Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 191245
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
745 AM CDT SUN APR 19 2015

.UPDATE...
ISSUED AT 715 AM CDT SUN APR 19 2015

UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 300 AM CDT SUN APR 19 2015

SFC ANALYSIS PUTS A SFC LOW PRES CENTER NEAR KBDH WITH A CDFNT
EXTENDING SWWD INTO THE SRN PLAINS BUT ALSO A SFC TROF EXTENDING
NWD INTO SRN MANITOBA. THESE FEATURES ARE UNDERNEATH A SHARP H5
LONGWAVE TROF AXIS OVER THE DAKOTAS AND THE LEE OF THE ROCKIES
WHILE A WEAKENED CUTOFF LOW EJECTS FROM THE SWRN CONUS. THE UPR
TROF WILL ABSORB THE SRN UPR LOW...AIDING IN EXPANDING THE TROF
OVER THE NRN-CENTRAL PLAINS AND INTO THE UPR- MID MISS RIVER
VALLEY REGIONS THRU TNGT. THOUGH THERE IS LITTLE DOUBT IN THESE
LARGER- SCALE FEATURES...THE CHALLENGE COMES IN HOW THE DRY SLOT
EVIDENT ON KMPX RADAR OVER THE CENTRAL PORTIONS OF THE CWFA...IN
FACT EVEN WELL- PLACE OVER THE I-35 CORRIDOR...WILL PLAY A FACTOR
IN THE RW- DISTRIBUTION OVER THE CWFA THRU THIS SHORT-TERM PERIOD.
HIGH CONFIDENCE REMAINS IN MUCH OF THE CWFA SEEING SPRINKLES TO
LIGHT RAIN SHOWERS THRU THE FIRST HALF OF THE DAY...BUT QPF
AMOUNTS WILL BE MUCH LESS THAN ANTICIPATED DUE TO THE LARGER AREA
OF DRY SLOTTING MOVG NEWD IN CONJUNCTION WITH THE SFC LOW.
HRRR/NAM/HOPWRF DO TRY TO FILL MOISTURE BACK INTO THE
AREA...RESULTING IN ADDITIONAL PRECIP THIS AFTN/EVE...BUT NOT
UNTIL THE CDFNT HAS SHIFTED TO THE MN/WI BORDER WHICH WOULD
CONFINE THE BULK OF THE PRECIP TO THE WRN WI COUNTY PORTION OF THE
WFO MPX CWFA. HAVE STRUCTURED GRIDDED POPS AS SUCH...DROPPING POPS
FROM W TO E THRU THE DAY TDA. IN ADDITION... THE MEAGER
INSTABILITY...LACK OF GOOD INSOLATION DUE TO EXTENSIVE CLOUD COVER
AND POORER LAPSE RATES INDICATE A MUCH LESSER CHC AT CONVECTION SO
HAVE OMITTED THUNDER MENTION THIS MRNG. PRECIP WILL GRADUALLY END
THIS EVE INTO THE EARLY MRNG HOURS SUCH THAT BY DAYBREAK MON
MRNG...PRECIP IS NO LONGER EXPECTED.

AS FOR TEMPERATURES...THE COLD FROPA WILL COMMENCE CAA FOR THE
AREA BUT THE EXPANSION OF THE UPPER TROF...MAKING FOR NW FLOW
ALOFT... WILL BE THE MAIN PLAYER IN BRINGING IN COLDER AIR THAT
WILL REMAIN IN PLACE GOING FORWARD. MILD TEMPS IN THE MID 40S TO
MID 50S THIS MRNG WILL ONLY RANGE FROM THE MID 50S TO MID 60S TDA.
WITH DEEP NW FLOW TNGT...LOWS WILL DROP TO THE MID-UPR 30S...WHICH
IS NEAR TO SLIGHTLY BELOW NORMAL FOR LATE APRIL.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 300 AM CDT SUN APR 19 2015

WATER VAPOR IMAGERY THIS MORNING CLEARLY SHOWED TWO DISTINCT
FEATURES OF CONCERN FOR THE LONG TERM PERIOD. THE UPPER LEVEL LOW
PUSHING FROM COLORADO INTO WESTERN KANSAS...AND A SHARP
SHORTWAVE TROUGH EXTENDING FROM THE SASKATCHEWAN/MANITOBA BORDER
THROUGH EXTREME EASTERN MONTANA AND WYOMING. THE UPPER LOW HAS
BEEN QUASI- STATIONARY FOR DAYS NOW...BUT THE PROGRESSIVE
SHORTWAVE WILL HELP IT FINALLY GAIN SOME STEAM TO THE EAST. BY
MONDAY MORNING...THE SHORTWAVE WILL DEEPEN AND BECOME A CLOSED LOW
AT 500MB AND THE CENTER OF IT WILL BE OVER WESTERN ONTARIO. AT
850MB AND THE SURFACE...WE`LL BE SQUARELY WITHIN THE COLD AIR
ADVECTION REGIME... AND STRONG NORTHWEST WINDS. DEEP MIXING AND A
STRONG PRESSURE GRADIENT ACROSS THE AREA ON MONDAY WILL PERSIST
INTO TUESDAY AS WELL AS LOW PRESSURE AT THE SURFACE OVER THE GREAT
LAKES MOVES NORTH TOWARD HUDSON BAY. A WIND ADVISORY WILL BE A
POSSIBILITY FOR MONDAY AFTERNOON...BUT LATER SHIFTS WILL MAKE THE
CALL ON THAT. GENERALLY...20 TO 30 MPH NORTHWEST WINDS WITH GUSTS
OF 30 TO 40 MPH ARE EXPECTED ON MONDAY...AND ABOUT 15 TO 25 MPH
WITH GUSTS TO 30 ON TUESDAY. TEMPERATURES WILL RUN ABOUT 10 TO 15
DEGREES BELOW NORMAL...SO A STARK DIFFERENCE FROM THE RECENT WARM
STRETCH WE`VE EXPERIENCED. IN TERMS OF PRECIPITATION...STILL
EXPECT SHOWERY ACTIVITY TO DEVELOP IN THE CYCLONIC FLOW ACROSS OUR
AREA FOR MONDAY AND TUESDAY. MID LEVEL LAPS RATES LOOK STEEP
ENOUGH TO HELP PRODUCE SAID SHOWERS. SURFACE TEMPERATURES WILL
COOL INTO THE LOW AND MID 30S MONDAY NIGHT...SO SNOW SHOWERS ARE
ALSO A POSSIBILITY DURING THAT TIME.

FOR WEDNESDAY THROUGH SATURDAY...THE MAIN FOCUS IS THE
AFOREMENTIONED UPPER LOW THAT WILL MOVE OVER THE NORTHERN GREAT
LAKES AND BECOME QUASI-STATIONARY...KEEPING OUR REGION IN THE
BACKSIDE OF THE TROUGH AND NORTHWEST FLOW...MEANING CONTINUED COOL
TEMPERATURES. TOWARD THE END OF THE WEEK...THE GFS AND ECMWF
REALLY BEGIN TO DIVERGE IN THEIR HANDLING OF THIS LOW. THE ECMWF
IS MORE PROGRESSIVE IN SLOWLY PUSHING IT EAST AND TRYING TO PUSH
THE UPPER RIDGE INTO THE UPPER MIDWEST BY NEXT WEEKEND. THE GFS
INDICATES A SECONDARY UPPER LOW TO THE NORTHWEST OF THE MAIN LOW
WILL BE PULLED SOUTH AND MOVE THROUGH THE WESTERN GREAT LAKES
REGION NEXT WEEKEND...WHICH WOULD KEEP US COOLER AND POSSIBLY GIVE
US SOME PRECIP. WITH THE DISAGREEMENT BEYOND THURSDAY...NOT TOO
CONFIDENT IN EITHER SOLUTION SO STUCK WITH A BROAD BLEND AT THIS
TIME.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 715 AM CDT SUN APR 19 2015

LOW PRES CENTER OVER WRN MN WITH TRAILING CDFNT WILL SLOWLY SLIDE
E ACRS MN INTO WI TDA. SIGNIFICANT WIND SHIFT AND LOW CEILINGS
WILL SURROUND THE FROPA...INCLUDING CEILINGS DOWN TO IFR LEVELS IN
WRN-CENTRAL MN AND TO LOW-END MVFR CEILINGS IN ERN MN INTO WRN
WI. LOW CHC OF IFR CEILINGS INTO KMSP AND POINTS E BUT CANNOT BE
RULED OUT. -SHRA ASSOCIATED WITH THE LOW PRES FEATURE WILL BE
QUITE LIGHT AND LITTLE TO NO VSBY RESTRICTIONS ARE EXPECTED.
HOWEVER...AS WINDS DROP OFF IN TUNE WITH THE WIND SHIFT...CEILINGS
WILL BRIEFLY DROP WITH THE DECOUPLING. ONCE THE WIND SHIFT OCCURS
AND LOW LEVEL MOISTURE STARTS TO BE SCOURED OUT...CEILINGS WILL
IMPROVE AND STRONG NW WINDS WILL PERSIST ALL THRU TNGT AND TMRW.
STRONGEST WINDS WILL COME CLOSE TO DAYBREAK TMRW...ALTHOUGH SWRN
MN /INCLUDING KRWF/ WILL BE SUBJECT TO 15G25KT WINDS THIS AFTN.
TRICKIEST PART WILL BE TIMING THE WIND SHIFTS THRU THE FIRST HALF
OF THE 19/12Z TAF...SO SOME AMENDMENTS MAY WELL BE NECESSARY.

KMSP...CEILINGS WILL BOUNCE CLOSE TO THE 1700FT THRESHOLD AT THE
START OF THE PERIOD THEN LIKELY REMAIN SUB-1700FT FOR MUCH OF THE
MRNG AS THE CDFNT APCHS. AS WINDS SWING AROUND TO NWLY...CONDS
WILL START TO IMPROVE. NOT LOOKING FOR MUCH VSBY RESTRICTIONS
OUTSIDE OF A VERY BRIEF MOD/HVY SHOWER...BUT THE BULK OF THE
PRECIP WILL NOT BE E OF MSP AIRPORT SO THE CHCS OF REDUCED VSBY
ARE QUITE REMOTE.

/OUTLOOK FOR KMSP/
MON...VFR WITH MVFR/-SHRA POSSIBLE. WINDS NW AT 20G35KTS.
TUE...VFR. WINDS NW AT 15G25KTS.
WED...VFR. WINDS NW AT 15G25KTS.

&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...SPD
AVIATION...JPC



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