Friday morning briefing from Jeff:
Extremely active weather expected Sunday
All severe weather modes (tornadoes, large hail, and damaging winds) along with flooding rainfall possible.
Powerful upper level storm system responsible for the damaging winds across Las Vegas on Thursday will approach and then cross TX this weekend result in widespread impacts over the region. Gulf moisture begins to return in earnest later today into Saturday as the upper level low over the four corners advances into NM and then N MX. Lift begins to spread across TX late Saturday and some models try and develop strong to severe thunderstorms over the SW parts of SE TX late Saturday afternoon into the evening hours. Strong lift, very high moisture levels, and good wind energy come to bear over the region on Sunday…which is looking to very much to be a significant weather day.
While details remain low confidence at this time range factors look in place for excessive rainfall over SE TX along with a potential good severe weather threat. Warm sector air mass appears uncapped and charged with instability from roughly the very early morning hours on Sunday into Sunday evening. Potential for supercells to evolve in the warm sector air mass with latest SPC outlook suggest significant tornado parameters will be in place Sunday morning. This appears to be in response to a warm front lifting across the area early Sunday and warm fronts historically like to host tornadic supercells.
Factors certainly look to be in place for a very wet Sunday with PWS surging to 1.8 inches over the area and at least one or two boundaries in place to help focus training excessive rainfall. First boundary will be a northward advancing warm front Sunday morning with the next being an incoming surface front from W TX. Both have produced flash flood setups over SE TX before with a very deep trough approaching from the west and good upper air venting of an extremely moist surface layer with dewpoints near 70. Widespread rainfall amounts of 2-4 inches will be possible with much higher totals where any sustained cell training develops. Latest WPC outlook has areas north of I-10 already outlooked for excessive rainfall and exceedance of flash flood guidance for Sunday. Moisture profiles would certainly support excessive rainfall rates of 2-3 inches per hour.
Severe weather parameters look favorable on Sunday and potentially the highest parameters we have seen yet this winter/spring. Low level jet increases overnight Saturday into Sunday with mid level winds increasing and veering with height helping to produce good speed and directional shear over the area. Low level shear values really ramp up early Sunday morning likely due to warm front over the region and the period from about 400am-noon Sunday may feature the highest tornado risk. CAPE values of 1500-2500 J/kg over the region suggest good instability across the northward advancing warm sector and will favor intense updrafts and threat for large damaging hail and strong winds into the afternoon hours on Sunday. The tornado risk may decrease some Sunday afternoon as strong forcing along and ahead of the advancing surface front favors more of a squall line.
Since this event is still about 2 days away exact locations of boundaries and fully realized parameters are still in flux for Sunday. Such uncertainties result in low to moderate confidence on where exactly the heaviest rains will fall and what severe mode and when is most likely. Better confidence will hopefully arrive over the next 24 hours. For example the GFS model QPF for BUSH IAH in the last two runs has varied from 4.58 inches to 2.07 inches.
***Have a way to receive weather warnings on Sunday. Make sure WEA (wireless emergency alerts) are “on” on your cell phone…this will tone your phone if a warning is issued for your location or you drive into a warning polygon***
SPC Day 3 (Sunday) Severe Weather Outlook:
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Ike
Member: National Weather Association