Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 051748
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1248 PM CDT TUE MAY 5 2015

.UPDATE...
ISSUED AT 1247 PM CDT TUE MAY 5 2015

THE FORECAST IS GENERALLY ON TRACK AS OF MIDDAY. SURFACE HIGH
PRESSURE REMAINS IN CONTROL..BUT THE RIDGE AXIS HAS TRANSLATED
EASTWARD TO EASTERN LAKE SUPERIOR. THIS IS RESULTING IN A SLOWLY
TIGHTENING PRESSURE GRADIENT OVER NRN MN EARLY THIS AFTERNOON..
ALONG WITH GRADUALLY INCREASING PRESSURE FALLS FROM THE DAKOTAS TO
THE CANADIAN PRAIRIE PROVINCES IN RESPONSE TO THE APPROACHING
WESTERN CONUS UPPER TROF.

SOME MID/HIGH LEVEL CLOUDS WILL INCREASE LATE THIS
AFTERNOON/EVENING ACROSS THE SOUTH AS SOUTHERLY FLOW JUST OFF THE
SURFACE CONTINUES TO INCREASE..BUT THE REMAINDER OF TODAY WILL BE
SUNNY IN MOST LOCALES. WINDS WILL CONTINUE TO SLOWLY INCREASE OUT
WEST IN CLOSER PROXIMITY TO THE TIGHTEST GRADIENT AND PRESSURE
FALLS..BUT WE WILL ALSO BE MIXING INTO A LAYER ALOFT WHERE WIND
SPEEDS IN THE 4-6 KFT LAYER AGL ARE WEAKER PER THE 12Z KMPX/KINL
SOUNDINGS..SO WE DO NOT EXPECT A CONTINUED ACCELERATION OF WINDS
AND GUST SPEEDS. WE HAVE ALREADY SEEN SOME EVIDENCE OF THAT WITH A
SHORT LIVED BURST OF 17-22 MPH GUSTS FOR 1-2 HRS AFTER BREAKING
THE MORNING INVERSION /WHERE THE MAX WIND SPEEDS WERE OBSERVED IN
THE SOUNDINGS/ OUT WEST..BUT SINCE THEN GUST SPEEDS HAVE
DIMINISHED A BIT. THE OTHER PRIMARY CHANGE WAS TO LOWER RELATIVE
HUMIDITY FORECASTS A BIT MORE..ESPECIALLY ACROSS THE NORTH WHERE
SOME LOCATIONS ARE AS LOW AS 12-14 PERCENT AS OF MIDDAY.
OTHERWISE..CHANGES WERE RELATIVELY MINOR AND UPDATES TO REFLECT
THE ABOVE THINKING ARE ALREADY AVAILABLE.

THE AVIATION DISCUSSION IS ALSO UPDATED BELOW FOR THE 18Z TAF
ISSUANCE.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 341 AM CDT TUE MAY 5 2015

HIGH PRESSURE DEPARTING TO THE EAST TODAY BEFORE A WARM FRONT LIFTS
NORTH INTO THE REGION ON WEDNESDAY LEADING TO INCREASED LOW-LEVEL
MOISTURE AND A CHANCE FOR RAIN. GENERALLY MILD TODAY THROUGH THE
SHORT TERM.

TODAY...DRY AND MILD. SUNNY...WITH INCREASING CLOUDS FROM SOUTH TO
NORTH LATE IN THE DAY ASSOCIATED WITH AN ENCROACHING WARM FRONT.
AFTERNOON RELATIVE HUMIDITY FALLING TO THE 15 TO 25 PERCENT RANGE
SIMILAR TO YESTERDAY. HIGH TEMPERATURES ALSO SIMILAR TO YESTERDAY
IN THE UPPER 60S TO LOW 70S. WINDS OVER LAND WILL BE OUT OF THE
SOUTHEAST AT 10 TO 15 MPH...STRONGEST FROM THE BRAINERD LAKES
REGION EAST TO THE INTERSTATE 35 CORRIDOR WHERE A FEW GUSTS UP TO
AROUND 20KTS WILL BE POSSIBLE. STRONGEST WINDS WILL NOT BE
COINCIDENT WITH THE LOWEST RELATIVE HUMIDITY...AND THUS DO NOT
EXPECT RH/WINDS TO APPROACH CRITICAL FIRE WEATHER CONDITIONS.

TONIGHT...INCREASING CLOUDS FROM SOUTH TO NORTH AS A WARM FRONT
MOVES ACROSS THE REGION. INCREASING LOW LEVEL MOISTURE THROUGH THE
NIGHT WITH DEW POINTS RISING INTO THE 50S BY TUESDAY MORNING. A
ROUND OF SHOWERS/T-STORMS WILL BE POSSIBLE ASSOCIATED WITH THE
INITIAL PUSH OF MOISTURE. THE LARGE-SCALE GUIDANCE WAS FAIRLY
AGGRESSIVE WITH REGARD TO PRECIP WITH ECMWF/GEM/GFS ALL DEPICTING A
FAIRLY WET SCENARIO WHILE THE HIGHER RES GUIDANCE WAS LESS
AGGRESSIVE. IN GENERAL...EXPECT A BRIEF 2-4 HOUR WINDOW OF LIGHT TO
MODERATE PRECIP IN ANY ONE LOCATION...WITH TOTAL RAINFALL AMOUNTS
FROM THIS FIRST ROUND OF PRECIP LESS THAN A TENTH OF AN INCH. DRY
AIR AT LOW/MID LEVELS COULD LIMIT PRECIP THAT ULTIMATELY REACHES THE
GROUND...AND AM ALSO NOT PARTICULARLY IMPRESSED WITH THERMODYNAMIC
PROFILE WITH REGARD TO SUPPORTING THUNDERSTORMS. LLJ DEVELOPMENT
WILL BE CRITICAL TO SUSTAINING STORMS...WHICH SHOULD OVERCOME THE
LESS-THAN-STELLAR MID-LEVEL LAPSE RATES AND MARGINAL MUCAPE.
OVERNIGHT LOWS IN THE UPPER 30S TO NEAR 40 WHERE SKIES REMAIN MOSTLY
CLEAR OVERNIGHT ALONG THE TIP OF THE ARROWHEAD...ELSEWHERE WARMER IN
THE 40S TO NEAR 50.

WEDNESDAY...FIRST ROUND OF SHOWERS/STORMS MOVES NORTH FOLLOWED BY A
SECOND ROUND OF PRECIPITATION IN THE LATE AFTERNOON...WITH PRECIP
POSSIBLY BEING DELAYED UNTIL THE EVENING HOURS. DID NOT WANT TO MAKE
ANY DRASTIC CHANGES TO POPS...BUT AT THIS POINT GUIDANCE IS TRENDING
TOWARDS A FAIRLY LENGTHY BREAK IN PRECIP. THIS IS DUE TO MID-LEVEL
RIDGING THAT WILL BRIEFLY DEVELOP OVER THE REGION DURING THE DAY
BEFORE THE MAIN UPPER LOW ARRIVES. LOW LEVEL FLOW WILL BE ALMOST DUE
SOUTH FROM THE GULF UP THROUGH THE UPPER MIDWEST WHICH WILL CAUSE
DEW POINT VALUES TO RISE TO NEAR 60...AND 0-1KM MIXING RATIO VALUES
NEAR 10 G/KG...APPROACHING TO EXCEEDING THE 90TH PERCENTILE
CLIMATOLOGY. HOWEVER...WITHOUT THE LARGE SCALE FORCING AVAILABLE TO
SUPPORT PRECIP NOR ANOTHER FRONTAL BOUNDARY PASSAGE TO PROVIDE SMALL
SCALE ASCENT...THIS WELL-ABOVE-NORMAL MOISTURE MAY NOT BE FULLY
UTILIZED TO BRING THE MUCH-NEEDED PRECIP ACROSS THE REGION. HIGHS
SIMILAR TO TUESDAY...UPPER 60S TO LOW 70S...WITH EAST WINDS ACROSS
WESTERN LAKE SUPERIOR LEADING TO COOLER TEMPERATURES BY LAKE
SUPERIOR AND ESPECIALLY ACROSS THE NORTH SHORE WHERE HIGHS MIGHT
ONLY REACH THE 50S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 341 AM CDT TUE MAY 5 2015

CONFIDENCE INCREASING FOR A WET AND UNSETTLED EXTENDED PERIOD.

A SHORT WAVE POSITIONED IN THE DAKOTAS WILL DEEPEN INTO A CLOSED
H85/SFC LOW OVER THE DAKOTAS WED NIGHT...PUSHING EAST ACROSS
NORTHWEST MINN THURSDAY...THEN WILL LIFT INTO ONTARIO FRIDAY. THE
STRENGTHENING PRESSURE GRADIENT FROM THE APPROACHING LOW AND
ASSOCIATED WARM FRONT WILL RESULT IN GUSTY SOUTHERLY WINDS FOR
INLAND AREAS. LOCATIONS NEAR LAKE SUPERIOR CAN EXPECT GUSTY EAST
WINDS WITH MUCH COOLER TEMPERATURES THROUGH THE END OF THE WEEK.

THE PROLONGED PERIOD OF RETURN FLOW AND INCREASED
MOISTURE/INSTABILITY WILL BRING PERIODS OF RAIN WITH EMBEDDED
THUNDERSTORMS WEDNESDAY NIGHT...MAINLY OVER THE MN ZONES. THE SFC
LOW WILL SWEEP A COLD FRONT ACROSS THE NORTHLAND DURING THE THURSDAY
AFTERNOON THROUGH THURSDAY NIGHT PERIOD...BRINGING THE BEST CHANCE
FOR WIDESPREAD RAIN AND THUNDERSTORMS. AT THIS TIME...LOCATIONS
NORTH CENTRAL MINNESOTA ARE EXPECTED TO RECEIVE THE BRUNT OF THE
PRECIPITATION...BEING NEAREST TO THE CENTER OF THE LOW AND BEST
FORCING. LATEST NAM/GFS BUFR SOUNDINGS AT KINL/KHIB/KELO ALL SUGGEST
A PERIOD OF HEAVY RAIN DURING THE LATE AFTERNOON/EARLY EVENING THURS
TIME FRAME AS PROFILES BECOME DEEPLY SATURATED WITH PWAT VALUES
APPROACHING 1.5" AND LONG SKINNY CAPE.

LATEST ECM/GEM/GFS ARE IN GOOD AGREEMENT THAT UPPER LVL RIDGING
RETURNS BRIEFLY AROUND SATURDAY...BEFORE ANOTHER AREA OF LOW
PRESSURE LIFTS ACROSS THE PLAINS AND INTO THE WESTERN LAKE SUPERIOR
REGION LATE IN THE WEEKEND AND INTO NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1247 PM CDT TUE MAY 5 2015

VFR CONDITIONS WILL CONTINUE ACROSS NE MINNESOTA AND NW WISCONSIN
THROUGH AT LEAST THIS EVENING. THE ESE TO SSE WINDS OF 5 TO 15 KNOTS
WILL WEAKEN THIS EVENING. THE LOW LEVEL JET THAT WILL DEVELOP
TONIGHT WILL HAVE SOUTHERLY WINDS OF 25 TO 35 KNOTS ALOFT. THIS IS
BORDERLINE FOR INCLUDING LLWS IN THE FORECAST. KEPT IT OUT FOR
NOW...BUT MIGHT NEED TO ADD LATER. SCATTERED SHOWERS AND ISOLATED
STORMS WILL DEVELOP IN THE LOW LEVEL JET LATER TONIGHT...SPREADING
FROM SOUTH TO NORTH. ADDED -SHRA TO FORECASTS...BUT KEPT -TSRA OUT
OF THE FORECAST DUE TO THE LOW CHANCES OF STORMS. THERE WILL LIKELY
BE LOWERING CIGS TO MVFR AT TERMINALS LATE TONIGHT AND WEDNESDAY
MORNING.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  66  45  62  51 /   0  30  40  40
INL  72  43  69  57 /   0  10  30  40
BRD  72  52  70  60 /   0  50  60  60
HYR  70  45  72  59 /   0  40  40  30
ASX  69  42  66  57 /   0  20  30  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&

$$






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