Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230407
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1107 PM CDT TUE APR 22 2014

.UPDATE...
ISSUED AT 1054 PM CDT TUE APR 22 2014

UPDATED TO INCLUDE 06Z AVIATION DISCUSSION.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 346 PM CDT TUE APR 22 2014

HIGH PRESSURE CENTERED OVER EASTERN MN THIS AFTERNOON WILL
CONTINUE TO MAKE SLOW BUT STEADY PROGRESS EAST OVERNIGHT AS A
LARGE STORM SYSTEM MOVES INTO THE INTER-MOUNTAIN WEST. AN UPPER
LEVEL RIDGE AXIS WILL LAG THE SFC RIDGE TONIGHT...KEEPING THE AREA
DRY UNTIL EARLY MORNING (~12Z). SE WINDS WILL DEVELOP ON THE
BACK SIDE OF THE HIGH ALSO HELPING TO KEEP THE PRECIP AT BAY AS IT
CONTINUES TO ADVECT IN LOWER DEWPOINTS (ESPECIALLY IN FAE E MN AND
W WI). DESPITE THESE CHALLENGES...MY EXPERIENCE IS THAT PRECIP
DEVELOPS QUICKER... OVERCOMING DRY LOW LEVEL AIR IN WARM ADVECTION
CASES LIKE THIS ONE. LOW PRESSURE DEVELOPS IN MONTANA OVERNIGHT
WITH A WARM FRONT STRETCHING INTO E SD LATE. WARM ADVECTION ALONG
THE FRONT WILL BE THE PRIMARY DRIVER FOR PRECIP GENERATION ALONG
WITH AN INITIAL SHORTWAVE ROUNDING THE BASE OF THE WESTERN TROUGH.
A BAND OF RAIN SHOULD EXPAND ALONG THE FRONT IN THE EASTERN
DAKOTAS LATE AND MOVE ACROSS MN DURING THE MORNING AND EARLY
AFTERNOON. POPS HAVE BEEN DRAWN TO REFLECT THIS BAND OF RAIN
MOVING ACROSS THE CWA DURING THE DAY. ANY INSTABILITY IS PROGGED
TO REMAIN SOUTH OF THE DEVELOPING LOW PRESSURE CENTER ALONG A COLD
FRONT...WHICH WOULD PLACE ANY T-STORM THREAT IN S SD/NEB AND IOWA.
I AM NOT COMPLETELY RULING OUT A RUMBLE OF THUNDER AS THE BAND OF
ELEVATED CONVECTION MOVES THROUGH TOMORROW...BUT TO REFLECT THE
DECREASED CHANCES...T WAS REMOVED FROM THE WX GRIDS. QPF WITH THIS
INITIAL BAND OF RAIN WILL GENERALLY RANGE FROM 0.1" TO 0.4"
(HIGHEST IN THE N & E PART OF THE CWA). MUCH MORE SUBSTANTIAL RAIN
WILL MATERIALIZE FROM THE SOUTH BEGINNING WED NIGHT AND THIS WILL
BE DISCUSSED IN MORE DETAIL IN THE LONG TERM DISCUSSION.

WINDS WILL BE ANOTHER CONCERN FOR TOMORROW AS THE GRADIENT REALLY
TIGHTENS UP IN ADVANCE OF THIS SYSTEM. TYPICALLY WINDY
SPOTS...ESPECIALLY ALONG THE BUFFALO RIDGE WILL SEE WINDS
INCREASING OUT OF THE SE TO THE TUNE OF 25-35 MPH WITH GUSTS AS
HIGH AS 45 MPH FROM LATE MORNING THROUGH LATE AFTN. UP TO 40KTS OF
WIND IS PROGGED BY THE MODELS AT THE TOP OF THE MIXED
LAYER...WHICH WOULD TRANSLATE INTO GUSTS APPROACHING 45 MPH. THE
ONLY POTENTIAL ISSUE WITH REALIZING WINDS THIS STRONG IS CLOUD
COVER...WHICH MAY INHIBIT MIXING FROM REACHING ITS FULL POTENTIAL.
WITH THAT SAID...AFTER COORDINATION WITH WFOS FSD AND ABR...A WIND
ADVISORY HAS BEEN HOISTED FOR THIS HAZARD.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 346 PM CDT TUE APR 22 2014

LOW LEVEL MOISTURE TRANSPORT WILL INCREASE WEDNESDAY NIGHT AHEAD
OF A LARGE LOW PRESSURE SYSTEM MOVING SLOWLY EAST FROM THE CENTRAL
PLAINS. THE NOSE OF THE MOISTURE TRANSPORT PUSHES INTO SOUTHERN
MINNESOTA DURING THE EVENING AND REACHES WESTERN WISCONSIN BY
DAYBREAK THURSDAY. PW VALUES ACROSS SOUTHERN MN INCREASE TO A
LITTLE MORE THAN AN INCH...WHICH IS 200 PERCENT OF NORMAL.
INSTABILITY IS ALSO INCREASING AS WELL WITH THUNDERSTORMS BECOMING
MORE LIKELY. VARIOUS MODEL SOLUTIONS FOR THE PAST FEW DAYS HAVE
BEEN POINTING AT A PRETTY GOOD CONVECTIVE PRECIPITATION EVENT
UNFOLDING ACROSS WESTERN IA WEDNESDAY EVENING AND SPREADING
NORTHEAST ACROSS SOUTHEAST MINNESOTA TO AROUND EAU CLAIRE BY
THURSDAY MORNING. RAIN AMOUNTS OF 1 TO 1.5 INCHES ARE POSSIBLE IN
THIS CORRIDOR ALTHOUGH THE LAYOUT AGAIN IS SIMILAR TO THIS PAST
SUNDAY NIGHT WHERE THE HEAVIEST RAIN WAS JUST SOUTH OF OUR CWA.
FARTHER NORTH...STRONG ADIABATIC OMEGA IS SEEN MOVING THROUGH ON
THE 295K THETA SURFACE ALONG WITH A BAND OF MID LEVEL
FRONTOGENESIS. RAIN AMOUNTS OF A HALF INCH OR MORE ARE LIKELY.
OVERALL...CATEGORICAL POPS COVER THE FA WEDNESDAY NIGHT.

ON THURSDAY...THE CENTER OF THE SURFACE LOW IS OVER IOWA WITH
AN INVERTED TROUGH EXTENDING TO THE NORTH ACROSS MINNESOTA. THESE
FEATURES WILL BE MOVING SLOWLY EAST WITH ANOTHER HIGH POP
DAY...ESPECIALLY FOR EASTERN MINNESOTA AND WESTERN WISCONSIN.
ANOTHER HALF INCH OF RAIN IS LIKELY. THE THREAT FOR SEVERE WEATHER
ON THURSDAY LOOKS NIL AT THIS TIME ACROSS OUR FA. SO WE WILL
HAVE TO MANUFACTURE OUR OWN FOR THE SEVERE WEATHER DRILLS THURSDAY
AFTERNOON AND EVENING.

DRIER AIR WORKS INTO AT LEAST THE SOUTHERN HALF OF MINNESOTA AND
ADJOINING AREAS OF WISCONSIN THURSDAY NIGHT AND FRIDAY...CUTTING
OFF THE PRECIPITATION. NORTHERN AREAS WILL STILL BE NEAR A
BAROCLINIC ZONE WITH THE THREAT FOR SHOWERS AND ISOLATED
THUNDERSTORMS. BY SATURDAY...IT LOOKS LIKE ALL OF THE AREA WILL BE
DRY. HOWEVER...THIS WILL NOT LAST LONG. A FAST MOVING SHORT WAVE
IS PROJECTED INTO THE FOUR CORNERS REGION BY SATURDAY NIGHT WITH
THIS FEATURE LIFTING INTO THE CENTRAL PLAINS BY SUNDAY. THIS WILL
BRING MORE WAA PRECIPITATION BACK INTO THE UPPER MISSISSIPPI
VALLEY REGION SATURDAY NIGHT AND CONTINUING OFF AND ON FOR SEVERAL
DAYS. THIS IS A LITTLE BIT OF A CHANGE FROM WHAT WE WERE SEEING
THE PAST FEW DAYS. TODAY...THE ECMWF HAS JOINED THE GFS ON TURNING
THE WAVE OVER THE CENTRAL PLAINS INTO A CUT-OFF LOW. A LOOK AT THE
HEMISPHERIC FLOW SHOWS THAT A CUT-OFF HIGH DEVELOPS OVER SOUTHERN
GREENLAND DURING THE WEEKEND WITH A REX BLOCK (HIGH OVER LOW)
DEVELOPING EARLY NEXT WEEK IN THE WESTERN ATLANTIC. WHILE THIS IS
OCCURRING...BOTH THE GFS AND ECMWF DEVELOP A SECOND REX BLOCK FROM
CENTRAL CANADA INTO THE CENTRAL PLAINS. QUITE THE SYMMETRY IN THE
ANIMATION OF THE NORTHERN HEMISPHERIC FLOW. ANYWAY...THERE/S NO
WHERE FOR OUR UPPER LOW TO GO WITH THE BLOCK DOWNSTREAM. IN FACT
OUR LOW IS ONLY FORECAST TO REACH THE EASTERN GREAT LAKES BY LATE
NEXT WEEK. HENCE...BELOW NORMAL TEMPERATURES WILL OCCUR THROUGH
THE LONG TERM PORTION OF THIS FORECAST. THIS SHOULD SEAL THE MONTH
OF APRIL BEING BELOW NORMAL HERE AT MSP. THIS WOULD BE 6 MONTHS IN
A ROW. ONE FINAL THING...WE HAD TO KEEP THE S WORD IN THE FORECAST
SUNDAY NIGHT AND MONDAY NIGHT WITH THE COLD THERMAL PROFILE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1054 PM CDT TUE APR 22 2014

VFR TO START FOR ALL SITES ALTHOUGH HIGH CLOUDS ARE STREAMING IN
FROM THE W AS HIGH PRES EXITS THE AREA AHEAD OF A SLOW-MOVING BUT
WELL-ORGANIZED STORM SYSTEM BREWING OVER THE PLAINS. AS THIS
SYSTEM SHIFTS ENE DURG THE DAY WEDNESDAY TWD THIS REGION...CLOUDS
WILL LOWER AND -SHRA/-RA WILL DEVELOP ACRS THE REGION MID-TO-LATE
MRNG. RAIN IS EXPECTED TO BE FAIRLY WIDESPREAD ACRS THE REGION
BUT AM NOT LOOKING FOR CONDS TO DROP MUCH BELOW UPPER-REGIONS OF
MVFR...IF AT ALL DURG THE DAYTIME HRS.MVFR CONDS WILL BE MORE
PREVALENT AFTER 00Z...WITH LIKELY SOME HEAVIER RAINS AFTER 00Z
WHICH MAY WELL PRODUCE IFR VSBY. NOT LOOKING FOR MUCH CB/TS SINCE
BEST INSTABILITY WILL BE S OF ALL TAF SITES...BUT WHILE ISOLD
CONVECTION CANNOT BE RULED OUT IN THE AFTN AND EVE HOURS...
CONFIDENCE JUST TOO LOW FOR INCLUSION ATTM. WINDS WILL SHIFT FROM
NE TO SE OVERNIGHT WITH SPEEDS CLOSE TO 5 KT. WINDS WILL SETTLE ON
SE FOR MUCH OF THE DAY TMRW...BUT A VERY TIGHT PRES GRADIENT WILL
SIGNIFICANTLY INCRS WIND SPEEDS THROUGHOUT THE DAY TMRW...
EVENTUALLY HITTING THE 15-25KT RANGE WITH HIGHER GUSTS TMRW AFTN
INTO TMRW EVE.

KMSP...VFR CONDS EXPECTED THROUGHOUT THE DAY TMRW...THEN WILL LOOK
FOR POTENTIALLY MVFR CIGS LATE TMRW AFTN INTO TMRW EVE AS A POTENT
STORM SYSTEM APPROACHES FROM THE SW. AHEAD OF THAT TIME...HIGH
CLOUDS WILL FILTER IN FROM THE W...GRADUALLY LOWERING AND
DEVELOPING INTO A CEILING. MIDLVL CIGS ARE THEN EXPECTED BY
DAYBREAK TMRW MRNG AND WILL PREVAIL THRU THE DAY. -SHRA/-RA WILL
DEVELOP BY LATE MRNG AND BE FAIRLY PERSISTENT THROUGHOUT THE DAY
BUT CHCS FOR CONDS TO DROP BELOW VFR ARE FAIRLY LOW...ALTHOUGH
CANNOT BE RULED OUT ESPECIALLY IF A HEAVIER SHOWER HAPPENS TO MOVE
OVER THE AIRPORT. MORE PREVALENT MVFR CONDS ARE EXPECTED TMRW EVE
ALONG WITH HEAVIER DOWNPOURS CREATING ENOUGH VSBY RESTRICTION TO
INCLUDE IFR CONDS. WINDS WILL VEER FROM E TO SE OVERNIGHT AND
REMAIN SE THRU TMRW. SPEEDS WILL INCREASE TO THE 15G25KT
AREA...AND POSSIBLY EVEN HIGHER...DURG THE DAY TMRW INTO TMRW EVE.

/OUTLOOK FOR KMSP/
THU...MVFR CONDS PSBL EARLY. SE WIND 5-15 KT SHIFTING NW.
THU NIGHT...VFR. NW WIND 5-10 KT.
FRI-SAT...VFR. N WIND 5-15 KT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WIND ADVISORY FROM 11 AM TO 6 PM CDT WEDNESDAY FOR MNZ047-
     054>056-064-065-073-074-082-091.

WI...NONE.
&&

$$

UPDATE...JPC
SHORT TERM...JCA
LONG TERM...RAH
AVIATION...JPC






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