694  
FXUS65 KPUB 201145  
AFDPUB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PUEBLO CO  
445 AM MST WED FEB 20 2019  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 438 AM MST WED FEB 20 2019  
 
SNOW HAS COME TO AN END ACROSS THE AREA EARLY THIS MORNING AS UPPER  
TROUGH PULLS AWAY INTO THE CENTRAL PLAINS, WITH JUST SOME LINGERING  
CLOUDS OVER THE CONTINENTAL DIVIDE AND THE CREST OF THE SANGRES, AND  
A COUPLE PATCHES OF STRATUS AND FOG ON THE PLAINS. FOR TODAY, BRIEF  
SHORT WAVE RIDGE DRIFTS ACROSS CO EARLY, BEFORE FLOW BEGINS TO BEND  
BACK TO THE SOUTHWEST BY LATE AFTERNOON AS NEXT UPPER SYSTEM DIGS  
INTO THE GREAT BASIN. FIRST HALF OF THE DAY SHOULD BE MAINLY DRY  
ACROSS THE REGION, WITH ONLY A FEW LIGHT FLURRIES OVER THE HIGHER  
PEAKS ALONG THE DIVIDE THROUGH MIDDAY. SNOW SHOWERS THEN GRADUALLY  
INCREASE IN COVERAGE OVER THE SAN JUANS AND LA GARITAS DURING THE  
AFTERNOON AS MID LEVEL MOISTURE DEEPENS, THOUGH ANY ACCUMS THROUGH  
SUNSET SHOULD BE RATHER LIGHT. WITH A DECREASE IN CLOUDS AND AT  
LEAST A WEAK WLY COMPONENT TO THE LOW LEVEL WIND FIELD, MOST AREAS  
SHOULD SEE MAX TEMPS WARM SEVERAL DEGF FROM THE PAST FEW DAYS,  
THOUGH READINGS AREA-WIDE WILL STILL BE WELL BELOW SEASONAL  
AVERAGES. TONIGHT, GREAT BASIN TROUGH CONTINUES TO DEEPEN, WITH  
STRENGTHENING MOIST SW FLOW ALONG THE CONTINENTAL DIVIDE. WINTER  
STORM WARNING LOOKS GOOD, AS SNOW SHOULD BECOME HEAVY ACROSS THE SAN  
JUANS/LA GARITAS OVERNIGHT, WITH SEVERAL INCHES OF ACCUMULATION BY  
EARLY THU MORNING. FARTHER NORTH ALONG THE DIVIDE, SNOW WILL  
DEVELOP, THOUGH ACCUMS WILL BE MUCH LIGHTER AS SW FLOW IS LESS  
FAVORABLE FOR HEAVY SNOW HERE. JUST INCREASING CLOUDS FARTHER EAST,  
WHICH WILL KEEP MIN TEMPS SLIGHTLY WARMER MANY AREAS VERSUS THE PAST  
FEW DAYS.  
   
LONG TERM
 
(THURSDAY THROUGH TUESDAY)  
ISSUED AT 438 AM MST WED FEB 20 2019  
 
THURSDAY - FRIDAY...  
 
THE AFOREMENTIONED UPPER LEVEL TROUGH CONTINUES TO SLOWLY DIG  
SOUTH THROUGH THE SOUTHWEST US THURSDAY AND FRIDAY. AN ASSOCIATED  
SOUTHWESTERLY 110+ KNOT 300 MB JET WILL REMAIN ORIENTED ACROSS THE  
MIDDLE OF THE STATE. FINALLY, THE UPPER TROUGH WILL BE POSITIONED  
TO DRIVE PACIFIC MOISTURE NORTHEAST INTO COLORADO. DETERMINISTIC  
AND ENSEMBLE MODEL GUIDANCE HAS BEEN CONSISTENT IN THE EARLY  
EVOLUTION OF THIS STORM SYSTEM, LEADING TO HIGH CONFIDENCE IN THE  
FORECAST DURING THIS PERIOD.  
 
THE SLOW MOVEMENT OF THE STORM SYSTEM WILL LEAD TO A PROLONGED  
PERIOD OF SNOWFALL ACROSS THE HIGH TERRAIN. THE MORE WIDESPREAD  
AND HEAVIER SNOW WILL BE CONFINED TO THE EASTERN SAN JUANS AND LA  
GARITAS DURING THE DAY THURSDAY WHERE QG FORCING FOR ASCENT AND  
OROGRAPHIC FLOW WILL BE MOST FAVORABLE. CONSIDERING STRONG  
SOUTHWEST FLOW INTO SOUTHWEST/SOUTH-CENTRAL COLORADO, THE EASTERN  
SAN JUANS ARE WELL POSITIONED TO RECEIVE THE MOST SNOWFALL FROM  
THIS SYSTEM. THE FORECAST STILL HAS ABOUT 1-3 FEET OF SNOWFALL,  
WITH THE WINTER STORM WARNING STILL LOOKING THROUGH 00Z FRIDAY  
EVENING. THE LA GARITAS, ALSO IN THE WINTER STORM WARNING, ARE  
EXPECTED TO SEE 12-18 INCHES OF SNOWFALL. SNOW WILL PICK UP OVER  
THE CENTRAL AND EASTERN MOUNTAINS THURSDAY NIGHT INTO FRIDAY AS  
THE SYSTEM SHIFTS EAST AND QG FORCING INCREASES OVER THOSE AREAS.  
IT CURRENTLY LOOKS LIKE THESE AREAS WILL RECEIVE HIGH END ADVISORY  
SNOW TOTALS, SO WILL HOLD OFF ON ISSUING HIGHLIGHTS. LOCATIONS IN  
THE SAN LUIS VALLEY AND UPPER ARKANSAS RIVER VALLEY SHOULD SEE  
1-4 INCHES OF SNOWFALL.  
 
THE PLAINS WILL REMAIN DRY THURSDAY AND FRIDAY AS THE UPPER  
TROUGH AND ASSOCIATED FORCING REMAINS WELL TO THE WEST, AND DRYING  
DOWNSLOPE FLOW SPREADS ACROSS THE PLAINS. THERE IS A CHANCE THAT  
AN ISOLATED SNOW SHOWER MOVES EAST OFF THE HIGH TERRAIN, BUT WOULD  
LIKELY STAY WEST OF I-25. DEEP VERTICAL MIXING EACH AFTERNOON AND  
STRONG FLOW ALOFT WILL LEAD TO BREEZY CONDITIONS ACROSS THE  
PLAINS EACH AFTERNOON AND EARLY EVENING, MAINLY ALONG THE SOUTHERN  
AND EASTERN PORTIONS OF THE PLAINS. TEMPERATURES WILL CONTINUE TO  
WARM, WITH HIGHS IN THE MID/UPPER 40S ON THURSDAY AND UPPER 40S  
TO LOW 50S ON FRIDAY.  
 
FRIDAY NIGHT - SATURDAY...  
 
THE UPPER TROUGH ACCELERATES EAST AND INTENSIFIES/CLOSES  
SOMEWHERE NEAR THE SOUTHEAST COLORADO AND NORTHEAST NEW MEXICO  
BORDER. ALTHOUGH THE LAST FEW ROUNDS OF MODEL CYCLES HAVE MOVED  
THE LOW EAST QUICKER THAN PREVIOUSLY, MODELS ARE COMING INTO  
AGREEMENT ON THE EXACT POSITION OF THE LOW AS IT ADVANCES EAST. BY  
12Z SATURDAY, THE ECMWF, GFS, FV3, CMC, AND NAM ALL HAVE THE  
UPPER LOW CENTERED OVER THE NORTHEAST NEW MEXICO AND OK/TX  
PANHANDLE REGION, SOUTH OF THE COLORADO BORDER, IN A FAVORABLE  
POSITION FOR PRECIP OVER SOUTHEAST COLORADO. ENSEMBLE SPREAD IS  
ALSO QUITE LOW, WITH MAIN DIFFERENCES LYING IN THE SPEED OF THE  
TROUGH AS IT EXITS ONTO THE PLAINS. GIVEN MODEL MODEL AGREEMENT ON  
THE POSITION OF THE LOW, BUT STILL TIMING FLUCTUATIONS AND TIME  
UNTIL EVENT, CONFIDENCE IN THIS PART OF THE FORECAST HAS INCREASED  
TO MODERATE.  
 
AS THE LOW SHIFTS EAST AND INTENSIFIES, QG FORCING AND  
ATMOSPHERIC MOISTURE WILL INCREASE OVER THE PLAINS, WITH TPW  
REACHING CLOSE TO 0.5". THE SYSTEM WILL ALSO DRIVE A COLD FRONT  
DOWN THE EASTERN COLORADO PLAINS DURING THE EVENING AS A SURFACE  
LOW DEEPENS AND EXITS EAST OUT OF SOUTHEAST COLORADO. RAIN AND  
SNOW SHOWERS WILL INCREASE ACROSS ALL OF THE PLAINS LATE FRIDAY  
AFTERNOON AND CONTINUE THROUGH THE EVENING. PRECIP WILL QUICKLY  
CHANGE TO ALL SNOW AND BECOME HEAVIEST EARLY SATURDAY MORNING  
BEHIND THE COLD FRONT ON THE WRAP AROUND PORTION OF THE SYSTEM AS  
ISENTROPIC SURFACES RAPIDLY RISE. GIVEN THE RELATIVELY QUICK  
MOVEMENT OF THE SYSTEM EAST, PRECIP CHANCES/AMOUNTS LOOK BEST OVER  
FAR EASTERN COLORADO NEAR THE KANSAS BORDER, BECOMING ISOLATED TO  
SCATTERED WITH ONLY LIGHT AMOUNTS OVER THE I-25 CORRIDOR. MODELS  
CONTINUE TO PRODUCE QPF UP TO 0.5" OVER THE FAR EASTERN PLAINS.  
SNOW ACCUMULATIONS OF AT LEAST A FEW INCHES SEEM PROBABLE ACROSS  
A PORTION OF THE EASTERN PLAINS EAST OF THE I-25 CORRIDOR, BUT  
SHOULD STAY RELATIVELY LIMITED CONSIDERING THE FAST EXIT OF THE  
LOW.  
 
PRECIP WILL LIKELY BE OVER ACROSS THE FORECAST AREA BY EARLY  
SATURDAY AFTERNOON. TEMPERATURES SATURDAY WILL ONLY BE SLIGHTLY  
COOLER, WITH HIGHS IN THE LOW TO MID 40S EXPECTED ACROSS THE  
PLAINS. BREEZY NORTH TO NORTHWEST WINDS DURING THE FIRST HALF OF  
THE DAY WILL BECOME LIGHT BY EVENING.  
 
SATURDAY NIGHT - TUESDAY...  
 
BEHIND THE TROUGH, UPPER LEVEL FLOW WILL BECOME WESTERLY AND  
RELATIVELY UNDISTURBED, LEADING TO MAINLY DRY CONDITIONS ACROSS  
THE FORECAST AREA. SUBTLE DISTURBANCES MAY BRING BRIEF PERIODS OF  
LIGHT SNOW SHOWERS TO THE CONTINENTAL DIVIDE, PARTICULARLY OVER  
THE CENTRAL MOUNTAINS. HIGH TEMPERATURES WILL GENERALLY SPAN THE  
40S ACROSS THE PLAINS, AND 30S IN THE HIGH VALLEYS.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 438 AM MST WED FEB 20 2019  
 
AT KALS, VFR TODAY AND TONIGHT, WITH SLOWLY LOWERING VFR CIGS AFTER  
00Z. MAY SEE AN ISOLATED -SHSN TOWARD EARLY THU MORNING AS PRECIP  
SPILLS EAST FROM THE CONTINENTAL DIVIDE, THOUGH CHANCE LOOKS TOO LOW  
TO INCLUDE IN THE 12Z TAF. AT KCOS, VFR TODAY AND TONIGHT, THOUGH  
WILL NEED TO WATCH AREA OF STRATUS AND FOG JUST SOUTHEAST OF THE  
TERMINAL EARLY THIS MORNING, AS WEAK SE WIND DEVELOPING AFTER  
SUNRISE MAY PUSH CLOUDS CLOSE TO THE AIRPORT 12Z-15Z. AT KPUB, WRN  
EDGE OF LOW CLOUDS AND FOG NEAR THE TERMINAL EARLY THIS MORNING,  
THOUGH SATELLITE TRENDS AND WEAK LOW LEVEL WLY WIND SUGGEST WORST  
VIS AND LOWEST CIGS MAY STAY JUST EAST OF THE AIRPORT. MAY SEE AN HR  
OR TWO OF MVFR OR IFR CONDITIONS IN THE 12Z-15Z PERIOD, THOUGH WILL  
WAIT UNTIL ISSUANCE TIME TO DECIDE ON EXTENT OF LOW CLOUDS. ONCE  
CLOUDS CLEAR BY MID-MORNING, VFR CONDITIONS EXPECTED FOR THE  
REMAINDER OF THE DAY AND TONIGHT.  
 

 
   
PUB WATCHES/WARNINGS/ADVISORIES
 
 
WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 5 PM MST FRIDAY  
FOR COZ066-068.  
 

 
 

 
 
SHORT TERM...PETERSEN  
LONG TERM...LINE  
AVIATION...PETERSEN  
 
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