Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 112156

National Weather Service Kansas City/Pleasant Hill MO
356 PM CST Wed Jan 11 2017

Issued at 355 PM CST WED JAN 11 2017

...Impactful winter storm increasingly possible this weekend...

Short Term (Tonight - Tomorrow):

A sharp cold front is moving through the forecast area this
afternoon with a sharp dichotomy of temperatures across the CWA. The
southern CWA has risen into the lower 70s while the northwestern CWA
is in the lower 30s. This front currently extending from MCI to IRK
will continue to push south across the rest of the CWA this evening
and with strong CAA in behind the front, temperatures will drop
below freezing across the entire CWA by tomorrow morning. Lows
tonight will fall into the mid teens north to the upper 20s south.
Models are suggesting that there is the potential for light freezing
drizzle across the southeastern CWA after midnight which could lead
to light glazing on roadways however most hi-res models are keeping
this precipitation southeast of the area. Continued cold air
advection will keep temperatures cool tomorrow with highs in the mid
20s to mid 30s.

Medium Range (Tomorrow night - Monday night):

By tomorrow night, the synoptic set up will be such that a closed
upper level trough will be dropping down the California coast. This
will allow Pacific moisture to filter into the area. At the surface,
the aforementioned cold front will reside across southeastern OK
through central AR with a surface ridge of high pressure across the
southeastern CONUS and eastern Gulf of Mexico. This will open up the
western Gulf and allow moisture to stream northward. This moisture
will override the cold front and freezing rain/drizzle will
overspread northern Arkansas and southern Missouri remaining south
of the CWA. The cold front will then begin to creep slowly northward
as a warm front into northern Arkansas during the day Friday. This
will introduce light freezing rain/freezing drizzle generally along
and south of the Missouri River during the day. Friday night, most
model are depicting a weak wave moving out of the southern Plains
into the area providing the lift for a better chance for freezing
rain across the CWA. Saturday, the forecast area with the exception
of perhaps the extreme southern CWA will remain below freezing
however precipitation looks to be light and scattered in nature.

Saturday night through Sunday night looks like the best timeframe to
see large amounts of ice accretion. Models are in good agreement
that the forecast area will have a stout warm nose of 3F to 5F
degrees between 3-9kft with a below freezing layer in the lowest
3kft Saturday night into Sunday. The upper level trough will begin
to push eastward across northern Mexico to near the western
Panhandle of Texas. A lead shortwave ejecting out from the south
Plains will lift into area overspread freezing rain across the area.
This freezing rain has the potential to produce significant ice
accumulations as PWAT values of near an inch will be extremely high
for January standards. This moisture influx from the Gulf with
continue into Sunday. The question is, when will temperatures move
above freezing on Sunday. The warmer GFS moves the freezing line to
northern Missouri by Sunday evening while the cooler EC keeps all
but the extreme southern CWA below freezing. Currently the cooler EC
is favored due to a persistent Arctic High residing across the Upper
Midwest which not ideal for a quick retreating warm front across the
area. If the EC solution does verify it is not out of the question
some areas could see an inch of ice accumulation whereas if the GFS
solution verifies we will only see a tenth to quarter of an inch if
ice. In any case a winter weather watch or winter weather advisory
will most likely be needed in the next 24 hours.

Even the coolest EC solution lifts the freezing line north of the
area by Monday as the upper level system ejects into the Central
Plains lifting the warm front north. And, perhaps the silver lining
to this ugly forecast is good melting should occur on Monday with
highs rising into the upper 30s to lower 50s although rain will
continue. Conditions will dry out for Tuesday and Wednesday.


.Aviation...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1127 AM CST WED JAN 11 2017

Southerly winds around 15kts with gusts to 25kts will be the rule
for the first 1 to 2 hours of the TAF pd before a cold frontal
passage swings winds around to the north around 15kts with gusts
to 25kts. Gusts will diminish tonight but winds will remain btn
10-15kts. Btn 07Z-09Z thru 13Z there may be a pd of MVFR cigs
which will affect the terminals however model disagreement leads
to low confidence.




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