Area Forecast Discussion
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FXUS64 KLUB 180812

Area Forecast Discussion
National Weather Service Lubbock TX
312 AM CDT Sat Aug 18 2018

The center of upper level ridging has retrograded westward toward
southern California while an upper level trough is topping the
ridge over the northern Cascades early this morning. A moist air
mass remains in place across the forecast area while a modest
upper level jet streak is moving eastward over the 4-corners. This
jet streak will move out over the central High Plains later today
with its favorable right rear quadrant helping to support and
sustain convective development that occurs later today and through
the night. Initially it will be difficult to pinpoint convective
initiation given the numerous low level boundaries that will be in
place across the area with this morning`s decaying convective
activity. The best overlap of favorable conditions currently
favors the northern half of the forecast area once again and will
run with high chance PoPs there tapering toward slight chance

Sunday`s forecast is a bit more complex with some uncertainty
regarding timing of the arrival and departure of a cold front.
This front will be driven by the short wave trough located over
the Pacific Northwest this morning as it moves onto the central
Plains. Models suggest a disturbed low level flow ahead of the
front in an area again dominated by remnant outflow boundaries, so
it is a bit difficult to ascertain the front`s arrival. However,
it appears that even the WRF-NAM delays the main frontal push
until late day, if not evening. That would suggest rain chances
remain needed even through Sunday night, favoring eastern counties
initially followed by southern. The front will push south of the
forecast area for Monday with dry weather likely at least through
the day Tuesday. At this point the models diverge enough to have
some fairly major ramifications on the forecast. The ECMWF pushes
the center of the ridge back over the forecast area in a position
similar to that of about five to seven days ago when little precip
occurred across the forecast area. The GFS keeps the ridge to the
west with a good chance of additonal late day and overnight
precipitation favoring the northern zones from Tuesday night
through the end of the week. The GFS ensemble mean favors the
middle ground and given the uncertainty have favored that approach
with the forecast with nothing more than slight chance of thunder
in the latter stages of the forecast.




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