Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 262253
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
553 PM CDT Thu Apr 26 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 319 PM CDT Thu Apr 26 2018

As of 20Z Thursday afternoon an upper level trough axis extended
from northern MN to eastern CO. An associated weak surface cold
front extended from the U.P. of MI into the TX panhandle,
bisecting the CWA. As the upper trough continues to elongate,
the front will continue to weaken and dissipate. Expect conditions
to remain dry as any precipitation will remain as virga with a
very dry layer beneath H8. Surface ridge across the northern
Plains will overspread the area tonight, yielding light winds and
clear skies. With lows in the 34-37 degree range and RH values
pushing 80 percent across north central KS, have issued a Frost
Advisory for these areas from 4 AM to 8 AM Friday morning. A
secondary shortwave trough will traverse the upper midwest Friday
afternoon, pushing another weak front through the region. Again,
only expect a wind shift to the north and little temperature
change. Highs tomorrow afternoon are progged to reach the low to
middle 70s.

.LONG TERM...(Friday night through Thursday)
Issued at 319 PM CDT Thu Apr 26 2018

The main takeaways from the long term period include a beautiful
spring weekend before the risk of severe thunderstorms next week.

Upper level ridging will overspread the central and northern
Plains Saturday. An associated surface ridge will slowly traverse
the CWA Saturday into Sunday morning. These features coupled
together yield clear skies and light winds. High temperatures are
progged to reach the upper 60s to near 70 Saturday afternoon. The
surface ridge will progress east the area Sunday, allowing
southerly surface flow and WAA to return the area. A tightening
pressure gradient in response to lee troughing along the front
range will yield 15-30 MPH winds Sunday afternoon. H85
temperatures nearing +12C will yield temperatures in the mid 70s
Sunday afternoon. We then turn our attention to the upper low
progged to be across the broad trough across the western CONUS. By
Monday an impressive EML plume will overspread the central
Plains. Further lee troughing is expected along the front-range,
yielding a tightening pressure gradient -- on the order of 8-10
mb -- and southerly winds up to 40 MPH. Uncertainty remains with
the extent of moisture return Monday afternoon and resultant
thunderstorm potential. With the main upper level speed max
remaining across the TX panhandle and NM, expect thunderstorm
activity, if any to remain very isolated and west of the CWA.

Monday Night: A slight chance exists for thunderstorms as a 50-60
kt LLJ overspreads the CWA. At this point in-time the impressive
EML should minimize thunderstorm potential with MUcin on the order
of >100 J/KG.

Tuesday/Tuesday Night: The main speed max will overspread much of
Kansas throughout the day with the main northeast to southwest
surface trough setting up across central and eastern KS.
Sufficient instability and shear would suggest the potential for
severe thunderstorms. Increasing moisture transport is expected
into the slowly moving front Tuesday night. With the front
remaining across the area, heavy rainfall is possible.

Wednesday: By Wednesday the front is progged to retreat northward,
setting the stage for a dryline/warm front triple point in the
central to eastern KS region. Again, sufficient instability and
shear will remain in place, yielding the potential for severe
thunderstorms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 546 PM CDT Thu Apr 26 2018

VFR conditions expected through the period. Light northwest winds
could have some low gusts early in the forecast. Winds become west
through the day ahead of a boundary coming in Friday night.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 4 AM to 8 AM CDT Friday for KSZ008-009-020-
021-034-035.

&&

$$

SHORT TERM...Baerg
LONG TERM...Baerg
AVIATION...67



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