Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 101749 AAC
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1249 PM CDT THU JUL 10 2014

.UPDATE...
SEE BELOW FOR AN UPDATED AVIATION FORECAST DISCUSSION.

SHORT WAVE INDUCED MID AND HIGH LEVEL CLOUDS AND SCATTERED LIGHT
SHOWERS/ISOLATED STORMS SLIDING EAST FROM WESTERN/CENTRAL SD THIS
MORNING. DIFFICULT TO SAY HOW THINGS WILL EVOLVE THROUGH THE
AFTERNOON AND EVENING AS CLOUD COVER WILL HOLD DOWN GOOD SURFACE
HEATING AND INCREASED INSTABILITY ALONG WITH ELEVATED
SHOWERS/STORMS MOVING THROUGH. INDICATIONS ARE THAT AN INCREASING
LLJ INTO THE EVENING HOURS WILL RESULT IN MORE NUMEROUS
SHOWER/STORM DEVELOPMENT FROM CENTRAL SD INTO NORTHEAST SD. THE
GFS WAS SHOWING THIS NEW DEVELOPMENT THIS EVENING. ALREADY HAVE IN
BEST CHANCES OF STORMS FOR THIS EVENING.


&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH SATURDAY
PRECIPITATION CHANCES THROUGHOUT THE SHORT TERM WILL BE THE
FORECAST CHALLENGE.

AS OF 9Z...A 30-40 KNOT LLJ IS LOCATED OVER WESTERN SOUTH DAKOTA
WITH SOME WEAK THUNDERSTORMS ENTERING EXTREME SW SD. THESE
THUNDERSTORMS SHOULD CONTINUE TRACKING SOUTHEASTWARD ALONG THE
BETTER INSTABILITY AXIS THROUGH THE EARLY MORNING HOURS. A WEAK
MID LEVEL IMPULSE CURRENTLY OVER CENTRAL MONTANA WILL MOVE ACROSS
THIS CWA DURING THE AFTERNOON HOURS TODAY. MODELS ARE SHOWING VERY
GOOD 0-6 KM BULK SHEAR VALUES...BUT LACK SIGNIFICANT CAPE. THE
THREAT FOR SEVERE STORMS TODAY LOOKS FAIRLY MINIMAL. HOWEVER THE
EXTREME SW PORTION OF THE CWA WILL HAVE A POTENTIAL OF SEEING
SEVERE STORMS LATE THIS AFTERNOON. MU-CAPE VALUES ARE HIGHEST
FROM KPIR AND POINTS SOUTH. THIS IS ALSO WHERE MODELS DEPICT 0-1
KM BULK SHEAR VALUES OF 20 TO 25 KNOTS. SPC DOES HAVE THE SW
PORTION OF THE CWA UNDER A SLIGHT RISK WHICH LOOKS REASONABLE. A
FAIRLY GOOD LLJ DEVELOPS TONIGHT WITH ADDITIONAL SHOWERS AND
THUNDERSTORMS LIKELY...ESPECIALLY FOR THE WATERTOWN AREA.

THE POTENTIAL FOR THUNDERSTORMS ON FRIDAY IS A LITTLE MORE UNCLEAR.
A FRONTAL BOUNDARY IS EXPECTED TO SLIDE ACROSS THE DAKOTAS LATE
TONIGHT AND THROUGH THE MORNING HOURS ON FRIDAY WITH MARKEDLY
DRIER AIR BEHIND THE FRONT. MODELS DO NOT AGREE WITH HOW FAR THE
FRONTAL BOUNDARY PUSHES SOUTH. BOTH THE HI-RES ARW/NMM AND THE
21Z/03Z SREF HANGS THE BOUNDARY ALONG HIGHWAY 14 WITH AT LEAST A
SLIGHT CHANCE FOR THUNDERSTORMS. THUS HAVE RE-INTRODUCED POPS BACK
INTO THE FORECAST FOR FRIDAY AFTERNOON.

THE FRONTAL BOUNDARY SHOULD BE SOUTH OF THE REGION BY SATURDAY. A
WEAK SHORT WAVE EMBEDDED WITHIN THE NORTHWEST ALOFT WILL BRING
ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS HOWEVER.


.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY

FORECAST FOCUS IS ON THE MAJOR PATTERN CHANGE EARLY
WEEK...SPECIFICALLY COOLER TEMPERATURE TRENDS.

SATURDAY NIGHT THROUGH SUNDAY NIGHT...FORECAST CONFIDENCE:
MODERATE

MASSIVE AND ANOMALOUSLY STRONG UPPER LEVEL CLOSED LOW OVER THE
HUDSON BAY REGION WILL BEGIN TO PIVOT SOUTHWARD LATE IN THE
WEEKEND. STILL EXPECTING SUNDAY TO BE A WARM DAY WITH HIGHS IN THE
80S...AS 850MB TEMPS REMAIN IN THE TEENS ABOVE ZERO. LINGERING
MOISTURE AND MODEST SYNOPTIC SCALE FORCING COULD PRODUCE A FEW
SHOWERS OR STORMS...ESPECIALLY SATURDAY NIGHT INTO EARLY SUNDAY.

MONDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE: MODERATE/HIGH

THE CORE OF THE ABOVE MENTIONED INTENSE UPPER LOW WILL CONTINUE TO
DROP SWD THROUGH THE GREAT LAKES REGION ON MONDAY. H5 HEIGHT
ANOMALIES AND 850MB TEMPERATURE ANOMALIES CONTINUE TO RANGE FROM
-2 TO -2.5 STD DEVIATIONS BELOW NORMAL. THE DAKOTAS WILL REMAIN ON
THE WESTERN PERIPHERY OF THE LOW WHICH WILL RESULT IN A DEEP AND
PERSISTENT NORTHERLY FLOW REGIME. THE 00Z GFS/ECMWF/GEM ARE NOW
COMING INTO BETTER AGREEMENT WITH TIMING OF THE COLD FRONT AND
MAGNITUDE OF THE COLDEST AIR. THE COOLEST READINGS ARE EXPECTED ON
MONDAY AND MONDAY NIGHT...WHEN H8 TEMPS DROP TO +4C TO +5C IN THE
FAR EAST...TO +8C TO +10C IN THE WEST. THIS COOL CANADIAN AIRMASS
IS EXPECTED TO REMAIN OVER THE REGION THROUGH WEDNESDAY. BASED ON
BETTER MODEL AGREEMENT...DECIDED TO DROP HIGH TEMPERATURES A GOOD
5 DEGREES ON MONDAY THROUGH TUESDAY. AS SUCH...FORECAST HIGHS ARE
NOW PRIMARILY IN THE MID 60S EAST...TO LOW 70S WEST. COMBINING
THESE TEMPS WITH BREEZY TO WINDY CONDITIONS ALONG WITH MOSTLY
CLOUDY SKIES AND CHANCE OF SHOWERS WILL DEFINITELY MAKE IT FEEL
LIKE EARLY FALL! NOT SOMETHING YOU EXPECT TO SEE IN MID-
JULY...CLIMATOLOGICALLY OUR WARMEST TIME OF THE YEAR...WOW.


&&

.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

A RETURN FLOW SURFACE PRESSURE PATTERN WILL KEEP WINDS
SOUTH-SOUTHEAST OVER MUCH OF THE TAF VALID PERIOD AT KABR/KATY. A
COLD FRONT APPROACHING FROM THE NORTHWEST SHOULD BEGIN TO SWITCH
WINDS AROUND TO NORTH-NORTHEAST AT KPIR/KMBG BY FRIDAY MORNING.
SOME OF THE AVAILABLE GUIDANCE SUGGESTS PREVAILING VFR CONDITIONS
MAY DIP INTO MVFR/IFR FLT CATEGORY /PARTICULARLY AT KATY/ DUE TO
POSSIBLE LOW CIGS LATER TONIGHT INTO FRIDAY MORNING GIVEN THE
AMOUNT OF AVAILABLE LOW LEVEL MOISTURE. IF THUNDERSTORMS DEVELOP
EARLY THIS EVENING AND RUMBLE OVER KABR/KATY...THE LIKELIHOOD OF
LOW CIGS DEVELOPING LATE TONIGHT/EARLY FRIDAY MORNING BEGINS TO
INCREASE. THERE IS ALSO A CHANCE OF THUNDERSTORMS DEVELOPING BY
EARLY THIS EVENING ALONG THIS APPROACHING COLD FRONT...AS WELL AS
IN THE LEE OF THE BLACK HILLS SURFACE LOW...WHICH COULD REACH ALL
THE WAY TO KMBG/KPIR BEFORE FIZZLING OUT. HOWEVER...THE KMBG/KPIR
TERMINALS STAND A BETTER CHANCE OF REMAINING VFR THROUGH THE
ENTIRE TAF VALID PERIOD.


&&

.CLIMATOLOGICALLY...
AN ANOMALOUSLY COLD LOW PRESSURE SYSTEM WILL
MOVE INTO UPPER MIDWEST EARLY NEXT WEEK. THE COMBINATION OF A COOL
CANADIAN AIRMASS ALONG WITH INCREASING CLOUDS AND A CHANCE FOR
SHOWERS COULD RESULT IN A FEW RECORD LOW HIGH TEMPERATURES ON
MONDAY. BELOW IS A LIST OF LOCATIONS THAT COULD SEE NEAR RECORD
COLD READINGS ON MONDAY:

...LOCATION......FORECAST....RECORD LOW HIGH TEMP...
WHEATON MN          65          72 IN 1949
SISSETON            66          70 IN 1993
WATERTOWN           66          61 IN 1962
ABERDEEN            68          65 IN 1962
MOBRIDGE            72          64 IN 1962
PIERRE              73          65 IN 1989


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

$$
UPDATE...MOHR
SHORT TERM...SD
LONG TERM...FOWLE
AVIATION...DORN
CLIMATOLOGY...FOWLE

WEATHER.GOV/ABERDEEN




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