Area Forecast Discussion
Issued by NWS Amarillo, TX

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300
FXUS64 KAMA 191744
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1244 PM CDT Thu Apr 19 2018

.AVIATION...

VFR conditions will prevail for the first 18-21 hours of the TAF
period before rain showers and low cigs move in from the west mid
morning Friday. For now, only included -shra at KDHT and KGUY
while leaving precip out at KAMA until next issuance. Some thunder
certainly can`t be ruled out and future issuances will have to
address this concern. Winds will be southeasterly through the
period, gusting to 25-30kt from time to time.

Simpson
&&

.PREV DISCUSSION... /Issued 521 AM CDT Thu Apr 19 2018/

DISCUSSION...

A rather contrasting forecasting package is going out this morning
compared to the last several months. We are forecasting a decent
chance at rain rather than fire weather. In other words, there is
finally a far better chance for rain than fire weather in the
short/near term periods. Although elevated fire weather conditions
exist today, it wont be the biggest story as showers and
thunderstorms highlight this forecast package on Friday and
Saturday.

Models are in pretty good agreement in the upper levels regarding
the transition of a 500 mb low over the Rockies into the Plains. Its
not until about Saturday we see some divergence between the
solutions. This is good and boost confidence for the chances of
rainfall over the 36-hour period beginning roughly on Friday
morning. Ahead of the upper level low, a subtle surface low will
begin to develop over eastern portions of Colorado, with
southeasterly winds over the Panhandles we should see dewpoints on
the rise into the lower 40s on Friday. This will result in
afternoon/early evening relative humidity values in the 70-90
percent range. Thats saying a lot. With the advection of moisture
into the area, we will likely see precipitable water values
approaching one inch or close to that amount. Upper level jet
dynamics combined with isentropic lift further suggest good
chances for rainfall. Omega values are strong and there is
evidence in forecast soundings of a deep moist column in the
atmosphere. All in all, things are pointing towards decent chances
of rainfall across most areas within the Panhandles. Does this
mean everyone will get rain? Probably not. However, this is the
best chance for widespread rainfall that we have seen in some time
now. Additionally, forecast soundings are showing elevated
instability somewhere around several hundred Joules per kilogram.
This alone does not scream severe weather, but bulk wind shear (0-
6km) values are approaching 50-60 knots and in some cases 70
knots. It usually takes a good balance of meteorological
parameters for severe weather to come to fruition, and this may be
too much severe for these storms to maintain a healthy life
cycle. As of now, widespread severe weather does not appear
likely, but given the shear values within the small instability,
one cannot rule out perhaps a rogue severe hail (one inch in
diameter) within the stronger updrafts.

Regarding the elevated fire weather concerns today, it does appear
to be a low end event due to relative humidity values dipping down
to the 10-15 percent range under 15 to 20 mph wind speeds. This will
be mainly for western parts of the combined Panhandles, and more so
far western portions along the New Mexico border.

Guerrero

&&

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

&&

$$

9/98



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