Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 030853
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
349 AM CDT MON AUG 3 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT MON AUG 3 2015

TODAY AND TONIGHT...SFC ANALYSIS DEPICTS A CDFNT FROM THE ERN GRT
LKS WSWWD OVER SRN MI TO NRN IL AND SRN IA. IT IS THIS FRONT WHICH
PUSHED THRU LATE YDA RESULTING IN THE MUCH COOLER/DRIER AIR
EXPERIENCED THIS MRNG WITH CLR SKIES. THIS COOLER/DRIER HIGH PRES
AIRMASS WILL REMAIN OVER THE AREA THRU TNGT...KEEPING MUCH OF THE
CLOUD COVER ASSOCIATED WITH THE DEEP HUDSON BAY UPR LVL LOW TO THE E
OF THE WFO MPX CWFA. THAT SAID...SOME WOBBLING OF THE LARGE UPR LOW
WITH SEVERAL SHORTWAVE SPOKES OF ENERGY ROTATING ARND THE UPR LOW
MAY BRING SOME CLOUD COVER TO FAR NERN PORTIONS OF THE CWFA THIS
AFTN BUT RAIN SHOWERS ARE EXPECTED TO REMAIN WELL OFF TO THE E. THE
UPR LOW WILL BEGIN TO MOVE FURTHER E TNGT WHILE RIDGING OUT WEST
EXPANDS SLIGHTLY EWD...MAKING FOR CLR SKIES UPCOMING TNGT INTO TUE
MRNG. AS ALLUDED TO AT THE START...TEMPERATURES WILL RUN NOTICEABLY
COOLER AND HUMIDITY LEVELS WILL BE MUCH LOWER. HIGHS TDA WILL HIT
THE MID-UPR 70S WHILE DEWPOINTS CAP OUT IN THE LWR 50S...AND THIS
WILL BE FOLLOWED BY LOWS EARLY TUE MRNG IN THE UPR 40S TO MID 50S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 349 AM CDT MON AUG 3 2015

THE LONG TERM PERIOD STARTS OFF QUIET AND PLEASANT. WITH THE UPPER
LOW STILL PARKED OVER HUDSON BAY...THE UPPER MIDWEST WILL CONTINUE
TO BE FED DRY NORTHWESTERLY FLOW FROM CANADA AS SURFACE HIGH
PRESSURE STAYS WITH US THROUGH THE DAY. HIGH TEMEPRATURES
APPROACHING 80 WITH DEW POINTS IN THE LOW 50S WILL FEEL VERY
COMFORTABLE FOR MOST. THERE COULD BE SOME CUMULUS DEVELOPMENT
DURING THE DAY AS CU RULE INDICATES SLIGHTLY NEGATIVE VALUES IN
EASTERN MN AND WESTERN WI...COINCIDING WITH CYCLONIC CIRCULATION
ON THE BACK SIDE OF THE LONG WAVE TROUGH.

THE FORECAST BECOMES QUITE MURKY WEDNESDAY AND BEYOND.
DISAGREEMENT AMONG THE LATEST DETERMINISTIC SOLUTIONS WAS
PRONOUNCED. WHILE THE GFS WOULD INDICATE THETA-E ADVECTION AND PV
ADVECTION CAUSING SHOWERS AND THUNDERSTORMS WEDNESDAY FOR WESTERN
MN...THE EC HOLDS THAT ACTIVITY OFF COMPLETELY...AND THE NAM IS A
TAD SLOWER THAN THE GFS AND KEEPS MOST OF THE PRECIP WEST OF OUR
AREA. THE GFS HAS BECOME AN OUTLIER IN HOW QUICKLY THE WAVE MOVES
EAST...SO TRENDED THE FORECAST TOWARD THE ECMWF/NAM...MEANING
BRINGING THE PRECIP IN SLOWER...BUT WITH ALL THE SPREAD IN THE
SOLUTIONS...KEPT SOME 20 TO 30 PERCENT POPS TO EXTREME WESTERN MN
DURING THE DAY ON WEDNESDAY...MAINLY LATE AFTERNOON. ON WEDNESDAY
NIGHT...THE EC AND CANADIAN INDICATE DECENT AGREEMENT IN WORKING A
MID LEVEL WAVE FROM ND ACROSS MN BY THURSDAY MORNING...AND
SPREADING PRECIP THROUGH DURING THAT TIME...BUT THE NAM IS
COMPLETELY DRY AND THE GFS WANTS THE PRECIP CONFINED TO SW MN WITH
THE VORTICITY MAX FROM THE POTENTIAL PRECIP EARLIER IN THE DAY.
THE EC AND GFS FINALLY DO AGREE ON ANOTHER SHORTWAVE QUICKLY
MOVING IN THURSDAY AFTERNOON AND THURSDAY NIGHT SPREADING BROAD
LIFT ACROSS THE AREA AND A SHOT FOR ADDITIONAL RAINFALL.

IN REALITY...DUE TO THE DIFFERENCES IN THE GUIDANCE...THERE IS A
LOT OF 20-40 PERCENT POPS CURRENTLY IN THE FORECAST FROM WEDNESDAY
THROUGH FRIDAY...BUT ONCE THE GUIDANCE CAN START TO OFFER A BETTER
SENSE OF WHAT WE CAN EXPECT TO ACTUALLY OCCUR...POPS WILL LIKELY
BE ABLE TO BE CONSOLIDATED SPATIALLY AND TEMPORALLY.

CONFIDENCE IN THE WEEKEND PRECIPITATION FORECAST IS EXTREMELY LOW
GIVEN THE VARIABILITY IN THE GUIDANCE AND HOW THE VARIOUS SOLUTIONS
FOR HANDLING THE WAVES WE FIRST MUST DEAL WITH WEDNESDAY THROUGH
FRIDAY. THE GFS AND EC BOTH INDICATE A CLOSED UPPER LOW PROGRESSING
EAST-SOUTHEAST FROM SOUTHERN CANADA THROUGH NORTHERN MN...BUT DIFFER
IN BOTH PLACEMENT AND TIMING. THE GENERIC ALLBLEND OF THE MODELS NOW
SMOTHERS THE ENTIRE AREA IN 20-30 POPS FOR THE ENTIRE
WEEKEND...LARGELY DUE TO THE TIMING DIFFERENCES IN THE HANDLING OF
THE UPPER LOW. WE`LL HAVE TO CARRY THESE LOW END/LOW CONFIDENCE POPS
UNTIL MORE CLARITY CAN BE GAINED FROM THE GUIDANCE IN FUTURE RUNS.


.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1047 PM CDT SUN AUG 2 2015

VFR CONDITIONS THROUGHOUT. NORTHWEST WINDS PICK UP MID
MORNING...WITH AFTERNOON GUSTS NEAR 20KTS.

KMSP...
VFR CONDITIONS THROUGHOUT. NORTHWEST WINDS PICK UP MID
MORNING...WITH AFTERNOON GUSTS NEAR 20KTS.

/OUTLOOK FOR KMSP/
TUE...VFR. WIND NW AT 5-10 KTS.
WED...VFR. CHC MVFR SHRA/TSRA. WIND E AT 5-10 KTS.
THU...VFR. CHC MVFR SHRA/TSRA. WIND E AT 10 KTS.


&&

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

$$

SHORT TERM...JPC
LONG TERM...SPD
AVIATION...JRB



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