Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 301753
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1253 PM CDT SUN AUG 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT SUN AUG 30 2015

A FEW AREAS OF FOG AND LOW STRATUS HAD DEVELOPED ACROSS THE REGION
ONCE AGAIN THIS MORNING...WITH SOME SITES REPORTING VISIBILITY LESS
THAN A MILE. THIS LOW LEVEL MOISTURE WILL QUICKLY MIX OUT AS
SOUTHERLY WINDS INCREASE THIS MORNING. WARM AIR ADVECTION WILL
OVERSPREAD THE REGION THIS AFTERNOON WHICH SHOULD ALLOW TEMPERATURE
TO WARM INTO THE 80S AT MOST LOCATIONS IN MINNESOTA...AND UPPER 70S
IN WISCONSIN. THE GFS/NAM/RAP GUIDANCE SHOWS POTENTIAL FOR 90 DEGREE
READINGS THIS AFTERNOON IN WESTERN MN...AND WOULD BUY THAT IF THE
BOUNDARY LAYER WINDS WERE CLOSER TO 220DEG AS OPPOSED TO
190DEG...BUT MORE IMPORTANTLY THE SMOKE SHOULD FILTER OUT THE
INTENSE SUNSHINE AND TRY TO KEEP TODAYS HIGHS IN CHECK.

CONTINUED WITH A DRY FORECAST...AND INCLUDED PATCHY FOG ALONG I-90
AND IN WEST CENTRAL WISCONSIN. HOWEVER NOT ANTICIPATING MUCH DENSE
FOG SINCE DEWPOINT DEPRESSIONS WILL BE A TAD LARGER...AND THE
SYNOPTIC PRESSURE GRADIENT WILL BE STRONGER WHICH SHOULD KEEP UP THE
SURFACE WINDS. OVERNIGHT LOWS WILL FALL INTO THE MID 60S ACROSS THE
AREA.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 330 AM CDT SUN AUG 30 2015

THE LARGE SCALE PATTERN WON/T CHANGE MUCH THROUGH THE PERIOD...
WITH SOUTHWEST UPPER FLOW PREVAILING AS THE WESTERN TROUGH AND
EASTERN RIDGE DON/T APPEAR TO MOVE MUCH UNTIL THE VERY END OF THE
FORECAST PERIOD. AS A RESULT... WE/LL SEE MAINLY WARM AND DRY
WEATHER. THERE WILL BE A FEW CHANCES FOR SOME PCPN AS SHORTWAVES
EJECT FROM THE WESTERN TROUGH AND SHEAR OUT AS THE TRY TO WORK
INTO THE UPPER RIDGE. EVENTUALLY... OVER THE WEEKEND... IT LOOKS
LIKE WE SHOULD GET ENOUGH EASTWARD SHIFT OF THE MAIN UPPER TROUGH
TO PUSH THE SURFACE LOW AND ASSOCIATED FRONTAL BOUNDARY INTO THE
AREA FOR MORE WIDESPREAD CHANCES OF PCPN. THE GUIDANCE IS IN
GENERAL AGREEMENT ON THE OVERALL LARGE SCALE PATTERN... ALTHOUGH
THERE ARE SOME DIFFERENCES IN HOW QUICKLY THE RIDGE BREAKS
DOWN/SHIFTS EAST... WHICH AFFECTS HOW QUICKLY WE SEE THE BETTER
CHANCES OF PCPN MOVE INTO THE AREA. THE ECMWF APPEARS TO BE
SLOWEST IN DOING SO... WHILE THE GFS... FIM... AND GEM ARE MORE
PROGRESSIVE. PATTERN RECOGNITION FOR THIS TIME OF YEAR WOULD
SUGGEST A SLOWER EVOLUTION MAY BE THE MORE LIKELY OUTCOME... BUT
THERE IS A FAIR AMOUNT OF SPREAD IN THE ECMWF ENSEMBLE MEMBERS...
SO TOUGH TO BE TOO CONFIDENT IN GOING WITH ONE PARTICULAR
SOLUTION. AS A RESULT... WILL GO WITH A CONSENSUS APPROACH... WITH
PERHAPS SLIGHTLY MORE WEIGHT ON THE ECMWF.

A WEAK SHORTWAVE WILL MOVE BY MAINLY TO OUR NORTHWEST MONDAY INTO
MONDAY NIGHT... WITH ANY PCPN PRIMARILY OCCURRING TO OUR NORTH.
INCLUDED SOME LOW CHANCE POPS OVER THE FAR NORTHWEST AND NORTH
MONDAY NIGHT ALONG THE REMNANTS OF THE WASHED OUT FRONT ASSOCIATED
WITH THAT UPPER WAVE. LINGERED SOME LOW CHANCE POPS OVER THE FAR
NORTH ON TUESDAY IN THE VICINITY OF THE BAROCLINIC ZONE... BUT
ANYTHING THAT OCCURS WOULD BE ISOLATED. THERE IS A CHANCE FOR SOME
SHRA/TSRA OVER THE SOUTH AND EAST TUESDAY NIGHT AND WEDNESDAY IN
ASSOCIATION WITH SOME ENHANCED WARM ADVECTION AND ELEVATED
INSTABILITY ADVERTISED BY THE MEDIUM RANGE GUIDANCE... BUT ONCE
AGAIN WOULD NOT EXPECT ANYTHING TO WIDE SPREAD GIVEN THE LACK OF
SIGNIFICANT/PERSISTENT LARGE SCALE FORCING. SIMILAR CONDITIONS
PERSIST ACROSS MUCH OF THE AREA WEDNESDAY NIGHT INTO THURSDAY...
SO WILL NEED TO CONTINUE SOME CHANCE POPS. HOWEVER... AT THIS
POINT WEDNESDAY NIGHT WOULD APPEAR TO BE THE BETTER TIME FRAME FOR
SHRA/TSRA GIVEN THE NOCTURNAL ENHANCEMENT OF THE LOW LEVEL JET.
WITH THE EXCEPTION OF HIGHLY ISOLATED ACTIVITY THURSDAY NIGHT AND
FRIDAY SHOULD BE DRY AS HEIGHTS RISE AND THE BETTER LOW-MID LEVEL
WARM ADVECTION LOOK TO REFOCUS BACK TO THE WEST AGAIN. HOWEVER...
AS WE HEAD INTO SATURDAY WE SHOULD SEE INCREASING CHANCES START TO
SHIFT EASTWARD INTO THE AREA FROM THE PLAINS AS THE MAIN WESTERN
TROUGH STARTS TO PUSH EAST INTO THE NORTHERN PLAINS. HOWEVER...
THIS IS ALSO WHEN SIGNIFICANT TIMING DIFFERENCES EXIST IN THE
GUIDANCE... SO IT/S STILL A BIT EARLY TO PIN DOWN WHEN/WHERE THE
BEST CHANCES FOR SHRA/TSRA WILL BE OVER THE WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1251 PM CDT SUN AUG 30 2015

STRONGER WINDS AND ASSOCIATED MECHANICAL MIXING HELPED CLEAN
STRATUS OUT MUCH FASTER THIS MORNING THAN WHAT WE SAW YESTERDAY.
REALLY...THE ONLY QUESTION THIS TAF PERIOD IS WHERE DOES THE
STRATUS RETURN TONIGHT. FORECAST SOUNDINGS FROM THE NAM LOOK LIKE
CARBON COPIES OF THIS MORNINGS SOUNDING HERE AT MPX...SO STRATUS
IS LOOKING LIKE A REAL POSSIBILITY FOR A THIRD NIGHT IN A ROW. ONE
BIG DIFFERENCE THOUGH BETWEEN TODAY AND YESTERDAY AS WE HAVE
STRONGER WINDS TODAY...WHICH MEANS BETTER BOUNDARY LAYER MIXING.
THIS IS WHAT ADDS UNCERTAINTY TO THE STRATUS FORECAST FOR
TONIGHT...IS THIS MIXING ENOUGH TO KEEP THE STRATUS FARTHER EAST
TONIGHT. FOR NOW...PLAYED UP THE STRATUS THREAT AT WIS TERMINALS
WHERE WINDS ARE WEAKEST TODAY...BUT IT IS CERTAINLY POSSIBLE TO
SEE STRATUS AS FAR WEST AS MSP/STC AGAIN TONIGHT.

KMSP...WILL BE VFR WITH SOUTH WINDS THE REST OF THE DAY. CURRENT
THINKING IS BETTER MIXING TODAY WILL MAKE IT MORE DIFFICULT TO GET
THE STRATUS GOING TONIGHT...BUT IF YOU WERE TO GO STRAIGHT OFF THE
NAM BUFR SOUNDING...MSP WILL SEE A REPEAT PERFORMANCE ON THE
STRATUS FOR A THIRD NIGHT IN A ROW. DECIDED TO GO THE SCT008 ROUTE
FOR NOW UNTIL THERE IS MORE CONFIDENCE ON WHERE STRATUS WILL END
UP TONIGHT.

/OUTLOOK FOR KMSP/

TUE-THU...VFR WINDS S 5-15 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...JRB
LONG TERM...999
AVIATION...MPG


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