Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 281436
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
936 AM CDT TUE APR 28 2015

.UPDATE...
ISSUED AT 935 AM CDT TUE APR 28 2015

THE NORTHERN RED RIVER VALLEY WAS STILL SOCKED IN WITH FOG SO
EXTENDED THE DENSE FOG ADVISORY THERE ANOTHER COUPLE OF HOURS. AS
SOON AS THAT WENT OUT THE OBS AT GFK STARTED GOING UP IN
VISIBILITY. FIGURES. THE WEB CAMS AT DRAYTON AND PEMBINA ARE STILL
SHOWING A LOT OF FOG...ALTHOUGH THERE HAS BEEN SLOW IMPROVEMENT
OVER THE PAST HOUR. WILL HANG ONTO THE ADVISORY FOR ANOTHER HALF
HOUR OR SO AND THEN CANCEL THE WHOLE THING AT ONCE.

UPDATE ISSUED AT 642 AM CDT TUE APR 28 2015

NOW THAT IT IS DAYLIGHT THE WEB CAMS ARE MORE HELP. THEY INDICATE
WIDESPREAD VERY LOW VSBY DUE TO DENSE FOG WITHIN THE
VALLEY...WITH MORE PATCHY DENSE FOG TO THE WEST WITHIN THE DEVILS
LAKE BASIN. AT ANY RATE...MOST AREAS ARE 1/4SM AND WILL CONTINUE
THE DENSE FOG ADVISORY.

THE HENDRUM-ADA WEBCAM IN SHOWING DENSE FOG...AND WILL EXTEND THE
DENSE FOG ADVISORY INTO THIS AREA.

THERE IS A ALSO DENSE FOG IN A SMALL AREA AROUND VALLEY CITY...BUT
THIS AREA IS DETACHED FROM THE MAIN FOG AREA AND REMAINS
ISOLATED.

HRRR/RAP INDICATES THAT THE FOG WILL DISSIPATE BY 9AM-10AM.

UPDATE ISSUED AT 507 AM CDT TUE APR 28 2015

THE ZERO TO 1/4SM VSBY OBSERVATIONS ARE BECOMING MORE WIDESPREAD
ACROSS NORTHEAST NORTH DAKOTA AND THE NORTHERN RED RIVER VALLEY.
LATEST RAP GUIDANCE INDICATES THAT WINDS JUST ABOVE THE SURFACE
ARE BECOMING CALM ACROSS THIS AREA (LOOKING AT 950MB-925MB
WINDS)...WHICH IS LIKELY ALLOWING THE FOG TO BECOME MORE MATURE
(DEVELOP MORE THAN JUST 5 FEET ABOVE THE SFC). WEB CAMS ARE
BEGINNING TO INDICATE VSBY REDUCTIONS AS WELL. SINCE THE FOG SEEMS
MORE WIDESPREAD NOW AND THICKER...ISSUED A DENSE FOG ADVISORY FOR
THIS AREA. WILL NEED TO WATCH AREAS TO THE SOUTH AND EAST...BUT
THERE MAY NOT BE ENOUGH TIME FOR FOG FORMATION ANYMORE.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 325 AM CDT TUE APR 28 2015

INITIAL CONCERN WILL BE THE DENSE FOG THAT HAS DEVELOPED ACROSS
NORTHEAST NORTH DAKOTA (LIGHT WINDS AND LOW LEVEL MOISTURE FROM
THE SHOWERS). AUTOMATED SENSORS INDICATING 0SM-1/4SM VSBY...BUT
DOT WEB CAMS INDICATE DECENT VISIBILITY. A FEW OB SITES NEAR THE
INTERNATIONAL BORDER NOW FLUCTUATING BETWEEN 1/4SM AND AOA 3SM.
A SHERIFF REPORT INDICATES THE FOG IS VERY SHALLOW (4-5 FEET ABOVE
THE GROUND). CURRENT THINKING IS THAT THE FOG BECOMES VERY DENSE
RIGHT AFTER THE RAIN ENDS...BUT THIS DENSE FOG BECOMES PATCHY
AFTER AN HOUR OR TWO. LOOKING AT MODEL SOUNDINGS...THIS MAKES SOME
SENSE WITH A VERY DRY AIRMASS ABOVE THE SFC COMBINED WITH WINDS
NEAR OR ABOVE 10 KNOTS JUST ABOVE THE SFC. WILL CONTINUE TO
MONITOR WEB CAMS AND OBSERVATIONS...BUT FOR NOW THINKING A DENSE
FOG ADVISORY IS NOT NEEDED (WILL ISSUE NOWCASTS).

THE BAND OF FRONTOGENESIS SHOWERS FROM FARGO TO BAUDETTE WILL
CONTINUE TO PROPAGATE EAST/SOUTHEAST...EXITING THE REGION SHORTLY
AFTER 12Z.

UPPER RIDGE WILL BUILD INTO THE REGION TODAY AND WEDNESDAY. CLEAR
SKY AND LIGHT WINDS EXPECTED FOR THIS PERIOD. DAYTIME HIGHS WILL
BE IN THE MID-UPPER 60S TODAY...AND INTO THE 70S ON WEDNESDAY. THE
MAIN CHALLENGE WILL BE MIN TEMPS TONIGHT CONSIDERING THE IDEAL
RADIATIONAL COOLING CONDITIONS. WENT NEAR MODEL DEW POINT VALUES
FOR MIN TEMPS WHICH IS 5F-10F BELOW MOST GUIDANCE.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 325 AM CDT TUE APR 28 2015

WEDNESDAY NIGHT-THURSDAY NIGHT...UPPER RIDGE WILL SLOWLY PROPAGATE
EASTWARD WITH AN UPPER TROUGH MOVING THROUGH THUR NIGHT. DRY
WEATHER THROUGH MUCH OF THURSDAY...WITH TEMPS IN THE 70S. AS THE
UPPER TROUGH MOVES THROUGH THE REGION ANTICIPATE A BAND OF SHOWERS
THUR NIGHT.

FRIDAY-MONDAY...A PROGRESSIVE SPLIT FLOW PATTERN IS
EXPECTED...WITH THE NORTHERN BRANCH OF THE JET GENERALLY
MEANDERING NEAR THE US/CANADA BORDER. THE FLOW WILL BE RATHER
ZONAL FOR MUCH OF THE PERIOD...WITH WELL ABOVE AVERAGE TEMPS
CONTINUING INTO THE START OF THE WEEKEND AND SATURDAY LOOKING TO
BE THE WARMEST DAY. THE GLOBAL MODELS DO ALL INDICATE A FRONTAL
PASSAGE LATE SAT OR SUN BRINGING MODESTLY COOLER TEMPS TO THE
REGION TO START NEXT WEEK. AS FAR AS PRECIP
GOES...TIMING/PLACEMENT ISSUES BETWEEN THE MODELS LEAD TO LOW
CONFIDENCE...WITH THE GEM/ECMWF TAKING A STRONGER SHORTWAVE TROUGH
ACROSS S CANADA OVER THE WEEKEND...AND THE GFS DIGGING A WAVE
TOWARDS THE INTERNATIONAL BORDER. THESE DIFFERENCES...IN ADDITION
TO PLACEMENT OF OTHER EMBEDDED WAVES...WOULD IMPACT BOTH THE
POSITION OF SFC FEATURES AND THE LOCATION OF BEST MOISTURE
TRANSPORT/FORCING. RIGHT NOW HAVE KEPT SOME LOW END POPS MAINLY
SAT NIGHT INTO SUN NIGHT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 642 AM CDT TUE APR 28 2015

AFTER EARLY MORNING DENSE FOG AND/OR IFR/MVFR
CONDITIONS...ANTICIPATE CLEARING SKY AND VFR CONDITIONS FOR THE
REMAINDER OF THE PERIOD. THERE IS A LOW PROBABILITY FOR FOG
FORMATION WED MORNING...BUT THIS PROBABILITY IS TOO LOW TO MENTION
ATTM.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...DENSE FOG ADVISORY UNTIL 11 AM CDT THIS MORNING FOR NDZ008-016-
     027-030.

MN...DENSE FOG ADVISORY UNTIL 11 AM CDT THIS MORNING FOR MNZ001-002-
     004-007.

&&

$$

UPDATE...JR
SHORT TERM...TG
LONG TERM...TG/MAKOWSKI
AVIATION...TG






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