Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 211731
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1231 PM CDT Wed Jun 21 2017

.AVIATION...
18Z Issuance...Overall sites will be VFR through the period;
however, a line of storms is expected to form and pass from
northwest to southeast which will drop conditions for a few hours
while storms pass the site. Southerly winds should persist with
gusts to 30 kts until after storms pass when gusts should calm.

Beat

&&

.PREV DISCUSSION... /Issued 434 AM CDT Wed Jun 21 2017/

DISCUSSION...

Noteworthy items include severe weather chances later today, and
then again the next couple of days, as well as thunderstorms chances
throughout the extended. Today and tomorrow still look warm, but on
the flip side this weekend looks to be below normal for highs with
Sunday in the 70s. There is also a chance for moderate to perhaps
heavy rainfall during the combined Friday night through Sunday
night timeframe.

In the upper levels, high pressure continues to dominate the desert
southwest, putting us under northwesterly flow aloft. This pattern
will be the overall norm through the extended. Tropical cyclone
Cindy is beginning to makes its impression on the southern CONUS
as well. Cindy will impact the south before getting consumed in
the mean flow aloft by Friday. Cindy will ultimately help bring in
moisture to the region where we will see some impact from this as
forecast soundings show very high precipitable water amounts
beginning Friday and going through the weekend.

Looking closer at today, we will have an axis of most unstable CAPE
around 2500-3500 J/kg collocated with bulk shear (0-6km) around 30-40
knots in the afternoon to early evening hours. Forecast soundings
are depicting an inverted-V sounding to begin the event with high
LCL heights. A surface trough axis should swing through the area
late afternoon and help initialize thunderstorms. Forecast
hodographs during the time of convective initiation suggest
thunderstorms should be pulse type thunderstorms with likelihood of
going to a more multicell/linear type convection later as storms
propagate south/southeastward. We will be strongly dependent on
afternoon heating for destabilization, but given the mid-level
(700-500mb) lapse rates increasing to around 7-8 C/km
thunderstorms should be able to get to severe strength with ample
instability and sufficient bulk shear. Wind and hail will be the
main threats today. Also, it does appear storms will be slow
movers with some of the faster storms moving around 30 mph, so
some locally higher rainfall amounts will be possible. However,
flooding should not be a problem today given the likelihood storms
will be somewhat "pulsey" in nature and training storms are not
expected.

Beyond today, there is another chance for thunderstorms Thursday and
Friday, but severe weather does not look as likely as today. That
being said, we could definitely have some strong to marginally
severe thunderstorms during this time period. Confidence beyond
Friday for severe weather is very low but thunderstorms are possible
nearly everyday in the forecast through Tuesday, so we shall see
what--if any--severe weather chances pop up later as we get
closer.

Of interest in the Friday night through Sunday night time period is
the chance for efficient rain producers. Climatologically speaking
this is an area that doesn`t receive much rainfall, so forecasting
any significant rainfall is always an outlier and therefore rather
difficult. That being said, models are hinting at precipitable water
amounts above 1.50" and in some cases approaching 2.00". To put this
into perspective, during this time period this would be well above
the 90th percentile. The maximum precipitable water from KAMA
soundings between 1952 and 2014 was 1.50" during the 00Z June 24th
to 12Z June 26th time period. Of course, this just means there is
the potential for the atmosphere to have lots of moisture, but we
need other ingredients to come into place so we can tap into this
moisture. One limiting factor is we wont have any surface
boundary to work with. In fact, after the cold front comes
through on Friday, we will have mostly am easterly component to
the wind Friday night through Sunday night. We will somewhat make
up for this with evidence of strong isentropic lift in regions of
high moisture. Overall the flow aloft is also weak so any storms
that do form will be slow movers. At least for now, the Friday
night through Sunday night time frame has the potential for some
efficient rain producers. Stay tuned.

Guerrero

&&

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

&&

$$

16/29



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