Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 262335
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
635 PM CDT SUN JUL 26 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 340 PM CDT SUN JUL 26 2015

BAND OF ENHANCED INSTABILITY HAS DEVELOPED AHEAD OF A WEAK SFC
TROUGH THAT STRETCHED FROM ABOUT MARSHALL DOWN TOWARD MASON CITY.
CAMS HAVE BEEN SHOWING ISOLATED SHOWERS/STORMS DEVELOPING AHEAD OF
THIS BOUNDARY ALL DAY...AND RADAR CONFIRMS THAT THAT IS INDEED
HAPPENING RIGHT NOW. FOLLOWING THE IDEA OF THE CAMS...THIS LOOKS TO
BE DIURNALLY DRIVEN...SO CARRIED AN ISO THUNDER WORDING IN THE
FORECAST UNTIL ABOUT SUNSET.

FOR THE REST OF THE PERIOD...DECIDED TO KEEP THE FORECAST DRY...AS
ALL OF THE CAMS AND THE ECMWF ARE DRY THROUGH THE PERIOD. WITH THAT
SAID...THERE ARE A COUPLE OF OUTSIDE CHANCES FOR SEEING PRECIP
MONDAY AFTERNOON...BUT RATHER THAN PLASTER LOW END POPS ACROSS A
LARGE SWATH OF THE AREA WHEN MOST PEOPLE WILL NOT SEE
ANYTHING...OPTED TO GO DRY. THE TWO AREAS TO WATCH THOUGH FOR MONDAY
AFTERNOON WOULD BE FAR ERN MN INTO WRN WI AND FAR WRN MN LATE IN THE
AFTERNOON. FOR THE MN/WI BORDER AREA...THEY WILL BE ON THE ERN EDGE
OF A MID-LEVEL WARM BUBBLE AND CAP AND WE COULD SEE A SHOWER OR TWO
POP HERE IN THE AFTERNOON...BUT WITH NO FORCING MECHANISM...FAVORED
A DRY FORECAST FOR NOW. FOR FAR WRN MN LATE MONDAY AFTERNOON...THEIR
CHANCE WILL COME AS THE LLJ AND ASSOCIATED MOISTURE TRANSPORT STARTS
TO PICK UP IN STRENGTH ACROSS THE DAKOTAS. WE COULD SEE ELEVATED
CONVECTION DEVELOP IN THE LLJ DURING THE AFTERNOON THAT MAY SNEAK
INTO WRN MN LATE IN THE AFTERNOON...THOUGH WE ARE NOT EXPECTING
PRECIP CHANCES TO REALLY START RAMPING UP UNTIL 3Z AND LATER ON
TUESDAY...WHICH WILL BE DISCUSSED IN MORE DETAIL IN THE LONG TERM
SECTION.

FOR TONIGHT...WITH THE WARM FRONT LIFT NORTH THROUGH IOWA...WE WILL
HAVE MOIST ESE WINDS THROUGH THE NIGHT. THIS IS A CLIMATOLOGICALLY
FAVORED DIRECTION FOR DEVELOPING LOW STRATUS AND FOG. SREF PROBS FOR
CIGS UNDER 3K FT DO SHOW THIS POTENTIAL FOR ALONG AND SOUTH OF THE
MN RIVER. THROUGH 9Z...THE HRRR SHOWS THE REGION BEING STRATUS
FREE...BUT THE 0-1KM RAP CONDENSATION PRESSURE DEFICITS /CPD/ GET
QUITE LOW IN SOUTH CENTRAL MN...SO WOULD NOT BE SURPRISED IF FOLKS
DOWN ALONG I-90 WAKE UP TO 1-2 MILE VSBYS AND 300 FOOT CIGS MONDAY
MORNING.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 340 PM CDT SUN JUL 26 2015

THE DEEP UPPER TROUGH TO OUR NORTHWEST OF THE FORECAST AREA WILL
PASS THROUGH THE NORTHERN ROCKIES...THEN BECOME A CLOSED OFF LOW
OVER AS IT MOVES EAST NORTHEAST ALONG THE US/CANADIAN BORDER AND
INTO SOUTHERN SASKATCHEWAN AND MANITOBA ON TUESDAY. THIS LOW IS
HIGHLY ANOMALOUS FOR LATE JULY WITH 150-160 METER 12HR 500MB
HEIGHT FALLS ALONG THE BORDER AND 180-200 METER FALLS NORTH OF THE
BORDER TUESDAY NIGHT...IT LOOKS MORE LIKE A SPRING/WINTER UPPER
LOW. THEREFORE...THE BEST SEVERE THREAT IS NORTH AND WEST OF THE
FORECAST...HOWEVER...LOCALLY WE EXPECT A LINE OF THUNDERSTORMS TO
PASS THROUGH THE FORECAST AREA MONDAY NIGHT INTO TUESDAY MORNING. LIFT
WILL ACCOMPANY THE APPROACHING TROUGH ALONG WITH A NOCTURNALLY
FAVORED TIME FOR STORMS TO DEVELOP WITHIN A LLJ/WARM AIR ADVECTION
REGIME ON MONDAY NIGHT. PWATS THAT APPROACH 2" - 2000 J/KG OF
MLCAPE - A 13500FT WARM LAYER - SUGGEST HEAVY RAIN AND THE THREAT
FOR FLASH FLOODING IS PROBABLY THE BIGGEST HAZARD. THE 925-700MB
MOISTURE TRANSPORT LEANS OVER THE FORECAST AREA DURING THE DAY
TUESDAY WITH THE SURFACE TROUGH PASSING THROUGH. THEREFORE...WE
COULD KEEP SHOWERS/STORMS MOST OF THE DAY AND AT THE VERY LEAST
CLOUD COVER COULD MEAN HIGHS ARE CLOSER TO 80 THAN THE UPPER 80S
CURRENTLY IN THE FORECAST. THE SPEED OF THE WARM FRONTAL PASSAGE
IS STILL SOMEWHAT UNCERTAIN...BUT THE MOISTURE TRANSPORT IS SOLID
BY TUESDAY MORNING. THE PRONOUNCED UPPER TROUGH AND BEST DYNAMICS
ARE NORTH OF THE AREA. THE COLD FRONT SHOULD FINALLY CLEAR THE
FORECAST AREA TUESDAY NIGHT...BRINGING IN LESS HUMID AIR WED-FRI AS
A SURFACE HIGH PRESSURE SYSTEM SLIDES ACROSS THE MID-MISSISSIPPI
RIVER VALLEY BENEATH NORTHWESTERLY FLOW ALOFT WHICH WILL PERSIST
THROUGH THE REMAINDER OF THE FORECAST PERIOD. WE ALSO THINK
WEDNESDAY COULD BRING W-NW WIND GUSTS BETWEEN 30-40MPH IN THE COOL
ADVECTION BEHIND THE COLD FRONT. TEMPERATURES SHOULD ALSO
GRADUALLY MODERATE BY FRIDAY BEFORE ANOTHER COLD FRONT MOVES
THROUGH THE ARE FOR THE FIRST HALF OF THE WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 635 PM CDT SUN JUL 26 2015

SCATTERED SHOWERS IN SOUTHERN MN WILL CONTINUE TO DISSIPATE
THROUGH SUNSET...AND VFR CONDITIONS UNDER MOSTLY CLEAR SKIES ARE
EXPECTED AT ALL TERMINALS FOR THE NEXT SEVERAL HOURS.
HOWEVER...A MOIST BOUNDARY LAYER...SOUTHEASTERLY FLOW...AND A
DEVELOPING INVERSION COULD LEAD TO THE DEVELOPMENT OF SOME PATCHY
FOG/LOW STRATUS ACROSS OUR REGION BY THE EARLY MORNING MONDAY.
HAVE INCLUDED LIFR CONDITIONS AT THE EAU TERMINAL FROM
10-13Z...WHERE WINDS COULD GO CALM UNDER A HIGH PRESSURE CENTER
AND CLIMATOLOGY FAVORS FOG DEVELOPMENT AT THIS LOCATION. SHORTLY
AFTER SUNRISE...FOG WILL DISSIPATE AND VFR CONDITIONS ARE EXPECTED
TO PREVAIL THROUGH THE REMAINDER OF THE PERIOD. A COUPLE MODELS
HAVE SHOWN SOME ISOLATED CONVECTION DEVELOPING OVER
WESTERN/CENTRAL MN BY MONDAY EVENING...BUT CONFIDENCE IS TOO LOW
TO INCLUDE ANY MENTION IN THE TAFS.

KMSP...WINDS WILL CONTINUE TO DECREASE TO BELOW 5 KTS OVERNIGHT
UNDER MOSTLY CLEAR SKIES. PATCHY FOG CANNOT BE RULED OUT AROUND
SUNRISE...BUT CHANCES OF SIGNIFICANT VISIBILITY REDUCTION REMAIN
LOW FOR NOW. SOUTHEASTERLY WINDS WILL INCREASE TO AROUND 10-15
KTS BY THE LATE MORNING AND AFTERNOON...AND VFR IS EXPECTED TO
PREVAIL WITH CLOUD COVER GRADUALLY INCREASING BY MONDAY EVENING.

/OUTLOOK FOR KMSP/
TUE...VFR WITH IFR/MVFR PSBL IN TSRA. WINDS S BCMG SW 10-20 KTS.
WED...VFR. WINDS W 15-20G30KTS.
THU...VFR. WINDS W 10-15 KTS.

&&

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

$$

SHORT TERM...MPG
LONG TERM...CLF
AVIATION...ADL



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