EF0 tornado, Maxwell, Nebraska, May 23, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
220 PM CDT SAT MAY 23 2009

.SYNOPSIS...
    HAND ANALYSIS OF THE 18Z SURFACE DATA SHOWED A QUASI-STATIONARY
BOUNDARY DRAPED FROM SOUTHERN IOWA...ACROSS SOUTHERN NEBRASKA...
NORTHWEST KANSAS...EASTERN COLORADO AND SOUTHERN NEW MEXICO...TO A
LOW ALONG THE NEW MEXICO-ARIZONA BORDER. IN THE UPPER LEVELS...THE
6.7 MICRON IMAGERY SHOWED A DEVELOPING WAVE UPSTREAM OF THE NORTHERN
PLAINS AT THE UTAH-NEVADA-ARIZONA JUNCTION. ALSO...THE NORTHERN GULF
SYSTEM HAD MOVED INLAND OVER SOUTHERN ALABAMA AND WAS WORKING ITS
WAY TOWARD THE NORTHWEST. THE RADAR MOSAIC SHOWED QUITE A FEW
CONVECTIVE CELLS DEVELOPING ALONG THE SURFACE BOUNDARY FROM CENTRAL
NEBRASKA NEAR BROKEN BOW TO NORTHWEST KANSAS WEST OF GOODLAND.
WIDESPREAD RAIN WAS ALSO INDICATED IN A BROAD AREA FROM NORTH
CENTRAL NEBRASKA TO THE EASTERN PANHANDLE.
&&

.SHORT TERM...TONIGHT THROUGH TUESDAY.
    WITH THE BOUNDARY IN THE AREA...THE THUNDERSTORM POTENTIAL FOR
TONIGHT IS HIGH OVER MOST OF WESTERN AND NORTH CENTRAL NEBRASKA.
MODIFYING THE MORNING SOUNDING FOR CURRENT TEMPERATURE AND DEWPOINT
RAISES THE MUCAPE TO 3400 J/KG...SO THE POTENTIAL FOR STRONG
UPDRAFTS AND HAIL COULD BE HIGH. HOWEVER...THE 6KM AGL SHEAR IS ONLY
ABOUT 12KT. THUS...IT MAY BE DIFFICULT TO SUSTAIN A STRONG UPDRAFT.
WITH WEAK VERTICAL WIND FIELDS AND PRECIPITABLE WATER EXCEEDING AN
INCH...THE GREATER THREAT IS HEAVY RAIN AND THE THREAT OF HAIL
LARGER THAN AN INCH IS LOW. ALSO...THE CURRENT RADAR AND SATELLITE
INDICATE THAT THE CONVECTION MAY BECOME ORGANIZED INTO A LINEAR
CONVECTIVE SYSTEM THAT WILL PROPAGATE ALONG THE SURFACE BOUNDARY.
    AS THE SURFACE FRONT LIFTS NORTH SUNDAY...THE GREATEST CHANCES
OF THUNDERSTORMS WILL BE OVER NORTH CENTRAL AND EASTERN NEBRASKA.
FOR SUNDAY NIGHT...SURFACE CYCLOGENESIS OVER WYOMING WILL SET THE
SCENE FOR ANOTHER FRONT CROSSING NEBRASKA AS THE SURFACE LOW MAKES
ITS WAY ACROSS THE NORTHERN PLAINS MONDAY AND MONDAY NIGHT. AS THE
SURFACE LOW AND UPPER TROUGH MOVE OUT OF THE CENTRAL PLAINS...THE
STORMS WILL CLEAR FROM THE WEST.
    AT THIS TIME...IT APPEARS THAT THE PREVAILING FLOW WILL STEER
THE GULF SYSTEM EAST OF THE AREA...AND THAT FEATURE WILL PROBABLY
NOT BE A PLAYER IN THE SCENARIO FOR CENTRAL AND WESTERN NEBRASKA.
STILL... OVER THE THREE DAY PERIOD...THERE IS POTENTIAL FOR AN INCH
OR MORE OF RAIN NORTH AND WEST OF AN ANW-BBW-LBF-IML LINE.

.MEDIUM AND LONG TERM...TUESDAY NIGHT THROUGH FRIDAY.
    WHEN COMPARED WITH THE GFS...THE GFS ENSEMBLE MEAN AND THE
DGEX...THE EUROPEAN MODEL APPEARS TO BE THE OUTLIER IN ITS SLIGHTLY
FASTER EASTWARD POSITION OF THE WESTERN UPPER RIDGE BY THE END OF
THE FORECAST PERIOD. HOWEVER...THE RESULTS ARE SIMILAR THROUGH LATE
SATURDAY, I.E., KEEPING THINGS DRY OVER MOST OF CENTRAL AND NORTH
CENTRAL NEBRASKA THROUGH THAT TIME AS THE RIDGE BUILDS IN THE WEST
AND THE UPPER FLOW BECOMES NORTHWEST OVER THE NORTHERN PLAINS. THE
GFS AND THE DGEX BOTH KEEP NEBRASKA AND THE HIGH PLAINS IN A WEAK
UPPER FLOW AND TEMPERATURE PATTERN WHILE THE EUROPEAN KEEPS THE WEAK
PATTERN OVER WESTERN NEBRASKA...COLORADO AND THE DESERT SOUTHWEST.
ALL THAT CONSIDERED...WE ARE LEANING TOWARD A BLEND OF THE EUROPEAN
AND GFS.
    AS THE UPPER TROUGH CLEARS THE HIGH PLAINS...THERE IS STILL A
SLIGHT CHANCE OF THUNDERSTORMS IN SOUTH CENTRAL AND SOUTHWEST
NEBRASKA TUESDAY NIGHT THROUGH THURSDAY. ON THURSDAY...A DRY LINE
DEVELOPS ON THE HIGH PLAINS FROM ALBERTA THROUGH THE U.S. HIGH
PLAINS INTO SOUTHWEST TEXAS. THIS SHOULD PROVIDE A TRIGGER FOR AT
LEAST ISOLATED THUNDERSTORMS IN WESTERN NEBRASKA THURSDAY AND
FRIDAY. LATE SATURDAY...THE CHANCES OF THUNDERSTORMS WILL INCREASE
AS A FRONT MAKES ITS WAY OUT OF CANADA TO THE NORTHERN PLAINS.
&&

.AVIATION...
    A FRONTAL BOUNDARY SLOWLY LIFTING NORTH ACROSS SOUTHERN NEBRASKA
WILL MARK THE TRANSITION FROM VFR CONDITIONS THIS AFTERNOON. LOW
CEILINGS HAVE PLAGUED THE KVTN TERMINAL SITE TODAY THAT IS EXPECTED
TO LIFT FROM LIFR TO POSSIBLY MVFR FOR A FEW HOURS THIS EVENING. A
STRONG DISTURBANCE LIFTING NORTHEAST LATE THIS AFTERNOON WILL
FURTHER IGNITE THUNDERSTORMS ACROSS THE SOUTHWEST THAT WILL IMPACT
THE KLBF TERMINAL THROUGH 02Z. BEYOND 03Z CEILINGS WILL DROP AS
MOISTURE CONTINUES TO DEEPEN IN THE UPSLOPE PATTERN NORTH OF THE
FRONT FOR BOTH TERMINALS TO LOWER TO IFR TO LIFR CONDITIONS THROUGH
15Z SUNDAY. MODELS ARE DOING A FAIR JOB WHERE MODERATE TO HEAVY
RAINFALL WILL BE POSSIBLE TONIGHT THAT MAY EASILY DROP VISIBILITIES
TO LESS THAN A MILE AS FOG REDEVELOPS AND BECOMES MORE WIDESPREAD.
LITTLE CHANGE IS EXPECTED IN THE PATTERN SUNDAY WITH CEILINGS ACROSS
THE SOUTHWEST LIFTING INTO VFR ACROSS THE SOUTHWEST TO INCLUDE KLBF
TERMINAL BEYOND 18Z.
&&

.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&

SHORT/MEDIUM/LONG TERM...SPRINGER
AVIATION...KECK

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
254 PM CDT SAT MAY 23 2009

NEZ004>010-022>029-035>038-056>059-069>071-094-241000-
SHERIDAN-EASTERN CHERRY-KEYA PAHA-BOYD-BROWN-ROCK-HOLT-GARDEN-
GRANT-HOOKER-THOMAS-BLAINE-LOUP-GARFIELD-WHEELER-ARTHUR-MCPHERSON-
LOGAN-CUSTER-DEUEL-KEITH-PERKINS-LINCOLN-CHASE-HAYES-FRONTIER-
WESTERN CHERRY-
254 PM CDT SAT MAY 23 2009 /154 PM MDT SAT MAY 23 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN AND
NORTH CENTRAL NEBRASKA.

.DAY ONE...TONIGHT.

THUNDERSTORMS ARE POSSIBLE THROUGHOUT THE OUTLOOK AREA TONIGHT.
STORM DEVELOPMENT WILL CONTINUE TO INCREASE IN COVERAGE THIS
EVENING ACROSS THE SOUTHWEST. THUNDERSTORMS ARE EXPECTED TO REMAIN
BELOW SEVERE LIMITS ALTHOUGH CANNOT BE RULED OUT ENTIRELY. AN
UPPER LEVEL DISTURBANCE LIFTING NORTHEAST WILL FURTHER HELP
INITIATE STORMS THAT WILL TRACK NORTHEAST SLOWLY THAT WILL BE
CAPABLE OF PRODUCING MODERATE TO HEAVY RAINFALL THROUGH 9 PM CDT.
SOME LOCATIONS COULD SEE OVER AN INCH OF RAINFALL AS STORMS MOVE
NORTHEAST.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THUNDERSTORMS ARE EXPECTED DAILY FROM SUNDAY THROUGH TUESDAY.
SEVERE THUNDERSTORMS ARE NOT EXPECTED...WHILE HEAVY RAIN IS
POSSIBLE THROUGH THE MEMORIAL HOLIDAY WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

&&

THIS PRODUCT IS NOW AVAILABLE...ALONG WITH OTHER WEATHER...
HYDROLOGICAL AND CLIMATOLOGICAL INFORMATION...AT
HTTP://WWW.WEATHER.GOV/NORTHPLATTE

KECK