000
FXUS63 KMPX 201958
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
258 PM CDT MON MAY 20 2013

.SHORT TERM...(TODAY AND TONIGHT)
EARLY AFTERNOON WATER VAPOR IMAGERY TOGETHER WITH RAP40 500MB
HEIGHTS...WINDS...OVERLAID WITH SURFACE PRESSURE SHOWED A VERTICALLY
STACKED CYCLONE OVER THE MN/DAKOTA BORDER. A WELL-DEFINED WARM FRONT
WAS ORIENTED WEST/EAST FROM THE ELBOW OF WESTERN MINNESOTA UP
THROUGH LAKE SUPERIOR...WITH A COLD FRONT EXTENDING SOUTHWEST
THROUGH CENTRAL NEBRASKA. ROTATING AROUND THE UPPER LEVEL LOW WAS A
SHORTWAVE OVER SOUTHEASTERN MINNESOTA WHICH WAS THE DRIVING FACTOR
BEHIND A FEW SCATTERED SHOWERS ALONG AND NORTH OF I94. 19Z SPC
MESOANALYSIS SHOWED 500J/KG OF SBCAPE IN THE WARM SECTOR OF THIS
CYCLONE...WITH NO CIN...THUS THE SCATTERED SHOWER ACTIVITY ONGOING
ACROSS THE REGION WILL PERSIST INTO THE EVENING HOURS. COULD SEE A
STRAY THUNDERSTORM AS WELL...BUT THE BEST DEEP LAYER SHEAR WILL BE
CONFINED ACROSS THE SOUTHEAST OF THE CWA. THEREFORE NOT ANTICIPATING
MUCH OF A THREAT FOR SEVERE WEATHER...ESPECIALLY CONSIDERING THE
CONTROLLED RELEASE OF CAPE EVIDENT ACROSS THE REGION VIA THE
CELLULAR CONVECTION.

TONIGHT THE SHOWERS SHOULD DECREASE IN COVERAGE ACROSS THE SOUTH...
WITH REDEVELOPMENT EXPECTED AGAIN ON TUESDAY AFTERNOON. THE SURFACE
LOW WILL GRADUALLY FILL AS IT SLOWLY MEANDERS EASTWARD. BUFR
FORECAST SOUNDINGS VIA BOTH THE NAM AND GFS SHOW MUCH SHALLOWER CAPE
PROFILE TUESDAY AFTERNOON WHEN COMPARED TO TODAY...SO HAVE REMOVED
THUNDER ACROSS THE WEST AND HAVE LOWERED TEMPS OVER THE ENTIRE
REGION. IN SHORT TUESDAY WILL BE A CLOUDY AND COOL DAY WITH LIGHT
RAIN SHOWERS EXPECTED ONCE AGAIN.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 247 PM CDT MON MAY 20 2013

WE WILL STILL BE DEALING WITH THE EFFECTS OF THE SLOWLY DEPARTING
UPPER LOW TUESDAY NIGHT INTO WEDNESDAY... WITH A CONTINUATION OF
SHOWER CHANCES OVER THE AREA... ENHANCED WITH THE DIURNAL CYCLE
AND PASSAGE OF INDIVIDUAL VORTICITY LOBES ACROSS THE AREA.
HOWEVER... THE TREND OF INSTABILITY AND SHEAR BEING DISPLACED EAST
WILL CONTINUE... SO CHANCES FOR SEVERE WEATHER WILL ALSO BE ON THE
DOWNWARD TREND THROUGH THE PERIOD AND BE FOCUSED EAST OF OUR AREA.
WE FINALLY LOOK TO GET ON THE BACKSIDE OF THE UPPER TROUGH
WEDNESDAY NIGHT... WITH SURFACE RIDGING NOSING IN FROM THE NORTH
BY THURSDAY. THE GFS... NAM... AND ECMWF ARE ALL IN DECENT
AGREEMENT ON THE TIMING OF THINGS... SO HAVE GOOD CONFIDENCE THAT
WE/LL FINALLY SEE A COMPLETELY DRY DAY BY THURSDAY. THE SURFACE
RIDGE WILL SLIDE EAST BY FRIDAY... WITH WARM ADVECTION STARTING TO
SETUP ACROSS THE AREA. AT THIS POINT... THE GFS AND ECMWF START TO
DIVERGE SOME... BUT MAINLY WITH THE DEGREE TO FORCING AND
INSTABILITY ALONG THE ELEVATED WARM FRONT... WITH THE ECMWF
ACTUALLY GENERATING PCPN SOONER AND FARTHER EAST THAN THE GFS. AT
THIS POINT... AM INCLINED TO GO WITH THE SLOWER SOLUTION AND KEEP
THINGS DRY THROUGH FRIDAY. HOWEVER... BY SATURDAY AND THEN THROUGH
THE REMAINDER OF THE FORECAST IT LOOKS LIKE WE/LL HAVE CHANCES FOR
SHRA/TSRA ACROSS THE AREA ONCE AGAIN AS LOW PRESSURE SITS OVER THE
CENTRAL PLAINS AND WE SEE A PROLONGED PERIOD OF WARM ADVECTION AND
ELEVATED INSTABILITY ACROSS THE AREA WITH THE PRIMARY SURFACE WARM
FRONTAL BOUNDARY SLOWLY LIFTING NORTH TOWARD THE REGION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1250 PM CDT MON MAY 20 2013

SHOWERS WILL CONTINUE TO INCREASE IN COVERAGE THIS
AFTERNOON...WITH A FEW ISOLATED THUNDERSTORMS POSSIBLE AS WELL.
COULD SEE VISBYS BRIEFLY DROP BENEATH THE HEAVIER SHOWERS...BUT
MAINLY EXPECTING VFR/MVFR. TONIGHT FORECAST GUIDANCE SHOWS CIGS
DROPPING AGAIN...WITH IFR/LIFR CONDITIONS ACROSS THE NORTH AT KAXN
AND KSTC.

KMSP...
SHOWERS WILL CONTINUE TO MOVE ACROSS THE METRO AREA TODAY...WITH
AN OUTSIDE CHANCE OF THUNDER AS WELL. HOWEVER THE COVERAGE FOR
THUNDER WILL BE SCARE SO REMOVED IT FROM THE AFTERNOON TIMING AND
HAVE JUST A SHORT VCTS THIS EVENING AS INDICATED BY THE SHORT TERM
HRRR AND HOPWRF MODELS. SHOWERS WILL DECREASE IN COVERAGE LATER
TONIGHT.

/OUTLOOK FOR KMSP/
WED...VFR/MVFR CIGS WITH -SHRA LIKELY. WINDS NE AT 05G10KTS.
THU...VFR. WINDS NE AT 10KTS.
FRI...VFR. WINDS SE AT 10G15KTS.


&&

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

$$

SHORT TERM...JRB
LONG TERM...
AVIATION...JRB