Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 011958
AFDMPX

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

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 258 PM CDT SAT AUG 1 2015

ACCAS CONTINUES TO INCREASE ACROSS CENTRAL AND SOUTHERN MN AT MID
AFTERNOON AS STRONG LOW/MID LEVEL THETA-E ADVECTION INCREASES.
SHOWERS HAVE BEGUN TO SPROUT ACROSS WEST CENTRAL MN...AHEAD OF A
SHORT WAVE AND SURFACE LOW PRESSURE SYSTEM LOCATED OVER THE
CENTRAL DAKOTAS. THE SHORT WAVE WILL MOVE INTO CENTRAL AND
SOUTHERN MN THIS EVENING AND REACH WESTERN WI LATE IN THE NIGHT.
FORCING AND INSTABILITY AHEAD OF THIS FEATURE SHOULD YIELD SCT
CONVECTION SPREADING ACROSS THE FA LATE THIS AFTERNOON AND
EVENING. CONSENSUS ON TIMING AND LOCATION BETWEEN THE CAMS IS
RATHER POOR WITH SOME SOLUTIONS NOT SHOWING MUCH AT ALL OCCURRING
TONIGHT. BASED ON THE TIMING OF THE SHORT WAVE...ALLOWED FOR SCT
THUNDERSTORMS TO SPREAD FROM WEST CENTRAL INTO CENTRAL MN FOR THE
REMAINDER OF THE AFTERNOON WITH THE ACTIVITY REACHING INTO THE
TWIN CITIES AND SOUTH CENTRAL MN DURING THE EARLY EVENING AND
ACROSS WEST CENTRAL WI DURING THE MID TO LATE EVENING HOURS.

THERE IS A THREAT FOR SEVERE STORMS THROUGH THE EVENING. THE BEST
CAPE AND LI INDICATIONS OVER THE NEXT FEW HOURS ARE FROM WEST
CENTRAL INTO SOUTH CENTRAL MN. THIS IS ALSO AT THE NOSE OF THE LOW
LEVEL MOISTURE TRANSPORT AND BETTER 0-1KM SHEAR. DCAPE VALUES
REMAIN WELL ABOVE 1000 J/KG AS WELL. THE AFOREMENTIONED AREA IS
ALSO WERE A FEW CAMS HAVE AN AXIS OF BEST UPDRAFT HELICTY. AS THE
EVENING PROGRESSES...THE LOW LEVEL JET WILL INCREASE AND SPREAD
NORTHEAST. THIS WOULD INCREASES THE SHEAR FOR STORMS ACROSS EAST
CENTRAL MN AND WEST CENTRAL WI. THIS AREA IS ALSO AHEAD OF THE
SURFACE WARM FRONT. ALL OF THE SHOWERS AND THUNDERSTORMS PUSH EAST
OF THE FA BY SUNDAY MORNING WITH THE WARM FRONT.

ANOTHER CONCERN OVERNIGHT IS THE POTENTIAL FOR FOG AND STRATUS
FROM CENTRAL MN INTO WEST CENTRAL WI IN THE WAKE OF THE EXPECTED
EVENING SHOWERS AND THUNDERSTORMS. THE BOUNDARY LAYER WILL BE
QUITE MOIST IN THE WAKE OF THE WARM FRONT ALONG WITH LIGHT WINDS
EXPECTED. CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE FOG AT THIS
TIME GIVEN THE VARIABILITY IN THE CAM SOLUTIONS ON THE SHOWERS AND
THUNDERSTORMS THROUGH THIS EVENING.

ON SUNDAY...A SURFACE COLD FRONT WILL LIE EAST-WEST ACROSS
CENTRAL MN IN THE MORNING...WITH A SLOW SOUTHEASTWARD PROGRESSION
DURING THE DAY. INSTABILITY INCREASES ONCE AGAIN AND SCT STORMS
ARE FORECAST FOR THE AFTERNOON FROM THE TWIN CITIES ON EAST. THESE
SHOULD BE EAST AND SOUTH OF THE AREA BY EVENING. THE THREAT FOR
SEVERE WEATHER WITH THESE STORMS ARE LOW AT THIS TIME.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 258 PM CDT SAT AUG 1 2015

LONG RANGE GUIDANCE CONTINUES TO STRUGGLE WITH DECIDING EXACTLY HOW
THE LARGE SCALE PATTERN WILL EVOLVE TOWARD THE END OF THE UPCOMING
WEEK. HOWEVER... THROUGH AT LEAST MIDWEEK THINGS ARE IN FAIRLY GOOD
AGREEMENT... AND ESSENTIALLY KEEP US QUIET/DRY THROUGH TUESDAY. NEXT
FEATURE OF INTEREST LOOKS TO AFFECT THE REGION AROUND WEDNESDAY...
ALTHOUGH THE GUIDANCE DIFFERS SUBSTANTIALLY ON THE STRENGTH OF THE
UPPER WAVE AND POSITION OF THE SURFACE LOW AND WARM FRONTAL
BOUNDARY. GFS IS MORE PRONOUNCED AND FARTHER NORTH... WHILE THE
ECMWF AND GEM ARE TO THE SOUTH. GIVEN THE UNCERTAINTY FROM WEDNESDAY
ONWARD WE WIND UP NEEDING TO INCLUDE CHANCE POPS FOR MOST OF THE
FORECAST PERIOD THROUGH SATURDAY... WITH THE HIGHEST POPS ON
THURSDAY WHEN THERE IS CURRENTLY THE BEST OVERLAP IN SOLUTIONS.

&&

.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...RAH
LONG TERM...99
AVIATION...RAH



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