Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 121034
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
434 AM CST Sun Nov 12 2017

.DISCUSSION...
Latest upper level analysis has shortwave trough entering the OH
Valley region with more vigorous upper trough spinning off Pac NW
coast. A dome of high pressure is evident over Baja Peninsula
into Mexico with broad anti-cyclonic flow, keeping an upper
stream of west-northwest winds over the southern plains. Very dry
mid and upper level subsiding air can be seen in the wake of the
OH valley shortwave, pushing east-southeast into TX/OK and points
eastward. This should be replaced with increasing moisture in the
500mb-200mb region as upper level moisture feeds around the high
pressure later this evening, however, the 800mb-500mb levels will
remain dry with a persistent EML in place. Beneath the EML, and
towards Earth`s surface, conditions are characterized by northeast
post-frontal winds, low level T/Td spreads of only 2-4 degrees F,
and a deck of low stratus that is forming in response to at least
weak upslope flow and a fairly moist BL. Some patchy fog or
perhaps drizzle can`t be ruled out through the morning hours
across most of the Panhandles. Clouds *should* begin clearing out
from west to east by mid-late morning or early afternoon for the
southeastern zones. Some models such as the NAM and RAP suggest a
deck of clouds may stick around for most if not all of the day in
the southeastern Texas Panhandle. Temperatures will largely depend
on timing of cloud departures and thus western zones can expect
to be slightly warmer than eastern zones with 50s for most
locations.

Winds will be veering through tonight becoming southerly by
Monday morning. This is in response to surface high pressure
pushing into the OH and upper MS Valleys in wake of upper
shortwave trough. In turn, low level Theta-E advection will
increase overnight through Monday, helping to further increase
surface dew points beneath the ever persistent EML (given
continued zonal flow aloft). The veering surface winds will lend
to some confluence in the low levels along with continued upslope
flow. Forecast model soundings continue to show fairly deep low
level moisture especially in the southeast Texas Panhandle
(saturated from near the surface up to about 800mb) along with
enough wind/wind shear to include areas of drizzle mainly after
06z through about 18z Monday. Areas further west going up the
caprock could see a mix of fog and drizzle or perhaps just low
clouds. Clouds and and fog/drizzle will once again retreat east
Monday as southwest winds increase in response to lee troughing.
The far eastern Panhandle may have to wait until Tuesday to get a
break in cloud cover.

The zonal flow aloft will continue through mid-week with another
shortwave crossing the central plains on Tuesday into Wednesday.
Deterministic models are hinting at a fairly strong jet streak
crossing the Rockies Tuesday with a surface trough developing over
the Raton Mesa. This should increase a pressure gradient across
the Panhandles with fairly gusty southwest winds the afternoon
for at least the southern zones. Min RH values may dip down
around 20 percent in the afternoon Tuesday as Temps rise well
above average ahead of a cold front late Tuesday evening into
early Wednesday. North winds behind the cold front are also
expected to be gusty through most of the day Wednesday.

Finally, fire weather concerns continue for the Thursday-Friday
timeframe as models show an amplifying trough digging over the
southern rockies with a strong mid/upper level jet advancing over
the Panhandles. The GFS is still about 6 hours faster than
ECMWF/Canadian and all models are trending slower on arrival of
the surface cold front Friday. It seems the models are having a
tough time with what is essentially a merger of the
southern/northern stream flows as a Pac NW trough digs south while
dome of high pressure persist over northern Mexico. For now, it
looks more and more like Thursday will be more limited to elevated
conditions in the western zones where mid/high clouds clear out
earlier in the day as west-southwest winds become gusty in the
afternoon. Friday looks to be more favorable for fire weather as
wind profiles show 50kt winds from about 800mb up to nearly 100kt
winds at 500mb. However, the timing of the surface cold front
will have a large impact on how favorable the thermal profile will
be (even though dew points will be decreasing rapidly behind the
front even though temperatures will also fall). Overall, the
ECMFW/Canadian solution should be most favorable as it holds the
front off until Friday afternoon allowing temperatures to warm in
presence of very gusty southwest winds. Either way, at least
elevated fire weather conditions looks likely Friday for a large
portion of the Panhandles.

Ward

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                56  43  64  48  78 /   5  20  10   0   0
Beaver OK                  54  41  62  43  73 /   0  10   5   0   5
Boise City OK              57  38  66  42  75 /   0   5   0   0   0
Borger TX                  56  45  66  52  77 /   0  10   5   0   0
Boys Ranch TX              59  42  70  45  80 /   0  10   0   0   0
Canyon TX                  57  43  64  47  79 /   5  20   5   0   0
Clarendon TX               57  45  62  50  76 /  10  20  10   5   0
Dalhart TX                 59  39  67  43  80 /   0   5   0   0   0
Guymon OK                  55  42  65  42  75 /   0   5   0   0   0
Hereford TX                58  44  65  48  80 /   0  10   5   0   0
Lipscomb TX                55  43  60  49  74 /   0  20  10   5   5
Pampa TX                   54  43  63  51  77 /   5  20  10   5   0
Shamrock TX                56  44  59  50  74 /  10  20  20   5   5
Wellington TX              57  46  60  50  76 /  10  20  20   5   5

&&

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

&&

$$

2/7



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