545
FXUS63 KFGF 230422
AFDFGF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
1022 PM CST SUN DEC 22 2024
KEY MESSAGES
- WINTRY MIX WITHIN SOUTHEAST NORTH DAKOTA INTO WEST-CENTRAL
MINNESOTA AFTER SUNSET INTO EARLY MONDAY MORNING MAY IMPACT
TRAVEL CONDITIONS FROM LIGHT ICING. THERE IS A 40% CHANCE OF A
GLAZE OF ICE THROUGH MONDAY MORNING.
- WARMING UP FOR THE HOLIDAY WEEK.
UPDATE
ISSUED AT 951 PM CST SUN DEC 22 2024
THE REFLECTIVITIES CONTINUE TO TAKE MORE OF A SSE TRACK, BUT THE
WINTER WEATHER ADVISORY IS STILL HOLDING UP. MAY NEED AN
EXTENSION ONCE WE REEVALUATE CONDITIONS IN THE NEXT FEW HOURS.
FORECAST REMAINS ON TRACK.
UPDATE ISSUED AT 716 PM CST SUN DEC 22 2024
STARTING TO SEE THE AREA OF MIXED PRECIPITATION MAKE ITS WAY
INTO SOUTHEASTERN NORTH DAKOTA. USE CAUTION OUT AND ABOUT AS
THINGS ARE EXPECTED TO BE SLICK WHERE THIS MIXED PRECIP FALLS.
FORECAST REMAINS ON TRACK.
DISCUSSION
ISSUED AT 315 PM CST SUN DEC 22 2024
..SYNOPSIS
WATER VAPOR SATELLITE IMAGERY THIS AFTERNOON REVEALS AN
ELONGATED, LOW AMPLITUDE SHORTWAVE TROUGH WITHIN ND/MT, WITH A
MODEST BUT PRESENT MID LEVEL JET HELPING FORCE AND PROPAGATE
THIS EAST- SOUTHEAST. RADAR AND SURFACE OBSERVATIONS/REPORTS
CONFIRMS AN AREA OF FREEZING RAIN WITHIN WEST AND CENTRAL ND.
RADAR RETURNS ARE SHOWING UP IN EASTERN ND INTO MN, ALTHOUGH A
NOTABLE DRY LAYER ROOTED AROUND 800 MB IS PREVENTING THESE
LEADING RADAR RETURNS FROM REACHING THE GROUND.
FORECAST GUIDANCE CONTINUES TO SUGGEST THIS DRY LAYER SHOULD
SATURATE AS THE MAIN WAVE MOVES THROUGH SOUTHEAST ND INTO
CENTRAL MN, ALLOWING A WINTRY MIX TO REACH THE GROUND, INCLUDING
FREEZING LIQUID. THIS CONTINUES THE POTENTIAL FOR LIGHT ICING IN
THESE LOCATIONS TONIGHT INTO MONDAY MORNING. ADDITIONALLY,
RECENT GUIDANCE IS SUGGESTING THE POSSIBILITY OF FREEZING
DRIZZLE ELSEWHERE THROUGH THE MORNING ON MONDAY. MORE ON THE
POTENTIAL FOR LIGHT ICING AND ASSOCIATED UNCERTAINTY CAN BE
FOUND BELOW.
LOW LEVEL MOISTURE TRAPPED UNDERNEATH AN INVERSION WILL ALSO
PROMOTE THE DEVELOPMENT OF FOG WITHIN PORTIONS OF OUR AREA,
INCLUDING THE POSSIBILITY OF DENSE FOG. LATEST GUIDANCE LIKE
HRRR AND HREF HOLDS RELATIVELY HIGHEST CHANCE (40%) FOR DENSE
FOG WITHIN EASTERN NORTH DAKOTA ALONG AND WEST OF THE RED RIVER
VALLEY TONIGHT INTO MONDAY MORNING. HOWEVER, AS IS COMMON WITH
FOG, CONFIDENCE IS LOW ON LOCATION AND COVERAGE OF DENSE FOG.
GETTING INTO NEXT WEEK, ENSEMBLE GUIDANCE WANTS TO PROPAGATE
UPPER RIDGING AND SPLIT FLOW EAST INTO THE CENTRAL CONUS BY
LATE NEXT WEEK. AS IT DOES THIS, SOME ENSEMBLE GUIDANCE FAVORS
EMBEDDED WEAKER SHORTWAVE TROUGHS WITHIN THE FLOW TO MOVE
THROUGH THE NORTHERN PLAINS/UPPER MIDWEST, WHICH MAY BRING BRIEF
PERIODS OF LIGHT PRECIPITATION. THIS REGIME ALSO FAVORS WARMER
THAN AVERAGE TEMPERATURES, INCLUDING TEMPERATURES NEAR OR JUST
ABOVE FREEZING. THIS WILL INFLUENCE PRECIPITATION TYPE, AND
ADDITIONAL BOUTS OF WINTRY MIX OR EVEN PLAIN RAIN WILL BE
POSSIBLE.
ENSEMBLE GUIDANCE DIFFERS IN EXACTLY HOW SPLIT FLOW MOVES INTO
THE CENTRAL CONUS AS WELL AS HOW THE UPPER RIDGE BREAKS DOWN AND
PROPAGATES EASTWARD. BUT ONE CLUSTER OF GUIDANCE DOES REVEAL
BROAD SOUTHWEST FLOW ALOFT OVER THE PLAINS AND MIDWEST BY LATE
NEXT WEEK, WITH UPPER TROUGHING NOW ATTEMPTING TO DIG INTO THE
WESTERN CONUS. THIS MAY PROMOTE A LARGER SYSTEM TO DEVELOP AND
MOVE THROUGH THE CENTRAL CONUS. UNCERTAINTY IN POTENTIAL
IMPACTS IS LARGE FROM THIS POTENTIAL SYSTEM LATE NEXT WEEK, NOT
ONLY DRIVEN BY DIFFERENCES IN SYNOPTIC EVOLUTION WITHIN ENSEMBLE
GUIDANCE, BUT ALSO WITH TEMPERATURES HOVERING AROUND FREEZING
LEADING TO UNCERTAINTY IN PRECIPITATION TYPE.
...POTENTIAL IMPACTS FROM ICING TONIGHT INTO MONDAY MORNING..
DESPITE THE SHORTWAVE AND ITS ASSOCIATED PRECIPITATION ALREADY
WITHIN CENTRAL ND, UNCERTAINTY LINGERS WITH RESPECT TO COVERAGE
OF LIGHT ICING. AS THE WAVE MOVES INTO CENTRAL MN, SYNOPTIC
FORCING STARTS TO WEAKEN AS THE MODEST JET MAINTAINING THE WAVE
STARTS TO LESSEN. THIS BRINGS UNCERTAINTY IN HOW MUCH PRECIP
MAY ACTUALLY BE ABLE TO PUNCH THROUGH THE DRY 800 MB LAYER.
THERE IS EVIDENCE OF MID LEVEL CONDITIONAL INSTABILITY ABOVE 700
MB WHICH INTRODUCES MORE SHOWERY-TYPE PRECIPITATION, AGAIN
LOWERING CONFIDENCE IN COVERAGE. IN OUR AREA, WE ALSO HAVE
DEEPER LOW LEVEL COLD LAYER UNDER WARM NOSE ALOFT. THIS MAY
PROMOTE SLEET IN ADDITION TO FREEZING RAIN. LASTLY, AS THE WAVE
MOVES EAST INTO MINNESOTA, COOLER AIR FILTERING IN BEHIND THE
DEPARTING MID LEVEL FORCING WILL HELP KEEP THE LOWEST 1 KM
SATURATED.
THE DEPARTING WAVE ALSO TAKES AWAY ICE NUCLEI ALOFT,
INTRODUCING POTENTIAL FOR FREEZING DRIZZLE. GUIDANCE DIFFERS IN
HOW DEEP THIS LOWEST, SUPERCOOLED LIQUID LAYER LINGERS OVER OUR
AREA, WITH SOME WHISKING MOISTURE AWAY BY MID MORNING, WHILE
OTHERS HOLD ONTO SUFFICIENTLY DEEP MOISTURE THROUGHOUT THE DAY
MONDAY.
LOOKING AT THE 12Z HREF SPECIFICALLY, NEIGHBORHOOD PROBABILITY
OF ICING 0.01" OR MORE IS AROUND 40% NEAR THE SD BORDER/TRI
STATE AREA TONIGHT INTO MONDAY MORNING.
THUS, WILL CONTINUE TO MESSAGE POTENTIAL FOR LIGHT ICING WITHIN
SOUTHEAST ND INTO WEST-CENTRAL MN VIA THE SPECIAL WEATHER
STATEMENT, BUT IF CONFIDENCE INCREASES IN MORE WIDESPREAD ICING,
A WINTER WEATHER ADVISORY MAY BE WARRANTED. DESPITE THE
UNCERTAINTY, WE ARE ALSO MESSAGING TO BE PREPARED FOR
POTENTIAL OF IMPACTED TRAVEL CONDITIONS FOR THE MONDAY MORNING
COMMUTE.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1022 PM CST SUN DEC 22 2024
CONDITIONS WILL CONTINUE TO DETERIORATE OVERNIGHT INTO MONDAY.
CEILINGS WILL DECREASE TO IFR/LIFR AT ALL TAF SITES BY AROUND
12Z MONDAY, WITH LOWER VSBYS POSSIBLE AROUND DVL. WINDS WILL BE
OUT OF THE NORTH, OR VARIABLE, ALL UNDER 10 KNOTS. INTO MONDAY
EVENING, WINDS WILL SHIFT SOUTHERLY BUT STILL BE LIGHT FOR THE
TAF PERIOD.
FGF WATCHES/WARNINGS/ADVISORIES
ND...WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR NDZ038-
039-049-052-053.
MN...WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR MNZ003-
024-027>032-040.
UPDATE...AH
DISCUSSION...CJ
AVIATION...AH
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