Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KMPX 211809
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
109 PM CDT SUN SEP 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 425 AM CDT SUN SEP 21 2014

TODAY-TONIGHT...SFC ANALYSIS SHOWS A CDFNT PUSHING ACRS LAKE MI
INTO LOWER MI WITH A SECONDARY CDFNT DRAPED FROM CENTRAL
MANITOBA PROVINCE THRU THE NRN GREAT LAKES INTO QUEBEC PROVINCE.
THE FIRST CDFNT WAS RESPONSIBLE FOR THE STRONG/SEVERE TSTMS THAT
PASSED THRU THIS REGION YDA...WHILE THE SECOND CDFNT IS MORE
REFLECTIVE OF THE UPR LVL VORT MAX DROPPING SEWD FROM S-CENTRAL
CANADA. CYCLONIC FLOW ARND THIS UPR VORT WITHIN COLD AIR ALOFT AND
LINGERING DEEP MOISTURE WILL PRODUCE SCTD SHWRS OVER WRN WI INTO
FAR ERN MN THRU THE FIRST HALF OF TDA. NO SEVERE WX WILL COME FROM
THIS...AND HIGHLY LIKELY THAT NO TSTMS WILL DEVELOP WITH A MUCH
MORE STABLE ATMOS IN PLACE. SO...HAVE KEPT POPS NO HIGHER THAN CHC
CATEGORY FROM DAYBREAK ON AS COVERAGE NOT EXPECTED TO BE ALL THAT
GREAT...AND QPF WILL BE QUITE LIGHT...GENERALLY ONLY UP TO A FEW
HUNDREDTHS TO BE RECEIVED. ANY AND ALL PRECIP SHOULD DISSIPATE AND
SHIFT OFF TO THE E BY MIDDAY WITH GRADUAL CLEARING EXPECTED
THEREAFTER AS HIGH PRES SLOWLY ARRIVES FROM THE W. DEEP DRY NW
FLOW FROM THE SFC UPWARD WILL PROMOTE CLEARING SKIES THIS EVENING
THRU THE OVERNIGHT HRS. THE ONLY QUESTION WILL BE THE COVERAGE OF
FOG OVERNIGHT AS CAA KICKS INTO HIGH GEAR WHILE WINDS DROP OFF
UNDER THE CLEARING SKIES. CROSSOVER TEMPS ARE CLOSE SO IT MAY WELL
BE A MATTER OF HOW MUCH MOISTURE CAN BE SCOURED OUT BEFORE THE
NIGHTLY INVERSION SETS IN. HAVE OPTED TO INCLUDE PATCHY FOG FOR
NRN AND ERN PORTIONS OF THE CWFA WHERE WINDS ARE MOST LIKELY TO GO
CALM AND WHERE COLDEST TEMPS ARE EXPECTED. WITH RESPECT TO THE
CAA...HIGHS TDA WILL BE NOTICEABLY COOLER THAN SATURDAY WITH HIGHS
RANGING FROM THE LWR 60S IN WRN WI TO THE UPR 60S TO ARND 70 IN
WRN MN. FOR TNGT...LOWS OUTSIDE THE TWIN CITIES METRO WILL DROP TO
THE LOW-MID 40S...WITH MIN TEMPS CLOSE TO 50 WITHIN THE TC METRO.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 425 AM CDT SUN SEP 21 2014

THE UPPER MIDWEST WILL FIND ITSELF ON THE WARM SIDE OF A HIGHLY
AMPLIFIED UPPER LEVEL PATTERN WHICH WILL LEAD TO TEMPERATURES THAT
WILL BE WELL ABOVE THE SEASONAL AVERAGE FOR LATE SEPTEMBER. DRY
WEATHER IS EXPECTED ASIDE FROM SCATTERED SHOWERS LATE TUESDAY
THROUGH WEDNESDAY.

EARLY MORNING WATER VAPOR IMAGERY WITH GFS 21.00 500MB HEIGHTS AND
WINDS SHOWED A DIGGING TROUGH OVER THE NORTHWEST PACIFIC WITH A
RIDGING OVER THE CANADIAN ROCKIES. MEANWHILE A WEAKENING OCCLUDED
PV ANOMALY WAS SITUATED ACROSS SOUTHERN CALIFORNIA...AND THIS
WILL BE THE FOCUS FOR PRECIP CHANCES EARLY IN THE PERIOD. FORECAST
SOUNDINGS SHOW DRY AIR IN THE LOWER LEVELS...SO MAY SEE MORE MID-
LEVEL SATURATION/CLOUDS THAN ACTUAL PRECIP. THEREFORE BROKE UP THE
POPS INTO 6HR BLOCKS TO INCREASE THE TEMPORAL RESOLUTION.
ALSO...FORECAST SOUNDINGS DO NOT SHOW ELEVATED INSTABILITY...SO
HAVE LOW CONFIDENCE IN UPRIGHT CONVECTION AND AS RESULT REMOVED
THE THUNDER MENTION FROM THE WEATHER GRIDS.

LOOKING AHEAD...WARM AIR MOVES ACROSS THE REGION AS THE UPPER
LEVEL PATTERN AMPLIFIES. WAS TEMPTED TO INCREASE POPS WELL ABOVE
GUIDANCE...BUT THERE ARE TWO VARIABLES THAT PREVENTED THIS. FIRST
OF ALL...FORECAST MODELS HINT AT A WEAK WAVE CUTTING OFF OVER THE
CORN BELT...AND THIS COULD LEAD TO MID/UPPER LEVEL CLOUDS WHICH
WILL SEVERELY LIMIT AFTERNOON HEATING. SECONDLY...SURFACE WINDS
MAY CONTAIN A SLIGHT EASTERLY COMPONENT. FORECAST SOUNDINGS SHOW
AFTERNOON MIXING WITH WINDS EVENTUALLY BECOMING 180-190DEG...BUT
IF CLOUDS MOVE IN THEN THE BOUNDARY LAYER MIXING WILL BE LESS THAN
CURRENTLY FORECAST. SINCE IT IS ONLY SUNDAY...HAVE PLENTY OF TIME
TO RAISE TEMPERATURES FOR THE LATTER HALF OF THE WEEK...SO WAS
CONTENT TO STICK WITH THE HIGHER END OF GUIDANCE...RATHER THAN
EXCEEDING IT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1249 PM CDT SUN SEP 21 2014

MAIN FOCUS TODAY IS CU FIELD WRAPPING AROUND THE BACK SIDE OF THE
UPPER LOW THAT IS MOVING EAST ACROSS THE GREAT LAKES. MUCH OF
EASTERN MN AND WESTERN WI HAS QUICKLY SEEN THE CU FIELD BECOME
SCATTER AND THAT TREND WILL CONTINUE THIS AFTERNOON. EXPECT VFR
CIGS FOR STC AND AREAS EAST. A THICKER CLOUD DECK TO THE WEST
CONTINUES STREAMING SOUTHWARD AND WILL CONTINUE MVFR CIGS AT AXN
AND RWF FOR THE NEXT FEW HOURS. TRIMMED BACK ON THE WIND GUSTS
GIVEN TRENDS HAVE BEEN A BIT LESS WINDY OVERALL THROUGH THE DAY SO
FAR. WINDS WILL REMAIN NORTHWESTERLY...AND THE CU FIELD WILL
CONTINUE TO DIMINISH TO CLEAR SKIES TONIGHT. CLEAR SKIES AND LIGHT
WINDS FROM THE WEST TO SOUTHWEST THROUGH TOMORROW ARE EXPECTED.

KMSP...VFR CIGS EXPECTED THROUGH THE PERIOD. HOWEVER...WILL HAVE
TO WATCH THE THICK CLOUD DECK TO THE WEST AS THE UPPER LOW PUSHES
EASTWARD. CURRENTLY ANTICIPATING THIS DEC TO SCATTER OUT THIS
AFTERNOON AND EVEN IF BKN CEILINGS MOVE BACK IN TO MSP...SHOULD BE
ABOVE 3K FT DUE TO DAYTIME HEATING.

/OUTLOOK FOR KMSP/
TUE...VFR. WINDS S 10 KTS.
WED...VFR. WINDS S 10-15 KTS.
THU...VFR. WINDS SSE 5-10 KTS.


&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...JRB
AVIATION...SPD






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.