Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 201119
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
619 AM CDT SUN APR 20 2014

.UPDATE...
ISSUED AT 610 AM CDT SUN APR 20 2014

UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 301 AM CDT SUN APR 20 2014

LATEST SURFACE ANALYSIS SHOWS A NICE SURFACE DEWPOINT GRADIENT
EXTENDING FROM SOUTHWEST MINNESOTA NORTHEAST INTO NORTHWEST
WISCONSIN. RAP 925-700MB LAYER MOISTURE CONVERGENCE SHOWS A DECENT
AREA OF DEEP MOISTURE CONVERGENCE ALONG THIS SAME GENERAL AXIS...
AND WE CONTINUE TO SEE SCATTERED SHRA DEVELOPING ALONG IT. THE RAP
SUGGESTS IT WILL REMAIN FAIRLY STATIONARY THROUGH AROUND 10Z THEN
SINK SOUTHEAST AND MAINLY JUST IMPACT THE FAR SOUTHEAST/EAST PORTION
OF THE FORECAST AREA. THE HRRR AND HOPWRF INDICATE A SIMILAR
EVOLUTION OF THINGS... WITH ACTIVITY DROPPING A BIT SOUTH AFTER 10Z
OR SO. HOWEVER... THE BAROCLINIC ZONE DOESN/T LOOK TO DROP TOO MUCH
FARTHER SOUTH THROUGH TONIGHT... SO ALTHOUGH WE SHOULD SEE ACTIVITY
GET SOUTH OF THE TWIN CITIES METRO THIS MORNING... IT DOESN/T LOOK
TO COMPLETELY EXIT THE FORECAST AREA ANYTIME SOON. IN FACT... THE
SHORTWAVE CURRENTLY EVIDENT OVER THE NORTHWEST CONUS IN WATER VAPOR
IMAGERY WILL MAKE ITS WAY EAST TOWARD THE AREA THIS EVENING. THIS
WILL MAINLY WORK TO GENERATE SOME PCPN WITH A SURFACE WAVE TO OUR
NORTH ALONG/NORTH OF THE CANADIAN BORDER TONIGHT INTO MONDAY
MORNING. HOWEVER... THE SOUTHERN EXTENSION OF THE UPPER WAVE LOOKS
LIKE IT WILL HELP GENERATE A WAVE ALONG THE STALLED BAROCLINIC ZONE
NEARLY THE SOUTHERN PORTION OF THE FORECAST AREA DURING THE
OVERNIGHT INTO EARLY MONDAY MORNING. THE GFS AND ECMWF BRING PCPN
FARTHER NORTH AGAIN LATER TONIGHT INTO MONDAY AS THIS OCCURS... AND
IT WOULD SEEM TO MAKE SENSE GIVEN THE ADDITIONAL FORCING AND AREA OF
ELEVATED INSTABILITY PROGGED TO MOVE THROUGH THE AREA ALONG/AHEAD OF
THE UPPER WAVE. SO... GENERALLY PUSHED POPS SOUTHWARD THROUGH THE
DAY TODAY... THEN LIFTED CHANCES NORTH AGAIN TONIGHT BEFORE
GRADUALLY SHIFTING THEM EASTWARD LATE TONIGHT AS WE FINALLY SEE SEE
SOME SURFACE RIDGING BEGIN TO MOVE IN FROM THE WEST.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 301 AM CDT SUN APR 20 2014

LONGER TERM CONCERNS INCLUDE FIRE WEATHER POTENTIAL MONDAY
AFTERNOON ACROSS THE WEST. THEN THE DEVELOPMENT OF THE WESTERN
CONUS TROUGH TOWARD MIDWEEK WITH THE THUNDER THREAT BUILDING EAST
INTO THE AREA WEDNESDAY INTO THURSDAY. ULTIMATE TIMING OF THE
TROUGH OVER THE AREA ALSO REMAINS A PROBLEM THROUGH THE REMAINDER
OF THE WEEK.

THE MODELS MAY HAVE SLOWED THE PROGRESSION OF THE FRONT ACROSS THE
REGION FOR MONDAY MORNING. WILL LEAVE A SMALL CHANCE OVER THE
EASTERN CWA THROUGH ABOUT MIDDAY MONDAY. THEN COOLER...DRIER AIR MOVES INTO
THE AREA WITH INCREASING NORTHWEST WINDS. WE SHOULD SEE A GENERAL
CLEARING SKY WITH PERHAPS SOME CUMULUS DEVELOPMENT OVER THE
CENTRAL AREA INTO MONDAY AFTERNOON AS THE COOLER AIR MOVES IN.
NORTHWEST WINDS 20-25 MPH ARE EXPECTED TO DEVELOP OVER THE WEST
INTO THE AFTERNOON AND RELATIVE HUMIDITY VALUES WILL DROP OFF TO
25 TO 30 PERCENT OVER THE SOUTHWEST IN THE AFTERNOON. WILL HAVE TO
MONITOR THIS REGION DURING THE DAY AND SEE IF DEWPOINTS DROP
FURTHER. WILL CONTINUE TO MENTION THE DRIER HUMIDITY AND WINDS IN
THE FIRE WEATHER DISCUSSION.

PLEASANT WEATHER EXPECTED FOR TUESDAY WITH LIGHTER WINDS AS THE
HIGH DROPS OVER THE AREA. THE WESTERN CONUS TROUGH MOVES EAST WITH
INCREASING MOISTURE AND INSTABILITY INCREASING ESPECIALLY WEDNESDAY
NIGHT INTO THURSDAY OVER THE AREA. WILL LIKELY SEE SOME INITIAL WAA
SHOWERS MOVE IN TUESDAY NIGHT. THE LLJ INCREASING TO THE WEST OVER
THE EASTERN DAKOTAS LATER WEDNESDAY NIGHT AND SPILLS INTO FAR
WESTERN MN LATE. THEN THIS WILL TRANSLATE EAST INTO WEDNESDAY WITH
THE CONTINUED CHANCE OF SHOWERS. SOME ISOLATED THUNDER WILL WORK
INTO WESTERN AREAS MAINLY DURING THE DAY WEDNESDAY. WE DID REMOVE
THE THUNDER THREAT FARTHER TO THE EAST.

THE TROUGH AND ASSOCIATED SURFACE LOW DEVELOPS TO THE NORTHEAST
WEDNESDAY NIGHT INTO FRIDAY. THE LONGER TERM MODELS REMAIN IN
DISAGREEMENT ON HOW FAST THE TROUGH MOVES THE THE AREA. THE GFS
REMAINS THE SLOWEST AND WILL LIKELY TREND THAT WAY FOR NOW. WILL
CONTINUE THUNDER THREAT OVER THE ENTIRE CWA WEDNESDAY NIGHT AND
THURSDAY. SEVERE WEATHER THREAT WILL BE LIMITED AS IT APPEARS THE
REAL WARM SECTOR MAY BE HAVE SOME DIFFICULTY PENETRATING THE
COOLER/CLOUDY AREA OVER MUCH OF MINNESOTA. IT STILL APPEARS IT
WILL GET COLD ENOUGH FOR AT LEAST A RAIN/SNOW MIX DEVELOPING
FRIDAY NIGHT INTO SATURDAY AND AGAIN SATURDAY NIGHT INTO SUNDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 610 AM CDT SUN APR 20 2014

PRIMARY ISSUES ARE AREAS OF FOG CURRENTLY OCCURRING... CHANCES FOR
SHRA THROUGH THE PERIOD... AND POSSIBILITY OF SOME THUNDER
TONIGHT. SHRA FROM OVERNIGHT HAS FINALLY SAGGED SOUTH OF MOST OF
THE AREA... ALTHOUGH KEAU COULD STILL SEE SOME FOR THE NEXT FEW
HOURS. THE ACTIVITY SHOULD STAY NEAR THE BOUNDARY TO OUR SOUTH FOR
MOST OF THE DAY... BUT AN UPPER WAVE WILL HELP TO ENHANCE A WAVE
ALONG THE FRONTAL BOUNDARY LATER TODAY INTO TONIGHT... WHICH
SHOULD WORK TO BRING SOME SHRA BACK NORTH AGAIN. AT THIS POINT DID
NOT INCLUDE TOO MUCH IN THE WAY OF PCPN... BUT TRIED TO REFLECT
SOME POTENTIAL AGAIN TONIGHT. OF GREATER CONCERN FOR THE SHORT
TERM IS THE FOG WHICH IS PRODUCING WIDESPREAD MVFR VISIBILITIES
AND SOME LOCALIZED IFR AND LIFR. LUCKILY SUNRISE WILL BE
OCCURRING... SO WE SHOULDN/T HAVE TOO MANY FOG CONCERNS BEYOND
13... EXCEPT NEAR KRNH WHERE THE LOSS OF LOWER CLOUDS HAS ALLOWED
FOR MORE EXTENSIVE FOG DEVELOPMENT. GENERALLY ALLOWED THINGS TO
BECOME VFR BETWEEN 13Z AND 14Z... WHICH SHOULD WORK OUT OK.

KMSP...MAIN UNCERTAINTY IS WITH THE FOG DURING THE FIRST HOUR
OR TWO OF THE TAF... WHICH COULD BRIEFLY GET DOWN TO AOB 1SM.
HOWEVER... GIVEN LACK OF CONFIDENCE IN THAT OCCURRING AND THE FACT
THAT IT WOULD BE BRIEF... DIDN/T GO QUITE THAT LOW IN THE
FORECAST. OTHER FORECAST CONCERN IS WITH PCPN RE-DEVELOPMENT OVER
THE AREA LATER TODAY/TONIGHT. TRIED TO CAPTURE A COUPLE OF
POTENTIAL TIME FRAMES WHEN SHRA LOOK MOST LIKELY NORTH OF A WEAK
SURFACE WAVE THIS EVENING AND AHEAD OF AN UPPER LEVEL TROUGH LATER
TONIGHT. COULD EASILY SEE THE TIMING VARY FROM CURRENT FORECAST...
SO THAT WILL LIKELY BE REFINED IN SUBSEQUENT FORECASTS.

/OUTLOOK FOR KMSP/
MONDAY AFTERNOON...VFR. NORTHWEST WIND 10 TO 20 KT.
MONDAY NIGHT...VFR. NORTHWEST WIND 10 TO 15 KT.
TUESDAY...VFR. NORTHWEST WIND LESS THAN 10 KT BECOMING VARIABLE
LESS THAN 5 KT.
TUESDAY NIGHT...VFR. SOUTHEAST WIND 5 TO 10 KT.
WEDNESDAY THROUGH THURSDAY...MVFR CEILINGS AND VISIBILITIES
EXPECTED WITH RAIN LIKELY. IFR CONDITIONS POSSIBLE ALONG WITH A
CHANCE OF THUNDERSTORMS. SOUTHEAST WIND 10 TO 20 KT BECOMING
SOUTHWEST.

&&

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

$$

UPDATE...
SHORT TERM...
LONG TERM...DWE
AVIATION...





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