Area Forecast Discussion
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FXUS64 KLUB 230928

Area Forecast Discussion
National Weather Service Lubbock TX
428 AM CDT Sat Sep 23 2017

Little has changed from previous shifts with respect to forecast
as a prolonged period of showers, a few thunderstorms and heavy
rainfall will begin in the west this evening, spreading east
tonight and areawide Sunday.

Large upper-level longwave trough over the western US will shift
east very slowly during the next few days then deamplify and lift
northeast over the central US by the middle of next week. Medium
range NWP output suggest that a weak cutoff low will develop over
the far southwestern US in the wake of longwave trough`s exit.
Meanwhile, abundant low-level moisture will be drawn northwest
across the region before a cold front propagates south across the
southern high plains Monday and Tuesday. NWP solutions continue to
differ on timing of front with the NAM and EC a little faster
than the GFS. The faster frontal progression seems more plausible
considering strength of airmass and convectively induced cold
pooling north of the front. Seasonably warm temperatures today
will significantly cool by Monday and remain below normal through
the forecast period.

Over the next 24 hours and in advance of cold front, it appears
the greatest threat of the heaviest rainfall will occur across
eastern New Mexico and possibly impacting Parmer and Bailey late
tonight or early Sunday. This shift discussed whether or not to
issue a Flash Flood Watch for these two counties and ultimately
decided against it due to the timing and limited duration of heavy
rainfall. Nevertheless, upcoming shifts will need to monitor this

Heavy rainfall and flood threat will increase areawide Sunday
night and continue through Tuesday as broad area of mid-level
moisture-rich lift overspreads strengthening low-level jet and
southward moving cold front. Greatest precipitable water content
will exist across the eastern portions of the Caprock and into the
Rolling plains with values in excess of 1.5 inches. That being
said, would not be surprised to many locations receiving in
between 3 and 4 inches of rain by late Tuesday as suggested by WPC
and supported by NWP output.

By Wednesday, heavy rainfall and flooding concerns should shift
south and east. Precipitation chances will begin to diminish in
earnest Thursday as drier airmass finally filters in from the
north. JH



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