Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 271118
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
618 AM CDT MON APR 27 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT MON APR 27 2015

SURFACE RIDGING CONTINUES TO EXTEND ACROSS ONTARIO AND THE UPPER
MISSISSIPPI VALLEY REGION EARLY THIS MORNING. THE LIGHT NORTHERLY
FLOW REMAINS QUITE DRY WITH SURFACE DEW POINTS IN THE TEENS AND
20S AT MANY LOCATIONS ACROSS THE FORECAST AREA OVERNIGHT. THE DAY
AHEAD WILL BE MUCH LIKE SUNDAY WITH ABUNDANT SUNSHINE...LOW
AFTERNOON RELATIVE HUMIDITY ALONG WITH LIGHT NORTHERLY WINDS.
HOWEVER...IT WILL BE A LITTLE WARMER TODAY AS 850MB TEMPERATURES
WARM 2 TO 3 DEG C OVER WHAT WAS OBSERVED AT 27/00Z. OUR SUNDAY
EVENING UPPER AIR PROFILE INDICATED MIXING REACHED AROUND 825MB.
THE 27/00Z GFS PROFILE DATA WAS A LITTLE BETTER (HIGHER) THAN THE
NAM WITH THE MIXING HEIGHTS FOR TODAY. GFS NSHARP DATA SHOWS HIGHS
THIS AFTERNOON OF 64 FOR KEAU...68 AT KMSP AND 72 FOR KDXX. THESE
VALUES ARE VERY CLOSE TO THE PREVIOUS GRIDDED FORECAST WITH ONLY
MINOR TWEAKS MADE. AFTERNOON MINIMUM HUMIDITY REACHES 15 TO 20
PERCENT ACROSS THE MN CWA WITH 20 TO 25 PERCENT IN WEST CENTRAL
WI. ONCE AGAIN...WINDS WILL BE RATHER LIGHT WITH THE FIRE WEATHER
RISK IN THE LIMITED TO ELEVATED CATEGORIES.

THE SURFACE RIDGE WILL BEGIN TO SLIP OFF TO THE EAST TONIGHT AS A
SHORT WAVE AND WEAK SURFACE FRONT APPROACH FROM THE NORTHERN
PLAINS. THESE FEATURES ARE A LITTLE SLOWER THAN THE PREVIOUS
FORECAST AND THE THREAT FOR SOME LIGHT SHOWERS WAS LIMITED TO
AREAS WEST OF A LAKE MILLE LACS TO REDWOOD FALLS LINE IN THE 09Z-
12Z TIME FRAME. LOWS TONIGHT WILL BE QUITE VARIED ACROSS THE FA
WITH CLEAR SKIES AND DRY AIR IN WEST CENTRAL WI TO INCREASING
CLOUDS AND SOUTHERLY FLOW IN WEST CENTRAL MN. HENCE...LOWS RANGE
FROM THE LOWER 30S TO LOWER 40S RESPECTIVELY FOR THE
AFOREMENTIONED AREAS.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 400 AM CDT MON APR 27 2015

THE MAIN TAKE AWAY FROM THE EXTENDED IS THE TRANSITION FROM A HIGHLY
AMPLIFIED FLOW THIS WEEK TO A MUCH MORE ZONAL FLOW FOR THE WEEKEND.
THE ONE OUTLIER IN THE DETERMINISTIC GUIDANCE OVERNIGHT WAS THE
GFS...WHICH IS MUCH MORE AGGRESSIVE WITH ENERGY MOVING ACROSS ERN
NOAM FOR THE END OF THE WEEK WHEN IT DEVELOPS A CLOSED H5 LOW OVER
THE MID-ATLANTIC WHILE THE GEM/ECMWF KEEP THAT WAVE MORE OPEN.
DESPITE THAT DIFFERENCE...ALL OF THE GUIDANCE ENDS UP IN A SIMILAR
LOCATION BY SUNDAY...WITH A WEAK TROUGH OVER CALIFORNIA BENEATH
QUASI-ZONAL FLOW ALONG THE CANADIAN BORDER.

DURING THE COURSE OF THE WEEK WE WILL SEE A WRN BUILD INTO THE
PLAINS. IT WILL REMAIN OVER THE CENTER OF THE CONTINENT UNTIL THE
END OF THE WEEK...WHEN THE DEEP UPPER LOWER OVER THE EAST COAST
FINALLY BREAKS DOWN...ALLOWING THE FLOW TO BECOME MORE PROGRESSIVE
TO ITS WEST. WE STILL LOOK TO HAVE TWO SHORT WAVES AND ASSOCIATED
WEAK FRONTS MOVE THROUGH TUESDAY AND AGAIN THU NIGHT/FRIDAY. IN BOTH
CASES...PRECIP POTENTIAL DOES NOT LOOK ALL THAT GREAT AND THEY
ACTUALLY SHARE SOME SIMILAR CHARACTERISTICS. BOTH WILL HAVE VERY DRY
LOW LEVEL AIR TO OVERCOME...NEITHER WILL BE TAPING INTO GULF
MOISTURE...AND BOTH WILL BE LACKING INSTABILITY. ABOUT THE ONLY
DIFFERENCE BETWEEN THE TWO IS SLIGHTLY BETTER SRLY FLOW OUT AHEAD OF
THE FRIDAY BOUNDARY...WITH BETTER CONVERGENCE AND CHANCES FOR PRECIP
GENERATION WITH THE FRIDAY WAVE. FOR THE GRIDS...WENT DRY WITH THE
FORECAST AFTER 18Z TUESDAY WITH DETERMINISTIC MODELS SHOWING LITTLE
QPF TUESDAY AFTERNOON...WITH THIS FEATURE LOOKING TO DO NOT MUCH
MORE THAN PRODUCE CLOUDY SKIES AND MAYBE A FEW SPRINKLES. FOR
FRIDAY...ENDED UP WITH BROAD-BRUSHED SLIGHT CHANCE POPS GIVEN TIMING
DIFFERENCE IN THE MODELS /GFS FASTER THAN THE ECMWF/. FOR
TEMPERATURES THIS WEEK...WITH DEEP MIXING EXPECTED...BLENDED IN SOME
MORE BIAS CORRECTED NUMBERS INTO THE INITIAL CR MODEL BLEND TO BOOST
HIGHS A FEW DEGREES GIVEN RECENT PERFORMANCE OF THE CR MODEL BLEND
IN DRY AND DEEPLY MIXED ENVIRONMENTS.

FOR THE WEEKEND...WHAT LOOKS LIKE A CERTAINTY IS SEEING ABOVE NORMAL
TEMPERATURES AS H85 TEMPS PUSH ABOVE 12C. DID BOOST HIGHS SOME FROM
THE INITIAL BLEND...BUT CURRENT H85 TEMPS FROM THE GFS/ECMWF WOULD
SUPPORT HIGHS WELL INTO THE 80S...THOUGH THAT WILL BE DEPENDENT ON
EXTENT OF CLOUD COVER AND OTHER SUCH DETAILS THAT ARE HARD TO PIN
DOWN AT THIS POINT. FOR PRECIP CHANCES OVER THE WEEKEND...THE
ECMWF/GFS ARE BEGINNING TO HONE IN ON A STRONGER FRONT...OR AT LEAST
A FRONT WITH BETTER MOISTURE RETURN MOVING THROUGH THE UPPER MS
VALLEY ON SUNDAY...WHEN CHANCE THUNDERSTORM POPS CURRENTLY EXIST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 617 AM CDT MON APR 27 2015

VFR CONDITIONS TO PREVAIL THROUGH THE TAF PERIOD. LIGHT AND
VARIABLE WINDS EARLY THIS MORNING BECOMING N TO NW AT 6-9 KNOTS
FOR THE LATE MORNING AND AFTERNOON HOURS. A WEAK COOL FRONT WILL
REACH KAXN NEAR THE END OF THE TAF PERIOD. A FEW SHOWERS ARE
POSSIBLE IN THE VICINITY OF THE FRONT WITH VCSH INDICATED AFTER
10Z.

KMSP...NO CONCERNS TODAY/TONIGHT. A DRY COLD FRONT WILL PASS THE
AIRFIELD LATE TUESDAY MORNING WITH CEILINGS AOA 050.

/OUTLOOK FOR KMSP/
TUE...VFR. WINDS NW 5-10 KTS.
WED...VFR. WINDS N 5-10 KTS.
THU...VFR. WINDS E 5-10 KTS BECOMING SE.
&&

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

$$

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



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