Area Forecast Discussion
Issued by NWS Amarillo, TX

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885
FXUS64 KAMA 201728
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1128 AM CST Tue Feb 20 2018

.AVIATION...
18Z Issuance...MVFR to VFR ceilings through the period with AMA
hanging on to MVFR possibly the whole time. Confidence of forecast
is low as models are not handling this well. Winds will be
northerly and stay around 10-15kts with a few 20kt gusts. Skies
will likely turn overcast again overnight and come back down to
MVFR. Precip or BR may be an issue starting after 05Z but
confidence is very low so have left out for now.

Beat

&&

.PREV DISCUSSION... /Issued 918 AM CST Tue Feb 20 2018/

UPDATE...
Updated grids for trends this morning, retaining cloud cover and
keeping temps down.

Beat

PREV DISCUSSION... /Issued 508 AM CST Tue Feb 20 2018/

AVIATION...
Our cold front continues to surge southward for the start of the
12Z TAF cycle. This will result in IFR ceilings and breezy
northerly winds of 15 to 20 kt with gusts up to 33 kt. This front
remains poorly handled in models so expect amendments. Have gone
with a gradual improvement to MVFR ceilings from north to south
between 17z and 22z. VFR conditions should return and prevail
through the overnight hours.

PREV DISCUSSION... /Issued 310 AM CST Tue Feb 20 2018/

DISCUSSION...A cold front draped across the northern Panhandles
is bringing temperatures in the upper teens to lower 20s in the
northern Panhandles, to the 50s to near 60 in the southern
Panhandles. Suffice it to say, this forecast is going to be quite
difficult as there is a great disparity between high-res guidance
and operational models, with poor initialization of the front by
nearly all models.  Lee side troughing, still active in New
Mexico this morning, may help keep southwesterly winds going
across the southwestern Panhandles, which could slow forward
progress of the arctic front. Given the tendency for model
guidance to project forward progression of this front to be too
slow, have opted to forecast all but the southwestern third of
the Texas Panhandle this afternoon being affected by cold air. The
airmass behind the front may saturate given low dew point
depressions, which could cause stratus to form in the wake of it`s
passage.

Attention turns toward Wednesday night into Thursday morning as
return southerly flow aloft may bring isentropic lift along the
frontal boundary. There is a decent chance of mixed wintry
precipitation in the form of snow, ice pellets and freezing rain
across the eastern Panhandles. The question remains as to how deep
of a warm nose may exist, as some guidance presents a warm nose
around 3k to 5k AGL as precipitation falls into the surface
boundary layer. Considering that water droplets may not be
supercooled as it impacts the surface, have collaborated with
neighbors about precipitation types late Wednesday and Thursday
morning. Monitoring of this situation is necessary given the
potential for a glaze of ice in the eastern half of the region if
the warm nose is more favorable than present projections.

During the afternoon on Thursday into Friday, southwesterly flow
will increase across the New Mexico Rockies that will help bring
warmer and drier conditions to the region. Drier conditions will
persist through next Tuesday before a possible incoming western
trough brings back moisture to the southern Panhandles. At this
point, have held with low end slight chance due to agreement
between the GFS and ECMWF. We`ve been here before, but one can
tell that a pattern shift may be in the offing early next week if
present projections hold.

Bieda

&&

.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.

&&

$$

16/3



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