Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Amarillo Texas
624 am CDT Friday Jul 31 2015
the combination of convection and patchy fog will lead to a low
confidence 12z taf issuance. A line of convection which is currently
affecting the kdht terminal should continue a slow eastward
progression to impact kguy and possibly kama before 15z. As stronger
embedded storms move over the terminal...we could see prevailing
conditions briefly drop to IFR/LIFR. Outside of these stronger storms
conditions hover right around MVFR to IFR due to fluctuating
visibilities. While on the topic of visibilities...patchy fog has
developed out ahead of the western cluster of storms. This has
allowed visibilities at kama drop to a half mile over the past hour.
This will likely be a brief occurrence as visibilities should improve
as the outflow from the western cluster moves across the terminal.
The combination of fog and convection should diminish at the
terminals around the middle of the day to allow conditions to improve
back to VFR. This improvement will be short lived as additional
convection is expected this afternoon/overnight. Prevailing
conditions will depend greatly on the location of the embedded storms
so expect adjustments by later issuance.
Previous discussion... /issued 452 am CDT Friday Jul 31 2015/
scattered thunderstorms across the Oklahoma and western Texas
panhandles this morning are slow moving...and efficient rainfall
producers. Setup remains somewhat similar to last few days in that
several ingredients for heavy rainfall line up across the panhandles.
Moisture plume shifting slightly westward this morning across New
Mexico...though upper level flow shifting to become more
northwesterly resulting in a setup for convection to drift into the
panhandles from the mountains. At the surface...moist upslope flow
will continue to keep a fairly decent moisture source across all of
the panhandles. Precipitable water values range from 1.5 to near 2 inches through
early Sunday as surface flow remains south to southeasterly. Outside
of convection arriving via northwest flow...a few ingredients cause
some uncertainty in the coverage of thunderstorms this afternoon and
evening. Lifting mechanism may be lacking across the area as a
weak...lingering surface boundary has drifted further south. Debris cloud
cover from this morning's convection may also contribute to available
instability. Overall effective shear is low...so while severe storms
are not expected a few could produce a wind threat. Heavy rainfall
and the potential for flooding/flash flooding is the primary threat.
Even though uncertainty is low in where exactly storms will
develop...any that do will be capable of producing heavy rain and
will have slow storm motion. Have opted to extend the Flash Flood
Watch through Saturday morning across the western panhandles.
Overall setup changes little over the next few days with upper level
flow northwesterly and surface moisture remaining in place. Timing of
shortwave impulses drifting into the area...along with orographically
induced convection will keep chances for precipitation across the
panhandles. Upper level heights begin rising on Sunday night and into
Monday and have adjusted blend probability of precipitation after Monday to concentrate on
areas of best chances...though this will likely change as forecast
confidence increases in extent of the upper level ridge building in
and drying the area out for a few days midweek.
Texas...Flash Flood Watch through Saturday morning for the following
zones: Dallam...Deaf Smith...Hartley...Moore...Oldham...
OK...Flash Flood Watch through Saturday morning for the following