Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 112341

Area Forecast Discussion
National Weather Service Topeka KS
541 PM CST Mon Dec 11 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 306 PM CST Mon Dec 11 2017

Strong winds will persist through the afternoon and despite
continued CAA, above average temperatures are expected on Tuesday.

The upper level pattern remains highly amplified with a blocking
pattern across the western CONUS. Broad northwesterly flow could
be found over the central U.S. with water vapor imagery depicting
a compact PV anomaly dropping southeastward through Iowa and
Illinois. At the surface, a 1004 mb cyclone was stacked beneath
the upper wave with a 1030 mb surface high following close on its
heels in Montana and Saskatchewan. A surface trough passed through
the region earlier in the day with winds veering to the northwest
throughout the morning. A modestly strong 20 ubar/km pressure
gradient coupled with strong mid to lower tropospheric flow of
40-70 kts and deep boundary layer mixing/momentum transport led to
strong winds of 20 to 25 kts with gusts of 35 to 40 kts. As the
low pulls eastward and diurnal decoupling takes place, winds will
decrease through the evening and remain below 10 kts on Tuesday as
the surface high passes through.

The cloud cover forecast is somewhat uncertain for this evening
and tonight owing to the stratus dropping southward across the
eastern half of Nebraska. While the location of the cloud shield
has been well-resolved by some of the high-res guidance, the
stratus has failed to mix-out as progged by most of the solutions.
Thus, have increased cloud cover for the afternoon and evening
but have the clouds exiting by midnight.

.LONG TERM...(Tuesday night through Monday)
Issued at 306 PM CST Mon Dec 11 2017

The West Coast block breaks down around the end of the work week,
but the forecast through much of the next seven days remains dry.

WAA ensues on the backside of the departing ridge on Tuesday
evening as downslope air spreads eastward. H850 temps will rise to
+10 C Wednesday morning ahead of a sharp H500 shortwave. The area
will see a near-repeat of today`s weather on Wednesday, complete
with gusty northwesterly winds and highs well above average in the
50s to near 60. A broader upper tropospheric wave will track
southeastward over the northern CONUS on Thursday coupled with a
weak surface trough reflection. Many medium range solutions bring
a deeper moisture plume attendant with this wave and produce light
precip in regions of upper level diffluence. This have increased
POPs for Thursday during the day/evening, but the overall impacts
with this precip should be minimal.

Longer range guidance begins to diverge significantly once the
upper pattern breaks down for the weekend. Both the GFS/EC are
hinting at the system for this weekend, though the morphology of
the system varies greatly amongst the solutions. At this point,
the bulk of any associated precip looks to stay south and east of
the CWA.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 537 PM CST Mon Dec 11 2017

Primary forecast element continues to be wind, with gusts slow to
decrease this evening but eventually becoming a lighter
northwesterly after midnight. Will shift more westerly tomorrow
afternoon but will wait for next issuance to add.


Issued at 306 PM CST Mon Dec 11 2017

Very high to locally extreme fire weather conditions will persist
for the rest of the afternoon along and south of the Kansas
River; however, a plume of higher moisture is working southward
from Nebraska and pushing dewpoints up into the mid to upper 20s.
RH values in these areas have risen into the 30 to 40 percent
range, and this trend should continue further south later today.
Winds will remain blustery from the NW at 15 to 25 mph with gusts
up to 40 mph.


Red Flag Warning until 6 PM CST this evening for KSZ020-021-



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