Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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637
FXUS65 KBOU 010322
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
822 PM MST SUN JAN 31 2016

.UPDATE...
ISSUED AT 759 PM MST SUN JAN 31 2016

LOW LEVEL FLOW HAS BECOME SELY ALONG THE FRONT RANGE WHICH HAS
SHIFTED STEADIER LIGHT SNOW IN AND NR THE NRN FOOTHILLS WHILE
FURTHER SOUTH ONLY VERY LIGHT SNOW/FLURRIES IS OCCURRING. APPEARS
THIS WILL BE THE NORM OVERNIGHT. QG FIELDS FM THE RAP SUGGEST SNOW
MAY GRADUALLY BECOME STEADIER BY SUNRISE THRU THE LATE MORNING.

MEANWHILE MAIN SYSTEM IS CURRENTLY INTENSIFYING OVER SRN
NEVADA/SRN CA AND WILL MOVE INTO THE FOUR CORNERS AREA BY 18Z MON
AN THEN EASTWARD INTO SERN CO BY MON EVENING. BELIEVE 700 MB LOW
WILL BE MORE CONSOLIDATED AND ALIGNED WITH THE UPPER LEVEL LOW SO
EXPECT INCREASING UPSLOPE FLOW BY EARLY AFTN WHICH WILL LEAD TO
HEAVIER SNOW INTO MON NIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 304 PM MST SUN JAN 31 2016

THE MOIST WESTERLY FLOW ALOFT IS BEGINNING TO BACK TO THE
SOUTHWEST AS AN UPPER TROUGH PUSHES ONSHORE OVER THE WEST COAST TO
DIG INTO THE DESERT SOUTHWEST TONIGHT. LIGHT SNOW HAS ALREADY
BEGUN TO PUSH NORTH INTO THE FORECAST AREA ALONG AN AREA OF
FRONTOGENESIS. THIS SNOW WILL INCREASE AS IT PUSHES NORTH THIS
EVENING...WHICH IS THE REASON FOR STAGGERING THE WINTER STORM
WARNING TIMES. THEN 700 MB FLOW BECOMES SOUTHERLY LATER THIS
EVENING INTO AFTER MIDNIGHT. THIS CAUSES A BIT OF CONCERN AS THIS
CAN DOWNSLOPE OVER THE PALMER DIVIDE AND CAUSE DRYING BETWEEN
THE PALMER RIDGE AND AREAS NORTH OF DENVER...HAVE DECREASED
SNOWFALL AMOUNTS OVERNIGHT IN THIS AREA SLIGHTLY...BUT BELIEVE
ENOUGH LOW LEVEL EASTERLY FLOW THAT MAY CYCLONE AROUND OVER THE
URBAN CORRIDOR SHOULD KEEP SNOW GOING. THE SOUTHERLY FLOW WILL
ALSO HELP INCREASE THE SNOWFALL ALONG THE NORTHERN STATE BORDER
ESPECIALLY BY THE CHEYENNE RIDGE AND THE NORTHERN URBAN CORRIDOR.

ON MONDAY...THE UPPER LOW IS FORECAST TO MOVE FROM NORTHERN
ARIZONA AND THEN BECOME ALMOST VERTICALLY STACKED OVER THE SURFACE
LOW OVER FAR SOUTHEASTERN COLORADO BY EVENING. UPWARD QG VERTICAL
VELOCITIES WILL BECOME MODERATE TO STRONG WHILE WINDS THROUGH A
DEEP LAYER BECOME UPSLOPE AND INCREASE IN SPEED. THIS WILL BRING
HEAVIER SNOWFALL BY LATE MORNING ACROSS THE PLAINS AND ALONG THE
EAST SLOPES OF THE FRONT RANGE AND FOOTHILLS. SNOWFALL RATES
SHOULD BE AROUND HALF AN INCH PER HOUR WITH SOME HIGHER RATES NEAR
THE HIGHER TERRAIN. THE MOUNTAINS WEST OF THE DIVIDE WILL NOT BE
FAVORED IN THE EASTERLY FLOW....SO AMOUNTS WILL BE FAR LESS. WINDS
WILL INCREASE OUT OF THE NORTHEAST DURING THE AFTERNOON OVER THE
PLAINS TO 15 TO 25 MPH WITH GUSTS OF 30 TO 35 MPH TO CREATE
HAZARDOUS TRAVEL CONDITIONS IN BLOWING AND DRIFTING SNOW.
VISIBILITIES WILL BE REDUCED TO LESS THAN A HALF MILE IN THESE
CONDITIONS. EXPECT 4 TO 6 INCHES TO FALL OVER THE PLAINS DURING
MONDAY MORNING AND AFTERNOON...AND 5 TO 10 INCHES IN THE HIGHER
TERRAIN.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 304 PM MST SUN JAN 31 2016

PROLONGED AND STRONG WINTER STORM WILL CONTINUE MONDAY NIGHT
BEFORE FINALLY TAPERING OFF TUESDAY. THE MODELS REMAIN QUITE
CONSISTENT WITH ONLY MINOR FLUCTUATIONS IN EACH MODEL RUN. IT
SHOULD STILL BE NOTED THE STORM IS JUST NOW MOVING ONSHORE SO
BETTER SAMPLING FOR THE EXACT TRACK SHOULD BE AVAILABLE IN THE 00Z
MODEL RUNS. THAT SAID...WE DO HAVE GOOD CONFIDENCE IN THE OVERALL
TRACK OF THE STORM BASED ON CURRENT SATELLITE IMAGERY. THE
EXPECTED TRACK TAKES THE MID LEVEL CIRCULATION CENTER IS EXPECTED
TO MOVE EAST/NORTHEAST FROM THE NORTHEAST CORNER OF NEW MEXICO
TOMORROW EVENING INTO SOUTHWEST KANSAS BY EARLY TUESDAY MORNING.
THERE IS STILL GOOD UPWARD Q-G LIFT AND THE BEST UPSLOPE COMPONENT
AS WELL AS INSTABILITY BELOW 600 MB THROUGH MONDAY EVENING. THOSE
FAVORABLE PARAMETERS START TO FADE OVERNIGHT MONDAY NIGHT. AS A
RESULT...THE HEAVIEST SNOW OF THIS EVENT SHOULD CONTINUE INTO
TOMORROW EVENING BEFORE STARTING A SLOW DECREASE LATE MONDAY NIGHT
INTO TUESDAY MORNING. ON THE EASTERN PLAINS...NORTHEAST WINDS 15
TO 25 MPH WITH GUSTS AROUND 35 MPH WILL LIKELY PRODUCE
CONSIDERABLE BLOWING AND DRIFTING SNOW. AT THIS TIME...WINDS ARE
JUST SHY OF BLIZZARD CRITERIA BUT WILL HAVE TO WATCH THIS
POTENTIAL MAINLY ALONG/EAST OF A LINE FROM AKRON TO LIMON AS
EXPECTED DEPTH OF SNOW AND DRIER NATURE OF SNOW ON THE BACK SIDE
OF STORM WILL ALSO ADD TO THE AMOUNT OF BLOWING/DRIFTING.

EXPECTED STORM TOTALS WILL BE QUITE HIGH OVER MOST OF THE FORECAST
AREA. REASONABLE AGREEMENT BETWEEN 7 AND 14 INCHES WILL FALL OVER
MOST OF THE PLAINS DURING THIS LONG DURATION EVENT...HEAVIEST
NEAR THE FOOTHILLS AND I-70 CORRIDOR EASTWARD ACROSS THE PLAINS.
IN THE FOOTHILLS AND FRONT RANGE MOUNTAINS...INITIAL EXPECTATIONS
ARE FOR 10-24 INCHES...WITH THE HEAVIER TOTALS ON EAST FACING
SLOPES OF THE FRONT RANGE. MEANWHILE...THE HIGH MOUNTAIN VALLEYS
OF GRAND AND JACKSON COUNTIES ARE LIKELY TO BE LARGELY DOWNSLOPED
MAINLY LATER IN THIS EVENT AS EASTERLY COMPONENT STRENGTHENS.

IT SHOULD BE NOTED SOME MODELS ARE HIGHER THAN THE FORECAST
TOTALS...BUT SOME BIAS IS NORMALLY NOTED ON THE HIGH SIDE...AND
NOT SURE HOW EFFICIENT DENDRITIC GROWTH WILL BE OUTSIDE OF THE
PERIODS OF HEAVIER SNOWFALL. WILL CERTAINLY MONITOR AND ADJUST THE
FORECAST AS EVENT UNFOLDS AND MORE CONFIDENCE IS HOPEFULLY
ACHIEVED AFTER THE SYSTEM MOVES ONSHORE.

ALL THAT SAID...DIFFICULT TRAVEL CONDITIONS ARE EXPECTED BOTH BY
ROAD AND AIR WITH DELAYS/CANCELLATIONS POSSIBLE THROUGH TUESDAY.
SOME RURAL OR SECONDARY ROADS MAY HAVE DIFFICULT TRAVEL BY MONDAY
NIGHT DUE TO SNOW DEPTH...AS WELL AS DRIFTING OUT ON THE EASTERN
PLAINS.

BY TUESDAY NIGHT...CONDITIONS IMPROVE WITH ONLY SOME LINGERING
LIGHT SNOW IN THE MOUNTAINS.

THE REST OF THE WEEK INTO NEXT WEEKEND WILL FEATURE NORTHWEST FLOW
ALLOWING EMBEDDED SHORT WAVES TO BRING A COUPLE PERIODS OF SNOW TO
THE MOUNTAINS AND BRIEF COOLDOWNS FOR THE PLAINS. ONE OF THESE
APPEARS LIKELY FOR LATE THURSDAY NIGHT INTO FRIDAY...WITH ANOTHER
TOWARD NEXT SUNDAY. OVERALL TEMPERATURES WILL RUN BELOW NORMAL
WITH FRESH SNOW COVER AND CHILLY NORTHWEST FLOW ALOFT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 759 PM MST SUN JAN 31 2016

ONLY EXPECT PERIODS OF VERY LIGHT SNOW OVERNIGHT WITH ADDITIONAL
ACCUMULATIONS UNDER AN INCH. INTENSITY COULD INCREASE SOME BY
SUNRISE HOWEVER HEAVIEST SNOWS WILL PROBABLY HOLD OFF UNTIL AROUND
NOON WHICH WILL CONTINUE INTO MON NIGHT AS STG STORM SYSTEM MOVES
INTO SERN CO. TOTAL SNOWFALL AT DIA WILL BE IN THE 8" TO 12"
RANGE WITH HIGHER AMOUNTS POSSIBLE AT APA AND BJC.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON MST TUESDAY
FOR COZ042-044-048>051.

WINTER STORM WARNING UNTIL NOON MST TUESDAY FOR COZ033>037.

WINTER STORM WARNING UNTIL NOON MST TUESDAY FOR COZ038>041-043-
045>047.

&&

$$

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



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