Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 152349
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
649 PM CDT FRI AUG 15 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 357 PM CDT FRI AUG 15 2014

RAIN HAS PUSHED WELL TO THE SOUTH INTO IOWA THIS AFTERNOON FROM
SOUTHWESTERN MN THIS MORNING. CONSIDERABLE CLOUDINESS CONTINUES...
PARTICULARLY OVER WRN MN WHERE LOWER CLOUDS ARE BEING OBSERVED IN
RICHER LOW LEVEL MOISTURE...WITH MORE FAIR WX CU ACROSS ERN MN
AND WRN WI. DEW POINTS HAVE RISEN A GOOD 5 TO 15 DEGREES ACROSS
THE CWA SINCE YESTERDAY AFTERNOON WITH WAA EXPECTED TO CONTINUE
THROUGH SATURDAY. MODELS ARE A BIT AT ODDS WITH RESPECT TO FOG AND
LOW STRATUS TONIGHT WITH THE HI-RES MODELS INCLUDING THE
HRRR...HOPWRF...AND RAP NOT SHOWING TOO MUCH...WHILE FORECAST
SOUNDINGS OF THE NAM AND GFS AND THEIR MOS PRODUCTS INDICATING MUCH
MORE IN THE WAY OF RICH BOUNDARY LAYER MOISTURE. GIVEN THE RECENT
DRY SPELL...I AM HESITANT TO BUY INTO WIDESPREAD DENSE FOG AND AM
THINKING MORE LOW CLOUD FORMATION...ESPECIALLY IF 15-20 KT WINDS
AROUND 1KFT VERIFIES. DID ADD AREAS OF FOG INTO THE GRIDS...BUT AT
THIS POINT IT SHOULD NOT BE ANYTHING TOO SIGNIFICANT OUTSIDE OF
AVIATION INTERESTS.

TONIGHT AND MOST OF SATURDAY IS LOOKING DRY. LITTLE IN THE WAY OF
FORCING WILL PRECLUDE DEVELOPMENT UNTIL SATURDAY AFTERNOON IN
CENTRAL MN AND NWRN WI WHEN A WEAK COOL FRONT ADVANCES SOUTH FROM
NORTHERN MINNESOTA AND LAKE SUPERIOR. THERE WILL BE A SECONDARY
AREA OF FORCING ACROSS SOUTHWESTERN MN WHERE A WEAK VORTICITY MAX
PUSHES IN DURING THE LATE AFTERNOON. HOWEVER...MID LEVEL RIDGING
WILL ALSO BE IN PLACE WHICH SHOULD LIMIT THE OVERALL COVERAGE TO
SLIGHT CHC TO LOW CHC RANGE INTO EVENING.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 357 PM CDT FRI AUG 15 2014

FOR THE LONG TERM...BEST CHANCE FOR PRECIP STILL LOOKS TO COME
MONDAY INTO TUESDAY...WHERE ONE WILL CONTINUE TO FIND LIKELY POPS.
AFTER THAT...MODEL DISAGREEMENT STARTS TO INCREASE
APPRECIABLY...THOUGH WE ARE STILL SEEING THE IDEA OF A TROUGH
SETTING UP ACROSS THE NORTHERN ROCKIES...THERE ARE JUST SIGNIFICANT
TIMING DIFFERENCES AS TO WHEN ENERGY FROM SAID TROUGH WORKS ACROSS
THE NORTHERN PLAINS.

WE WILL BE STARTING OFF THIS PERIOD WITH HIGH PRESSURE AGAIN
BUILDING SOUTH ACROSS THE GREAT LAKES FROM WESTERN ONTARIO. THIS
WILL PUSH A WEAK COLD INTO SW MN SATURDAY NIGHT...HELPING CONFINE
THE INSTABILITY THROUGH SUNDAY INTO SW MN AS WELL...AS DRIER AIR
WORKS IN FROM THE NORTHEAST. HAVE MAINTAINED SOME 20 POPS OUT IN SW
MN FOR AREAS THAT ARE EXPECTED TO BE NEAR THE BOUNDARY. HAVE GONE NO
HIGHER THAN THAT WITH POPS AS OUTSIDE OF THAT WEAK SFC
BOUNDARY...THE FORCING IS NIL AS AN H5 ANTICYCLONE WILL BE DRIFTING
OVER MN...WITH NO LLJ SUPPORT TO SPEAK OF EITHER WITH H85 RIDGING
MOVING THROUGH AS WELL.

FOR MONDAY...PRECIP CHANCES WILL BE ON THE INCREASE AS THE UPPER LOW
CURRENTLY SPINNING ACROSS WASHINGTON WORKS THROUGH THE RIDGE AND
COMES DIVING ACROSS MN MONDAY AND ACROSS WI TUESDAY. THIS HAS BEEN A
FAIRLY STABLE SIGNAL IN THE MODELS THE PAST FEW DAYS...SO CONTINUED
TO RUN WITH LIKELY POPS...THOUGH SLOWED THEIR EWRD PROGRESSION
ACROSS THE AREA SUNDAY NIGHT INTO MONDAY...AS ONCE AGAIN WE WILL
HAVE VERY DRY HIGH PRESSURE OVER THE GREAT LAKES HELPING TO SLOW THE
EWRD PROGRESSION OF MOISTURE/PRECIP WITH THIS SYSTEM. STILL LOOKS
GOOD FOR A WIDESPREAD QUARTER TO ONE INCH WITH THIS SYSTEM...BUT
DOES NOT LOOK LIKE HEAVY PRECIP WILL BE MUCH OF A THREAT...AS
MOISTURE TRANSPORT DOES NOT LOOK TO GET CARRIED AWAY...WITH THE LLJ
ONLY TOPPING OUT AROUND 20 KTS...AND THE PW PLUME ASSOCIATED WITH
THIS PRECIP WILL ONLY BE AROUND 1.5 INCHES. WE JUST LOOK TO HAVE
GOOD UPPER DIFFLUENCE AND FORCING WITH THE H5 WAVE DROPPING ACROSS
THE AREA. SEVERE THREAT LOOKS MINIMAL AS WELL AS BOTH THERMODYNAMIC
AND KINEMATIC FIELDS LOOK WEAK...JUST LOOKS LIKE SOME MUCH NEEDED
LIGHT-MODERATE RAIN AT THIS POINT.

FROM TUESDAY AND BEYOND...MODEL DISCREPANCIES INCREASE QUITE A BIT
WITH THE WAVE AS IT MOVES FROM MN TOWARD THE GREAT LAKES. THE
GEM/GFS MAINTAIN A DEEPER/STRONGER UPPER WAVE ACROSS MN/WI...WHILE
THE ECMWF ALLOWS IT TO GET ABSORBED INTO THE MAIN BELT OF
WESTERLIES. THIS DIFFERENCE IN TURN INFLUENCES HOW THE MODELS BEGIN
TO BRING THE DEVELOPING TROUGH IN THE NRN ROCKIES OUT INTO THE
PLAINS. THE GEM/GFS SOLUTION KEEPS THE UPPER LOW OVER THE GREAT
LAKES LONGER...WHICH IN TURN KEEPS ENERGY WITH THE WRN TROUGH HELD
UP OUT WEST UNTIL THE WEEKEND. THE ECMWF ALLOWS FOR A MUCH MORE
PROGRESSIVE PATTERN WITH RESPECT TO THE TROUGH...BRINGING PIECES OF
THE TROUGH ACROSS THE UPPER MS VALLEY ON THURSDAY AND AGAIN OVER THE
WEEKEND. THE GFS/GEM SOLUTION WOULD KEEP ANY ENERGY FROM THE WRN
TROUGH GETTING HERE UNTIL THE WEEKEND...WITH WEDNESDAY THROUGH
FRIDAY OF NEXT WEEK BEING MAINLY DRY AS WE STAY UNDER MORE OF THE
INFLUENCE OF AN UPPER RIDGE...AS THE INFLUENCE OF THE UPPER THROUGH
REMAINS TO THE NORTHWEST. GIVEN THE SPREAD IN MODELS...KEPT CLOSE TO
GFS/ECMWF BLEND FOR POPS...WHICH MEANS POPS TUESDAY ARE MAINLY TO
THE EAST /CLOSER TO THE UPPER LOW/...WEDNESDAY IS MAINLY DRY...WHILE
THU/FRI SEES THE RETURN OF 20-30 POPS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 649 PM CDT FRI AUG 15 2014

CONFIDENCE REMAINS HIGH ON FOG/STRATUS DEVELOPING LATE THIS
EVENING ACROSS THE MN RIVER VALLEY AND SPREADING NORTH AND EAST
THROUGH THE NIGHT AS THE LOW LEVEL FLOW INCREASES FROM THE
SOUTHWEST. LOW MVFR/IFR CEILINGS SATURDAY MORNING GRADUALLY
BECOMING VFR BY LATE MORNING. OVERALL...LITTLE CHANGE IN THE
CURRENT TAF PACKAGE OVER THE PREVIOUS ONE. A COLD FRONT WILL REACH
KAXN AND KSTC NEAR THE END OF THE TAF PERIOD (22Z-24Z). A FEW
SHRA/TSRA ARE POSSIBLE ALONG THE BOUNDARY. THE FRONT AND THE
THREAT OF PRECIPITATION WILL REACH INTO THE TWIN CITIES SATURDAY
EVENING. LIGHT SOUTHERLY WINDS TONIGHT AND SATURDAY MORNING BECOMING
LIGHT SOUTHWEST TO WEST IN THE AFTERNOON AND NORTHERLY IN THE
EVENING.

KMSP...STILL EXPECT LOW MVFR/IFR CEILINGS DURING THE LATE NIGHT
AND MORNING HOURS ON SATURDAY. THE CEILINGS WILL LIFT AND SCT OUT
BY AFTERNOON. SMALL THREAT FOR A SHOWER OR ISOLATED THUNDERSTORM
SATURDAY EVENING AS A COLD FRONT MOVES THROUGH.

/OUTLOOK FOR KMSP/

SUN...VFR. WIND E 5-10 KTS.
MON...VFR/MVFR WITH TSRA LIKELY AFTN/NIGHT. WINDS S 5-10 KTS.
TUE...VFR/MVFR WITH TSRA POSSIBLE. WIND NW 5-10 KTS.

&&

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

$$

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





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