Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 310319
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
819 PM MST SAT JAN 30 2016

.UPDATE...
ISSUED AT 757 PM MST SAT JAN 30 2016

BAND OF SNOW IS MOVING ACROSS NERN CO IN ASSOCIATION WITH FAVORED
LEFT FNT RGN OF UPPER LVL JET. BOTH THE RAP AND HRRR KEEP MAIN
ACTIVITY FM DENVER TO AKRON NORTHWARD THROUGH MIDNIGHT WITH
ACTIVITY GRADUALLY DECREASING AFTER 09Z. A FEW AREAS COULD
RECEIVE ADVISORY CRITERIA SNOW. CURRENTLY THE HRRR AND RAP ARE
FOCUSING THIS MAINLY OVER CENTRAL PORTIONS OF WELD COUNTY INTO FAR
ERN LARIMER...HOWEVER RADAR TRENDS SUGGEST THIS MAY END BEING
FURTHER SOUTH. AT THIS POINT CONFIDENCE IS NOT HIGH ENOUGH TO
ISSUE ANY ADVISORIES.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 330 PM MST SAT JAN 30 2016

SNOW CONTINUES OVER THE MOUNTAINS THIS AFTERNOON...THOUGH WARMER
TEMPERATURES HAVE PROHIBITED MUCH ACCUMULATION SO FAR AND ROADS
VIA WEBCAMS LOOK MAINLY WET. THIS WILL BE CHANGING SOON AS THE JET
MAX APPROACHES AND A COLD FRONT IS PUSHING SOUTH ACROSS THE AREA.
THIS WILL HELP INCREASE SNOWFALL RATES AND COOL TEMPERATURES. AN
EAST-WEST JET INDUCED SNOWBAND IS STILL PROGGED BY ALMOST ALL
MODELS TO PUSH SOUTH ACROSS THE MOUNTAINS THIS EVENING. THIS BAND
WILL BE ABLE TO PRODUCE SNOWFALL RATES OF UP TO 2 INCHES PER HOUR.
THIS WILL PRODUCE HAZARDOUS TRAVEL CONDITIONS IN HEAVY SNOW AND
NEAR WHITEOUT CONDITIONS WITH BLOWING SNOW. EXPECT ANOTHER 4 TO 8
INCHES TO FALL OVER THE NORTHERN MOUNTAINS AND HIGHER AMOUNTS OVER
THE MOUNTAINS NEAR THE I70 CORRIDOR.

OVER THE PLAINS...THE COLD FRONT AS ALREADY PUSHED THROUGH WITH
COOLING TEMPERATURES. A FEW SHOWERS NEAR THE CO/WY BORDER WILL BE
RAIN MIXED WITH SNOW. THE AFOREMENTIONED JET INDUCED SNOWBAND IS
EXPECTED TO PUSH SOUTH ACROSS THE PLAINS THIS EVENING...ABLE TO
PRODUCE ABOUT AN INCH PER HOUR OR POSSIBLY MORE SNOWFALL RATES.
WARM GROUND TEMPERATURES FROM TODAY WILL LIKELY MELT THE INITIAL
SNOW BUT SHOULD QUICKLY TURN TO SLUSH AS COLD AIR CONTINUES TO
FILTER IN BEFORE SNOW ACCUMULATES. OVERALL...LOOK FOR 1 TO 2
INCHES FROM THE SNOWBAND WITH ISOLATED AREAS OF 3 TO 4 INCHES
POSSIBLE IF THE BAND STRENGTHENS MORE OR LINGERS OVER A CERTAIN
AREA. ONCE THE SNOWBAND PUSHES SOUTH AND DISSIPATES...EXPECT A
SLIGHT CHANCE OF LIGHT SNOW TO REMAIN FOR THE REST OF THE NIGHT.

SNOW WILL HAVE DECREASED OVER THE NORTHERN MOUNTAINS SUNDAY WITH
ONLY AN INCH OR SO ACCUMULATION...WHILE LIGHT SNOW WILL CONTINUE
OVER THE MOUNTAINS NEAR THE I70 CORRIDOR WITH ANOTHER 2 TO 4
INCHES. HIGH SURFACE PRESSURE OVER WY AND NE WILL KEEP LIGHT
UPSLOPE FLOW OVER THE PLAINS. THIS WILL KEEP A SLIGHT CHANCE OF
SNOW MAINLY OVER THE URBAN CORRIDOR AND UP AGAINST THE FOOTHILLS.
ANY ACCUMULATION WILL BE LIGHT...MAINLY BELOW AN INCH. HIGH
TEMPERATURES WILL BE IN THE LOW TO UPPER 30S...THE WARMER
TEMPERATURES OUT OVER THE EASTERN PLAINS.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 PM MST SAT JAN 30 2016

...LONG DURATION WINTER STORM WITH HEAVY SNOW POTENTIAL ACROSS THE
REGION...

UPPER LEVEL TROUGH CURRENTLY WELL OUT IN THE PACIFIC WILL FINALLY
MOVE ONSHORE TOMORROW EVENING...AND THEN TRACK INTO THE GREAT
BASIN SUNDAY NIGHT. FROM THERE...IT WILL INTENSIFY SLIGHTLY AND
EXPECTED TO MOVE EAST FROM NEAR OR JUST SOUTH OF THE FOUR CORNERS
AREA TOWARD SOUTHWEST KANSAS BY EARLY TUESDAY MORNING. MODELS
REMAIN QUITE CONSISTENT OVERALL WITH ITS TRACK...WITH GENERALLY
MINOR FLUCTUATIONS FROM RUN TO RUN AND BETWEEN THE INDIVIDUAL
MODELS AS WELL. DESPITE THE RATHER GOOD AGREEMENT...IT SHOULD BE
NOTED THE STORM IS STILL OVER THE PACIFIC AND NOT A TREMENDOUS
AMOUNT OF DATA INCORPORATED INTO THE MODELS YET.

FOR SUNDAY NIGHT...MODELS HAVE REMAINED RATHER CONSISTENT SHOWING
GENERALLY LIGHT SNOW SPREADING EAST ACROSS THE PLAINS. THIS
OCCURS AS DEEP Q-G LIFT ARRIVES AND A WEAK BUT DEEP UPSLOPE
COMPONENT DEVELOPS. THE UPSLOPE COMPONENT WILL INTENSIFY MONDAY
AND MONDAY NIGHT AS THE UPPER TROUGH GETS SOME NEGATIVE TILT TO
IT. EARLY ON IN THIS EVENT...SUNDAY NIGHT INTO MONDAY
MORNING...THE FLOW IS EAST/SOUTHEAST WHICH ACTUALLY FAVORS
LOCATIONS NORTH OF DENVER. THEN...AS THE UPPER LOW PULLS BY FLOW
TURNS MORE NORTHEASTERLY MONDAY AFTERNOON AND MONDAY NIGHT...AND
EVENTUALLY NORTHERLY BY TUESDAY MORNING. AS A RESULT...THE
HEAVIEST SNOW IS EXPECTED TO SHIFT SOUTHWARD TO THE PALMER DIVIDE
AREA DURING THIS TIME. IT SHOULD BE NOTED WE DONT SEE SNOWFALL
RATES AS BEING TOO HEAVY AT ANY ONE TIME DURING THIS STORM...BUT
THE DURATION OF THIS STORM COULD VERY WELL ADD UP TO HEAVY STORM
TOTAL AMOUNTS BEFORE FINALLY DECREASING TUESDAY MORNING.

FAVORABLE FACTORS FOR HEAVY TOTAL ACCUMULATIONS WOULD BE...CURRENT
EXPECTED TRACK OF THE 700 MB CIRCULATION CENTER NEAR OR JUST NORTH
OF THE COLORADO/NEW MEXICO BORDER...LONG DURATION...PERSISTENT AND
DEEP Q-G LIFT...PERSISTENT AND DEEP UPSLOPE FLOW...AND A
DENDRITIC GROWTH REGIME WITH BEST VERTICAL MOTION THROUGH THE -12C
TO -16C LAYER. GOING AGAINST IT WOULD BE MARGINAL LAPSE RATES AND
LACK OF A TROWAL AS GULF MOISTURE DOES NOT APPEAR TO GET WRAPPED
INTO THIS STORM WHILE ITS AFFECTING OUR FORECAST AREA. BOTH OF
THOSE NEGATIVE FACTORS ARE SOMEWHAT CONCERNING...BUT THE LONG
DURATION OF AT LEAST LIGHT TO AT TIMES MODERATE SNOWFALL SHOULD BE
ENOUGH TO BRING SUBSTANTIAL SNOW ACCUMULATIONS TO MOST OF THE
FORECAST AREA. MANY LOCATIONS ON THE PLAINS WILL HAVE POTENTIAL TO
SEE 6-12 INCHES...BUT FAVORED UPSLOPE AREAS OF THE
FOOTHILLS/EASTERN SLOPE OF THE FRONT RANGE COULD SEE 2 FEET. WILL
GO AHEAD AND HOIST A WINTER STORM WATCH BEGINNING TOMORROW NIGHT
FOR MOST OF THE FORECAST AREA...AND KEEP IT TIL NOON TUESDAY.

BEYOND TUESDAY...PERSISTENT NORTHWEST FLOW ALOFT WILL KEEP A
CHANCE OF SNOW IN THE MOUNTAINS WITH PASSING SHORT WAVES. THE
PLAINS SHOULD REMAIN MAINLY DRY WITH DOWNSLOPE COMPONENT...BUT
CANT RULE OUT A COUPLE BACK DOOR COLD FRONTS. THIS WOULD ACT TO
KEEP TEMPERATURES BELOW NORMAL ON AVERAGE THROUGH NEXT WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 757 PM MST SAT JAN 30 2016

BAND OF MDT SNOW WILL AFFECT DIA FOR THE NEXT FEW HOURS. IF THIS
ACTIVITY STALLS THEN IT COULD LINGER THROUGH MIDNIGHT WITH
SNOWFALL RATES UP TO 1 INCH PER HOUR. FOR NOW WILL KEEP SNOW
AMOUNTS IN THE 2 TO 3 INCH RANGE. LIGHTER SNOW MAY OCCUR THRU 2 AM
BEFORE GRADUALLY ENDING BY 4 AM.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH TUESDAY
MORNING FOR COZ048-050-051.

WINTER STORM WATCH FROM SUNDAY EVENING THROUGH TUESDAY MORNING
FOR COZ033>037.

WINTER STORM WARNING UNTIL 6 AM MST SUNDAY FOR COZ031-033-034.

WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH TUESDAY
MORNING FOR COZ038>047-049.

&&

$$

UPDATE...RPK
SHORT TERM...KRIEDERMAN
LONG TERM...BARJENBRUCH
AVIATION...RPK


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