Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 210514
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1214 AM CDT THU MAY 21 2015

.UPDATE...
ISSUED AT 1209 AM CDT THU MAY 21 2015

NO MAJOR CHANGES MADE FOR THIS UPDATE. BROUGHT TEMPERATURES IN
LINE WITH LATEST OBSERVATION TRENDS. THIS GENERALLY RESULTED IN A
DECREASE OF OVERNIGHT LOW TEMPERATURES ACROSS THE SOUTHWEST AND AN
INCREASE ACROSS THE NORTHEAST.

UPDATE
ISSUED AT 936 PM CDT WED MAY 20 2015

FORECAST REMAINS ON TRACK. CLOUDS TRYING TO PUSH NORTH RUNNING
INTO A HIGH PRESSURE RIDGE EXTENDING THROUGH CENTRAL SD INTO
WESTERN NORTH DAKOTA. PARTLY CLOUDY CONDITIONS SHOULD CONTINUE
NORTH AND EAST...MOSTLY CLEAR WEST AND SOUTH.

UPDATE
ISSUED AT 627 PM CDT WED MAY 20 2015

NO MAJOR DEVIATIONS FROM THE INHERITED FORECAST FOR THE EARLY
EVENING UPDATE ISSUANCE.

WEAK/SUBTLE SFC BOUNDARY (ASSOCIATED WITH AN EMBEDDED WAVE
DROPPING SOUTH OUT OF CANADA) WILL SLOWLY MEANDER/DRIFT WEST THEN
SOUTH TONIGHT INTO THURSDAY. ONLY WEATHER IMPACTS WITH THIS
FEATURE WILL BE REFLECTED IN SFC WIND FIELDS AND PERHAPS SOME
CLOUDS AT 8-11FT AGL.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 305 PM CDT WED MAY 20 2015

LATE WEDNESDAY AFTERNOON AN H500 REX BLOCK PATTERN WAS ORIENTED
FROM WESTERN CANADA TO THE SOUTHWEST US. ACROSS EASTERN CANADA/US AN
UPPER LOW IS FORECAST TO MOVE SOUTHEAST. A WEAK BACK DOOR COLD
FRONT AND SOME SCATTERED CLOUDS WILL MOVE THROUGH NORTHERN AND
EASTERN NORTH DAKOTA LATE TONIGHT AND THURSDAY. COULD SEE SOME
SCATTERED FROST SOUTHWEST TONIGHT BUT OVERALL WARMER TEMPERATURES
SO DO NOT THINK IT WARRANTS A FROST ADVISORY TONIGHT. BASED ON
NAM/GFS H850 TEMPERATURES SHOULD SEE SIMILAR HIGH TEMPERATURES OR
A DEGREE OR TWO COLDER ON THURSDAY THAN TODAY NORTHEAST. ACROSS
THE WEST H850 TEMPERATURES A BIT WARMER THAN TODAY BY ABOUT 3 TO 4
DEGREES...SO LOOKS LIKE CLOSER TO MID 70S WEST THROUGH SOUTH
CENTRAL FOR HIGHS ON THURSDAY. OTHER THAN SOME SCATTERED CLOUDS
ASSOCIATED WITH THE WEAK FRONTAL BOUNDARY EXPECT MOSTLY CLEAR
TONIGHT AND MOSTLY SUNNY THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 305 PM CDT WED MAY 20 2015

MODEL AGREEMENT THROUGH FRIDAY CONTINUES WITH A DRY AND WARM
FORECAST. AN UNSETTLED PERIOD LOOKS TO OCCUR SATURDAY THROUGH
WEDNESDAY. HOWEVER MODEL DIFFERENCES ARISE BEYOND FRIDAY. LATEST
WATER VAPOR IMAGERY SHOWS TWO CLOSED UPPER LOWS...THE INITIAL
CIRCULATING AT 39N/125W...AND THE SECOND CIRCULATION AT 44N/137W. AS
THESE UPPER LOWS DROP INTO THE SOUTHWEST IN THE COMING DAYS...THE
ECMWF AND CANADIAN GEM ARE MORE IN LINE WITH THE PATH AND TIMING OF
THE INITIAL 700MB-500MB CLOSED UPPER LOW FOR SATURDAY VERSUS THE
GFS. THE ECMWF AND CANADIAN MODEL MOVE THE CLOSED SYSTEM INTO
NORTHEAST WYOMING/SOUTHEAST MONTANA BY 00Z SUN...WHEREAS THE GFS HAS
THE LOW INTO SOUTH CENTRAL NORTH DAKOTA. THE SECONDARY CLOSED LOW
MENTIONED ABOVE FOLLOWS FOR SUNDAY. THE TRACK OF THE LOW PER ECMWF
IS FARTHEST WEST...THE GFS IS FARTHEST EAST...WITH THE CANADIAN NEAR
THE MIDDLE. ANOTHER SYSTEM IS SLATED FOR TUESDAY INTO WEDNESDAY.
OVERALL...DESPITE A FAIRLY HIGH CONFIDENCE IN A AN UNSETTLED PERIOD
SATURDAY THROUGH WEDNESDAY...THE UNCERTAINTY ON THE EVOLUTION AND
TRACK OF THE WEEKEND SYSTEMS PUTS IN QUESTION THE AREAL
COVERAGE/PLACEMENT FOR SHOWERS AND INSTABILITY AREAS FOR
THUNDERSTORMS. HIGHEST POPS REMAIN OVER SOUTHERN NORTH DAKOTA
SATURDAY AND THEN EXPAND SLOWLY NORTH SUNDAY. IN TERMS OF THE
POTENTIAL FOR SEVERE THUNDERSTORMS...WILL NEED TO MONITOR AND SEE
HOW THINGS ALIGN ONCE MODELS COME TOGETHER ON A MORE DECISIVE
EVOLUTION AND TRACK OF THE ABOVE SYNOPTIC SYSTEM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1209 AM CDT THU MAY 21 2015

VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...AJ
SHORT TERM...WAA
LONG TERM...KS
AVIATION...AJ


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