Area Forecast Discussion
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298
FXUS64 KLUB 281742
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1242 PM CDT Fri Apr 28 2017

.AVIATION...
VFR conditions are likely to collapse to MVFR toward midnight at
all sites following cold FROPA. CDS should see the best window
for TS (some may be severe with large hail) after midnight along
the trailing elevated front, so TEMPO +TSRA has been inserted
there from 1-4 AM.

MVFR ceilings could fall to IFR at all sites Sat morning, but
later TAFs will be able to address this with greater certainty.
Else, steady southerly winds will veer N at 15-20 knots behind
the front.

&&

.PREV DISCUSSION... /issued 441 AM CDT Fri Apr 28 2017/

SHORT TERM...
Precipitation chances will increase as early as this afternoon as an
upper level low moves southeastward across the four corners region.
At the same time an upper level jet will amplify to our west placing
West Texas on the favorable downwind side of the upper level jet. We
will also see this lift complemented by a cold front late Friday
night into early Saturday morning. However, limited amounts of
quality moisture will keep precipitation chances limited and in
question.

After an early morning cold front early Friday morning, low level
winds will quickly swing back around to the southeast by the
afternoon. However, low level moisture return will be paltry by the
time upper level lift arrives. Better moisture will be limited to
mid and upper levels. This will be the case until another cold front
arrives late tonight into early Saturday allowing better low level
moisture to fill in. Best chances for precipitation will be tonight
into early Saturday along and behind the front. There will likely be
just enough instability to see some isolated thunder embedded within
precipitation. Greater instability will exist east of the area and
norther in the Panhandle where isentropic lift will be maximized
tonight. Also, high based isolated thunderstorms will be possible
this afternoon in the southwestern Texas Panhandle as the lift acts
upon the mid and upper level moisture. Low level moisture levels
will be so low that virga bombs may end up being the only result.

LONG TERM...
Solutions still in good agreement that a potent late winter storm
digging through the southern Rockies early Saturday will abruptly
turn northeast Saturday night across our northwest corner, then
into the eastern Panhandle Sunday. A cold front will continue
pressing southward Saturday with shallow low level saturation
while upper flow will back further. Drying will follow in mid
level behind an early Saturday impulse ejecting through the
eastern Panhandle, while more potent differential vorticity
advection with the main low will renew lift Saturday evening and
moisture aloft will increase again favoring eastern zones.
Solutions indicate adequate mid level cooling and instability for
mention of (elevated) thunder Saturday evening favoring our
eastern zones, with a lean towards generic showers elsewhere
although there very well could also be a burst of convectively-
aided precipitation elsewhere though struggling with drier air
aloft.

Dynamic cooling and lower level cold advection should turn
chances increasingly towards a snow or rain snow mix by late
Saturday across our northwest corner, very much as in the previous
forecast. Passage of the upper low Saturday night will allow
deformation axis precipitation chances across the Panhandle,
perhaps edging as far south as our northern row of counties late
Saturday night. Again, snow would be equally or mostly favored
especially on the Caprock. The current scenario favors snow totals
mostly around an inch or less, though unlikely to accumulate on
the relatively warmer pavement. However, any adjustment of the
track of the upper low in the next day will require adjusting snow
totals as well; high confidence in the precise storm track is
typically limited 24 hours out. Skies may begin clearing late
Saturday night though winds likely will remain breezy and not be a
huge factor for radiational cooling. However, the pure cold
advection alone may bring on freezing conditions Sunday morning
over much of our northwest third of the area and freeze products
seem probable at this point.

The upper low will continue into the central plains Sunday with
stiff northwest winds on the backside in our area owing to tight
surface pressure and low to mid level height gradients. Skies
should be tending clearer Sunday, but it will still be brisk. May
need a wind advisory as well on Sunday. Mid and upper level
warming will begin late Sunday into Monday, but winds will be much
lighter Sunday night. Light freeze conditions could be an issue
again early Monday for some areas.

Warming will kick in after daybreak Monday, and highs will bounce
back well into the 70s. Monday appears to be a very nice day with
modest afternoon breezes mostly around 20 mph or less expected. A
low amplitude upper trough will steer from the central Rockies
southeast into the southern Plains Tuesday pulling another front
into the area by late in the day, leading to modest cooling.
Trimmed thunder chances back mainly to our northeast corner
Tuesday night as moisture should be a struggle. Drier and
gradually warmer conditions will close out the week with an upper
ridge axis approaching from the west. RMcQueen

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

93



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