407  
FXUS63 KBIS 172353  
AFDBIS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BISMARCK ND  
553 PM CST TUE DEC 17 2024  
   
KEY MESSAGES  
 
- HIGH CHANCES FOR MEASURABLE SNOW WEDNESDAY INTO THURSDAY, WITH  
A 60 PERCENT CHANCE OF AT LEAST 6 INCHES OF SNOW ACROSS  
NORTHERN NORTH DAKOTA AND INTO THE NORTHERN JAMES RIVER  
VALLEY. A WINTER STORM WATCH HAS BEEN ISSUED.  
 
- MEDIUM CHANCES OF IMPACTFUL BLOWING SNOW WEDNESDAY AFTERNOON  
THROUGH THURSDAY MORNING. VISIBILITY COULD BE SIGNIFICANTLY  
REDUCED, ESPECIALLY IN OPEN COUNTRY.  
 
- THERE IS A MEDIUM CHANCE OF FREEZING RAIN WEDNESDAY AFTERNOON  
AND EVENING IN AREAS SOUTH AND WEST OF THE MISSOURI RIVER,  
WHICH COULD LEAD TO A GLAZE OF ICE.  
 
- TEMPERATURES COOL THROUGH THE REST OF THE WEEK. OVERNIGHT  
LOWS AS COLD AS 15 DEGREES BELOW ZERO ARE FORECAST IN NORTHERN  
NORTH DAKOTA WEDNESDAY AND FRIDAY MORNING.  
 
- ABOVE NORMAL TEMPERATURES ARE STRONGLY FAVORED FOR NEXT WEEK  
AROUND THE CHRISTMAS HOLIDAY.  
 
 
   
UPDATE  
 
ISSUED AT 539 PM CST TUE DEC 17 2024  
 
EARLIER GUIDANCE HAD CLOUDS CLEARING OUT RATHER QUICKLY TONIGHT,  
BUT LOOKING AT THE LATEST OBSERVATIONS THAT SEEMS UNLIKELY. WE  
ALSO CONTINUE TO SEE SOME LIGHT SNOW/FLURRIES WHEREVER CLOUD  
COVER IS. THUS, WE DECIDED TO MENTION FLURRIES ANYWHERE ACROSS  
THE FORECAST AREA WHERE CLOUD COVER WAS FORECAST TO BE 60  
PERCENT OR GREATER THROUGH 15Z WEDNESDAY. OTHERWISE, NO MAJOR  
CHANGES WERE NEEDED FOR THIS UPDATE AND JUST BLENDED IN THE  
LATEST OBSERVATIONS TO THE GOING FORECAST.  
 
 
   
DISCUSSION  
 
ISSUED AT 405 PM CST TUE DEC 17 2024  
 
NO MAJOR WEATHER IN THE NEAR TERM FORECAST, WITH ON AND OFF  
LIGHT SNOW ONGOING UNDERNEATH AN EXPANSIVE LOW STRATUS DECK  
ACROSS THE STATE, AS WEAK, EMBEDDED IMPULSES MOVE THROUGH  
CYCLONIC FLOW ALOFT. HIGHS THIS AFTERNOON WILL BE IN THE UPPER  
TEENS TO UPPER 20S, WITH RELATIVELY LIGHT NORTHWEST WINDS AS  
HIGH PRESSURE CENTERED TO OUR NORTHWEST CONTINUES TO BUILD INTO  
THE REGION. QUIET BUT CHILLY TONIGHT, ALTHOUGH SOME UNCERTAINTY  
IN OVERNIGHT LOWS IF LOW CLOUDS DON'T MOVE OUT AS MUCH AS  
EXPECTED. CURRENT FORECAST HAS LOWS DROPPING TO AROUND 10  
DEGREES BELOW ZERO ACROSS FAR NORTHERN NORTH DAKOTA, AND THE  
SINGLE DIGITS ABOVE ZERO ELSEWHERE.  
 
THE MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS IS AN ALBERTA  
CLIPPER THAT IS PROGGED TO DEVELOP OVER THE NORTHERN ROCKIES  
BEFORE DIVING THROUGH MONTANA AND THE DAKOTAS, BRINGING  
IMPACTFUL WINTER WEATHER WEDNESDAY AND THURSDAY. A HYBRID SYSTEM  
WITH A MIX OF SYNOPTIC AND MESOSCALE FORCING HAS MADE THIS A  
TRICKY FORECAST. THERE IS HIGH CONFIDENCE IN A LARGE AREA OF  
ADVISORY-LEVEL SNOW ACROSS NORTHWEST AND PARTS OF CENTRAL NORTH  
DAKOTA FROM SUFFICIENT SYNOPTIC SCALE FORCING, WITH MID-LEVEL  
HEIGHT FALLS AND WARM AIR ADVECTION OVERSPREADING THE FORECAST  
AREA AHEAD OF THE APPROACHING SHORTWAVE. DETERMINISTIC GUIDANCE  
HAS BEEN CONSISTENT IN ADVERTISING MODERATE FRONTOGENESIS  
OVERLAID WITH SUFFICIENT Q-VECTOR CONVERGENCE AND MODESTLY STEEP  
MID- LEVEL LAPSE RATES, WITH THE HREF SNOWBAND PROBABILITY  
TRACKER PAGE AGREEING WITH THIS POTENTIAL BY HIGHLIGHTING A  
NORTHWEST-SOUTHEAST ORIENTED BAND IN VARIOUS MEMBERS. ASSUMING  
A BROAD 15:1 SNOW RATIO, WE UTILIZED 12Z HREF NEIGHBORHOOD  
PROBABILITIES OF 0.40 INCHES OF QPF TO HIGHLIGHT THE MOST LIKELY  
AREA OF SNOWFALL OF AT LEAST 6 INCHES. IN COLLABORATION WITH FGF,  
DECIDED THERE WAS ENOUGH CONFIDENCE FOR A WINTER STORM WATCH FOR  
AREAS FROM DIVIDE AND WILLIAMS COUNTIES, TO ROLETTE AND PIERCE,  
DOWN TO FOSTER AND STUTSMAN COUNTIES. BROADLY, THERE IS A 60  
PERCENT CHANCE FOR AT LEAST 6 INCHES OF SNOW IN THESE AREAS,  
WITH A LOW CHANCE OF EXCEEDING 8 INCHES. WE DO RECOGNIZE THAT  
THE POTENTIAL FOR SOMEWHERE IN AN AREA TO RECEIVE HEAVY SNOW IS  
LIKELY HIGHER THAN POINT-SPECIFIC PROBABILITIES WILL SHOW, AS  
THESE SIGNALS CAN GET WASHED OUT IN ENSEMBLE GUIDANCE.  
 
FORECAST SNOW AMOUNTS DECREASE TO THE SOUTH, BUT STRONGER WINDS WILL  
LEAD TO MORE SIGNIFICANT BLOWING SNOW CONCERNS. VERY STRONG  
WINDS ARE LIKELY IN PARTS OF WESTERN AND SOUTHERN NORTH DAKOTA  
WITH THIS SYSTEM, WITH STRONG PRESSURE RISES AND COLD AIR  
ADVECTION. THE TIMING OF THESE FEATURES ISN'T AS FAVORABLE FOR  
UPPER END WINDS, HOWEVER, AS THE MAIN PUSH OF WINDS WILL BE  
MOVING IN AROUND MIDNIGHT WEDNESDAY NIGHT, CONTINUING INTO  
THURSDAY MORNING. 12Z DATA SHOWS A HIGH LIKELIHOOD OF WIND GUSTS  
OF AT LEAST 50 MPH ACROSS SOUTHWEST NORTH DAKOTA, WITH A BROAD  
40 TO 50 PERCENT CHANCE OF WINDS REACHING 60 MPH. ANY  
PRECIPITATION FALLING COULD HELP IN MIXING DOWN STRONGER WINDS  
AS WELL, WITH FORECAST SOUNDINGS SHOWING A BRIEF PERIOD OF 65  
MPH WINDS AT THE TOP OF THE MIXED LAYER. NOT SURE HOW WIDESPREAD  
THOSE HIGHER END WINDS WILL BE, BUT IT CERTAINLY LOOKS POSSIBLE  
THAT WE HAVE ISOLATED GUSTS UP TO 60 MPH OVERNIGHT WEDNESDAY  
INTO THURSDAY MORNING.  
 
A WINTER WEATHER ADVISORY WILL LIKELY BE NEEDED FOR AREAS SOUTH OF  
THE WINTER STORM WATCH FOR LOWER SNOW AMOUNTS AND BLOWING SNOW,  
AS WINDS BECOME STRONGER IN THIS AREA. COUNTIES WITHOUT MUCH  
SNOW AND BLOWING SNOW WILL NEED TO BE IN A WIND ADVISORY, BUT  
THERE IS UNCERTAINTY ON WHERE THIS DIVIDING LINE WILL END UP, IN  
CASE THERE IS A SOUTHWARD SHIFT. WE DID ISSUE A SPECIAL WEATHER  
STATEMENT FOR COUNTIES NOT IN THE WATCH, WITH A GENERAL 1 TO 3  
INCHES OF SNOW FAVORED IN A LINE FROM WATFORD CITY, TO GARRISON,  
TO ELLENDALE, AND LOWER AMOUNTS SOUTH.  
 
THE OTHER POTENTIAL HAZARD IS FREEZING RAIN, FOCUSED IN AREAS  
SOUTH AND WEST OF THE MISSOURI RIVER. DETERMINISTIC GUIDANCE  
BRINGS IN A SWATH OF WARM AIR ALOFT WEDNESDAY EVENING, WITH  
SOUNDINGS SHOWING A BRIEF WINDOW OF ENOUGH OF A WARM NOSE TO  
FAVOR FREEZING RAIN. FAR SOUTHWEST NORTH DAKOTA MIGHT BE TOO  
WARM AT THE SURFACE FOR FREEZING RAIN, WITH FORECAST HIGHS IN  
THE UPPER 30S ON WEDNESDAY, SO THERE MIGHT BE A SWEET SPOT IN  
COUNTIES IMMEDIATELY ALONG THE RIVER THAT END UP WITH THE MAIN  
FREEZING RAIN. HIGH-RES MODEL RUNS ARE SHOWING THIS MIXED  
P-TYPE AS WELL, WITH SOME RAIN IN THE FAR SOUTHWEST WHERE TEMPS  
ARE WARMER. CURRENTLY ADVERTISING A MEDIUM CHANCE OF FREEZING  
RAIN THAT COULD LEAD TO A GLAZE OF ICE, BUT NOT A LOT OF  
CONFIDENCE IN HOW P-TYPES WILL EVOLVE IN THIS NARROW WINDOW. BY  
THE TIME IT GETS TO LATE WEDNESDAY NIGHT / EARLY THURSDAY  
MORNING, PRECIPITATION IS EXPECTED TO BE ALL SNOW.  
 
AS THE CLIPPER DROPS SOUTHEAST THROUGH THE DAY THURSDAY, SNOW  
CHANCES WILL TAPER OFF FROM NORTHWEST TO SOUTHEAST, WITH LIGHT  
SNOW LINGERING THROUGH THE AFTERNOON IN THE JAMES RIVER VALLEY.  
THE SURFACE PRESSURE GRADIENT WILL WEAKEN RELATIVELY QUICKLY,  
LETTING WINDS DIMINISH THROUGH THE DAY, DECREASING THE BLOWING  
SNOW THREAT BEFORE WEAK WINDS OVERNIGHT. A STOUT SURFACE HIGH  
PRESSURE WILL BUILD IN BEHIND THE EXITING SYSTEM, BRINGING A  
PUSH OF ARCTIC AIR THURSDAY NIGHT INTO FRIDAY, WHICH NBM  
TEMPERATURE PERCENTILES SHOW AS THE COLDEST NIGHT OF THE PERIOD.  
FORECAST LOWS RANGE FROM 15 DEGREES BELOW ZERO NORTH TO AROUND  
ZERO SOUTHWEST. WE WILL LIKELY BE APPROACHING COLD WEATHER  
ADVISORY CRITERIA ACROSS THE NORTH (30 BELOW), BUT NOT SURE WE  
WILL REACH THAT THRESHOLD.  
 
ANOTHER SHOT OF SNOW IS POSSIBLE ON FRIDAY (20 TO 35 PERCENT  
CHANCE) AS A PROGRESSIVE, SHALLOW SHORTWAVE MOVES THROUGH  
NORTHWEST FLOW. THE PROBABILITY OF EXCEEDING ONE INCH OF SNOW  
WITH THIS WAVE IS LOW. HIGHS ON FRIDAY AND SATURDAY WILL VARY  
SIGNIFICANTLY ACROSS THE STATE, RANGING FROM AROUND 10 DEGREES  
NORTH CENTRAL AND EAST TO AROUND FREEZING SOUTHWEST, AS UPPER  
RIDGING BEGINS TO BUILD OUT WEST.  
 
THE RIDGE AXIS BEGINS TO SHIFT WEST AND FLATTEN LATE IN THE  
WEEKEND, WARMING TEMPERATURES TO NEAR NORMAL EAST AND WELL ABOVE  
NORMAL WEST. THERE ARE SOME SIGNS OF A WAVE MOVING THROUGH ON  
SUNDAY, BUT BLENDED PRECIPITATION CHANCES ARE STILL VERY LOW.  
FOR THE WEEK OF CHRISTMAS, CONTINUED HIGH CONFIDENCE IN ABOVE  
AVERAGE TEMPERATURES, WITH A MEDIUM PROBABILITY OF HIGHS  
EXCEEDING 40 DEGREES F ON MONDAY AND CHRISTMAS EVE IN SOUTHWEST  
NORTH DAKOTA. SEASONABLY MILD TEMPERATURES ARE FAVORED TO  
CONTINUE THROUGH THE WEEK, ALTHOUGH IT SHOULD BE NOTED THAT THE  
PATTERN IS NOT NECESSARILY DRY, SO THE FORECAST IS STILL WORTH  
WATCHING IF YOU HAVE HOLIDAY TRAVEL PLANS.  
 
 
   
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/  
 
ISSUED AT 539 PM CST TUE DEC 17 2024  
 
WIDESPREAD AND INTERMITTENT MVFR CEILINGS WILL LIKELY CONTINUE  
THROUGH MUCH OF THE NIGHT ACROSS MOST OF WESTERN AND CENTRAL  
NORTH DAKOTA. THAT BEING SAID, KDIK AND KMOT MAY SEE CEILINGS  
LIFT OR SCATTER OUT TO VFR CATEGORIES AT SOME POINT TONIGHT.  
OTHER AREAS MAY SEE SOME IMPROVEMENT LATER WEDNESDAY MORNING.  
SOME LIGHT SNOW FLURRIES ARE ALSO POSSIBLE WHEREVER THE LOWER  
CEILINGS ARE LOCATED. A CLIPPER SYSTEM APPROACHES TOMORROW,  
LEADING TO LOWERING CEILINGS AND INCREASING PRECIPITATION  
CHANCES. THE BEST CHANCES WILL BE ACROSS THE NORTH CENTRAL AND  
NORTHWEST (KXWA AND KMOT) BUT WE WILL SEE SOME LOWER CHANCES OF  
SNOW AT KDIK WEDNESDAY AFTERNOON AS WELL. PRECIPITATION CHANCES  
BECOME MORE WIDESPREAD AFTER THE 00Z TAF PERIOD. KXWA AND KMOT  
WILL LIKELY SEE SOME IFR VISIBILITIES BY WEDNESDAY AFTERNOON AS  
PREVAILING SNOW MOVES IN AND WINDS INCREASE.  
 
 
   
BIS WATCHES/WARNINGS/ADVISORIES  
 
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY  
MORNING FOR NDZ001>003-009>011.  
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY  
AFTERNOON FOR NDZ004-005-012-013-022-023-025-037.  
 
 
 
 
 
UPDATE...ZH  
DISCUSSION...JONES  
AVIATION...ZH  
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