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Showing results for tags 'May'.
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Looks like a fairly active pattern over the latter part of this week and perhaps early next week particularly for the western side of our region.....Obviously severe is always a short fuse situation but it was most interesting to see SPC start actually using Day 6 severe outlooks (and potentially beyond).
Now that model agreement among the GFS ensembles, the GFS operational, the ECMWF, and the ECMWF ensembles are coming into more general agreement re: the timing of our next severe threat, I've decided to start a thread. For starters, models are keying in on a general re-loading pattern over the next five to six days with a +PNA giving way to a -PNA and a broad Western trough setting up. At the same time the MJO is forecast to be in or entering into a weak Phase 1 state over the Atlantic and W Africa with little real change in the -NAO state. Models are showing a high-quality warm sector setting up over the srn Plains by days four and five with a Sonoran EML overspreading nrn TX, OK, and KS. By day five broad lee cyclogenesis is forecast to occur east of the Rockies, with a broad southerly return flow advecting a seasonably moist air mass north. While there are capping issues to contend with, especially with the positively tilted trough forecast to set up, overall the set-up would support about a three-day period for convection beginning perhaps with initation along the dryline as early as day four. Given relatively weak deep-layer shear the threat for tornadoes and severe wx generally is likely to be fairly localized, which could either be a bane or a boon to chasers depending on how the mesoscale sets up. Still, it's better than nothing! SPC seems interested: AS A WRN U.S. UPPER TROUGH EVOLVES/DEEPENS THROUGH EARLY NEXT WEEK...SEVERE RISK WILL REMAIN LOW. HOWEVER...WITH HIGH-PLAINS LOW PRESSURE EVOLVING AHEAD OF THE TROUGH THUS SUPPORTING WIDESPREAD SLY LOW-LEVEL FLOW INTO THE CENTRAL CONUS...STEADILY MODIFYING GULF AIR WILL CONTINUE BEING ADVECTED NWD THROUGH MIDWEEK. BY THE WED-FRI TIME PERIOD /DAYS 6-8/...INCREASINGLY WIDESPREAD MODERATE CAPE SHOULD BE AVAILABLE ACROSS A LARGE PORTION OF THE CENTRAL THIRD OF THE COUNTRY...THUS SUPPORTING AN INCREASE IN SEVERE POTENTIAL. WITH THAT BEING SAID HOWEVER...MAJOR MODEL DIFFERENCES PERSIST WITH RESPECT TO EVOLUTION OF WRN U.S. UPPER TROUGHING. WHILE THE GFS ADVANCES A LARGE TROUGH -- COMPRISED OF PHASED NRN- AND SRN-STREAM SYSTEMS -- EWD INTO THE PLAINS THROUGH THE LATTER HALF OF THE PERIOD...THE ECMWF DEPICTS A SIMILARLY-TIMED NRN STREAM TROUGH ADVANCE INTO THE NRN PLAINS BUT A STATIONARY -- OR EVEN RETROGRADING -- SRN-STREAM PORTION OF THE TROUGH. WITH SUBSTANTIAL VARIATIONS ALSO THEREFORE MANIFEST IN THE SURFACE PATTERN ACROSS THE PLAINS VICINITY...TEMPORALLY AND SPATIALLY DELINEATING RISK AREAS REMAINS DIFFICULT ATTM. HOWEVER...AS UNCERTAINTY DIMINISHES WITH TIME AND RISK AREAS BECOME MORE CLEAR...EXPECT SEVERE WEATHER PROBABILITY AREAS TO BE INTRODUCED IN LATER FORECASTS ACROSS PORTIONS OF THE PLAINS STATES AND VICINITY.