Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250802
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
302 AM CDT MON AUG 25 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 300 AM CDT MON AUG 25 2014

NO SIGNIFICANT WEATHER CONCERNS EXIST THIS PERIOD AS THE FRONT NOW
WORKING ACROSS SE MN AND WRN WI WILL CONTINUE TO SAG SOUTHEAST
TODAY. ALOFT...UPPER LOW CURRENTLY SPINNING INTO SRN MANITOBA WILL
BE HEADING FOR HUDSON BAY...WHILE THE SUBTROPICAL RIDGE WILL
REMAIN ANCHORED FROM THE SRN MS VALLEY INTO THE ERN GREAT LAKES.
THIS WILL PUT THE UPPER MS VALLEY WITHIN A BELT OF WSW UPPER WINDS
THAT WILL FEATURE A SERIES OF WEAK SHORT WAVES /THE FIRST OF WHICH
IS ALREADY IN NE COLORADO/ RIPPLING THROUGH IT THIS AFTERNOON AND
TONIGHT. HOWEVER...WHILE THESE WAVES ARE COMING ACROSS THE
REGION...AT THE SFC HIGH PRESSURE WILL BE ROTATING AROUND THE SRN
CANADA LOW ACROSS THE DAKOTAS AND INTO MN. SFC DEWPS WILL BE FALLING
IN THE 40S/50S BY TONIGHT...AND THIS DRY LOW LEVEL AIR WILL MAKE IT
SO THAT THESE UPPER WAVES COMING AT US TONIGHT ARE NOT ABLE TO DO
MUCH MORE THAN INCREASE THE AMOUNT OF MID LEVEL CLOUDS. THROUGH 12Z
TUESDAY...THE VAST MAJORITY OF BOTH CAMS AND DETERMINISTIC MODELS
CAME IN DRY WITH RESPECT TO THE MPX CWA...WHICH MAKES SENSE WHEN
LOOKING AT ISENTROPIC FORCING ON THE 310K SFC AND FGEN IN THE H7-H6
LAYER...BOTH OF WHICH ARE CONFINED TO IOWA. SHOULD SEE A TIGHT
PRECIP GRADIENT ACROSS NRN IA...BUT NOT EXPECTING ANY MEASURABLE
PRECIP AS FAR NORTH AS I-90...SO REMOVED ANY POPS IN THE SHORT TERM
IN THE WAKE OF THIS MORNING COLD FRONT.

FOR TEMPERATURES...THE COOLER/DRIER AIR WILL BE SLOW TO TAKE OVER IN
WRN WI...WITH A PRETTY TIGHT GRADIENT IN 925MB TEMPS EXPECTED ACROSS
THE MPX AREA...WITH VALUES RANGING FROM 20-22C OUT BY EAU TO 10-12C
OVER BY AXN THIS AFTERNOON. THIS WILL RESULT IN A FAIRLY DECENT TEMP
GRADIENT ACROSS THE AREA TODAY...WITH A STILL MUGGY MID 80S IN THE
EAST...WHILE THE NW CWA WILL STRUGGLE TO HIT 70 IN A MUCH MORE
PLEASANT AIRMASS. TONIGHT...WITH THE HIGH AND DRY AIR MOVING
IN...WILL SEE TEMPS DROP OFF PRETTY QUICK...WITH A COOL MORNING
EXPECTED WHERE CLOUD COVER IS LIMITED. SHOULD HAVE NO PROBLEMS
GETTING TEMPS IN WEST CENTRAL AND CENTRAL MN DOWN INTO THE 40S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 300 AM CDT MON AUG 25 2014

MEDIUM RANGE DETERMINISTIC AND ENSEMBLE GUIDANCE IS IN DECENT
AGREEMENT ON THE LARGE SCALE EVOLUTION OF THINGS OVER THE UPCOMING
WEEK. THE HIGHLY AMPLIFIED PATTERN CURRENTLY IN PLACE LOOKS TO
FLATTEN AND BECOME ZONAL BY MIDWEEK... THEN TREND BACK TOWARD SOME
AMPLIFICATION WITH A SIMILAR LOOKING SHORTWAVE/UPPER LOW /TO WHAT
WE CURRENTLY SEE/ WORKING THROUGH THE NORTHERN PLAINS AGAIN TOWARD
THE END OF NEXT WEEKEND. THE MAIN DISAGREEMENT AMONGST THE
GUIDANCE CONTINUES TO BE WHERE THE OLD FRONTAL BOUNDARY/BAROCLINIC
ZONE WILL LOITER FOR MUCH OF THE WEEK AS HIGH PRESSURE SITS OVER
THE UPPER MISSISSIPPI VALLEY INTO THE GREAT LAKES. THE TREND TO
SHOVE IT FARTHER SOUTH OVER THE FIRST PART OF THE WEEK PERSISTED
INTO THE LATEST RUNS... WHICH MEANS IT SHOULD ONLY BE A CONCERN
FOR OUR FAR SOUTHERN CWFA AT BEST THROUGH MIDWEEK. HOWEVER...
AFTER THAT POINT THERE IS QUITE A BIT OF SPREAD IN HOW QUICKLY IT
WILL LIFT BACK TO THE NORTH AND WHERE SHRA/TSRA WILL DEVELOP IN
THE RETURN FLOW AND LOW-MID LEVEL THETA-E ADVECTION. GIVEN THE
UNCERTAINTY... TENDED TO GO WITH LOWER POPS TOWARD THE END OF THE
FORECAST PERIOD THAN WHAT MIGHT BE EXPECTED FROM INDIVIDUAL
SOLUTIONS SUCH AS THE ECMWF. IT ISN/T TO SAY THAT THERE ISN/T A
DECENT LIKELIHOOD OF PCPN DURING THE THURSDAY THROUGH SUNDAY TIME
PERIOD... BUT WOULD RATHER BE CONSERVATIVE ON POPS THAN GLOSS OVER
SEVERAL DAYS WITH LOW POPS AND GIVE THE LIKELY FALSE IMPRESSION
THAT IT WILL BE A WASHOUT.

SURFACE RIDGING WILL CONTINUE TO BUILD OVER THE REGION ON
TUESDAY... AND SHOULD CONTINUE TO PROVIDE A DRY NORTH/NORTHEAST
FLOW THROUGH WEDNESDAY. KEPT SOME LOW POPS OVER THE FAR SOUTH JUST
IN CASE ANY ACTIVITY SNEAKS INTO THAT AREA AFTER DEVELOPING NEAR
THE OLD FRONTAL BOUNDARY WELL TO THE SOUTH. SHOULD FINALLY SEE
SOME MOISTURE RETURN BY THURSDAY ALONG WITH AN INVERTED SURFACE
TROUGH WORKING ITS WAY INTO THE SOUTHERN HALF OF THE AREA. THIS
WILL RESULT IN THE NEED TO MENTION POPS OVER MOST OF THE AREA FROM
THURSDAY INTO EARLY FRIDAY. WILL THEN ALLOW FOR LOW OR NO POPS FOR
MOST OF THE AREA INTO THE END OF THE FORECAST PERIOD AS THE
SURFACE TROUGH PUSHES BACK TO THE SOUTHEAST AND THE NEXT SYSTEM
SLOWLY MOVES FROM THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS
OVER THE WEEKEND. AS MENTIONED EARLIER... THERE IS SOME
POSSIBILITY THAT THE SURFACE TROUGH AND ASSOCIATED
THERMAL/INSTABILITY GRADIENT WON/T SHIFT SUFFICIENTLY SOUTHEAST TO
DRY US OUT FROM FRIDAY THROUGH THE WEEKEND. THE ECMWF CERTAINLY
IMPLIES SUCH A SCENARIO.. AND WOULD NECESSITATE PCPN MENTION FOR
MUCH OF THAT TIME FRAME. HOWEVER... AS DISCUSSED... WILL BE
CONSERVATIVE AT THIS POINT AND KEEP POPS OUT OF MOST OF THE AREA
RATHER THAN BLANKETING A THREE DAY PERIOD WITH CHANCE POPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1216 AM CDT MON AUG 25 2014

WILL START THE PERIOD WITH THE COLD FRONT WORKING ACROSS WI. LINE
OF STORMS WILL CLEAR EAU BY 8Z...AND AFTER THAT REST OF THE TAF
PERIOD WILL BE PRECIP FREE. HAVE SEEN GOOD PUSH OF DRY AIR INTO
WRN/CENTRAL MN BEHIND THE FRONT...BUT IT IS LOSING ITS UMPH GOING
INTO ERN MN/WRN WI...SO WILL HAVE TO WATCH FOR FOG FORMATION EAST
OF I-35 AS SKIES CLEAR OUT IN THE WAKE OF THE FRONT. RNH/EAU
WOULD HAVE THE GREATEST THREAT FOR FG DEPENDING ON EXTENT OF
CLEARING BEHIND THE FRONT BEFORE SUNRISE. WILL HAVE MAINLY CLEAR
SKIES MUCH OF THE DAY MONDAY...BUT WE WILL HAVE TO WATCH MVFR CIGS
ADVANCING ACROSS NODAK THAT WILL BE APPROACHING AXN LATE IN THE
AFTERNOON...THOUGH AT THIS POINT THEY LOOK TO REMAIN NORTH OF
AXN/STC.

KMSP...NO ISSUES EXPECTED THIS TAF PERIOD...WITH ARRIVAL OF DRIER
AIR BEHIND THE FRONT FINALLY GIVING US A MORNING WHERE WE WILL NOT
HAVE TO MONITOR STRATUS EXPANDING ACROSS THE LANDSCAPE. IN
GENERAL...THIS IS A HIGH CONFIDENCE TAF...WITH NOT MUCH VARIATION
FROM WHAT IS FORECAST EXPECTED.

/OUTLOOK FOR KMSP/
TUE...VFR. WINDS NNW 5-10 KTS.
WED...VFR. WINDS NE 5-10 KTS.
THU...MVFR POSSIBLE WITH CHC SHRA/TSRA. WINDS E 5-10 KTS.


&&

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

$$

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







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