Area Forecast Discussion
Issued by NWS Twin Cities, MN

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448
FXUS63 KMPX 220013
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
713 PM CDT THU MAY 21 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 421 PM CDT THU MAY 21 2015

BREEZY NW WINDS HAVE DEVELOPED WITHIN A DRY...WELL MIXED BOUNDARY
LAYER BEHIND A COLD FRONT THAT NOW SITS FROM IOWA OVER TO A SFC LOW
MOVING THROUGH SE QUEBEC TOWARD NEW ENGLAND. BEING THIS FAR WEST
ALONG THE FRONT...THE ATMO IS TO DRY TO DO MUCH MORE THAN POP A HIGH
BASED CU FIELD OVER WI. BEHIND THIS FRONT...HIGH PRESSURE WILL SLIDE
ACROSS THE AREA TONIGHT. GIVEN DEWPS CURRENTLY IN THE
20S/30S...LIGHT WINDS AND CLEAR SKIES WILL ALLOW FOR ANOTHER LARGE
DIURNAL DROP IN TEMPERATURES...LIKELY ON THE ORDER OF 30+ DEGS AT
LOCATIONS THAT RESPOND WELL TO RADIATIONAL COOLING CONDITIONS. AS A
RESULT...FAVORED LOWS TOWARD A PRETTY EVEN BLEND OF THE MAV/MET...
WHICH RESULTED IN THE FORECAST READING A FEW DEGREES
COLDER THAN IT DID PREVIOUSLY...ESPECIALLY  NORTH OF I-94.

THE WEATHER FOR FRIDAY IS NOT EXPECTED TO BE MUCH MORE EXCITING
EITHER. HIGH PRESSURE WILL BE SLIDING ACROSS MICHIGAN...WHICH WILL
ALLOW MUCH LIGHTER WINDS TO FLIP AROUND TO THE SOUTH TO SOUTHEAST.
SKIES WILL BE CLEAR AS WELL...WITH AIRMASS MODIFICATION RESULTING IN
HIGHS TOMORROW 2 OR 3 DEGS WARMER THAN TODAY. IN OTHER WORDS IT WILL
BE AN ABSOLUTELY BEAUTIFUL WAY TO START THE LONG HOLIDAY WEEKEND!

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 421 PM CDT THU MAY 21 2015

THE START OF THE HOLIDAY WEEKEND BEGINS A FAIRLY ACTIVE PERIOD OF
WEATHER THAT WILL TAKE US INTO EARLY NEXT WEEK. THE GFS CONTINUES
TO BE THE FASTER OF SOLUTIONS WITH RESPECT TO THE ONSET OF PRECIP
ON SATURDAY WHEN COMPARED TO THE ECMWF. THE 21.12/18Z NAM ALSO
GENERATES SOME LIGHT QPF BY SATURDAY AFTERNOON WITH THE FIRST WAVE
OF WARM ADVECTION AND ISENTROPIC LIFT. THE ECMWF KEEPS THE AREA
DRY THROUGH SATURDAY AND EVEN THE MORE AGGRESSIVE GFS HAS PUSHED
MOST OF THE ACTIVITY BACK UNTIL SATURDAY NIGHT WHEN THE 925-850MB
MOISTURE TRANSPORT BEGINS TO INCREASE AND SPREAD NORTHEAST OUT OF
THE CENTRAL PLAINS. THE UPPER LEVEL TROUGH STARTS TO PUSH EAST
SATURDAY EVENING...WITH PIECES OF ENERGY KICKING OUT OF THE LONG
WAVE THROUGH MONDAY. THE PRECIPITABLE WATER TAKES A NOTABLE JUMP
SATURDAY NIGHT INTO SUNDAY AND GETS CLOSE TO THE CLIMATOLOGICAL
MAX FOR MID MAY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA.
SO...THE COMBINATION OF PWATS NEAR 1.75"...TALL SKINNY CAPE ON THE
ORDER OF 750-1000 J/KG...A FAIRLY DEEP WARM LAYER CLOSE TO 12KFT AND
THE POTENTIAL FOR SLOW STORMS SUGGEST THAT HEAVY RAIN IS THE
BIGGEST POTENTIAL HAZARD THIS WEEKEND. THE INSTABILITY AND SHEAR
/ESPECIALLY DEEP LAYER SHEAR/ ARE TOO MARGINAL AT THIS POINT TO
BE TOO CONCERNED. THE 21.12Z GFS DOES HAVE DECENT OVERLAP IN THE
CAPE AND SHEAR FIELDS IN EASTERN MN AND WESTERN WI MONDAY
AFTERNOON...BUT THE ECMWF IS MUCH WEAKER AND FARTHER SOUTH WITH
THE STRONGER WIND FIELDS. SO...THE BETTER THREAT FOR STRONG TO
SEVERE STORMS LOOKS LIKE IOWA UNLESS THE MASS FIELDS AND MOMENTUM
FIELDS SHIFT NORTH OVER THE NEXT COUPLE DAYS. TO SUMMARIZE...THE
CHANCE FOR RAIN ON SATURDAY IS SHAKY AND DEFINITELY MUCH BETTER ON
SUNDAY. THE WHOLE WEEKEND WILL LIKELY FEATURE A LOT OF CLOUD
COVER...BUT MILD TEMPS AND INCREASING HUMIDITY. WHILE THE TIMING
OF PRECIP EVENTS STILL NEEDS REFINEMENT...THE RISK FOR WET WEATHER
SHOULD PERSIST AT LEAST THROUGH THE DAY ON MONDAY GIVEN THE SLOWER
TRENDS IN THE AVAILABLE GUIDANCE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 713 PM CDT THU MAY 21 2015

EXCELLENT AVIATION WEATHER WITH SKC AS HIGH PRESSURE BUILDS IN.
NORTHWEST WINDS NEAR 10 KNOTS THIS EVENING WILL BECOME LIGHT AND
VARIABLE AFTER SUNSET. WINDS ON FRIDAY WILL BECOME SOUTHERLY BY
LATE MORNING WITH SPEEDS OF 6-9 KNOTS FOR THE AFTERNOON.

KMSP...VFR WITH NO CONCERNS.

/OUTLOOK FOR KMSP/
SAT...VFR. SLGT CHC -SHRA/-TSRA. WINDS S 5 TO 10 KTS.
SUN...VFR. CHC SHRA/TSRA WITH MVFR OR LOWER CONDITIONS.
      WINDS SE 10 KTS.
MON...VFR. CHC SHRA/TSRA WITH MVFR OR LOWER CONDITIONS.
      WINDS S 10 KTS.

&&

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

$$

SHORT TERM...MPG
LONG TERM...CLF
AVIATION...RAH



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