Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 011730
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1230 PM CDT SAT AUG 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT SAT AUG 1 2015

THE MAIN CONCERN IN THE SHORT TERM IS THE CHANCE FOR SEVERE
WEATHER LATE THIS AFTERNOON AND TONIGHT. A STRENGTHENING SURFACE
LOW IS STILL FORECAST TO MOVE SOUTHEAST TOWARD OUR AREA FROM NORTH
DAKOTA...WITH A WARM FRONT PUSHING EAST INTO WESTERN MN THIS
AFTERNOON...AND CONTINUING EAST TONIGHT. LOW LEVEL THETA-E
ADVECTION WILL BE QUITE STRONG AS SOUTHWESTERLY FLOW DEVELOPS
BEHIND THE WARM FRONT. SURFACE DEW POINTS SHOULD RISE WELL INTO
THE 60S ACROSS SOUTHWESTERN MN TODAY AND EXPAND EASTWARD TONIGHT.
MEANWHILE...THE LONGWAVE TROUGH OVER EASTERN NORTH AMERICA WILL
START TO SINK SOUTH AS THE MAIN UPPER LOW OVER HUDSON BAY STARTS
TO PUSH SOUTH. DEEP CYCLONIC FLOW FOR OUR AREA WILL RESULT. MID
LEVEL LAPSE RATES GREATER THAN 7C/KM WILL BE IN PLACE BY THIS
EVENING. SO...POPS EXPAND QUICKLY FROM WEST TO EAST ACROSS THE
AREA LATE THIS AFTERNOON. THE HI-RES CAMS DON/T OFFER GREAT
AGREEMENT...BUT THEY DO SUGGEST THE IDEA OF INITIAL THUNDERSTORMS
DEVELOPING LATE THIS AFTERNOON AHEAD OF A LARGER CLUSTER OF
THUNDERSTORMS EXPECTED AFTER 00Z. A STRENGTHENING LLJ WITH A
VEERING PROFILE AND WIND SPEEDS INCREASING WITH HEIGHT WILL
PROVIDE DEEP LAYER SHEAR VALUES IN EXCESS OF 40 KNOTS...COMBINED
WITH MUCAPE VALUES OF 2000-3000 J/KG. SUPERCELLS WILL CERTAINLY BE
POSSIBLE...ESPECIALLY WITH THE INITIAL DEVELOPMENT...AND ALL FORMS
OF SEVERE WEATHER WOULD BE POSSIBLE WITH THESE. AS THE EVENING
PROGRESSES...EXPECT STORMS TO CONGEAL INTO A CLUSTER AND POSSIBLE
MCS AFTER DARK. THE MAIN CONCERN WOULD THEN BE DOWNBURST WIND
POTENTIAL...AS THE PREVIOUS DISCUSSION MENTIONED...THE FORWARD
PROPAGATING CORFIDI VECTORS SUGGEST THAT IF AN MCS FORMS...IT
COULD SCREAM ACROSS THE AREA AT 60-70 MPH. HOWEVER...THE CAMS
LEAVE A LOT TO BE DESIRED IN TERMS OF AGREEMENT RIGHT NOW. THE
TIMING/PLACEMENT/AND INITIATION OF STORMS VARY QUITE A BIT SO POPS
WERE INCREASED INTO THE LIKELY CATEGORY FOR A PORTION OF THE CWA.
BY SUNDAY MORNING...MOST OF THE ACTIVITY SHOULD BE TO OUR SOUTH
AND EAST...BUT STILL CARRY SOME LOW END POPS IN WESTERN WI AS WE
MOVE THE OVERNIGHT STORMS EAST OF OUR AREA.

AS FAR AS TEMPERATURES ARE CONCERNED...WINDS WILL TURN
SOUTHWESTERLY BY THIS AFTERNOON...AND TEMPERATURES ARE GENERALLY
EXPECTED TO BE ABOUT 5 DEGREES WARMER THAN YESTERDAY AS THE WARM
FRONT PUSHES EAST...AND LOW LEVEL WARM AIR ADVECTION INCREASES
THIS AFTERNOON. DEW POINTS WILL BE ON THE RISE AS WELL...WITH MOST
OF THE AREA SEEING DEW POINTS IN THE MID 60S BY THIS EVENING...AND
OVERNIGHT LOWS WILL BE HELD IN THE MID 60S AS WELL THANKS TO THE
BOUNDARY LAYER MOISTURE.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 400 AM CDT SAT AUG 1 2015

SUNDAY...THE AFOREMENTIONED SFC LOW PRES SYSTEM WILL CENTER ITSELF
JUST NE OF THE MSP METRO BY DAYBREAK SUN MRNG WITH ITS CDFNT
SNAKING WSWWD ALONG THE MN/IA BORDER. MUCH...IF NOT ALL...ANY
OVERNIGHT ACTIVITY SHOULD BE WELL E OF THE WFO MPX CWFA BY SUN
MRNG. HOWEVER...EFFECTIVE CAA AND DRY AIR INTRUSION WILL NOT
COMMENCE UNTIL LATE IN THE DAY WITH THE DEPARTURE OF THE CDFNT SO
DEWPOINTS IN THE LOW 60S...AIDING MODEST INSTABILITY...PLUS THE
LLVL JET INVOF WRN WI WILL STILL ALLOW FOR THE POTENTIAL FOR STORM
RE-DEVELOPMENT SUN AFTN IN WRN WI. COVERAGE WILL BE SCATTERED AT
BEST...WITH BEST STORM STRENGTH WELL OFF TO THE SE IN THE WARM
SECTOR SO WILL NOT BE LOOKING FOR SEVERE WX DEVELOPMENT IN THE
CWFA. STORM POTENTIAL DROPS OFF WITH THE LOSS OF DAYLIGHT SUN...
SO AM ABLE TO RUN WITH A DRY FCST FOR SUN NIGHT.

MONDAY-TUESDAY...COOLER AND DRIER AIR WILL BE FELT ACRS THE CWFA
MON AND TUE AS CANADIAN HIGH PRES MOVES INTO THE AREA UNDERNEATH
DRY NW FLOW ALOFT. THIS WILL KEEP HIGH TEMPS IN THE 70S /AFTER
HIGHS PREVAILED IN THE 80S OVER THE WEEKEND/. DEWPOINTS WILL FALL
BACK TO THE LOW-MID 50S...MAKING FOR VERY COMFORTABLE CONDITIONS
FOR EARLY AUGUST.

WEDNESDAY-FRIDAY...CONFIDENCE IN THE FORECAST BEGINS TO WANE FOR
THE LATTER HALF OF THE UPCOMING WEEK AS MODEL DIFFERENCES IN THE
SYNOPTIC SETUP PLUS TIMING DIFFERENCES OF LOW PRESSURE CENTER
PROGRESSIONS PLUS UPPER LEVEL DISTURBANCES MAKE TRYING TO PINPOINT
WHICH DAYS ARE BETTER THAN OTHERS FOR THE POTENTIAL FOR PRECIP.
THERE IS ENOUGH CONFIDENCE TO RUN WITH AT LEAST CHC POPS FOR MUCH
OF THE PERIOD BUT ANYTHING HIGHER IS QUITE PROBLEMATIC TO
ADVERTISE. OF GREATER CONFIDENCE IS THAT THE COOL AIR WILL REMAIN
IN PLACE THROUGH THE LATTER HALF OF THE WEEK. HIGHS WILL REMAIN IN
THE 70S WHILE LOWS WILL REMAIN IN THE 50S TO AROUND 60.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1230 PM CDT SAT AUG 1 2015

TWO CONCERNS GOING FORWARD. THE FIRST IS TSRA DEVELOPMENT THIS
AFTERNOON AND EVENING AND THE SECOND IS THE POTENTIAL FOR MVFR OR
LOWER CIGS/VSBYS LATE TONIGHT FROM CENTRAL MN INTO WEST CENTRAL WI
DUE TO SHRA/TSRA THIS AFTERNOON/EVENING AND ALSO MOIST LOW LEVEL
CONDITIONS AHEAD OF AN APPROACHING COLD FRONT OVERNIGHT. BEGINNING
WITH THE FIRST CONCERN...SHORT TERM SOLUTIONS CONTINUE TO MEANDER
AROUND ON TIMING AND LOCATION WITH THE TSRA THIS AFTERNOON AND
EVENING. A FEW NOW SUGGEST NOTHING AT ALL. HENCE...CONFIDENCE IS
WANING A BIT. HOWEVER...ONE CAN/T OVERLOOK THE SHORT WAVE IN THE
CENTRAL DAKOTAS AND THE DRYING NOTED IN THE WV IMAGERY. AT THIS
POINT...I/M GOING TO USE TEMPO GROUPS OUT AHEAD OF THE PASSAGE OF
THIS SHORT WAVE. CAN/T USE PROB GROUPS DUE TO THE NINE HOUR RULE.
THE SECOND CONCERN DEALS WITH LOW 60 DEW POINTS TONIGHT AHEAD OF
THE COLD FRONT ALONG WITH LIGHT WINDS AND POTENTIAL WETTING GOING
INTO THE EVENING. CONFIDENCE IS NOT HIGH ON THIS SCENARIO (MVFR
CONDITIONS). THEREFORE...SOME FEW-SCT015-020 MENTIONED FOR NOW.
FINALLY...THE COLD FRONT WILL BE MOVING THROUGH THE TWIN CITIES
AND WESTERN WI SUNDAY AFTERNOON. THERE COULD BE SOME STORMS
DEVELOP ALONG AND AHEAD OF THE FRONT WHICH COULD IMPACT
KMSP...KRNH AND KEAU.

KMSP...VFR EXPECTED THROUGH THE PERIOD OUTSIDE OF ANY SHRA/TSRA
DEVELOPMENT. SOME SPRINKLES POSSIBLE LATE THIS AFTERNOON AS MID
LEVEL CLOUDINESS INCREASE WITH TSRA STILL POSSIBLE IN THE EARLY
EVENING. ANOTHER CHANCE FOR TSRA SUNDAY AFTERNOON AS A COLD FRONT
MOVES THROUGH BETWEEN 18Z-21Z.

/OUTLOOK FOR KMSP/
SUN NGT...VFR. WIND NW 5-10KTS.
MON...VFR. WIND NW 10-15KTS.
TUE...VFR. WIND N 5-10KTS.

&&

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

$$

SHORT TERM...SPD
LONG TERM...JPC
AVIATION...RAH


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