Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 282102
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
402 PM CDT FRI AUG 28 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 244 PM CDT FRI AUG 28 2015

THE MPX AREA THIS AFTERNOON SITS BETWEEN AN AREA OF LOW PRESSURE
SLOWLY MOVING EAST ACROSS IOWA AND A LOW PRESSURE TROUGH THAT
SITS FROM NODAK BACK INTO NW ONTARIO. WE HAVE SEEN ABOUT A 40 KT
LLJ BUILD NORTH TO THE ERN IA/MN BORDER...WHICH HAS ALLOWED LIGHT
RAIN TO BUILD ABOUT AS FAR NORTH AS EAU CLAIRE...BUT NO FURTHER
NORTHWARD EXPANSION IS EXPECTED. COOL CLOUD TOPS ASSOCIATED WITH
THE PRECIP SHIELD ON THE NOSE OF THE LLJ AND WITHIN A ZONE OF
H85-H6 FGEN IS MOVING ENE AT ABOUT 12 MPH. BASED ON CURRENT
SPEED...THE RAIN SHOULD CLEAR THE EAU CLAIRE SHORTLY AFTER 21Z AND
LOOKS TO COMPLETELY BE OUT OF THE MPX AREA AFTER 03Z. ONLY REAL
CHANGES NEEDED TO THE POP/WX FORECAST WERE TO ONE...SPEED UP THE
DEPARTURE OF THE RAIN THIS EVENING AND TWO...REMOVE THUNDER...AS
INSTABILITY HAS REMAINED CONFINED CLOSER TO THE SFC LOW DOWN NEAR
DES MOINES.

OTHER AREA TO WATCH FOR PRECIP IS THE TROUGH TO OUR NORTH. 20Z
SPC MESO ANALYSIS SHOWS MLCAPES BETWEEN 2000 AND 3000 J/KG HAVE
DEVELOPED AHEAD OF THE BOUNDARY FROM ERN NODAK ACROSS THE
INTERNATIONAL BORDER. THE CAMS HAVE BEEN FAIRLY CONSISTENT WITH
DEVELOPING A SCT LINE OF THUNDERSTORMS ALONG THIS BOUNDARY LATE
THIS AFTERNOON FROM FARGO TO EAST OF INL UP IN THE ARROWHEAD.
THE QUESTION WITH THIS ACTIVITY IS HOW FAR SOUTH DOES IT MAKE IT
TONIGHT. FOR NOW...HAVE KEPT THE FORECAST DRY ACROSS CENTRAL MN
THROUGH TONIGHT...BUT WILL HAVE TO SEE WHAT HAPPENS WITH THIS
CONVECTION TO THE NORTH THIS EVENING...AS SOME DECAYING SHOWERS
MOVING INTO CENTRAL MN BETWEEN 6Z AND 9Z CAN NOT BE COMPLETELY
RULED OUT.

THE BIGGER ISSUE FOR TONIGHT THOUGH WILL BE THE THREAT FOR
WIDESPREAD DENSE FOG. TONIGHT...THE MPX AREA WILL FIND ITSELF IN A
CULL BETWEEN THE LOW MOVING ACROSS IOWA THE TROUGH TO THE NORTH.
CLOUDS ARE ALSO SLOWLY CLEARING OUT FROM WEST TO EAST AND COMBINED
WITH LIGHT WINDS...WE WILL SEE EXCELLENT RADIATIONAL COOLING
CONDITIONS SETUP. GUIDANCE IS IN GOOD AGREEMENT WITH LOWS DIPPING
DOWN INTO THE MID 50S...WHICH IS 5 TO 10 DEGREES LOWER THAN OUR
DEWPOINTS THIS AFTERNOON...SO WE WILL BE PRIMED FOR DENSE
FOG/STRATUS. THERE WILL BE A SWEET SPOT THOUGH FOR GETTING FOG
TONIGHT...TO THE EAST OF WEST CENTRAL MN...WHERE SOUTH WINDS LOOK
TO REMAIN ELEVATED ENOUGH TO KEEP THE ATMOS MIXED AND FOG AT
BAY...AND TO THE WEST OF WHERE THE UPPER CLOUD SHIELD ASSOCIATED
WITH THE WAVE DOWN IN IOWA RIGHT NOW ENDS UP. RIGHT NOW...THE
CLOUD SHIELD LOOKS TO GET ABOUT AS FAR EAST AS AN ALBERT
LEA/HASTINGS/BLOOMER LINE. BETWEEN THE CLOUD LINE EAST AND THE
MIXING WEST WE DID BEEF UP THE FOG MENTION.

AFTER THE FOG BURNS OFF...THE REST OF SATURDAY WILL BE PERFECT
WITH MOSTLY SUNNY SKIES AND LIGHT SOUTH WINDS. H85 TEMPS AROUND
24C...WHICH WOULD SUPPORT HIGHS AROUND 90 WILL REMAIN IN THE
CENTRAL DAKOTAS...WITH H85 TEMPS HERE BETWEEN 16C AND 20C...WHICH
CORRESPONDS TO HIGHS IN THE UPPER 70S/LOWER 80S.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 244 PM CDT FRI AUG 28 2015

GENERALLY WARM AND UNEVENTFUL EXTENDED PORTION OF THE FORECAST
FOR THIS ISSUANCE.

UPR LVL RIDGING CURRENTLY OVER THE WRN CONUS WILL STEADILY SLIDE
EWD OVER THE WEEKEND AND SETTLE OVER THE ERN CONUS FOR MUCH OF
THE UPCOMING WEEK. INCRD H5 HEIGHTS WILL ALLOW FOR A SLOW WARMING
OF TEMPERATURES TO UNSEASONABLY WARM LEVELS FOR THE END OF AUGUST
INTO EARLY SEPTEMBER. HIGHS WILL COMMONLY RESIDE IN THE MID-UPR
80S WITH LOWS IN THE MID 60S TO ARND 70. THERE MAY BE A HIGH-LEVEL
THIN LAYER OF SMOKE OVER THE WEEKEND INCOMING FROM THE WRN CONUS
FIRES BUT NOTHING THAT SHOULD IMPACT AIR QUALITY.

AS FOR SENSIBLE WX FEATURES...THE DEEP RIDGING ALOFT ORIGINATING
FROM THE SWRN CONUS WILL ALSO ALLOW WARMER HIGH PRES TO TAKE UP
RESIDENCE AT THE SFC. THIS WILL PREVENT AN APPROACHING COLD FRONT
FROM THE CANADIAN ROCKIES THRU THE NRN PLAINS TO EXIT THE DAKOTAS.
AS SUCH...ANY SYNOPTIC SCALE SYSTEMS WILL NOT MAKE IT TO THIS
REGION...THUS MITIGATING ANYTHING OTHER THAN AIRMASS POP-UP SHWRS
TSTMS SHOULD ANY WEAK MIDLVL SHORTWAVE DISTURBANCES MAKE IT THIS
FAR E FOR MUCH OF THE WEEK. ANY POPS HAVE BEEN CAPPED AT NO
HIGHER THAN 20 PERCENT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 106 PM CDT FRI AUG 28 2015

RAINFALL PUSHED INTO EAU LATE THIS MORNING AND THIS WILL BE THE
ONLY TERMINAL IMPACTED BY RAIN THIS PERIOD. RAINFALL AREA IS
SLOW MOVING...SO KEPT THE 21Z END TIME PREVIOUS TAF HAD...THOUGH
IT COULD BE AS LATE AS 23Z BEFORE RAIN FINALLY ENDS.
OTHERWISE...MAIN ISSUE FOR TONIGHT WILL BE THE POTENTIAL FOR LOW
STRATUS/DENSE FOG. THIS MORNING...WE SAW MAINLY LOW STRATUS FORM
OVER NORTH CENTRAL MN TO THE NW OF THE UPPER CLOUD SHIELD
ASSOCIATED WITH THE IOWA SYSTEM. TONIGHT...THIS SAME REGION WILL
BE CENTERED RIGHT ON THE MPX CWA. MOST MODELS SHOW LOWS TONIGHT
FALLING 5-10 DEGS BELOW CURRENT DEWPOINTS...SO DENSE FOG IS
LOOKING PRETTY LIKELY EAST OF WEST CENTRAL MN...WHERE STRONG SFC
WINDS WILL KEEP LOW LEVELS MIXED AND WEST OF WHERE THE UPPER CLOUD
SHIELD WITH THE SYSTEM TO OUR SOUTH ENDS UP. THIS WOULD PUT
RWF/STC/MSP/RNH IN A FAVORED REGION FOR SEEING DENSE FOG. FOR
NOW...HIT FOG HARDEST AT THE FIELDS FOG HAPPENS THE MOST
CLIMATOLOGICALLY IN THAT LIST...WHICH IS STC/RNH. EAU COULD HAVE
ISSUES WITH FG AS WELL...BUT LOOKS LIKE THEY MAY KEEP HIGHER
CLOUDS THROUGH THE NIGHT...WHICH WOULD KEEP VSBYS HIGHER. AFTER
FOG BURNS OFF...SAT LOOKS TO BRING SKC SKIES AND SE WINDS OF 5 KTS
OR LESS.

KMSP...CONCERN IS GROWING THAT MSP MAY BE DEALING WITH LIFR
CONDITIONS LATE TONIGHT INTO SAT MORNING. DENSE FOG IS LIKELY AT
THE SATELLITE AIRPORTS TOWARD THE FRINGE OF THE TWIN CITIES
METRO. THIS WILL BE A RADIATION FOG...WHICH IS TOUGH TO GET AT
MSP. INSTEAD...CURRENT THINKING IS THAT 200-300 FT STRATUS MAY
DEVELOP AS FOG SURROUNDING THE AIRPORT TRIES TO MOVE IN...WITH VIS
GETTING DOWN TO 2 OR 3 SM. FOR NOW JUST HINTED AT THE POSSIBILITY
OF THIS HAPPENING WITH THE 10Z LINE AND WILL HAVE TO MONITOR THIS
POTENTIAL CLOSELY TONIGHT.

/OUTLOOK FOR KMSP/
SUN-TUE...VFR. WINDS S 5-15 KTS.

&&

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

$$

SHORT TERM...MPG
LONG TERM...JPC
AVIATION...MPG


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