000
FXUS63 KDMX 201728
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1228 PM CDT MON MAY 20 2013

.UPDATE...
ISSUED AT 1222 PM CDT MON MAY 20 2013

LOWERED TMAX ACROSS THE NORTH FOR THE AFTERNOON AS CLOUDS HAVE
INCREASED MORE RAPIDLY THERE AND SHOWERS SHOULD DEVELOP LATER IN
THE AFTERNOON. DEW POINTS SLIGHTLY LOWER ACROSS EAST AND SOUTHEAST
AS WELL. TIMING OF POSSIBLE STORMS STILL LOOKS LIKE LATE AFTERNOON
OR EVENING SOUTHEAST INTO THE EVENING HOURS.

&&

.SHORT TERM.../TODAY /...
ISSUED AT 350 AM CDT MON MAY 20 2013

AREA OF SURFACE LOW PRESSURE OFF TO THE NORTHWEST ACROSS EASTERN
SD...WITH ASSOCIATED COLD FRONT STRETCHING SOUTHWARD ACROSS CENTRAL
NE INTO EXTREME NW KS. DRY SLOT CURRENTLY PUSHING THROUGH KS INTO
ERN NE...WILL CONTINUE TO PUSH ENE INTO IOWA THROUGH THE NEXT FEW
HOURS...WHICH SHOULD KEEP ANY PRECIP OFF TO THE SOUTHEAST THROUGH
SUNRISE POSSIBLY CLIPPING THE FAR SOUTHEASTERN CWA. OTHERWISE
ANOTHER VORT LOBE ROTATING AROUND THE UPPER LOW SITUATED OVER THE
WESTERN DAKOTAS WILL ROTATE THROUGH NORTHWEST IOWA THIS
MORNING...BRINGING THE POSSIBILITY OF SOME SHOWER/THUNDERSTORMS
TOWARD MID/LATE MORNING ACROSS THE FAR NORTHWESTERN CWA. REMAINDER
OF THE CWA SHOULD SEE MAINLY DRY CONDITIONS THROUGH MUCH OF THE
DAY...WITH SOUTHERLY FLOW AND MOISTURE CONTINUING TO PUSH BACK INTO
THE EASTERN CWA. SOUNDINGS INDICATING EASTERN CWA TO BECOME
DESTABILIZE AROUND 21-00Z WITH CAPE VALUES IN THE 1500 TO 2500 J/KG
AND SUFFICIENT DEEP LAYER SHEAR. THEREFORE HAVE POPS RETURNING THIS
AFTERNOON ACROSS THE REMAINDER OF THE CWA...WITH GREATEST CHANCE FOR
SEVERE WEATHER ALSO WITH THIS MID/LATE AFTERNOON ACTIVITY ACROSS THE
EAST/SOUTHEASTERN CWA.

TEMPERATURES EXPECTED TO BE A BIT COOLER TODAY WITH SLIGHTLY COOLER
AIRMASS ALOFT...WITH COOLEST TEMPS ACROSS THE NORTHWEST WHERE
CLOUDS/PRECIP CHANCES EXPECTED THROUGHOUT THE DAY. OVERALL HIGHS IN
THE 70S NORTH TO LOW/MID 80S SOUTH. SOUTHERLY WINDS TO BE BREEZY
AGAIN TODAY AS STRONGER WINDS ALOFT MIX TO THE SURFACE.

.LONG TERM.../TONIGHT THROUGH SATURDAY/...
ISSUED AT 350 AM CDT MON MAY 20 2013

CONVECTION WILL BE ONGOING THIS EVENING BUT WILL BE DEPARTING
QUICKLY TO THE NORTHEAST AS THE SHORTWAVE PASSES THROUGH THE
STATE. ANY SEVERE CONVECTION WILL LIKELY BE EARLY THIS EVENING IN
THE SOUTHEAST PRIOR TO MORE STABLE AIRMASS AND PRECIPITATION
DEPARTURE BY LATE EVENING. AFTER MIDNIGHT TONIGHT...MUCH OF THE
AREA SHOULD SEE LITTLE IF ANY RAINFALL AS DRIER AIR ENTERS THE
STATE AND SUBSIDENCE INCREASES...ESPECIALLY IN THE SOUTH. MUCH OF
TUESDAY ALSO APPEARS DRY ALTHOUGH SOME AFTERNOON REDEVELOPMENT
REMAIN POSSIBLE AS UPPER LOW SLIPS TOWARD THE STATE. THIS LOW WILL
SLIDE ACROSS NORTHERN IOWA ON WEDNESDAY WITH THE THREAT OF
SCATTERED SHOWERS PERSISTING THROUGH THE DAY. IN ADDITION...A
THERMAL TROF WILL CROSS INTO IOWA DURING THE DAY AND HAVE BEGUN
TRENDING TEMPERATURES DOWNWARD ON TUESDAY AND ESPECIALLY INTO
WEDNESDAY AS THE COLDER AIR ENTERS THE STATE.

A BRIEF RESPITE FROM PRECIPITATION CHANCES IS EXPECTED WEDNESDAY
NIGHT INTO FRIDAY AS WEAK SURFACE RIDGING SLIDES ACROSS THE STATE.
HOWEVER...BY LATE IN THE WORK WEEK...A LARGE WESTERN TROF IS
FORECAST TO DEVELOP BY BOTH THE GFS AND EURO. IOWA WILL BE LOCATED
UNDERNEATH THE UPPER RIDGE IN AN AREA OF LOW LEVEL MOISTURE
TRANSPORT AND WARM ADVECTION. SEVERAL SHORTWAVES ARE EXPECTED TO
EJECT OUT OF THE LARGE WESTERN TROF AND TOWARD THE MIDWEST
STARTING FRIDAY NIGHT AND CONTINUING INTO THE WEEKEND. IT APPEARS
THAT SEVERAL ROUNDS OF CONVECTION WILL OCCUR IN IOWA DURING THIS
TIME WITH THE POSSIBILITY OF LOCALIZED HEAVY RAINS AND SOME SEVERE
WEATHER. HOWEVER...DETAILS OF THE THREATS WILL HAVE TO BE HAMMERED
OUT AS THE TIMEFRAME APPROACHES.

&&

.AVIATION...20/18Z
 ISSUED AT 1222 PM CDT MON MAY 20 2013

PRIMARY CONCERNS ARE WINDS AND TIMING OF CONVECTION THIS AFTERNOON
AND EVENING. PREVIOUS TIMING LOOKS GOOD WTIH SOME SCT ACTIVITY
DEVELOPING IN THE AFTERNOON/EVENING HOURS UNTIL INSTABILITY
LESSENS. AREA OF CLOUDS OVER NORTHERN IOWA MVFR AND WILL CONTINUE
TO HOLD ON AS AREA MOVES EAST NORTHEAST. SHOWERS SHOULD DEVELOP
NORTHWEST AS WELL. WINDS PICK UP AGAIN TUESDAY AFTER MIXING BEGINS
AROUND 14 TO 15Z.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...REV
SHORT TERM...BEERENDS
LONG TERM...COGIL
AVIATION...REV