Area Forecast Discussion
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FXUS64 KLUB 202352

Area Forecast Discussion
National Weather Service Lubbock TX
652 PM CDT Sun May 20 2018

VFR will continue this evening, but light moistening upslope
breezes will bring the risk for stratus and fog development late
tonight. There is a good shot of MVFR conditions developing after
8-10Z, with a risk of IFR to LIFR toward dawn. KLBB and KPVW
appear to have the highest risk of IFR conditions around and
shortly after daybreak and a TEMPO has been included to address
this. Ceilings should gradually lift to VFR by late morning or
early Monday afternoon. Winds will be on the light side through
the period. There may be a slight chance of convection at the
terminals tomorrow, but confidence in both development and
coverage/location is far too low for inclusion in the TAFS.


.PREV DISCUSSION... /issued 239 PM CDT Sun May 20 2018/

Seasonably cool surface ridging throughout the region this
afternoon is set to drift eastward tonight ahead of shortwave
ridging aloft. This will spur steady return flow overnight with
dewpoints returning to around 60 or higher for much of the region
by daybreak. Although most model soundings reveal a classic
stratus layer accompanying this moisture advection, last night`s
heavy rainfall may even support some fog development at times.
PoP-wise, values were trimmed back considerably tonight as
background ascent will largely be absent under weak height rises
and anticyclonic flow. Aside from some errant storms developing
in SRN NM tonight along the nose of a southeasterly LLJ,
prospects for this activity to survive much beyond our western
zones through Monday morning appear slim.

Departure of the shortwave ridging by Monday night should allow
for a more unsettled SW flow regime to expand across the Caprock.
However, the mean steering flow is largely meridional which could
easily keep nocturnal storms from eastern NM restricted once again
to our western zones. Some CAMs do show aggressive outflow
propagations eastward resulting in a broader reach of precip, but
as a whole we have lowered PoPs off the Caprock Monday night and
opted for some likelies near the NM border. Potential for severe
modes is less than recent days as lapse rates trend weaker with
diminishing shear to boot. If anything, heavy rain and flooding
prospects may steal the show as slow storm motions combine with
PWATs rising to 1 inch or more.

Beyond Monday night, convective chances will hinge largely on any
embedded waves in weak SW flow (20 knots or less at 500 mb),
outflow boundaries, and even remnant MCVs. The dryline will be
nowhere near our CWA as moisture remains backed into eastern NM
each day, so PoPs were generally kept on the conservative side for
now. Opted to keep higher chances in our western zones most days
and nights in expectation of upslope storms wandering NE from the
higher terrain. Otherwise, upper ridging with rising thicknesses
will serve to lower PWATs by late week and bring a lull to precip
chances. However, potential for an active NW flow regime is
increasing by the weekend as upper ridging retrogrades to near
the Continental Divide. The ECMWF recently came around to the GFS
regarding this transition which further raises confidence in a
return to some precip for Memorial Day weekend.




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