Area Forecast Discussion
Issued by NWS Des Moines, IA

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDMX 021805
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1205 PM CST MON MAR 2 2015

.SHORT TERM /TODAY/...
ISSUED AT 325 AM CST MON MAR 2 2015

MID-LEVEL THETA-E ADVECTION ONGOING ACROSS NORTHERN KANSAS AND
SOUTHWEST NEBRASKA WILL LIFT NORTHEAST INTO SOUTHWEST IOWA LATE THIS
MORNING AND ACROSS THE REMAINDER OF THE AREA THIS AFTERNOON. CLOUDS
WILL INCREASE DURING THIS PERIOD WITH BASES REMAINING FAIRLY HIGH AT
7 KFT OR ABOVE. THERE WILL BE DESCENT VERTICAL ASCENT WITHIN THE
CLOUD LAYER FOR HYDROMETEOR FORMATION WITH ADDITIONAL FORCING
PROVIDED BY A WEAK SHORT WAVE PASSING THROUGH. THAT SAID...DRY AIR
WILL REMAIN PREVALENT BELOW 7 KFT WITH A SIGNIFICANT AMOUNT OF
EVAPORATION OCCURRING TO DESCENDING LIGHT SNOW. HAVE INCLUDED
FLURRIES OVER THE CENTRAL AND NORTH FOR THE AFTERNOON HOWEVER NO
IMPACTFUL WEATHER THROUGH THE AFTERNOON. SFC FLOW THROUGH THE DAY
WILL STILL BE ORIGINATING FROM THE HIGH PRESSURE THAT IS DEPARTING
TO THE EAST. WITH INCREASING CLOUDS DURING THE DAY AND ONLY WEAK TO
NEUTRAL ADVECTION AT THE SFC...TEMPERATURES WILL BE SIMILAR TO SUNDAY
WITH HIGHS IN THE MID 20S TO LOW 30S.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 325 AM CST MON MAR 2 2015

CHALLENGING FORECAST FOR BEGINNING OF EXTENDED AS LARGE SYSTEM IS
SET TO IMPACT THE AREA. SYSTEM WILL BRING A WIDE VARIETY OF
WEATHER AND POTENTIAL HAZARDS TO THE CWA AND WILL NEED TO BE
MONITORED CLOSELY AS THERE IS STILL MUCH FORECAST UNCERTAINTY IN
TIMING AND PLACEMENT OF THREATS. A LARGE AREA OF LOW PRESSURE WILL
PUSH EAST ACROSS CANADA AS SURFACE LOW LIFTS NORTHEAST FROM
ROCKIES. AHEAD OF SOUTHERN LOW WILL SEE INCREASE IN MOISTURE AND
WAA WILL SPREAD INTO STATE OVERNIGHT. MODELS ARE GENERALLY IN GOOD
AGREEMENT WITH HANDLING OF SYSTEM THOUGH TIMING IS DIFFERENT.
HOWEVER...GOOD AGREEMENT ON A SLOWER SATURATION TONIGHT AND HAVE
CUT BACK ON POPS OVERNIGHT AS PRECIP CHANCES INCREASE GENERALLY
FROM SOUTHWEST TO NORTHEAST AS MOISTURE INCREASES. AS SOUTHERN LOW
LIFTS INTO IOWA STRONG BOUNDARY ASSOCIATED WITH NORTHERN LOW WILL
PUSH INTO STATE QUICKLY SHOVING ENTIRE SYSTEM EASTWARD. MODELS ARE
A BIT FASTER WITH THE PROGRESSION AND HAVE THEREFORE CUT BACK ON
POPS FOR LATE TUESDAY. LATEST TRENDS ARE FOR LOW TO PUSH INTO
CENTRAL IOWA TUESDAY WHICH MAY HELP LIMIT PRECIPITATION ACROSS
THE SOUTHEAST AND CENTRAL PORTIONS OF THE CWA WITH DRY SLOT.
HOWEVER...GENERALLY APPEARS TO BE TO MAIN ARES FOR PRECIPITATION
CHANCES...ACROSS THE NORTH AND THE SOUTH. THESE TWO AREAS ALSO
POSE THE BIGGEST THREATS FOR HAZARDOUS WEATHER...WITH
PRECIPITATION TYPE CHALLENGES IN THE SOUTH AND SNOW/WIND CONCERNS
IN THE NORTH.

AS SYSTEM LIFTS NORTH OVERNIGHT TONIGHT WILL SEE GENERALLY A MIX
OF PRECIPITATION ACROSS SOUTHERN CWA LIFTING INTO CENTRAL CWA.
MODEL SOUNDINGS INDICATE ENOUGH OF A WARM LAYER WITHIN THE COLUMN
TO SEE FREEZING RAIN ACROSS THE SOUTH AND SLEET FURTHER NORTH.
MAIN THREAT WILL BE BETWEEN 06Z-18Z TUESDAY. NAM IS QUITE A BIT
COLDER AT THE SURFACE WHICH KEEPS PRECIPITATION FREEZING RAIN FOR
LONGER THAN GFS WHICH WARMS SURFACE TEMPERATURES QUICKLY WITH A
RETURN TO RAIN. HOWEVER...MODELS ARE A BIT COOLER OVERALL AND HAVE
BUMPED TEMPERATURES DOWN A FEW DEGREES FOR TONIGHT/TUESDAY WHICH
KEEPS LONGER DURATION FOR MIX IN CWA...THOUGH THINK NAM IS TOO
AGGRESSIVE. HOWEVER...A BRIEF PERIOD OVERNIGHT AND INTO THE EARLY
MORNING HOURS OF FREEZING RAIN SEEMS LIKELY ACROSS MUCH OF
SOUTHERN/CENTRAL CWA. AS SYSTEM LIFTS COULD SEE FREEZING RAIN
REACHING I-80 CORRIDOR VERY NEAR 12Z/MORNING COMMUTE. WITH ROAD
SURFACE VALUES WELL BELOW FREEZING COULD SEE HAZARDOUS TRAVEL.
HOWEVER...GIVEN UNCERTAINTY IN PLACEMENT OF RAIN/FREEZING RAIN
LINE AND DURATION OF ICING POTENTIAL HAVE NOT ISSUED HEADLINES
ATTM. THOUGH...WILL LIKELY NEED A HEADLINE FOR THE EARLY MORNING
HOURS.

FOCUS THEN SHIFTS TO SNOW/WIND POTENTIAL ACROSS NORTHERN CWA
TUESDAY. LATEST MODEL SOUNDINGS BRING IP/SN/FZRA MIX
FURTHER NORTH...INTO KALO...AND HAVE ALSO TRENDED THIS WAY
ATTM...THOUGH FURTHER NORTHWEST PRECIP WILL REMAIN SNOW
THROUGHOUT EVENT. AS BOUNDARY DROPS SOUTH WILL SEE TRANSITION
ACROSS CWA. WITH SLIGHTLY FASTER MODEL TRENDS HAVE BEGUN
TRANSITION TO SNOW SOONER IN THE AFTERNOON TUESDAY ACROSS THE CWA.
HOWEVER AS MODEL TRENDS CONTINUE DOWN WITH QPF...HAVE FOLLOWED
THIS TREND AND CONTINUE TO CUT BACK ON SNOW AMOUNTS IN THE NORTH.
STILL HAVE CONCERN WILL HOW SNOW PHASES WITH WIND. GFS IS MORE
AGGRESSIVE WITH SNOWFALL OCCURRING WITH STRONGER WINDS...THOUGH
NAM INCREASES WINDS AFTER SNOWFALL HAS CEASED. THOUGH WINDS WILL
INCREASE NEAR/BEHIND BOUNDARY WILL LIKELY COMBINE WITH FALLING
SNOW OR FRESH FALLEN SNOW TO CREATE HAZARDOUS CONDITIONS. CONCERN
WITH NORTHERN SYSTEM IS HOW LONG THESE CONDITIONS WILL LAST...WITH
GENERAL FASTER PROGRESSION OF SYSTEM FEEL IT WILL BE LIMITED TO
BRIEF PERIODS...THOUGH COULD STILL BE NEAR-BLIZZARD AT TIMES.
AGAIN...HAVE OPTED FOR NO HEADLINES ATTM TO ALLOW FOR FURTHER
REFINEMENT IN TIMING AND LOCATION...ESPECIALLY GIVEN CONTINUED
DOWNWARD TREND WITH SNOWFALL FORECAST.

AS SYSTEM QUICKLY PUSHES OUT TUESDAY INTO WEDNESDAY HIGH PRESSURE
WILL ONCE AGAIN DROP SOUTH INTO IOWA...BRINGING VERY COLD
TEMPERATURES. HAVE DROPPED TEMPERATURES DOWN A FEW DEGREES FOR
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT WITH ANTICIPATED FRESH
SNOWFALL. WINDS WILL REMAIN STRONG THROUGH EARLY WEDNESDAY WHICH
WILL ALLOW FOR ANOTHER ROUND OF DANGEROUSLY COLD WIND CHILL
VALUES. AS HIGH SHIFTS EAST SOUTHERLY SURFACE FLOW WILL RETURN
WHICH WILL HELP TO BRING A WARMING TREND THROUGH THE REMAINDER OF
THE EXTENDED...ALONG WITH GENERALLY DRY CONDITIONS.

&&

.AVIATION...02/18Z
ISSUED AT 1205 PM CST MON MAR 2 2015

VFR CONDITIONS WITH LOWERING CIGS ARE IN PLACE STATEWIDE AT 18Z.
CONDITIONS SHOULD DEGRADE TO LOW END MVFR SW-NE LATE THIS EVENING
HOWEVER AS WINTRY PRECIPITATION DEVELOPS. THIS WILL LIKELY BE ON
THE LIGHT SIDE AT TAF SITES...BUT STILL MAY CAUSE ISSUES. TYPES
WILL VERY FROM RAIN/FREEZING RAIN SOUTH...TO SLEET/SNOW NORTH.
EVENT SHOULD TRANSITION TO JUST DRIZZLE OR FREEZING RAIN BY
TUESDAY MORNING AS WINDS VEER AND SYSTEM DEPARTS.

&&

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

$$

SHORT TERM...DONAVON
LONG TERM...AWB
AVIATION...SMALL



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.