Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 232148
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
448 PM CDT MON MAY 23 2016

.Discussion...
The primary challenge for this forecast will again be diurnal cycle
of the dryline each day and thunderstorm potential. See previously
issued mesoscale discussion for convective/severe potential this
afternoon and evening. Additional updates will be sent based on
observational trends and short term guidance.

One additional short term concern is additional heavy rain in the
eastern Texas Panhandle and we have decided to issue a small Flash
Flood Watch for two counties to account for this. Many areas of
Donley and Collingsworth counties received around 2 inches of rain
and locally higher. Flash flooding occurred last evening and
additional flash flooding may occur with any heavy rain producing
thunderstorms. GPS precipitable water values from Childress site show
marked decrease in values from this time yesterday, at least
partially due to 0-2 km layer average trajectories from convectively
overturned air mass to our southeast from overnight, and partially
from veering aloft and drier mid-levels. Nevertheless, best estimates
are 1-1.25 inch PWAT values which will be supportive of heavy rain.
Bunkers storm motions for right-mover supercells is faster than
yesterday but still relatively slow.

No significant changes were needed to the previous forecast. The
trough in the west will gradually move toward our area with mid-
level flow gradually increase. Dryline should mix east again
tomorrow afternoon and slow once it moves east of the caprock into
deeper moisture. Ahead of the dryline MLCAPE values could rise to
very high levels (~4,000+ J/KG) supporting severe thunderstorm
potential. Mid-level flow of 25-30 knots particularly impressive low
level backed south-southeasterly flow should yield 35-40 knots 0-6 km
bulk shear, sufficient for storm organization and persistence. Flow
near the equilibrium level should be stronger than previous days as
upper jet seen on 1.5 PVU surface overspreads the region. This should
lead to larger storm depth shear values which should favor
supercells that are slightly less HP with greater potential for
significant hail sizes (stronger anvil layer winds). Neutral to
possibly slightly increasing mid-level heights is one potential
negative and could at least keep activity isolated. We will watch
trends and observational data as the time nears for possible
perturbations aloft that may aid in convective development.

Dryline should become more synoptically-active and mix far enough on
Wednesday but could be barely in the eastern Panhandles Thursday for
a threat of more thunderstorms. We will watch the trends of the
guidance and make adjustments as this potential nears. If the main
upper trough slows/deepens, there would be a better chances for more
of the eastern Panhandles to be involved. Thunderstorms may be
possible at least across the northern Texas Panhandle and Oklahoma
Panhandle Friday until this upper trough moves east. Not much of a
cold surge is expected in the wake of this trough and as another
western CONUS trough deepens next weekend, low-level response should
quickly bring better moisture back into the Panhandles and at least
subtle lift should be sufficient for thunderstorms again by Sunday.
Medium range guidance differs on timing of subtle shortwaves embedded
within the larger trough so details are not clear at this time range
but confidence is expected to increase later this week.

BRB

&&

.Mesoscale Update... /Issued 1250 PM CDT MON MAY 23 2016/
Early this afternoon, an upper-level low pressure system was in
place over southern Saskatchewan with a trough extending across the
Pacific Northwest. An upper-level ridge extends from South Texas to
the Great Lakes. Flow over the Panhandles will be generally weak as
the area will be between the northern and southern stream jet speed
maxima, with wind speeds aloft only peaking at around 40 kts through
250mb today. Meanwhile a surface low which has slipped into the
northern Panhandles overnight will slowly lift northeastward
throughout this afternoon. The dryline will stretch southward from
the low this afternoon, likely along a Claude-Pampa-Slapout line by
late afternoon. Dewpoints to the east of the dryline will hold steady
in the mid/upper 60s to low 70s, while dropping into the 30s and 40s
to its west. This will keep the best moisture and instability axis
focused along a corridor from the Low Rolling Plains of Texas through
western Oklahoma (clipping the southeastern TX Panhandle). Forecast
soundings indicate upwards of 3000-4000 J/kg of MLCAPE will develop
in that corridor, though some capping will remain. Thinking is that
any storm initiation today will be more closely tied to the dryline
where the cap is more likely to be broken. Storm motion will then be
to the east and northeast at around 20-30 kts, though clusters of
storms could develop by late evening as storms exit the Panhandles
and build southeastward into better moisture.

NF

&&

.Preliminary Point Temps/Pops...
Amarillo TX                89  62  89  59  89 /  10  20  10  10   0
Beaver OK                  86  65  92  62  92 /  20  20  20  10   0
Boise City OK              82  53  87  56  86 /   5   5  10   0   0
Borger TX                  89  64  92  61  91 /  10  20  10  10   0
Boys Ranch TX              92  58  92  59  91 /  10   5  10   5   0
Canyon TX                  92  61  91  58  90 /  10  10  10   5   0
Clarendon TX               86  64  88  61  91 /  40  50  30  20   5
Dalhart TX                 87  54  89  56  87 /   5   5   5   0   0
Guymon OK                  87  60  91  58  90 /  10  10  10  10   0
Hereford TX                92  59  91  57  90 /  10  10  10   5   0
Lipscomb TX                87  66  90  63  92 /  30  30  30  20   0
Pampa TX                   88  64  88  61  89 /  20  30  20  10   5
Shamrock TX                84  66  88  64  92 /  50  50  30  20   5
Wellington TX              86  66  88  65  93 /  50  50  30  20   5

&&

.AMA Watches/Warnings/Advisories...
TX...Flash Flood Watch until 4 AM CDT Tuesday for the following
     zones: Collingsworth...Donley.

OK...NONE.

&&

$$

6/17



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