748  
ACUS02 KWNS 201713  
SWODY2  
SPC AC 201712  
 
DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1112 AM CST MON JAN 20 2020  
 
VALID 211200Z - 221200Z  
   
..NO SEVERE THUNDERSTORM AREAS FORECAST
 
 
   
..SUMMARY
 
 
SHOWERS, AND POSSIBLY A FEW LIGHTNING FLASHES, MAY AFFECT PORTIONS  
OF THE PACIFIC NORTHWEST COASTAL VICINITY, ESPECIALLY TUESDAY  
MORNING.  
   
..SYNOPSIS
 
 
A PROGRESSIVE UPPER LEVEL PATTERN WILL IS FORECAST ON TUESDAY ACROSS  
THE CONUS. AN UPPER LEVEL RIDGE OVER THE NORTHEASTERN PACIFIC WILL  
MIGRATE EASTWARD TOWARD THE PACIFIC COAST BY THE END OF THE PERIOD.  
IN ADVANCE OF THE UPPER RIDGE, A SHORTWAVE TROUGH WILL MIGRATE  
ACROSS THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES, WHILE A  
LARGER-SCALE WESTERN TROUGH PROGRESSES EASTWARD OVER THE PLAINS.  
SHOWERS AND A FEW LIGHTNING FLASHES ARE POSSIBLE ALONG THE PACIFIC  
NORTHWEST COAST, MAINLY PRIOR TO 00Z, WHERE STEEP LAPSE RATES AND  
MODEST INSTABILITY/VERTICAL SHEAR WILL BE IN PLACE. MIDLEVEL  
SUBSIDENCE WILL INCREASE DURING THE EVENING AS THE TROUGH AXIS MOVES  
EASTWARD TOWARD THE NORTHERN ROCKIES.  
 
ACROSS THE PLAINS, A LEE TROUGH WILL DEVELOP AS THE UPPER TROUGH  
SPREADS EASTWARD OVERNIGHT. PRECIPITATION WILL DEVELOP AS MIDLEVEL  
WARM ADVECTION INCREASES ON STRONG SOUTHERLY LOW/MID LEVEL FLOW.  
POOR LAPSE RATES AND WEAK INSTABILITY WILL PRECLUDE THUNDERSTORM  
POTENTIAL HOWEVER. ACROSS THE EAST, STRONG SURFACE HIGH PRESSURE  
WILL RESULT IN MAINLY DRY AND STABLE CONDITIONS.  
   
..MAXIMUM RISK BY HAZARD
 
 
TORNADO: <2% - NONE  
WIND: <5% - NONE  
HAIL: <5% - NONE  
 
..LEITMAN.. 01/20/2020  
 

 
 
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