740
FXUS63 KBIS 211217
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
617 AM CST SAT DEC 21 2024
KEY MESSAGES
- THERE IS A 30 TO 50 PERCENT CHANCE OF LIGHT FREEZING RAIN
ACROSS NORTHWEST AND CENTRAL NORTH DAKOTA ON SUNDAY. THE
HIGHEST PROBABILITIES ARE ACROSS THE NORTH.
- A WARMING TREND IS EXPECTED THIS WEEKEND THROUGH EARLY NEXT
WEEK, WITH ABOVE NORMAL TEMPERATURES FAVORED STATEWIDE FROM
CHRISTMAS EVE THROUGH THE END OF THE WEEK.
UPDATE
ISSUED AT 617 AM CST SAT DEC 21 2024
MAIN CHANGE WITH THIS UPDATE WAS TO ADD IN SLIGHT CHANCE POPS
AND PATCHY FOG ACROSS THE NORTH CENTRAL AND PARTS OF THE
NORTHWEST THAT ARE UNDERNEATH LOW STRATUS. WE'RE SEEING
INTERMITTENT OBSERVATIONS ACROSS THIS AREA OF LIGHT SNOW, PATCHY
FOG, OR BOTH. STRATUS DECK IS SLOWLY CLEARING FROM WEST TO EAST,
ALTHOUGH LATEST HIGH-RES GUIDANCE STILL WANTS TO HANG ON TO
CLOUD COVER IN THE NORTH CENTRAL THROUGH THE DAY BEFORE OUR NEXT
WAVE MOVES IN. MADE SOME TWEAKS TO CLOUD COVER AS WELL.
DISCUSSION
ISSUED AT 343 AM CST SAT DEC 21 2024
THIS MORNING, THE SYNOPTIC PATTERN WAS DOMINATED BY RIDGING OVER
THE NORTHERN ROCKIES, WITH AN UPSTREAM TROUGH OFF THE COAST OF
THE PACIFIC NORTHWEST, AND TROUGHING OVER THE NORTHEAST CONUS.
NORTHWEST FLOW ALOFT WAS PRESENT OVER THE DAKOTAS, WITH THE
FORECAST AREA PLACED IN BETWEEN A SURFACE HIGH OVER CENTRAL
MINNESOTA, AND A LOW ANALYZED IN SOUTHEAST ALBERTA. LOW CLOUDS
HAVE BEEN PRESENT OVER MUCH OF THE AREA THROUGH THE NIGHT, WITH
MOIST SOUTHERLY FLOW ON THE WEST SIDE OF THE SURFACE HIGH. SOME
PATCHY FOG COULD DEVELOP UNDERNEATH THE STRATUS DECK, ALTHOUGH
HAVE YET TO SEE ANY VISIBILITY REDUCTIONS.
QUIET WEATHER IS FORECAST TODAY AS THE UPPER RIDGE AXIS BEGINS
TO NUDGE INTO THE STATE, LEADING TO SEASONABLY WARM TEMPERATURES
IN SOUTHWEST NORTH DAKOTA WHERE FORECAST HIGHS ARE IN THE MID
40S. TEMPERATURES DECREASE TO THE NORTH AND EAST, WITH HIGHS IN
THE UPPER TEENS FROM THE TURTLE MOUNTAINS TO THE JAMES RIVER
VALLEY. THERE ARE SOME QUESTIONS ON HOW QUICKLY CLOUD COVER WILL
DIMINISH, BUT THE NORTH CENTRAL HAS THE HIGHEST LIKELIHOOD OF
MOSTLY CLOUDY SKIES THROUGH THE DAY.
MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS COMES FROM A
PROGRESSIVE UPPER SHORTWAVE AND CLOSED LOW MOVING THROUGH ON
SUNDAY, BRINGING MODEST PRECIPITATION CHANCES STARTING SUNDAY
MORNING IN THE WEST AND PUSHING ACROSS THE STATE THROUGH THE
DAY, ENDING SUNDAY EVENING IN THE CENTRAL AND EAST. THERE ARE
STILL A LOT OF QUESTIONS REGARDING PRECIPITATION TYPES, WITH
WARM AIR ALOFT ON TOP OF COOLER SURFACE TEMPERATURES, ESPECIALLY
NORTH AND EAST, FOR MUCH OF SUNDAY. SOME OF THE INITIAL HIGH-
RESOLUTION GUIDANCE SHOWS AN INITIAL WAVE OF PRECIPITATION THAT
WOULD LIKELY BE THE MAIN WAVE OF FREEZING RAIN, AS THERE IS
STRONG ENSEMBLE CONSENSUS ON 850MB TEMPERATURES ABOVE FREEZING.
THEN WE WILL LIKELY SEE A LULL IN PRECIPITATION CHANCES BEFORE
THE UPPER LOW COMES THROUGH, WRAPPING IN COLDER AIR AND
EVENTUALLY TRANSITIONING PRECIPITATION TO MOSTLY SNOW BY SUNDAY
EVENING. THE 00Z HREF HAS A HIGH PROBABILITY OF SURFACE
TEMPERATURES ABOVE FREEZING FOR AREAS SOUTH AND WEST OF THE
MISSOURI RIVER, WITH NBM P-TYPE PROBABILITIES STRONGLY FAVORING
RAIN IN THESE AREAS THROUGH MUCH OF SUNDAY. THIS IS THE AREA
LEAST LIKELY TO SEE ANY FREEZING RAIN, ALTHOUGH IT CANNOT BE
RULED OUT.
ONE AREA OF UNCERTAINTY COMES FROM FORECAST SOUNDINGS THAT SHOW
A SIGNIFICANT DRY LAYER, SO ALTHOUGH THERE IS A LOW-LEVEL WARM
NOSE THAT WOULD SUPPORT FREEZING RAIN AS THE DOMINANT P-TYPE,
CONFIDENCE IS SOMEWHAT LOW IN PRECIPITATION MAKING IT TO THE
SURFACE, AT LEAST INITIALLY. SOME SOUNDINGS ALSO ADVERTISE THE
COLUMN COOLING ENOUGH AFTER AN HOUR OR TWO TO FAVOR SNOW
COMPARED TO FREEZING RAIN, SO THE WINDOW OF MIXED PRECIPITATION
COULD BE RELATIVELY SHORT LIVED FOR SOME LOCATIONS. ENSEMBLE
MEMBERS GENERALLY FAVOR THE "HEAVIEST" QPF (LOW CHANCE OF
EXCEEDING 0.10 INCH OF LIQUID) FROM WILLISTON TO CARRINGTON, BUT
IT IS WORTH NOTING THAT ONE CLUSTER, ALONG WITH SOME RECENT
CAMS RUNS, DO HAVE THIS FURTHER NORTH. WE ARE ADVERTISING A 30
TO 50 PERCENT CHANCE OF FREEZING RAIN NORTHWEST AND CENTRAL,
ALTHOUGH CURRENT WEATHER GRIDS ARE PRIMARILY A MIX OF FREEZING
RAIN AND SNOW. IT IS WORTH NOTING THAT THE HREF IS HIGHLIGHTING
A LOW CHANCE FOR BANDED SNOW ALONG THE INTERNATIONAL BORDER,
ALTHOUGH THE PROBABILITY FOR AT LEAST ONE INCH OF SNOW IS ONLY
AROUND 10 PERCENT.
THE MAIN STORY FOR THE WEEK OF CHRISTMAS IS ABOVE AVERAGE
TEMPERATURES LIKELY, WITH RELATIVELY LOW SPREAD IN NBM
TEMPERATURE PERCENTILES SIGNALING GOOD AGREEMENT AMONG ENSEMBLE
MEMBERS. BROAD RIDGING INTO THE SOUTHERN CANADIAN PRAIRIES WILL
SHIFT EAST MIDWEEK, WITH MORE ZONAL TO MAYBE EVEN SOUTHWEST FLOW
ALOFT LATE IN THE WEEK. LATEST DETERMINISTIC NBM HAS HIGHS ON
CHRISTMAS EVE FROM AROUND FREEZING NORTH AND EAST TO THE MID 40S
SOUTHWEST, WITH SLIGHTLY COOLER HIGHS OF THE LOWER 30S TO LOWER
40S ON CHRISTMAS DAY. CHANCES FOR PRECIPITATION REMAIN LOW
THROUGH THE WEEK. THERE ARE SOME SIGNS OF A PATTERN SWITCH NEXT
WEEKEND INTO THE WEEK OF NEW YEARS, WITH NBM TEMPERATURES
BEGINNING TO COOL AND PRECIPITATION CHANCES INCREASING.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 617 AM CST SAT DEC 21 2024
LOW VFR TO MVFR CEILINGS CONTINUE ACROSS MUCH OF CENTRAL NORTH
DAKOTA, IMPACTING KMOT AND KJMS, AND JUST EAST OF KBIS. SOME
PATCHY FOG AND INTERMITTENT LIGHT SNOW IS POSSIBLE AT KMOT FOR
THE NEXT FEW HOURS. OTHERWISE QUIET THROUGH MOST OF THE TAF
PERIOD, WITH CLOUDS SLOWLY CLEARING OUT AND VFR CONDITIONS
EXPECTED BY 00Z AT ALL TERMINALS. ANOTHER ROUND OF LOW CLOUDS
MOVES INTO NORTHERN NORTH DAKOTA LATE IN THE TAF PERIOD,
IMPACTING KXWA/KMOT.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...JONES
DISCUSSION...JONES
AVIATION...JONES
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