AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1146 AM CST THU NOV 19 2015
.SHORT TERM /TONIGHT/...
ISSUED AT 522 AM CST THU NOV 19 2015
STRONG SUBSIDENCE BEHIND THE DEPARTING SYSTEM WILL PRODUCE A STRONG
WEST WIND ACROSS IOWA TODAY. THE STRONGEST WINDS ATOP THE MIXED
LAYER PEAK BETWEEN 14Z AND 20Z THEN QUICKLY DROP OFF SO THIS WILL BE
THE PERIOD OF STRONGEST WINDS. WINDS AT THE TOP OF THE MIXED LAYER
REACH ABOUT 43KTS AND WHILE THE BUFKIT SOUNDINGS WANT TO DEEPEN THE
MIXED LAYER TO ABOUT 750MB...I AM NOT SURE WE WILL BE MIXING THAT
DEEP BUT I DO NOT SEE A PROBLEM MIXING TO 800 MB. THERE MAY BE A
FEW GUSTS TO AROUND 50 MPH DURING THE PERIOD OF BEST MIXING BUT THIS
SHOULDN`T LAST MORE THAN AN HOUR OR TWO. OTHERWISE WE WILL BE QUITE
A BIT COOLER TODAY DESPITE THE SUNSHINE WE WILL SEE. HIGHS TODAY
WILL ONLY BE IN THE UPPER 30S NORTH TO THE MID 40S SOUTH AND THIS
WILL BE WARM COMPARED TO THE WEEKEND. AS MENTIONED EARLIER...BY
LATE AFTERNOON WINDS WILL BEGIN TO REALLY DROP OFF. THE ADVISORY
MAY BE RUNNING A LITTLE LONG BUT A FEW WIND GUSTS ESPECIALLY ACROSS
THE NORTH WILL LIKELY LINGER INTO THE LATE AFTERNOON HOURS.
.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 522 AM CST THU NOV 19 2015
WITH WINDS ENTERING THE SHORT TERM REALM...MAIN CONCERNS IN THE LONG
TERM BECOME SNOW FRIDAY INTO EARLY SATURDAY AND COLD AFTERWARDS.
FRI THROUGH SAT MORNING...FIRST SNOWFALL OF THE SEASON IS ON TAP FOR
A GOOD MAJORITY OF THE STATE DURING THIS TIME FRAME. NOT MUCH HAS
CHANGED WITH THIS FORECAST ISSUANCE AS MODELS ARE IN PRETTY GOOD
AGREEMENT ON TIMING...FORCING...ETC. PICK YOUR FORCING
MECHANISM...AND IT WILL PLAY A FACTOR IN THIS EVENT. TAKING A LOOK
AT THE LIST...JET CIRCULATIONS ARE THE LEAST IMPACTFUL WITH ONLY
GLANCING BLOWS FROM THE 250MB EXIT REGION AT THE END OF THE EVENT
AND 500MB ENTRANCE REGION AT THE BEGINNING. ISENTROPIC LIFT THROUGH
THE SATURATED AND DGZ AREAS IS QUITE GOOD WITH 50MB OVER 50 MILES OR
LESS. THETA-E/WAA AT THE LOW AND MID LEVELS ALSO SEES A BIG PUSH
THROUGH THE EVENT WITH SOUTHERLY FLOW AHEAD OF THE WAVE. NOT TO BE
LEFT OUT...FRONTOGENETICAL LIFT IN THE MID LEVELS LINES UP WELL
WITH PREVIOUSLY MENTIONED FORCINGS ACROSS CENTRAL AND NORTHERN
IOWA...WHILE FRONTOGENETICAL LIFT IN THE LOW LEVELS RESIDES
FURTHER SOUTH WHERE OTHER SUPPORT IS LACKING. WITHIN THE DGZ
RESULTING OMEGA VALUES...AS ONE COULD IMAGINE AT THIS
POINT...RESIDE IN THE -10 TO -15 MICROBAR/S RANGE AND WHEN COUPLED
WITH A DGZ DEPTH POSSIBLY APPROACHING 2KM...COULD EASILY RESULT IN
PERIODS OF MODERATE TO HEAVY SNOWFALL. CURRENTLY...OVERALL
SNOWFALL TOTALS CONTINUE TO BE IN THE 4 TO 8 INCH RANGE FOR A
LARGE PORTION OF CENTRAL AND NORTHERN IOWA. ONE ITEM TO CONTINUE
TO MONITOR THAT MAY SQUASH SOME SNOWFALL AMOUNTS ARE DRY LOW
LEVELS THAT WILL EARLY SNOWFALL MUST FALL THROUGH/OVERCOME. WINTER
STORM WATCH REMAINS LARGELY UNCHANGED...BUT HAVE ADDED THE LAST 3
NORTHERN COUNTIES IN THE CWA WITH FORECASTED AMOUNTS STRONGLY
SUGGESTING SO.
SAT MORNING ONWARD...THE SYSTEM WILL EXIT THE REGION FAIRLY
QUICKLY...LEAVING BEHIND IT QUIET WEATHER AND THE FIRST TRULY
COLD/FRIGID TEMPERATURES OF THE SEASON. HIGHS WILL RESIDE IN THE
MID TO UPPER 20S FOR MOST THROUGH THE WEEKEND...ALONG WITH LOWS
INTO THE UPPER SINGLE DIGITS ACROSS THE NORTHERN HALF OF THE STATE
SUNDAY MORNING. QUIET WEATHER WILL CONTINUE THROUGH THE FIRST HALF
OF THE WEEK AND WILL SEE TEMPS WARM BACK INTO THE 40S AND 50S WITH
SOME RETURN FLOW AS HIGH PRESSURE WILL RESIDE SE OF THE REGION.
THE NEXT ROUND OF POTENTIALLY CONSEQUENTIAL WEATHER REMAINS ON
TRACK TO PUSH INTO THE REGION THANKSGIVING DAY AND FRIDAY AS A
TROUGH DIGS INTO THE SW U.S. INDUCING SW FLOW ACROSS THE REGION.
ANY PRECIP THAT COMES OF IT WILL BE RAIN.
&&
.AVIATION...19/18Z
ISSUED AT 1135 AM CST THU NOV 19 2015
CONDITIONS WILL BE VFR THROUGH PERIOD. WINDS WILL BE STRONG AND
GUSTY FROM THE WEST TO NORTHWEST THROUGH 00Z...WITH GUSTS TO 35
TO 40KTS OR HIGHER AND SUSTAINED WINDS OF 20 TO 25KT. WINDS WILL
DIMINISH AFTER 00Z. WINDS WILL SHIFT TO THE SOUTH TO SOUTHEAST
NEAR 12Z...AND WILL INCREASE AGAIN AFTER 12Z. WILL SEE INCREASING
CLOUD COVER FOR END OF PERIOD WITH RA/SN POSSIBLE AT SITES BEYOND
PERIOD.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR ADAIR-ADAMS-
APPANOOSE-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-
CASS-CERRO GORDO-CLARKE-CRAWFORD-DALLAS-DAVIS-DECATUR-EMMET-
FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-
JASPER-KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-PALO
ALTO-POCAHONTAS-POLK-POWESHIEK-RINGGOLD-SAC-STORY-TAMA-TAYLOR-
UNION-WAPELLO-WARREN-WAYNE-WEBSTER-WINNEBAGO-WORTH-WRIGHT.
WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH LATE FRIDAY
NIGHT FOR ADAIR-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CASS-
CERRO GORDO-DALLAS-FRANKLIN-GRUNDY-GUTHRIE-HAMILTON-HARDIN-
JASPER-MADISON-MAHASKA-MARION-MARSHALL-POLK-POWESHIEK-STORY-TAMA-
WARREN-WORTH.
WINTER STORM WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT
FOR CALHOUN-CARROLL-CRAWFORD-EMMET-GREENE-HANCOCK-HUMBOLDT-
KOSSUTH-PALO ALTO-POCAHONTAS-SAC-WEBSTER-WINNEBAGO-WRIGHT.
&&
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