000
FXUS65 KGGW 180246
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
846 PM MDT FRI MAY 17 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
UPDATE...INCREASED POPS SUBSTANTIALLY WHERE A FAIRLY STEADY BAND
OF RAIN SHOWERS EXISTS ACROSS MUCH OF PHILLIPS COUNTY EXTENDING SOUTHEAST
THROUGH PETROLEUM AND GARFIELD COUNTY. THIS BAND THEN EXTENDS EASTWARD
THROUGH PRAIRIE COUNTY AND WIBAUX COUNTY AS WELL. EXPECTING THE
SHOWER ACTIVITY TO SPREAD INTO SOUTHERN VALLEY...MCCONE...AND
DAWSON COUNTIES OVER THE NEXT FEW HOURS. MODELS CONTINUE TO SHOW
THE HEAVIEST RAINFALL ACCUMULATIONS ACROSS SOUTHEASTERN PORTIONS
OF THE CWA THROUGH TONIGHT AND SO AM STICKING WITH HIGHER QPF
THERE FOR NOW. SOME OF THE NORTHEASTERN ZONES MAY SEE A BETTER
CHANCE FOR RAIN TOWARD MORNING AND DURING THE DAY ON SATURDAY. WILL
TAKE A LOOK AT THE LATEST 00Z GUIDANCE AND MAKE ANY NECESSARY
CHANGES WITH THE MORNING PACKAGE. IT DOES APPEAR THAT RAIN CHANCES
WILL CONTINUE FOR NORTHEAST MONTANA THROUGH THE WEEKEND AS A
SURFACE LOW HANGS AROUND OVER THE DAKOTAS AND AS PULSES OF
SHORTWAVE ENERGY PROPAGATE THROUGH SOUTHWEST FLOW ALOFT. MALIAWCO

PREVIOUS SHORT TERM DISCUSSION...
THE UPPER LEVEL FLOW SPLITS AS THE POLAR JET CROSSES OVER THE
WESTERN COAST WITH THE SOUTHERN BRANCH DIGGING OUT A TROUGH OVER
THE FOUR CORNERS AREA AND THE NORTHERN BRANCH PRODUCING A RIDGE
OVER WESTERN CANADA. FOR THE NEXT FEW DAYS...MONTANA WILL RECEIVE
SOME UNSETTLED WEATHER WITH PIECES OF MID LEVEL ENERGY MOVING UP
FROM THE SOUTHWEST TROUGH. A SURFACE LOW ALSO SETS UP OVER THE
WESTERN DAKOTAS WHICH WILL SERVE TO BRING MOISTURE INTO THE AREA
FROM THE EAST AND SOUTHEAST. Q-VECTOR CONVERGENCES SHOWS ALMOST
CONTINUOUS WEAK TO MODERATE DYNAMIC FORCING THROUGH MONDAY
AFTERNOON. FORECAST SOUNDINGS ALSO SHOW AN EXTENDED PERIOD OF
SATURATION...INDICATIVE OF A RAIN EVENT WITH AROUND AN INCH TO 2
INCHES OF TOTAL ACCUMULATION OVER THE NEXT FEW DAYS.

FORECAST SOUNDINGS ALSO HAVE SOME MODEST AMOUNT OF INSTABILITY IN
THEM...BUT WITH LITTLE CAP AND A HIGH PRECIPITABLE WATER CONTENT...THUS
EXPECT RAIN SHOWERS TO BE THE MAIN FEATURE WITH A FEW LOW-TOPPED
THUNDER SHOWERS AT TIMES.  MARTIN

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
THE FORECAST MODELS ARE IN REASONABLE AGREEMENT ON THE OVERALL
PATTERN...BUT CONTINUE TO STRUGGLE IN THE ALL IMPORTANT FINER
DETAILS. NORTHEAST MONTANA WILL REMAIN UNDER THE INFLUENCE OF A
WET CUT OFF UPPER LOW THROUGH TUESDAY. UPPER RIDGING LOOKS TO
BUILD IN BRIEFLY BY MIDWEEK POSSIBLY BRINGING A SHORT LIVED DRYING
TREND...WITH ANOTHER UPPER LOW PUSHING IN FROM THE WEST FOR LATE
IN THE WEEK FOR A RETURN TO MORE UNSETTLED CONDITIONS. OVERALL NO
SIGNIFICANT COOL DOWNS OR WARM UPS ARE EXPECTED...AS TEMPS LARGELY
HANG NEAR SEASONAL NORMALS. ONLY TWEAK TO THE GOING FORECAST WAS
TO TREND UP POPS FOR SUNDAY NIGHT AND MONDAY THANKS TO THE LINGERING
UPPER LOW. OTHERWISE THE GOING FORECAST STANDS. GILCHRIST

PREVIOUS
LONG TERM DISCUSSION...MONDAY THROUGH WEDNESDAY...NORTHEAST
MONTANA WILL REMAIN IN A VERY UNSETTLED PATTERN. A SURFACE LOW
PRESSURE SYSTEM WILL TRACK NORTHEASTWARD FROM SOUTH AND EAST OF
OUR FORECAST AREA TOWARDS THE GREAT LAKES REGION. THIS LOW WILL
BECOME VERTICALLY STACKED AS AN UPPER LEVEL TROUGH ACROSS THE
WESTERN U.S. CLOSES OFF AS IT ALSO LIFTS NORTH AND EASTWARD. THIS
SYSTEM WILL BE ASSOCIATED WITH AN ABUNDANCE OF MOISTURE...AND SO
KEPT POPS IN THE LIKELY RANGE FOR MONDAY...GRADUALLY TAPERING THEM
DOWN TO THE CHANCE AND SLIGHT CHANCE RANGE TOWARDS THE MIDDLE OF
THE WEEK AS THE LOW PRESSURE GRADUALLY LETS GO OF ITS INFLUENCE ON
THE CWA. THE 00Z ECMWF IS A BIT SLOWER WITH THE GFS A BIT MORE
PROGRESSIVE WITH THE EXIT TIME OF THIS SYSTEM AND SO OVERALL
CONFIDENCE IS A BIT LOWER TOWARDS THE MIDDLE OF THE WEEK.
NEVERTHELESS...THIS WILL PROVIDE A GOOD OPPORTUNITY FOR STEADY
RAIN SHOWER ACTIVITY AS WELL AS A FEW THUNDERSTORMS THROUGH THE
PERIOD. WILL KEEP TEMPERATURES IN A GRADUAL MODERATING TREND
TOWARDS THE MIDDLE PORTION OF THE WEEK AS THE UPPER LEVEL TROUGH
EVENTUALLY BECOMES REPLACED BY A VERY SMALL SHORTWAVE RIDGE THAT
ATTEMPTS TO BUILD IN DURING THE MIDDLE OF THE WEEK.

WEDNESDAY NIGHT AND BEYOND...ANOTHER UPPER LEVEL TROUGH IS
EXPECTED TO SWING IN FROM THE PACIFIC NORTHWEST AS IT CLOSES
OFF...WHICH WILL BRING ANOTHER ROUND OF PRECIPITATION CHANCES.
THEREFORE KEPT MENTION OF SHOWERS IN THE GRIDS. KEPT TEMPERATURES
FAIRLY STEADY WITH 850MB TEMPERATURES NOT EXHIBITING MUCH CHANGE
TOWARDS THE SECOND HALF OF THE WEEK ACROSS THE FORECAST AREA.
LOOKING AT FAIRLY SEASONABLE READINGS OVERALL BASED ON CURRENT
GUIDANCE. MALIAWCO


&&

.AVIATION...
VFR. AREAS OF SHOWERS WILL CONTINUE TO MOVE THROUGH NORTHEAST
MONTANA OVERNIGHT. IT LOOKS LIKE THE HEAVIEST SHOWERS WILL STAY
WELL TO OUR SOUTH AND EAST SO VFR CONDITIONS SHOULD PREVAIL.

ADDITIONAL SHOWERS ARE EXPECTED TO REDEVELOP OVER EASTERN MONTANA
SATURDAY POSSIBLY BRINGING SCATTERED MVFR CONDITIONS. JAMBA

&&

.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW- MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.

MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS AND LOCALIZED URBAN
FLOODING AS THE EVENT PERSISTS. SOME FLOODING MAY BECOME AN
ISSUE... ESPECIALLY FOR THE EASTERN AND SOUTHERN COUNTIES WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

WEATHER.GOV/GLASGOW