Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 281731
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1231 PM CDT TUE APR 28 2015

.UPDATE...FOR 18Z AVIATION DISCUSSION BELOW

&&

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 403 AM CDT TUE APR 28 2015

THE LONG TERM WILL FEATURE A DECIDEDLY MORE SUMMER-LIKE UPPER AIR
PATTERN...ONCE THE DEEP AND PERSISTENT ERN NOAM UPPER LOW LIFTS INTO
THE ATLANTIC THIS WEEKEND...SETTING UP A WAVY ZONAL FLOW ACROSS THE
NRN CONUS THIS WEEKEND INTO NEXT WEEK.

THE LONG TERM WILL START WITH AN UPPER RIDGE BUILDING ACROSS THE
PLAINS AS AN UPPER LOW DIVES SOUTH THROUGH THE WRN GREAT LAKES ON
THE WRN EDGE OF THE ERN NOAM UPPER LOW. THIS WILL LIKELY LEAD TO
INCREASED CLOUD COVER ACROSS WRN WI ON WEDNESDAY...THOUGH ANY
INSTABILITY DRIVEN SHOWERS BENEATH THE UPPER COLD POOL LOOK TO STAY
OVER ERN WI. THIS FEATURE MOVES TOWARD INDIANA WEDNESDAY
NIGHT...TAKING THE CLOUD COVER WITH IT. AT THE SFC...DRY HIGH
PRESSURE WILL DOMINATE THE REGION WEDNESDAY AND THURSDAY. DEEP
MIXING IS EXPECTED BOTH DAYS...AND AS WE HAVE SEEN THROUGHOUT THIS
SPRING...THIS CALLS FOR LOWERING DEWPOINTS BELOW GUIDANCE AND
FAVORING BIAS CORRECTED FORECASTS FOR HIGHS...WHICH WAS DONE BOTH
DAYS.

THURSDAY NIGHT...MODELS CONTINUE TO SHOW ANOTHER SHORTWAVE AND COLD
FRONT MOVING THROUGH THE AREA WITH MAINLY MINOR TIMING DIFFERENCES
NOTED. UNLIKE TODAYS FRONT...THIS FRONT WILL MAINTAIN BETTER
DEFINITION COMING INTO MN...WITH RAINFALL CHANCES LOOKING MORE
LIKELY WITH THIS FRONT THURSDAY NIGHT INTO FRIDAY. HOWEVER...LIKE
TODAYS FRONT...IT WILL BE WASHING OUT FRIDAY AFTERNOON AS THE
SHORTWAVE BECOMES SHEARED OUT...MEANING RAINFALL CHANCES ARE BETTER
TO THE WEST AS OPPOSED TO THE EAST. DID RAISE POPS INTO THE HIGH
CHANCE CATEGORY FOR WRN MN LATE THURSDAY NIGHT AS MODEL AGREEMENT IS
LOOKING BETTER ON RAIN MOVING INTO THE WEST LATE THURSDAY NIGHT. DID
REMOVE THUNDER WITH THIS SYSTEM AS WELL AS BOTH THE GFS AND ECMWF
SHOW NO INSTABILITY PRESENT WITH THE WAVE AS IT MOVES THROUGH.

FOR THE WEEKEND...WITH ZONAL FLOW SETTING UP...WE WILL SEE A PLUME
OF RATHER MILD H85 AIR MOVE INTO THE UPPER MS VALLEY IN THE WAKE OF
FRIDAYS SYSTEM...WITH THE ECMWF CONTINUING TO SHOW H85 TEMPS IN
EXCESS OF +12C. DID ADD SOME BIAS CORRECTED CONSENSUS GRIDS INTO THE
INITIAL CENTRAL REGION BLEND FOR HIGHS ON SATURDAY TO GET MORE MID
70S TO LOWER 80S IN THE GRIDS FOR SATURDAY...WHICH LOOKS TO OFFER
SOME SUNNY SKIES BEFORE THE WARM FRONT ARRIVES SATURDAY NIGHT. AS
FOR THAT WARM FRONT...THOUGH SPREAD IS TYPICAL OF WHAT YOU WOULD
EXPECT THIS FAR OUT FOR SATURDAY NIGHT THROUGH SUNDAY NIGHT...THE
GFS/GEM/ECMWF ALL AGREE ON THE GENERAL IDEA OF A WARM FRONT LIFTING
NORTH INTO THE AREA SATURDAY NIGHT...FOLLOWED BY A COLD FRONT OR SFC
LOW PASSAGE SUNDAY INTO SUNDAY NIGHT. THIS SYSTEM WILL BE BRINGING
UP SOME MODIFIED TROPICAL AIR...WITH DEWPS LIKELY INTO THE
60S...WHICH WILL RESULT IN A DECENT AMOUNT OF INSTABILITY FOR THE
SYSTEM COMING THROUGH SUNDAY. THOUGH KINEMATIC FIELDS ARE MARGINAL
FOR ANY SORT OF SEVER POTENTIAL...PLENTY OF INSTABILITY LOOKS TO
EXIST TO GIVE US A GOOD SHOT AT SOME THUNDERSTORMS. AS A
RESULT...HAVE FAIRLY WIDESPREAD CHANCE POPS SUNDAY INTO SUNDAY
NIGHT...WITH THE THUNDER WORDING MORE THAN WARRANTED IN THE FORECAST
THIS TIME AROUND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1230 PM CDT TUE APR 28 2015

THE BAND OF LIGHT SHOWERS ACROSS CENTRAL/EAST CENTRAL MN WILL
GRADUALLY DIMINISH AS IT ENTERS WEST CENTRAL WI THIS AFTERNOON.
ASSOCIATED CIGS/VSBYS ARE EXPECTED TO REMAIN IN THE LOW-END VFR
CATEGORY. THE MAIN SITE TO EXPERIENCE NOTABLE REDUCTIONS TO IFR
WILL BE KAXN...UNTIL MID AFTERNOON WHEN RUC 0.5KM AGL
CONDENSATIONAL PRESSURE DEFICITS INDICATE IMPROVEMENT. BY
00Z...ALL SITES SHOULD BE VFR WITH ONLY FEW-SCT CLOUDS AOA 10KFT.
WINDS WILL BE NNW AROUND 10-12KTS TODAY...THEN BECOME LIGHT NNE
THIS EVE INTO WEDNESDAY.

KMSP...
MAIN WINDOW FOR SHOWERS IS BETWEEN 18Z AND 22Z...WITH A LIGHTNING
STRIKE OR TWO POSSIBLE IN THE VICINITY OF THE FIELD DURING THAT
TIME AS WELL. CIGS AROUND 5KFT THIS AFTERNOON...WITH CLEARING THIS
EVE.

/OUTLOOK FOR KMSP/
WED NIGHT...VFR. WINDS ENE 5-10 KTS.
THU...VFR. WINDS E 5-10 KTS.
FRI...VFR. CHANCE OF SHOWERS. WINDS S 10 KTS.
SAT...VFR. WINDS WSW 5-10 KTS.

&&

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

$$

SHORT TERM...RAH
LONG TERM...MPG
AVIATION...LS



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