Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 181730
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
1230 PM CDT MON AUG 18 2014

.UPDATE...
ISSUED AT 1230 PM CDT MON AUG 18 2014

THE SPC NON-SUPERCELL PARAMETER HAS BEEN INCREASING OVER THE PAST
COUPLE HOURS ALONG THE SFC TROUGH...AND IS NOW INTO THE 1-2 RANGE.
THERE IS SUFFICIENT LOW LEVEL CAPE AND SFC VORTICITY ALONG THIS
FEATURE...ALTHOUGH THE LOW LEVEL LAPSE RATES ARE STILL LOW. AT ANY
RATE...GIVEN THE UPPER CIRCULATION OVERHEAD...THERE IS THE
POTENTIAL FOR FUNNEL CLOUDS...AND POSSIBLY A WEAK TORNADO. WILL
EVALUATE THE ACTIVITY AND ISSUE A STATEMENT IF THIS POTENTIAL
BECOMES MORE LIKELY.

UPDATE ISSUED AT 1003 AM CDT MON AUG 18 2014

FORECAST THINKING REMAINS VALID AND ONLY MINIMAL CHANGES ARE
REQUIRED FOR TODAY. CURRENTLY...THE RADAR INDICATES MORE
WIDESPREAD SHOWERS ACROSS THE NORTHERN VALLEY INTO NORTHWEST
MINNESOTA. THIS ACTIVITY IN AN AREA OF HIGHER 850MB MOISTURE AND
WEAK WARM AIR ADVECTION...WHICH WILL CONTINUE THROUGH MUCH OF THE
MORNING HOURS. ANTICIPATE COVERAGE OF SHOWERS TO INCREASE THIS
AFTERNOON ALONG AND EAST OF THE VALLEY WITH COLD POOL OVERHEAD
COMBINED WITH SOME HEATING (AND SYNOPTIC FORCING).

PWATS WILL REMAIN AROUND 1.4 INCHES...AND LOCALIZED HEAVY RAIN
POSSIBLE. OTHERWISE...INSTABILITY EXPECTED TO REMAIN WEAK
CONSIDERING LOW CONVECTIVE TEMPS KEEPING CLOUDS AROUND...AND VERY
WEAK DEEP LAYER SHEAR.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 340 AM CDT MON AUG 18 2014

EARLY AM WV IMAGERY SHOWS THE MAIN UPPER LOW PUSHING SOUTHEASTWARD
ACROSS MANITOBA. CONVECTION THAT FIRED LATE YESTERDAY HAS
WEAKENED...BUT SOME RE-DEVELOPMENT HAS OCCURRED OVERNIGHT AS THE
UPPER FORCING STRENGTHENS ASSOCIATED WITH THE UPPER LOW. WITH A
WEAK SFC TROUGH ACROSS THE REGION AND GENERALLY LIGHT WINDS...SOME
FOG HAS DEVELOPED...MOST NOTABLY IN WC MN. THE FOG HAS BEEN QUITE
DENSE TO THE SOUTHEAST OVER CENTRAL MN...SO A CONCERN OVER THE
NEXT FEW HOURS WILL BE FOG COVERAGE AND DENSITY IN THIS AREA.

THE MAIN CHALLENGE LATER IN THE DAY WILL BE PRECIP CHANCES. WITH
THE SFC TROUGH SLOWLY WORKING EAST AND THE UPPER LOW
SOUTHEASTWARD...EXPECT SOME SHOWERS AND THUNDER (ALTHOUGH SEVERE
IS NOT EXPECTED). THE NAM/GFS/ECMWF ALL INDICATE THE HIGHEST QPF
WILL BE ACROSS THE EASTERN CWA...CLOSER TO THE SFC TROUGH AND
STRONGEST UPPER FORCING THIS AFTERNOON. PWATS WILL BE AROUND 1.4
INCHES THIS AFTERNOON OVER THE EAST...SO THERE WILL BE SOME
HEAVIER DOWNPOURS IN SPOTS. CURRENT FORECAST TEMPS ARE IN THE
MID/UPPER 70S...BUT CLOUD COVER WILL PLAY A ROLE ON TEMP TRENDS
TODAY.

THE UPPER LOW WILL MOVE EAST ACROSS NORTHERN MINNESOTA TONIGHT.
MUCH OF THE AREA WILL DRY OUT OVERNIGHT...WITH SOME SHOWERS
PERSISTING MAINLY EAST OF THE VALLEY. WITH LIGHT WINDS AND NOT
MUCH CHANGE IN SFC MOISTURE...THERE COULD SOME FOG DEVELOPMENT
POTENTIALLY.

WEAK SFC RIDGING WILL SPREAD ACROSS THE REGION TUESDAY UNDERNEATH
SHORTWAVE RIDGING ALOFT. THE UPPER LOW ACROSS THE WESTERN GREAT
LAKES MAY BE CLOSE ENOUGH TO PROVIDE A FEW DIURNAL SHOWERS/STORMS
EAST OF THE VALLEY. WOULD ALSO EXPECT DIURNAL CU DEVELOPMENT TO BE
GREATEST IN THIS AREA. OTHERWISE...TUESDAY SHOULD BE A PLEASANT
DAY WITH LIGHT WINDS AND SEASONABLE TEMPS.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 340 AM CDT MON AUG 18 2014

UPPER TROUGHING DEVELOPING OVER THE WESTERN US BY TUESDAY NIGHT WILL
AID IN SFC LOW PRESSURE DEVELOPMENT ACROSS THE HIGH PLAINS...WITH
SFC WINDS BECOMING SOUTHERLY DOWNSTREAM. THE GLOBAL MODELS DEPICT A
SHORTWAVE TROUGH LIFTING NORTHEASTWARD INTO THE N PLAINS ON
WEDNESDAY AS THE UPPER FLOW BECOMES SOUTHWESTERLY. THE
GEM/NAM/ECMWF ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING AND
POSITION OF THE WAVE...WHILE THE GFS IS FARTHER SOUTH. THE MODEL
CONSENSUS WOULD YIELD THE HIGHEST RAIN CHANCES LATE WED/WED NIGHT
WITHIN THE WARM...MOIST ADVECTION ZONE AHEAD OF THE WAVE. TEMPS
WILL CONTINUE NEAR AVERAGE FOR MID-WEEK.

00Z RUNS OF ECMWF/GEM/GFS ALL INDICATE A 500 MB TROUGH OVER WRN
CANADA INTO NRN ROCKIES.  SEVERAL SHORT WAVES WILL COME OUT OF THE
EASTERN PACIFIC INTO THE NRN ROCKIES AND THEN INTO NRN PLAINS IN THE
THURSDAY THROUGH SUNDAY PERIOD.  TIMING AND STRENGTH OF EACH WAVE IS
AS YOU SUSPECT VARIABLE RUN TO RUN AND MODEL TO MODEL.  BUT SOME
AGREEMENT IS THAT ONE SUCH WAVE AND RAIN MAKER WILL MOVE ACROSS
THURSDAY WITH ANOTHER SYSTEM FRI NIGHT INTO SATURDAY.  GRADUALLY
COOLER THRU THE PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1230 PM CDT MON AUG 18 2014

SFC LOW PRESSURE OVER THE FAR NORTHERN RED RIVER VALLEY WILL
RESULT IN VARIABLE WIND CONDS WITHIN AND EAST OF THE VALLEY AS
WELL AS MULTIPLE LAYERS OF CLOUD DECKS PREDOMINANTLY IN THE MVFR
RANGE. WINDS WILL SHIFT NW IN EASTERN ND AND MAY BECOME GUSTY IN
VCNTY OF TSTM ACTIVITY EXPECTED TO IMPACT MAINLY FAR AND BJI THIS
AFTN. TSTM ACTIVITY WILL TAPER OFF IN EARLY EVENING HOWEVER MVFR
CIGS OVER TVF AND BJI WILL STRUGGLE TO GET OUT OF MVFR RANGE UNTIL
TOMORROW MORNING. FOG IS A POTENTIAL AT BOTH TVF AND GFK...WHERE
WINDS WILL BE THE LIGHTEST OR CALM.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&

$$

UPDATE...TG
SHORT TERM...MAKOWSKI
LONG TERM...MAKOWSKI/RIDDLE
AVIATION...SPEICHER




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