840
FXUS63 KBIS 191835
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1235 PM CST THU DEC 19 2024
KEY MESSAGES
- BLOWING SNOW ACROSS CENTRAL NORTH DAKOTA THIS MORNING AND
AFTERNOON COULD CAUSE NEAR-BLIZZARD CONDITIONS AT TIMES IN
RURAL AREAS. SNOWFALL WILL END FROM WEST TO EAST INTO THE
EARLY AFTERNOON.
- STRONG NORTHWEST WINDS GUSTING AS HIGH AS 60 MPH ACROSS
SOUTHWEST AND FAR SOUTH CENTRAL NORTH DAKOTA THIS MORNING WILL
GRADUALLY TAPER THIS AFTERNOON.
- COLD TODAY AND TONIGHT, WITH NIGHTTIME TEMPERATURES IN THE
TEENS BELOW ZERO ACROSS THE NORTH.
- LOW TO MEDIUM CHANCES FOR LIGHT SNOW ACCUMULATIONS ACROSS
NORTHWEST AND CENTRAL NORTH DAKOTA ON FRIDAY.
- A SLOW WARMING TREND IS EXPECTED THIS WEEKEND THROUGH
CHRISTMAS, WHEN ABOVE NORMAL TEMPERATURES ARE FAVORED.
UPDATE
ISSUED AT 1226 PM CST THU DEC 19 2024
CONDITIONS CONTINUE TO GRADUALLY IMPROVE ON THE BACK SIDE OF THE
DEPARTING SYSTEM, SO WAS ABLE TO TRIM SOME ADDITIONAL COUNTIES
OFF THE ADVISORY/WARNING, WITH SKIES CLEARING OVER MUCH OF THE
WEST. WITH THAT SAID, IT APPEARS THAT SOME CLOUDS ARE COMING OFF
THE OPEN PORTION OF LAKE SAKAKAWEA, SO HAVE ADDED SOME LOW
CHANCES FOR SNOW IN THE AREAS SOUTH OF THE LAKE THROUGH THIS
AFTERNOON. AS FOR WINDS, SPEEDS HAVE BEEN GRADUALLY DIMINISHING
OVER THE WEST, SO WAS ABLE TO TRIM OFF THE NORTH END OF THE HIGH
WIND WARNING, AND ANTICIPATE THE REST WILL BE ABLE TO EXPIRE A
LITTLE LATER THIS AFTERNOON.
UPDATE
ISSUED AT 950 AM CST THU DEC 19 2024
SURFACE LOW HAS SHIFTED INTO NORTHEAST SOUTH DAKOTA, WITH THE
BACK EDGE OF THE SNOW STRETCHING FROM NEAR CARSON NORTHWARD
THROUGH HAZEN TO WEST OF MINOT, WHICH CONTINUES TO PUSH OFF TO
THE SOUTHEAST. FOR MID-MORNING UPDATE HAVE CLEARED WESTERN
COUNTIES OUT OF THE WINTER STORM WARNING, AND EXPECT TO CLEAR
OUT QUITE A FEW MORE BY MID-DAY AS THE SNOW CONTINUES ITS SHIFT
TO THE SOUTHEAST.
UPDATE
ISSUED AT 628 AM CST THU DEC 19 2024
AT 6 AM CST, THE CENTER OF LOW PRESSURE WAS ANALYZED OVER NORTHERN
KIDDER COUNTY. THE STRONG NORTHWESTERLY WINDS HAVE ALREADY PUSHED AS
FAR EAST AS LOGAN AND MCINTOSH COUNTIES AS OF THIS WRITING. MAXIMUM
GUSTS ACROSS THE SOUTHWEST AND SOUTH CENTRAL HAVE MOSTLY SETTLED IN
THE 45 TO 55 MPH RANGE, BUT THERE ARE STILL OCCASIONAL GUSTS AS HIGH
AS 65 MPH WITHIN THE HIGH WIND WARNING.
THE WESTERN EDGE OF FALLING SNOW IS NOW LOCATED FROM NEAR
PLENTYWOOD, MT TO THE WESTERN END OF THE STANDING ROCK RESERVATION.
A CONSISTENT WEST-TO-EAST ENDING OF SNOWFALL IS EXPECTED
THROUGH THE MORNING, EXITING THE JAMES RIVER VALLEY BY MID
AFTERNOON.
SO FAR, BLOWING SNOW DOES NOT APPEAR TO BE CAUSING SIGNIFICANT
VISIBILITY RESTRICTIONS ON ITS OWN. EVEN WHERE SNOW IS STILL
FALLING, VISIBILITY HAS MOSTLY BEEN OBSERVED ABOVE ONE HALF MILE.
THE STRONGEST WINDS THUS FAR THOUGH HAVE BEEN LIMITED TO AREAS THAT
RECEIVED LOWER SNOW AMOUNTS AND A LIGHT GLAZE OF ICE FROM FREEZING
RAIN ON TOP OF THE FRESH SNOW.
THE SEGMENT OF THE WINTER WEATHER ADVISORY FROM GOLDEN VALLEY TO
SIOUX COUNTIES WAS ALLOWED TO EXPIRE ON TIME, AND ALL OTHER
HEADLINES REMAIN VALID.
DISCUSSION
ISSUED AT 409 AM CST THU DEC 19 2024
AN ALBERTA CLIPPER CONTINUES TO BRING HAZARDOUS WEATHER ACROSS
WESTERN AND CENTRAL NORTH DAKOTA EARLY THIS MORNING. AT 4 AM CST,
THE CENTER OF SURFACE LOW PRESSURE WAS LOCATED JUST NORTHEAST OF
BISMARCK. THIS IS A SLIGHT SOUTHWARD SHIFT FROM WHAT HAD PREVIOUSLY
BEEN FORECAST, BUT THAT SHIFT IN AND OF ITSELF DOES NOT APPEAR TO BE
CAUSING ANY DRAMATIC CHANGES TO IMPACTS OR EXPECTED OUTCOMES. THE
SURFACE LOW WILL CONTINUE TO TRACK SOUTHEAST ACROSS THE STATE THIS
MORNING, BECOMING STACKED WITH ITS PARENT UPPER LOW OVER THE
SOUTHERN RED RIVER VALLEY BY MIDDAY.
OBSERVATIONAL DATA SHOW SNOW THROUGH THE WARM CONVEYOR BELT OVER
EASTERN NORTH DAKOTA WRAPPING AROUND ACROSS THE NORTH AND NOW BACK
THROUGH THE WEST AND INTO FAR SOUTH CENTRAL. WITHIN THIS AREA OF
SNOW, FREEZING RAIN HAS BEEN A MORE COMMON PRECIPITATION TYPE OWING
TO MID TO UPPER LEVEL DRY SLOTTING AND WARMER AIR ALOFT. IMPACTS
FROM ICING HAVE BEEN MORE PROLIFIC THAN ANTICIPATED. THE
SOUTHWESTERN-MOST SEGMENT OF THE WINTER WEATHER ADVISORY WAS
EXTENDED UNTIL 5 AM CST ON ACCOUNT MIXED PRECIPITATION PERSISTING
AND WITH STRONG WINDS NOW BEING ADDED TO THE EQUATION. AS THE LOW
BRINGS MUCH COLDER AIR AROUND ITS BACKSIDE, PROBABILITIES FOR
FREEZING RAIN AS A TYPE WILL DECREASE. BY 7 AM CST, WE ARE EXPECTING
ALL PRECIPITATION TO HAVE TRANSITIONED BACK TO SNOW, WHICH AT THAT
TIME SHOULD STILL BE FALLING OVER MOST AREAS ALONG AND EAST OF THE
HIGHWAY 83 CORRIDOR. SNOWFALL SHOULD END FROM WEST TO EAST THIS
MORNING THROUGH THE EARLY AFTERNOON.
A VERY TIGHT PRESSURE GRADIENT WITH STRONG COLD AIR ADVECTION AND
RAPID PRESSURE RISES WILL PROMOTE MOMENTUM TRANSFER OF 45-55 KTS TO
THE SURFACE ACROSS SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA THIS
MORNING. GUSTS IN THE 55-60 MPH HAVE BECOME MORE COMMON SINCE 2 AM
MST, AND A MAXIMUM GUST OF 62 MPH WAS RECORDED AT HETTINGER.
COUNTIES BORDERING THE HIGH WIND WARNING COULD SEE ISOLATED GUSTS TO
60 MPH, BUT THE EXPECTED COVERAGE AND DURATION OF HIGHER GUSTS DOES
NOT WARRANT AN EXPANSION OF THE WARNING AT THIS TIME. THE STRONGEST
BOUNDARY LAYER WINDS WILL GRADUALLY WANE LATER THIS MORNING INTO THE
AFTERNOON, BUT SURFACE WINDS WILL REMAIN GUSTY THROUGH THE
AFTERNOON, ESPECIALLY SOUTH OF THE INTERSTATE.
THERE IS INCREASED CONFIDENCE IN AN OVERLAP OF STRONG WINDS WITH
FRESHLY ACCUMULATED SNOWFALL FROM NORTHWEST TO SOUTH CENTRAL NORTH
DAKOTA LATER THIS MORNING. HOWEVER, THE FREEZING RAIN HAS INTRODUCED
SOME UNCERTAINTY ON HOW MUCH OF THE SNOW WILL BE BLOWABLE. WE STILL
THINK THE MOST LIKELY OUTCOME IS FOR IMPACTFUL BLOWING SNOW IN THESE
AREAS, WITH POTENTIALLY SIGNIFICANT GROUND DRIFTING AND VISIBILITY
REDUCED TO HALF A MILE IN OPEN AREAS AT TIMES. A REASONABLE WORST
CASE SCENARIO STILL INCLUDES NEAR-BLIZZARD CONDITIONS, BUT AT THE
OTHER END OF THE FORECAST SPECTRUM, IT IS NOT INCONCEIVABLE THAT THE
FREEZING RAIN COULD RENDER BLOWING SNOW A MINOR TO NON ISSUE. NO
CHANGES WILL BE MADE TO ANY WINTER WEATHER HEADLINES UNTIL WE CAN
OBSERVE HOW THE SNOW AND WINDS INTERACT.
EARLY MORNING TEMPERATURES RANGE FROM NEAR ZERO ALONG THE CANADIAN
BORDER TO ABOVE FREEZING DIRECTLY SOUTH OF THE SURFACE LOW. AREAS
THAT HAVE YET TO SEE THE COLD FRONTAL PASSAGE WILL EXPERIENCE
TEMPERATURES QUICKLY FALLING INTO THE SINGLE DIGITS ABOVE ZERO ONCE
THE FRONT MOVES THROUGH. LOW TEMPERATURES TONIGHT ARE EXPECTED TO
FALL BELOW ZERO, WITH TEENS BELOW ACROSS THE NORTH. SURFACE HIGH
PRESSURE IS FORECAST TO SLIDE ACROSS THE STATE TONIGHT, WHICH WOULD
USUALLY PROMOTE STRONG RADIATIONAL COOLING FOR TEMPERATURES TO
PLUMMET INTO THE LOWER QUARTILE OF NBM GUIDANCE. WHILE THIS STILL
COULD OCCUR ON SOME SCALE, THERE IS UNCERTAINTY IN CLOUD COVER. SOME
FOG COULD ALSO DEVELOP ACROSS NORTHWEST AND CENTRAL PARTS OF THE
STATE LATER TONIGHT INTO FRIDAY MORNING. EVEN IF TEMPERATURES DO
FALL INTO THE 20S BELOW IN NORTH CENTRAL NORTH DAKOTA, WHICH IS THE
MOST LIKELY AREA FOR THAT TO OCCUR, WINDS SHOULD BE LIGHT ENOUGH TO
PREVENT WIND CHILLS FROM REACHING HAZARDOUS VALUES COLDER THAN 25
BELOW.
WARM AIR ADVECTION AND ISENTROPIC ASCENT ATTENDANT TO A LOW-
AMPLITUDE SHORTWAVE MOVING SOUTHEAST ACROSS THE CANADIAN PRAIRIE
PROVINCES COULD SPREAD LIGHT SNOW ACROSS MUCH OF WESTERN AND CENTRAL
NORTH DAKOTA ON FRIDAY. THE HIGHEST PROBABILITIES FOR MEASURABLE SNOW
ARE AROUND 60 PERCENT ACROSS THE FAR NORTH, DECREASING TO NEAR ZERO
IN THE SOUTHWEST. NORTH CENTRAL NORTH DAKOTA HAS MEDIUM ODDS FOR
EXCEEDING ONE INCH OF NEW ACCUMULATION, BUT VERY LOW ODDS FOR
REACHING 2 INCHES. ELSEWHERE, ONLY A DUSTING AT MOST IS FAVORED.
A SLOW BUT STEADY WARMING TREND WILL COMMENCE ON FRIDAY, BUT EASTERN
PARTS OF THE STATE WILL STILL STRUGGLE TO CLIMB OUT OF THE SINGLE
DIGITS ABOVE ZERO. SATURDAY WILL LIKELY SEE SOUTHWEST PARTS OF THE
STATE WITH HIGHS ABOVE FREEZING, AND BY SUNDAY ALL OF WESTERN AND
CENTRAL NORTH DAKOTA COULD HAVE HIGHS AT LEAST IN THE 20S. THE
WARMING TREND LOOKS TO CONTINUE THROUGH CHRISTMAS DAY, WHEN THE NBM
IS SHOWING MEDIUM TO HIGH CONFIDENCE (GIVEN THE FORECAST TIME RANGE)
IN WIDESPREAD HIGHS IN THE 30S.
THE ONLY NOTABLE CHANCE OF PRECIPITATION IN ENSEMBLE GUIDANCE FOR
THE EXTENDED RANGE FALLS ON SUNDAY, WITH ONLY A 20 PERCENT CHANCE IN
THE NBM AT THIS TIME. ALL ENSEMBLE CLUSTERS DO IMPLY A SHORTWAVE
TRAVERSING THE NORTHERN PLAINS, BUT WITH ONLY LIGHT QPF. EVERY
CLUSTER ALSO HAS MEDIUM TO HIGH PROBABILITIES OF TEMPERATURES ALOFT
ABOVE FREEZING, WHICH COULD LEAD TO MIXED TYPES SHOULD PRECIPITATION
OCCUR.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1226 PM CST THU DEC 19 2024
CONDITIONS HAVE BEEN IMPROVING FROM NORTHWEST TO SOUTHEAST,
THOUGH BLOWING SNOW REMAINS A FACTOR OVER MUCH OF CENTRAL NORTH
DAKOTA AND THE JAMES RIVER VALLEY, BRINGING AREAS OF IFR
VISIBILITY. CONDITIONS WILL IMPROVE AS WE GO THROUGH THE
AFTERNOON AND EVENING WITH WIND DIMINISHING. SOME PATCHY FOG
WILL BE POSSIBLE OVER NORTHWEST AND CENTRAL NORTH DAKOTA
OVERNIGHT. SOME LIGHT SNOW WILL START TO MOVE INTO WESTERN PARTS
OF NORTH DAKOTA FRIDAY MORNING, POSSIBLY BRINGING SOME AREAS OF
MVFR VISIBILITY.
BIS WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 3 PM CST THIS AFTERNOON FOR NDZ004-
005-012-013.
WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR
NDZ022.
WINTER STORM WARNING UNTIL 6 PM CST THIS EVENING FOR NDZ023-
025.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
NDZ035>037-046>048-050-051.
HIGH WIND WARNING UNTIL 3 PM CST /2 PM MST/ THIS AFTERNOON FOR
NDZ040>045.
UPDATE...JJS
DISCUSSION...HOLLAN
AVIATION...JJS
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