Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 201954
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
254 PM CDT SUN JUL 20 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 221 PM CDT SUN JUL 20 2014

TONIGHT AND MONDAY...SFC ANALYSIS PUTS A WMFNT NOW WELL N OF THE WFO
MPX CWFA...AND EVEN N OF THE INTERNATIONAL BORDER...WHILE A SFC
CDFNT DRAPES FROM ERN MANITOBA THEN WWD THRU ND INTO MT. THE INFLUX
OF DEEPER MOISTURE IS ON AS SFC DEWPOINTS HAVE RISEN TO THE MID 60S
THRU LWR 70S ALREADY...AND PWATS HAVE INCREASED TO OVER 1.5 INCHES.
THERE ARE SOME AREAS OF LOWER CLOUDS BUT BY AND LARGE THE AREA
CONTINUES TO BE PARTLY TO MOSTLY CLEAR AND IS EXPECTED TO REMAIN AS
SUCH OVERNIGHT INTO TMRW. THERE ARE SOME INDICATIONS OF POTENTIALLY
SOME LOW STRATUS OVERNIGHT BUT DECOUPLING WILL ALLOW MOISTURE TO
SETTLE...BUT FOG STABILITY INDICES AND CROSSOVER TEMPS DO FAVOR THE
FORMATION OF AT LEAST LIGHT FOG FOR MUCH OF THE AREA...OWING TO THE
PLENTIFUL NEAR-SFC MOISTURE. SO...HAVE INCLUDED AREAS OF FOG IN THE
FCST. THIS SFC MOISTURE WILL ONLY INCRS DURG THE DAY TMRW WITH THE
AREA SQUARELY WITHIN THE WARM SECTOR OF THIS SYSTEM. DEWPOINTS WILL
CONTINUE TO CLIMB...INTO THE LWR TO MID 70S...HIGHEST IN WRN MN.
WITH SFC TEMPS CLIMBING INTO THE LOW 90S FOR MUCH OF THE CWFA /ONLY
FAR ERN PORTIONS OF THE CWFA WILL HOLD IN THE 80S/...HIGH HEAT
INDICES WILL BE A PROBLEM AS ADVERTISED IN THE ONGOING EXCESSIVE
HEAT WARNINGS AND HEAT ADVISORIES. HAVE MADE NO CHANGES TO THE
TIMING OR CONFIGURATION OF THE PRODUCTS SINCE ALL LOOKS WELL THIS
AFTN. THE NEXT TOPIC BECOMES THE POTENTIAL OR PRECIPITATION. FOR THE
REST OF TDA INTO TNGT AND THE FIRST HALF OF TMRW...THE ENTIRE CWFA
LOOKS TO REMAIN DRY. GRANTED...THERE IS A WEAK SHORTWAVE DISTURBANCE
PROGGED TO SWING THRU NWRN INTO NERN MN THIS EVE INTO THE EARLY MRNG
HRS. THIS IS ALSO IN CONJUNCTION WITH A SFC PRE-FRONTAL TROF...AND
THESE FEATURES MAY BE ABLE TO USE THE DEEP MOISTURE IN PLACE TO
SPARK OFF A FEW SHWRS/TSTMS FOR NWRN PORTIONS OF THE CWFA. CHANCES
ARE LOW FOR SEEING ANY STORMS...BUT THE POTENTIAL IS THERE FOR ANY
STORMS THAT FORM TO BE STRONG-TO-SEVERE GIVEN THE INSTABILITY IN
PLACE...WITH SBCAPE NEARLY 3000 J/KG...LI DOWN TO -6 DEG C AND
MODEST LAPSE RATES WITH NEARLY NO CINH. HOWEVER...THESE WOULD BE
ISOLD AT BEST. BY TMRW AFTN...IN ADVANCE OF THE SFC FRONT...ONCE THE
CAP BREAKS IN THE AFTN...STORMS WILL FIRE IN FAR NWRN MN AND BEGIN
TO SHIFT EWD. STILL SOME TIMING ISSUES BUT CHCS CERTAINLY INCRS IN
THE LATE AFTN. NOT LOOKING FOR MUCH IN THE WAY OF SEVERE STORMS TMRW
AFTN...THAT IS PRETTY MUCH RESERVED FOR THE MON NIGHT PERIOD PER THE
SPC SWODY2 DISCUSSION.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 221 PM CDT SUN JUL 20 2014

AT THIS TIME... THE MAIN ITEM OF CONCERN FOR THIS PORTION OF THE
FORECAST IS THE POTENTIAL FOR SEVERE WEATHER MONDAY EVENING INTO
THE OVERNIGHT HOURS. THE DAY 2 OUTLOOK WAS UPDATED TO INCLUDE A
MODERATE RISK ACROSS THE AREA GIVEN THE POTENTIAL FOR A WIDESPREAD
DAMAGING WIND EVENT. WITH TEMPERATURES CLIMBING ABOVE 90 AND
DEWPOINTS GETTING INTO THE 70S... INSTABILITY WILL BE EXTREME
MONDAY AFTERNOON INTO MONDAY EVENING... WITH FORECAST SOUNDINGS
INDICATING MLCAPE VALUES AOA 4500 J/KG ACROSS MUCH OF THE AREA.
THE WARM FRONT SHOULD BE JUST NORTH OF THE AREA... WITH THE
SURFACE LOW OVER CENTRAL SOUTH DAKOTA BY LATE AFTERNOON. A
SHORTWAVE WHICH WAS EJECTED FROM THE UPPER TROUGH OFF THE
CALIFORNIA COAST WILL CONTINUE TO MAKE ITS WAY EASTWARD AROUND THE
PERIPHERY OF THE UPPER RIDGE TONIGHT INTO MONDAY. THIS FEATURE
SHOULD PROVIDE SUFFICIENT FORCING TO OVERCOME THE CAP AND GET
STORMS GOING TO OUR WEST MONDAY AFTERNOON... MOST LIKELY OVER
NORTH DAKOTA. THIS ACTIVITY SHOULD THEN GROW UPSCALE AS INDIVIDUAL
COLD POOLS COALESCE AND MOVE EASTWARD AS AN MCS WITH THE MEAN
FLOW... BUT COULD THEN TAKE A SOUTHEASTWARD DIVE TOWARD INTO THE
DIFFLUENT THICKNESSES AND INTO THE AREA WHERE HIGHER INSTABILITY
WILL BE PRESENT. THIS WOULD BRING THE MCS INTO OUR NORTHWESTERN
AREA SOMETIME DURING THE EARLY EVENING... WITH IT MOVING EAST AND
EVENTUALLY SOUTHEASTWARD THROUGH CENTRAL AND EAST CENTRAL
MINNESOTA AND PERHAPS WEST CENTRAL WISCONSIN BY MIDNIGHT OR
SHORTLY THEREAFTER. EXACTLY HOW THINGS EVOLVE IS CERTAINLY STILL A
BIG QUESTION AT THIS POINT... BUT GIVEN THE THERMODYNAMIC SETUP...
PRESENCE OF THE NEARLY STATIONARY WARM FRONT... AND THE SHORTWAVE
FORCING... THE OCCURRENCE OF AN MCS SEEMS LIKELY. THE MAIN
UNCERTAINTY AT THIS POINT IS EXACTLY WHERE SUCH A FEATURE WILL
TRACK... WITH THE I-94 CORRIDOR AND POINTS NORTH APPEARING MOST
LIKELY AT THIS POINT IN TIME. DAMAGING WIND GUSTS LOOK TO BE THE
PRIMARY CONCERN ONCE THE SYSTEM GROWS UPSCALE... ALTHOUGH WIND
DRIVEN LARGE HAIL COULD CERTAINLY BE A CONCERN GIVEN THE LARGE
CAPE VALUES THAT WILL BE IN PLACE. A FEW TORNADOES AND DISCRETE
SUPERCELLS COULD BE AN ISSUE INITIALLY... ALTHOUGH THAT CONVECTIVE
MODE SHOULD MAINLY IMPACT LOCATIONS TO OUR NORTHWEST. THE CAM
SOLUTIONS WHICH EXTEND OUT SUFFICIENTLY IN TIME... HIRES-WINDOW
NMMB/ARW AND THE NAM CONUS-NEST... SHOW A SIMILAR EVOLUTION WITH
CONVECTION OVER THE DAKOTAS GROWING UPSCALE INTO A LARGE BOWING
MCS WHICH THEY MOVE THROUGH NORTHERN/CENTRAL MINNESOTA DURING THE
EVENING HOURS. NEEDLESS TO SAY... WILL NEED TO MONITOR THINGS AND
TRY TO GET A BETTER HANDLE ON TIMING AND LOCATION AS WE HEAD
THROUGH THE NIGHT AND INTO THE DAY ON MONDAY. THE SPCNMM WAS MORE
ROBUST THAN OTHER CAMS IN DEVELOPING SOME OVERNIGHT CONVECTION
TONIGHT THAT COULD COMPLICATE THE SITUATION MONDAY
AFTERNOON/NIGHT... BUT IT APPEARS TO BE MOSTLY ALONE IN ITS
DEPICTION WITH THE HOPWRF AND OTHER SOLUTIONS NOT SHOWING MUCH IF
ANYTHING LATER TONIGHT.

ONCE WE GET TOMORROW NIGHT/S ACTIVITY OUT OF THE WAY... WE/LL ONCE
AGAIN LOOK AT THE LARGE SCALE PATTERN TRYING TO SHIFT BACK TOWARD
THE GENERAL SETUP WE/VE SEEN SINCE LAST FALL. SHORTWAVE RIDGING
WILL BRIEFLY TRY TO RE-ESTABLISH ITSELF OVER THE AREA DURING THE
MIDDLE OF THE WEEK IN THE WAKE OF THE MONDAY-TUESDAY SHORTWAVE...
BUT THAT APPEARS TO BE SHORT-LIVED. AN UPPER LOW CURRENTLY SOUTH
OF ALASKA IS PROGGED BY THE GFS AND ECMWF TO COME ASHORE IN THE
PACIFIC NORTHWEST BY WEDNESDAY EVENING THEN PUSH EASTWARD AND
DEPRESS THE RIDGE ALONG THE US/CANADA BORDER BEFORE DIVING
SOUTHEASTWARD AND REINFORCING THE LARGE SCALE UPPER TROUGH OVER
EASTERN NORTH AMERICA OVER THE WEEKEND. THIS SCENARIO PUTS US IN
WESTERLY OR NORTHWESTERLY UPPER FLOW FOR MOST OF THE REMAINDER OF
THE FORECAST PERIOD. THE EXCEPTION WILL BE A BRIEF PERIOD OF WEST-
SOUTHWESTERLY FLOW AND FORCING AHEAD OF THE LATE WEEK/WEEKEND
SHORTWAVE. IN TERMS OF THE DETAILS... WE MAY SEE SOME STRATIFORM
PCPN LINGER OVERNIGHT MONDAY NIGHT IN THE WAKE OF THE EXPECTED
MCS/SEVERE WEATHER... WITH HIGH PRESSURE BUILDING INTO THE AREA ON
TUESDAY. HOWEVER... THE GFS AND ECMWF HINT AT ENOUGH POST FRONTAL
INSTABILITY FOR SOME SHRA/TSRA AGAIN TUESDAY AFTERNOON INTO
TUESDAY EVENING OVER THE EASTERN PORTION OF THE AREA BEFORE THE
BONAFIDE DRY AIR ARRIVES. ONCE THAT OCCURS... WE LOOK TO BE PCPN-
FREE THROUGH THURSDAY. WE/LL THEN SEE CHANCES FOR PCPN RETURN AND
MOVE WEST TO EAST ACROSS THE AREA THURSDAY NIGHT THROUGH FRIDAY AS
THE SHORTWAVE CURRENTLY SOUTH OF ALASKA MAKES AN APPEARANCE OVER
OUR AREA. WE/LL THEN SEE THE MID-UPPER LEVEL COLD POOL SETTLE INTO
THE AREA OVER THE WEEKEND... SETTING THE STAGE FOR MOSTLY
DIURNALLY DRIVEN SHRA AND PERHAPS TS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1224 PM CDT SUN JUL 20 2014

WARM FRONT WILL CONTINUE TO LIFT NE THRU THE REGION TDA...WITH A
TIGHT PRES GRADIENT ON ITS LEADING EDGE PLUS DEEP MIXING PRODUCING
BREEZY/GUSTY WINDS THRU THIS EVE. WINDS SETTLE DOWN TO THE 5-10 KT
RANGE TMRW THEN PICK UP AGAIN AFTER DAYBREAK TMRW TO 8-12 KT WITH
OCNL HIGHER GUSTS. MID- AND UPR-LVL CLOUDS WILL PREVAIL THROUGHOUT
THIS TAF PERIOD...WITH THE MIDLVL CLOUDS DISSIPATING OVERNIGHT.
ONLY SHOT AT PRECIP LOOKS TO BE KAXN WHICH WILL BE IN CLOSEST
PROXIMITY TO AN UPR LVL SHORTWAVE MOVG THRU. TIMING LOOKS TO BE
MID-TO-LATE EVENING FOR ANY CONVECTION. NO OTHER TAF SITES HAVE
PRECIP AS ANY PRECIP LOOKS TO DISSIPATE BEFORE DRIVING ANY FURTHER
SE. THE STRONG LOW LEVEL INFLUX OF MOISTURE WITH ENOUGH DECOUPLING
OVERNIGHT WILL CREATE AREAS OF MVFR FOG ACRS MUCH OF S-CENTRAL MN
INTO WRN WI TONIGHT. ONCE THIS DISSIPATES SHORTLY AFTER
DAYBREAK...VSBY RESTRICTIONS MAY WELL TAKE THE FORM OF HAZE.
ATTM...HAVE ONLY INDICATED 6SM BUT IT IS VERY POSSIBLE MUCH OF THE
DAY COULD HOLD IN THE 4-5SM VSBY RANGE DUE TO HAZE.

KMSP...NO PRECIP CONCERNS THRU TMRW AFTN AND NO CEILING ISSUES
EXPECTED. MAIN CONCERNS WILL BE PRE-DAWN AND DAYBREAK MVFR VSBY
ARND THE TIME OF THE MORNING PUSH...THEN HAZE FOR MUCH OF THE DAY.
WILL ADVERTISE 6SM HZ BUT VSBY COULD BE LOWER FROM TIME TO TIME
DURG THE DAY TMRW WITH THE HIGH DEWPOINTS IN PLACE.

/OUTLOOK FOR KMSP/
MON...VFR. WINDS S 10-15KTS.
MON NIGHT...MAINLY VFR. STRONG TSTMS LIKELY WITH OCNL PERIODS OF
MVFR/IFR. WINDS S 10KTS...HIGHER IN TSTMS.
TUE...VFR WITH IFR/TSRA POSSIBLE IN THE MORNING. WINDS SW 10 KTS
BECOMING NW.
WED...VFR. WINDS NE 10KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR MNZ041>045-
     047>059-064>067-073>078-082>085-091>093.

     EXCESSIVE HEAT WARNING FROM 11 AM TO 9 PM CDT MONDAY FOR
     MNZ060>063-068>070.

WI...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR WIZ014-023-024.

&&

$$

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





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