside from some low clouds this afternoon, little sensible
weather is forecast for the rest of the day and into the weekend.

A highly amplified upper tropospheric pattern was in place over
the CONUS this afternoon with a sharp blocking west coast ridge
extending from off the Baja California to Barrow, Alaska. Broad
northwesterly flow is well established over the central CONUS with
several weak perturbations embedded in the flow. At the surface,
a corridor of stratus/stratocu stretches from the Siouxland to
Manhattan. This stratus has been gradually building southeastward
and this idea has been well-resolved by the short-range guidance.
This same guidance, however, have struggled with the morphology of
the cloud shield. Most guidance earlier in the day had the
stratus decaying by the early afternoon, which has not transpired
as of yet in the satellite/observational data. Thus, have
increased sky cover for the rest of the afternoon for much of the
forecast area.

A weak boundary will slide through tonight but will be
accompanied by little more than a wind shift more towards the
north. Surface ridging builds in for Saturday with a H850
downslope-modified airmass building in behind the ridge axis.
Highs on Saturday will be a few degrees warmer given the increase
in temps aloft with light northwesterly winds.

.LONG TERM...(Saturday night through Friday)
Issued at 200 PM CST Fri Dec 8 2017

The end of the weekend and much of next week will feature quiet
weather. A warmup is in store for Sunday, with temps falling back
to near/slightly above normal for the remainder of the week.

Continued downslope WAA late Saturday and Sunday morning will set
the stage for a very warm Sunday afternoon. H850 temps will top
out around +8 to +10 C with corresponding surface temps rising
into the low 60s, aided by ample BL mixing and large dewpoint
depressions. An elevated to very high fire danger will exist along
and west of the Flint Hills on Sunday owing to afternoon RH
values falling to near 20 percent. A broad barotropic surface
trough axis slides through Monday morning, with winds increasing
to 15 to 25 mph with gusts over 35 mph in the wake of the front.
While RH values will be slightly higher owing to increasing CAA
throughout the day, a very high fire danger will exist during the
afternoon.

The synoptic pattern then repeats itself--another surface ridge
axis sliding through on Tuesday, increasing WAA late Tuesday into
Wednesday, followed by another clipper surface trough late in the
day on Wednesday. The region looks to remain under some downslope
air influence for the remainder of the week with the upper level
pattern finally breaking down next weekend. None of the
aforementioned waves will have sufficient moisture to work with,
and the going forecast for the next seven days remains dry.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1130 PM CST Fri Dec 8 2017

Forecast is primarily a wind shift, with west winds becoming
northwest with some gusts for Saturday but tapering off late
afternoon into the evening hours. MVFR clouds in Iowa worth noting
but appear to stay out of our area overnight, and with at least
some wind in the boundary layer think visby will stay VFR as well.

&&

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

$$

SHORT TERM...Skow
LONG TERM...Skow
AVIATION...67


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