757
FXUS63 KFGF 171427
AFDFGF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
827 AM CST TUE DEC 17 2024
KEY MESSAGES
- A FAST MOVING SYSTEM WILL BRING A LOW CHANCE FOR A DUSTING OF
LIGHT SNOW THIS AFTERNOON AND EVENING, MAINLY FOR THE SOUTHERN
RED RIVER VALLEY AND WEST CENTRAL MINNESOTA.
- MINOR WINTER IMPACTS ARE EXPECTED WEDNESDAY INTO THURSDAY
ACROSS MUCH OF EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
DUE TO ACCUMULATING SNOW AND BLOWING SNOW.
- THERE IS A 30 PERCENT CHANCE FOR MODERATE TRAVEL IMPACTS AS A
NARROW HEAVY SNOW BAND DEVELOPS. IMPACTS COULD EXTEND WELL
INTO THURSDAY AFTER SNOW ENDS DUE TO A CHANCE FOR BLOWING SNOW
AND REDUCED VISIBILITY IN NORTH DAKOTA.
UPDATE
ISSUED AT 815 AM CST TUE DEC 17 2024
FLURRIES ARE CHANGING TO AND/OR MIXING WITH FREEZING DRIZZLE
THIS MORNING WITHIN THE RED RIVER VALLEY. WHILE HARD TO SAY JUST
HOW FAR REACHING THIS GOES WITH CORROBORATING REPORTS MORE
SPARSE THAN WIDESPREAD, INGREDIENTS ARE THERE TO KEEP THIS
POSSIBLE THROUGH THE MORNING. FORECAST GUIDANCE STRONGLY
SUGGESTS SATURATION ALOFT TO INTRODUCE ICE ALOFT, FAVORING LIGHT
SNOW IN LIEU OF FREEZING LIQUID. NEVERTHELESS, INCREASING THE
MESSAGING OF POTENTIALLY SLIPPERY CONDITIONS ON UNTREATED
SURFACES FROM FREEZING DRIZZLE THIS MORNING.
UPDATE
ISSUED AT 652 AM CST TUE DEC 17 2024
FLURRIES HAVE BEEN REPORTED/OBSERVED AT DIFFERENT LOCATIONS IN
OUR AREA UNDER THE LINGERING LOW STRATUS, AND LIGHTER RETURNS
ARE STARTING TO FILL IN AS THE SHORTWAVE APPROACHES. IMPACTS ARE
STILL EXPECTED TO BE MINIMAL (DUSTING AT THE MOST IN THE SOUTH).
AS FLURRIES ARE GOING TO BE A BIT HIGHER IN COVERAGE, I EXPANDED
THE MENTION IN OUR AREA THROUGH THE DAY. OTHERWISE, THE FORECAST
IN THE SHORT TERM IS ON TRACK.
DISCUSSION
ISSUED AT 348 AM CST TUE DEC 17 2024
..SYNOPSIS
THE LARGE SCALE PATTERN ACROSS THE NORTHERN US CONTINUES TO FEATURE
ZONAL FLOW AND ACTIVE/PROGRESSIVE SHORTWAVE PASSAGES. FALLING
HEIGHTS MID WEEK SUPPORTS A PERIOD OF COLDER TEMPERATURES. THIS IS
SHORT LIVED THOUGH, AS THERE IS A STRONG CONSENSUS IN ENSEMBLES FOR
RIDGING TO BUILD FROM THE WESTERN US INTO THE NORTHERN PLAINS WITH
RISING HEIGHTS AND A SIGNAL FOR ABOVE AVERAGE (NEAR OR ABOVE 32) BY
EARLY NEXT WEEK. THE SHIFT TOWARDS RIDGING WILL PUT AN END TO MORE
ORGANIZED SYSTEMS AND MEASURABLE PRECIPITATION CHANCES FOR AWHILE.
IT SHOULD BE NOTED THOUGH, THIS TIME OF YEAR WARMER TEMPERATURES
NEAR FREEZING OFTEN RAISES THE POTENTIAL FOR FOG/FREEZING FOG AND
DRIZZLE/FREEZING DRIZZLE EVENTS DEPENDING ON LOW LEVEL PATTERNS IN
PROXIMITY OF SNOW PACK. THESE LOW LEVEL PATTERNS ARE NOT WELL
RESOLVED OUTSIDE OF 48HR.
..LOW CHANCE FOR LIGHT SNOW TODAY
A POSITIVE TILTED/PROGRESSIVE SHORTWAVE JUST NOW ORGANIZING OVER
WESTERN MONTANA/WYOMING IS EXPECTED TO QUICKLY PASS THROUGH THE
REGION LATER THIS AFTERNOON AND EVENING. THE BASE OF THE TROUGH
WHERE THE STRONGER SYNOPTIC ASCENT INTERSECTS A BAROCLINIC ZONE IS
SHOWN TO BE WELL SOUTH OF OUR CWA (TOWARDS SOUTHERN SD/MN). ON THE
NORTHERN PART OF THE WAVE THAT PASSES THROUGH OUR AREA FLURRIES AND
VERY LIGHT SNOW IS SHOWN BY CAMS WHICH MAY BE SUPPORT A DUSTING
(HREF PMM SHOWS A FEW TENTHS IN THE SOUTHERN RRV). COVERAGE AND
AMOUNTS OF ACCUMULATING SNOW MAY BE LOW, HOWEVER A DUSTING COULD
STILL BE ENOUGH TO CAUSE A FEW SLICK SPOTS DURING THE EVENING
COMMUTE.
..MINOR TO MODERATE WINTER IMPACTS WEDNESDAY AND THURSDAY
A STRONGER (BUT STILL PROGRESSIVE) CLIPPER-TYPE SYSTEM IS STILL IN
LINE TO TRACK THROUGH OUR REGION WEDNESDAY THROUGH THURSDAY, WITH
THE MAIN PERIODS OF IMPACT WEDNESDAY EVENING THROUGH MIDDAY
THURSDAY. THERE IS STRONG CONSENSUS ON THE GENERAL 500MB PATTERN,
THOUGH CLUSTERS STILL SHOW SOME SPREAD IN THE STRENGTH AND EVENTUAL
TRACK OF THE 700 MB LOW CENTER AS IT INTERACTS WITH AN ELEVATED
BAROCLINIC ZONE. DEEP SATURATION IN DENDRITIC LAYER WOULD SUPPORT
HIGHER SLR AS THE EVENT UNFOLDS, WHICH IS CURRENTLY ACCOUNTED FOR.
DUE TO THE STRONG CONSENSUS IN THE SYNOPTIC PATTERN ENSEMBLE BASED
PROBABILITIES IN ALL SCENARIOS NOW SUPPORT A SWATH OF LIGHT TO
MODERATE SNOW ACCUMULATIONS AND PWSSI SHOWS 70-80% PROBS FOR MINOR
(ADVISORY) IMPACTS FROM ACCUMULATING SNOW AND BLOWING SNOW FROM
EASTERN ND AND ACROSS MUCH OF NORTHWEST/WEST CENTRAL MN. SNOW
PROBABILITIES TO EXCEED 2" ARE IN THE 60-90% RANGE ACROSS MUCH OF
OUR AREA (EXCEPT THE FAR NORTHEAST TOWARDS LAKE OF THE WOODS WHICH
IS FARTHER FROM THE MAIN TRACK).
THERE IS STILL A SIGNAL FOR A PERIOD OF STRONGLY POSITIVE 800-700MB
FRONTOGENESIS PARALLEL TO THE 700MB LOW CENTER WHERE THE ELEVATED
BAROCLINIC ZONE SETS UP (NORTH OF THE STALLED WARM FRONT). THERE
ISN'T A STRONG SIGNAL FOR INSTABILITY, BUT THE PRESENTS OF
FRONTOGENESIS IN THIS LAYER AS THE WAVE FIRST KICKS OUT RAISES THE
POTENTIAL FOR A MORE INTENSE MESOSCALE BAND AND HIGHER RATES WITHIN
THE BROADER SYNOPTIC SNOW BEFORE KICKING EAST-SOUTHEAST. THIS IS THE
FEATURE OF INTEREST AND IS REFLECTED IN GUIDANCE THAT SHOWS HIGHER
TOTALS (PROBABILITY FOR 6"+ ARE 30% IN THE DEVILS LAKE BASIN
DECREASING TO 20% TO THE SOUTHEAST). AS MESOSCALE FEATURES TEND TO
CARRY A LOWER PREDICTABILITY HORIZON ON LOCATION/COVERAGE OF IMPACTS
(AND CURRENT PROBS ARE 30%) A WATCH IS NOT BEING CONSIDERED AT THIS
TIME.
REGARDING WIND/BLOWING SNOW: THE STRONGEST CAA, PRESSURE RISES, AND
PRESSURE GRADIENT CONTINUES TO BE SHOWN TO TRACK TO THE WEST OF OUR
CWA. DUE TO FALLING TEMPERATURES AND AT LEAST BREEZY WINDS SOME
BLOWING SNOW IMPACTS WOULD BE ANTICIPATED, AND COULD LINGER AFTER
THE MAIN SNOW ENDS THURSDAY. STRONGEST WINDS (GUSTING TO 35 MPH) BUT
EVEN WITH NEW BLOWABLE SNOW SUSTAINED WINDS AND TEMPERATURES STILL
LIMIT COVERAGE OF IMPACTS TO DRIFTING AND LOCALIZED/SPORADIC NEAR
WHITEOUT CONDITIONS IN OPEN COUNTRY (ADVISORY TYPE IMPACTS).
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 529 AM CST TUE DEC 17 2024
LOW STRATUS RESPONSIBLE FOR MVFR CEILINGS WILL TEND TO PREVAIL
ACROSS MUCH OF EASTERN ND AND NORTHWEST MN THROUGH THIS
AFTERNOON, WITH IMPROVING TRENDS (TO VFR) FROM WEST TO EAST THIS
EVENING AND OVERNIGHT. MVFR (AND A LOW CHANCE FOR IFR) CEILINGS
ARE MORE LIKELY TO REMAIN IN PLACE AT KBJI THROUGH THE ENTIRE
TAF PERIOD. WINDS WILL PREVAIL FROM THE NORTHWEST UNDER 10KT
DURING THE DAYTIME PERIOD AND OVERNIGHT TONIGHT AS SURFACE
GRADIENT REMAINS RELATIVELY WEAK.
FGF WATCHES/WARNINGS/ADVISORIES
ND...NONE.
MN...NONE.
UPDATE...CJ/DJR
DISCUSSION...DJR
AVIATION...DJR
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