000
FXUS63 KDMX 220922
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
322 AM CST SAT NOV 22 2008

.SHORT TERM /TODAY/...
THE MAIN FORECAST ISSUE TODAY WILL BE PRECIP TRENDS AND SNOW AMOUNTS
AS AN UPPER LOW TRAVERSES IOWA. A NARROW BAND OF SNOW MOVED ACROSS
PARTS OF NORTHERN IOWA OVERNIGHT AND CURRENTLY EXTENDS FROM CHARLES
CITY TO MARSHALLTOWN. SNOWFALL AMOUNTS REPORTED HAVE BEEN LIMITED TO
A FEW TENTHS OF AN INCH. SNOW IS QUICKLY ENDING BEHIND THE BAND TO
THE WEST IN A NARROW SUBSIDENCE AXIS...BUT FORCING WILL RETURN AFTER
12Z IN THE FAR NORTHWEST COUNTIES THEN SPREAD SOUTHEAST THROUGH THE
MORNING. THE NAM/RUC HAVE A GOOD HANDLE ON THE CURRENT WEATHER AND
WILL BE FOLLOWED CLOSELY FOR PRECIP TIMING AND COVERAGE. THE HEAVIER
SNOWS...AROUND A COUPLE INCHES...ARE EXPECTED IN THE POCAHONTAS-FORT
DODGE-SAC CITY AREAS...WITH LESSOR AMOUNTS GENERALLY AN INCH OR LESS
ELSEWHERE. CROSS SECTIONS INDICATE A 1-3 HOUR PERIOD OF DECENT LIFT
IN THE DENDRITIC LAYER ACROSS THE NORTHWEST PORTION OF THE CWA AND
SOME WEAK INSTABILITY ALOFT. THIS AREA IS ALSO HIGHLIGHTED BY A
POSITIVE PV PRESSURE ADVECTION MAX THROUGH THE MORNING INTO EARLY
AFTERNOON. FORCING WILL QUICKLY EXIT THE CWA TO THE EAST BY LATE
AFTERNOON.

.LONG TERM /TONIGHT-FRIDAY/...

THE AREA OF LOW PRESSURE WILL LOOSE ITS IDENTITY BY THIS EVENING
WITH THE STATE REMAINING UNDER SOUTHERLY FLOW ALONG WITH VERY DRY
MID LEVELS IN PLACE. SOME STRATUS MAY PERSIST ESPECIALLY THIS
EVENING THOUGH IT SHOULD SCATTER BY MIDNIGHT. SUNDAY WILL WARMER
WITH ABOVE SEASONAL TEMPERATURES EXPECTED. A COUPLE OF SYSTEMS WILL
BE CONVERGING ON CENTRAL IOWA BY LATE SUNDAY. A COLD FRONT WILL
ENTER NORTHWEST IOWA WITH AND WILL BE MOISTURE STARVED. AT THE SAME
TIME...A SURGE OF GULF MOISTURE WILL BE LIFTING NORTHWARD AND WILL
REACH THE FAR SOUTHEAST SUNDAY EVENING. A STRATUS SHIELD WILL LIKELY
BE LIFTING NORTH ALONG WITH THE MOISTURE WITH A MOISTURE DEPTH OF
AROUND 5 KFT. DECENT LIFT IN THE MOIST LAYER WOULD SUGGEST SOME
DRIZZLE OR LIGHT RAIN IS POSSIBLE SUNDAY EVENING FOR A BRIEF PERIOD
OVER THE SOUTHEAST. THE BOUNDARY FROM THE NORTHWEST WILL PUSH THE
MOISTURE QUICKLY TO THE EAST ENDING PRECIPITATION CHANCES. HAVE
MAINTAINED SLIGHT CHANCES ALONG THE BOUNDARY TO THE NORTH WITH RAIN
OR SNOW. LOW LEVELS REMAIN RELATIVELY WARM AND WET BULBS ABOVE 0 C
THROUGH THE PERIOD OF PRECIPITATION CHANCES THEREFORE SNOW CHANCES
WILL BE LIMITED.

NUMEROUS STRONG SYSTEMS PASSING SLOWING THROUGH THE FLOW NEXT WEEK.
A STRONG CLOSED LOW WILL DROP SOUTH OUT OF MANITOBA AND THROUGH THE
WESTERN GREAT LAKES ON MONDAY. THIS WILL RESULT IN WINDY CONDITIONS
MONDAY AND MONDAY NIGHT AND COLDER AIR SPILLING SOUTH. COULD
APPROACH WIND ADVISORY CONDITIONS OVER THE NORTHEAST MONDAY
AFTERNOON. FALLING TEMPERATURES ARE ALSO POSSIBLE BY MONDAY
AFTERNOON. THIS SYSTEM WILL THEN LINGER OVER THE NORTHEASTERN CONUS
THROUGH MID WEEK. AS THIS OCCURS...ANOTHER STRONG SYSTEM WILL MOVE
INTO THE INTERMOUNTAIN WEST AND MOVE SLOWLY EAST. CURRENT FORECAST
FOR MOSTLY DRY CONDITIONS THROUGH THANKSGIVING STILL ON TRACK THOUGH
THERE IS THE POTENTIAL THE WESTERN SYSTEM WILL BRING PRECIPITATION
TO PORTIONS OF THE FORECAST AREA BY FRIDAY. NO CHANGE TO THE
FORECAST DURING THIS PERIOD YET AND EXPECT MODEL SOLUTIONS TO BECOME
MODIFIED OVER NEXT SEVERAL DAYS AS THEY TRY TO RESOLVE THIS HIGHLY
ACTIVE PATTERN.

&&

.AVIATION...22/06Z
UPPER LOW IN SOUTH DAKOTA WILL CONTINUE TO DRIFT TOWARD IOWA
OVERNIGHT BEFORE PASSING THROUGH THE STATE ON SATURDAY.  WIDESPREAD
VFR CIGS WL CONTINUE ACROSS THE STATE TONIGHT AS WAA PERSISTS.  SOME
LIGHT SNOW IS FORECAST TO DEVELOP AFTER MIDNIGHT ACRS NORTHERN
PORTIONS OF THE STATE WITH MVFR CIGS AND VSBYS.  THIS AREA OF SNOW
WL PUSH EAST OF THE STATE BY MORNING...HOWEVER ADDITIONAL SNOW WILL
MOVE INTO WESTERN PORTIONS OF THE STATE BY DAYBREAK AS UPPER LOW
ENTERS IOWA.  MVFR CONDITIONS WITH AREAS OF IFR WL OCCUR WITH THIS
SNOW AS WELL...HOWEVER WILL SEE A GRADUAL IMPROVEMENT IN TIME AS THE
PRECIPITATION SLOWLY DIMINISHES WITH THE WEAKENING SYSTEM.  SFC
WINDS WL REMAIN OUT OF THE SSE DURING THE ENTIRE PERIOD.

&&

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

&&

$$

SHORT TERM...KINNEY
LONG TERM...DONAVON
AVIATION...COGIL

NWS DMX Office Area Forecast Discussion