Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 261044
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
544 AM CDT FRI SEP 26 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 356 AM CDT FRI SEP 26 2014

MAIN CONCERNS IN THE SHORT TERM REVOLVE AROUND FOG COVERAGE THIS
MORNING ACROSS ERN MN/WRN WI...ALONG WITH HOW WARM TO GO WITH HIGHS
TODAY.

WATER VAPOR IMAGERY THIS MORNING NICELY SHOWS THE LARGE UPPER RIDGE
IN PLACE FROM THE PAC NW TROUGH UP TOWARD THE SOUTHWESTERN SHORES OF
HUDSON BAY AND OVER TOWARD THE CANADIAN MARITIMES. A REMNANT UPPER
LOW WAS WORKING SW BENEATH THIS CRESTING RIDGE INTO NRN MO...THOUGH
IT IS PRETTY MOISTURE STAVED. THE ONLY CHANGE EXPECTED WITH THE
UPPER AIR PATTERN DURING THE SHORT TERM IS THAT THE REMNANT UPPER
LOW WILL BE SLOWLY WORKING TOWARD SRN MN BY THE END OF THE PERIOD.

HIGH PRESSURE THIS MORNING IS CENTERED OVER LOWER MICHIGAN/SW
ONTARIO. THE WRN PERIPHERY OF THIS HIGH HAS SHIFTED EAST WITH THE
HIGH AS WELL...NOW OVER ERN MN/WRN WI. THE SHIFTING OF THE RIDGE TO
THE EAST...ALONG WITH THE MUCH WARMER TEMPERATURES THU AFTERNOON AS
COMPARED TO WED AFTERNOON HAS ALLOWED FOR THE FOG TO BE MUCH LESS OF
AN ISSUE OVER WRN MN THIS MORNING...DESPITE THE HIGHER DEWPOINTS.
INSTEAD THE DENSE FOG ZONE HAS SHIFTED EAST TOWARD ERN MN/WRN WI. TO
THIS POINT...HAVE NOT SEEN WIDESPREAD VIS AT 1/4SM OR LESS...SO NO
ADVY HAS BEEN ISSUED...BUT IF VISIBILITIES REALLY TREND DOWN
HARD...MAY STILL NEED TO MENTION SOMETHING OUT THERE FOR AREAS
MAINLY EAST OF I-35.

FOR HIGHS TODAY...GUIDANCE SAYS MAINLY MID/UPPER 70S WITH A FEW 80S
OUT IN THE WEST. HOWEVER...BUFR SOUNDINGS SHOW MOST LOCATIONS MIXING
UP TO 850-825 MB AND USING THE MIX DOWN TOOL UP TO THAT LEVEL
SUGGESTS HIGHS BEING A FEW DEGREES WARMER THAN GUIDANCE. USED A MIX
DOWN UP TO 825MB AS THE MAIN INPUT INTO THE FORECAST HIGHS FOR
TODAY...BLENDED WITH THE CONSENSUS BLEND. RESULTED IN HIGHS ABOUT 5
DEGREES WARM THAN YESTERDAY IN WI /LESS CLOUDS/...A COUPLE OF
DEGREES WARMER IN ERN MN...AND A COUPLE OF DEGREES COOLER IN WRN
MN...AS THE PERSISTENT SE LOW LEVEL WINDS LOOK TO PUSH THE CORE OF
925-850 WARM NOSE BACK TO THE WEST.

FOR TONIGHT...AS THE UPPER LOW BEGINS TO LIFT NORTH...WILL LIKELY
SEE CLOUDS IN THE 4K-6K FOOT LEVEL MOVE UP FROM IOWA. THESE
CLOUDS...COMBINED WITH THE CONTINUED EWRD SHIFT IN THE SFC HIGH
SHOULD LEAD TO EVEN LESS COVERAGE IN FOG SATURDAY MORNING THAN WHAT
WE ARE SEEING THIS MORNING.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 356 AM CDT FRI SEP 26 2014

A RATHER BUSY LONG TERM WITH ESSENTIALLY FOUR DIFFERENT WEATHER
SYSTEMS TO DEAL WITH. THE MAIN CONCERNS DURING THE PERIOD ARE
DURING THE WEEKEND AND REVOLVE AROUND PRECIPITATION CHANCES ON
SATURDAY ALONG WITH HIGH TEMPERATURES FOR SATURDAY AND SUNDAY.

THE LONG TERM PERIOD BEGINS WITH AN UPPER LOW OVER IA THAT WILL
DRIFT INTO SW MN SATURDAY AFTERNOON AND THEN OPEN UP SATURDAY NIGHT
BEFORE DRIFTING OFF TO THE SOUTHEAST ON SUNDAY. ONE BY ONE OVER
THE PAST FEW NIGHTS THE VARIOUS DETERMINISTIC MODELS HAVE BEEN
SHOWING SOME LIGHT SHOWERS ACROSS MAINLY THE MN CWA ON SATURDAY.
THIS IS IN THE LEFT EXIT REGION OF A WEAK UPPER JET POKING INTO
THE FA. FOLLOWED THE LEAD OF THE DAY SHIFT AND EXPANDED THE SLIGHT
CHANCES POPS FARTHER NORTH AND SOUTH. EVEN SPC HAS INTRODUCED
GENERAL THUNDER ON DAY 2 ALTHOUGH WRF SOLUTIONS SUGGESTS THIS
IS MAINLY IN IA.

HIGH TEMPERATURES BOTH SATURDAY AND SUNDAY SHOULD BE IN THE UPPER
70S TO LOWER 80S FROM EAST TO WEST. MODELS ARE TRENDING BACK TO
MORE OF A SSW LOW LEVEL FLOW WITH THE SURFACE WINDS ON SATURDAY
MORE 190 WITH WINDS UP TROUGH H85 FROM 200. THE CONCERN IS THAT
HIGHS ON SATURDAY MAY NOT BE WARM ENOUGH WITH THE LOWER 80S IN THE
MN RIVER VALLEY AFTER SEEING HIGHS ON THURSDAY IN THE MIDDLE TO
UPPER 80S. GRANTED H85 TEMPERATURES YESTERDAY WERE IN THE 16-18
DEG C RANGE WHILE ON SATURDAY IT IS PROGGED TO BE CLOSER TO 16 DEG
C. MIX-DOWN FROM AROUND H85 CONFIRMED HIGHS IN THE LOWER 80S. KEPT
THE TWIN CITIES AROUND 80 FOR BOTH SATURDAY AND SUNDAY WITH MIX-
DOWN SUGGESTING POTENTIAL FOR LOWER 80S. THE HIGHS WILL DEPEND ON
HOW MUCH CLOUD COVER WE HAVE WHICH IS CRITICAL ON SATURDAY. NAM
SIMULATED IR IS SHOWING SOME RATHER LARGE AREAS OF LOW CLOUDS
ACROSS EASTERN MN AND WESTERN WI SATURDAY AFTERNOON.

THE NEXT THREAT FOR PRECIPITATION IS ON MONDAY WITH A BACKDOOR
COLD FRONT DROPPING SOUTHWARD ACROSS THE FA. OVER THE PAST FEW
NIGHTS THE GFS HAD BEEN QUITE AGGRESSIVE WITH A STRONG SHORT WAVE
MOVING SOUTHEAST ACROSS THE WESTERN GREAT LAKES. THIS DID MATCH
WELL WITH THE GEFS NOR THE ECMWF. NOW WITH THE 26.00Z RUNS...THE
GFS IS SHOWING LESS INTEREST WHILE THE ECMWF HAS BECOME MUCH MORE
AMPLIFIED WITH THE SHORT WAVE. LOOKING AT THE BEST LAYER MOISTURE
AND FORCING INDICATED THAT CENTRAL MN THROUGH WEST CENTRAL WI WAS
THE BEST PLACE FOR SOME LOW CHANCE POPS. KEPT THE TWIN CITIES OUT
OF THE SHOWERS FOR MONDAY.

NEXT UP IS A SHORT WAVE MOVING INTO THE PLAINS MONDAY NIGHT. THIS
FEATURE IS CURRENTLY A CLOSED LOW TO THE NW OF KSFO. MODEL TRENDS
CONTINUE TO SLOW THE EASTWARD PROGRESSION OF THIS FEATURE WITH IT
BECOMING NEGATIVELY TILTED WITH TIME DUE TO THE BLOCKY PATTERN
DEVELOPING OVER THE EASTERN THIRD OF THE CONUS. THIS FEATURE WILL
EVENTUALLY MOVE ACROSS US TUESDAY AND TUESDAY NIGHT WITH SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS. A CHANGE WAS MADE TO DIMINISH
POPS MONDAY NIGHT IN THE MN CWA AS MUCH AS POSSIBLE DUE TO THE
SLOWING.

FINALLY...A SECOND SHORT WAVE WILL FOLLOW THE AFOREMENTIONED ONE.
THIS FEATURE IS SHOWING A LITTLE LESS AMPLIFICATION OVER OUR AREA
DURING THE LATTER HALF OF THE WEEK THAN WHAT PREVIOUS RUNS HAVE
SHOWN OVER THE PAST SEVERAL NIGHTS. SOME OF THIS IS DUE TO LESS
PHASING IN THE NORTHERN AND SOUTHERN STREAMS OVER US THAN WAS
PROJECTED. THE ECMWF FAVORS MORE ENERGY IN THE NORTHERN STREAM
WHILE THE GFS IS PUTTING MORE ENERGY IN THE SOUTHERN STREAM. THE
BOTTOM LINE IS THAT RAIN IS LIKELY ACROSS SOUTHERN MN THROUGH
WESTERN WISCONSIN FROM WEDNESDAY NIGHT INTO THURSDAY WITH A
WIDESPREAD HALF INCH TO ONE INCH RAINFALL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 528 AM CDT FRI SEP 26 2014

CLOUDS ASSOCIATED WITH UPPER LOW IN IOWA PUT A STOP TO FOG THAT
WAS DEVELOPING ACROSS ERN MN/WRN WI. AS A RESULT...SHIFTED FOCUS
OF WI TERMINALS FROM FOG TO THESE 5K-6K FT CLOUDS. THE
SIGNIFICANTLY WARMER TEMPS COMBINED WITH PERSISTENT SE WINDS HAS
KEPT MN SITES MAINLY VFR...SO IMPROVED CONDITIONS AT MN TERMINALS
FROM WHAT WAS IN THE INITIAL 6Z TAF PACKAGE. TONIGHT...SAID UPPER
LOW WILL START DRIFTING TOWARD MN...WITH BOTH THE GFS/NAM SHOWING
CLOUDS CURRENTLY DOWN ACROSS IA WORKING UP ACROSS MN FRIDAY NIGHT.
THESE CLOUDS AND WINDS WILL LIMIT FOG AGAIN SATURDAY MORNING.

KMSP...ARRIVAL OF CLOUDS AROUND 5K FT PUT A QUICK END TO THE FOG
THREAT THIS MORNING. ANOTHER ROUND OF CLOUDS AROUND 6K FEET AND
CONTINUED SE WINDS WILL KEEP ANY FOG/STRATUS AT BAY AGAIN FRIDAY
NIGHT. ANY THREAT FOR A STRAY SHOWER SATURDAY LOOKS TO COME AFTER
18Z.

/OUTLOOK FOR KMSP/
SAT...VFR. ISOLD SHRA. WINDS SSE 10-15 KTS.
SUN...VFR. WINDS S AT 10KTS.
MON...VFR. WINDS BCMG 5 KTS.

&&

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

$$

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






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