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000
FXUS65 KGGW 222029
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
229 PM MDT WED MAY 22 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
A TIGHT SURFACE PRESSURE GRADIENT IS APPARENT OVER CENTRAL AND
EASTERN MONTANA WHERE SOUTHEAST WIND HAS PICKED UP STRONGLY.
MODELS SUGGEST THIS GRADIENT WILL TIGHTEN TONIGHT AND THURSDAY.
THERE IS A WIND ADVISORY FOR FORT PECK LAKE IN EFFECT THAT
CONTINUE THROUGH THURSDAY EVENING. THE SURFACE HIGH OVER SOUTHERN
SASKATCHEWAN WHICH HELPED TO PRODUCE THE PRESSURE GRADIENT IS ALSO
CLEARING CLOUDS OUT OF THE AREA.

NORTHEAST MONTANA REMAINS BETWEEN SYSTEMS IN A NARROW UPPER LEVEL
RIDGE. BUT THE STRONG LOW CHURNING OVER WASHINGTON/OREGON WILL
NUDGE A COLD FRONT OVER THE DIVIDE TONIGHT. WITH PACIFIC MOISTURE
PICKED UP AND EJECTED NORTH INTO THE REGION...CENTRAL MONTANA CAN
EXPECT SHOWERS AND THUNDERSTORMS TONIGHT AND THURSDAY. SOME OF
THIS ACTIVITY MIGHT AFFECT OUR FAR WESTERN COUNTIES BY THURSDAY.

THURSDAY NIGHT AND FRIDAY...AN EMBEDDED SHORTWAVE SPINNING AROUND
THE LOW WILL SEND ANOTHER COLD FRONT ACROSS NORTHEAST MONTANA
FIRST BRINGING A BETTER CHANCE FOR STORMS IN THE EVENING AND
POSSIBLY ON FRIDAY. BOTH GFS AND THE NAM SUGGEST THE WAVE WILL BE
PUSHED NORTH ACROSS THE INTERNATIONAL BOUNDARY FRIDAY SENDING MOST
STORMS INTO CANADA. SO A FEW THUNDERSTORMS ARE POSSIBLE.

EXPECT NEAR NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES DURING
THE SHORT TERM PERIOD. WIND WILL LIGHTEN UP ON FRIDAY BEHIND THE
FRONT. SCT


.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
THE GOING FORECAST LARGELY STANDS AND WELL REPRESENTS THE UPCOMING
EXCELLENT POTENTIAL FOR SHOWERS AND THUNDERSTORMS AS NORTHEAST
MONTANA REMAINS UNDER THE INFLUENCE OF AN UPPER TROUGH THROUGH THE
EXTENDED PERIOD. TIMING INDIVIDUAL DISTURBANCES UNDER THE UPPER
TROUGH WILL BE DIFFICULT...THUS THE MORE BROAD-BRUSHED FORECAST
LOOKS GOOD. SATURDAY AND POSSIBLE SUNDAY CONTINUE TO LOOK GOOD
FOR STRONGER STORM DEVELOPMENT...ESPECIALLY ACROSS THE EAST WHERE
A STRONG MOISTURE PUSH FROM THE GULF OF MEXICO WILL ALLOW FOR
STEEP LAPSE RATES AND FAVORABLE SHEAR PROFILES. THE ONLY
SIGNIFICANT TWEAK MADE WAS TO TREND DOWN POPS SLIGHTLY FOR FRIDAY
EVENING AS MODELS HAVE TRENDED A BIT DRIER. REMAINDER OF FORECAST
STANDS. GILCHRIST

PREVIOUS DISCUSSION...FRIDAY NIGHT THROUGH SATURDAY NIGHT...A CLOSED
UPPER LEVEL LOW SITUATED OFF OF THE PACIFIC NORTHWEST WILL SEND
LOBES OF SHORTWAVE ENERGY THROUGH SOUTHWEST FLOW ALOFT INTO
NORTHEAST MONTANA THROUGH THE EXTENDED. THE PRECISE TIMING OF
THESE SHORTWAVE FEATURES WILL BE CRITICAL IN DETERMINING THE
POTENTIAL FOR CONVECTION INITIATION ON ANY GIVEN DAY. IF A TIME
OCCURS WHERE THE SHORTWAVE ENERGY TRACKS THROUGH NE MT DURING PEAK
HEATING AND COINCIDENT WITH THE BEST INSTABILITY...THERE COULD BE
RESULTANT STRONG THUNDERSTORM DEVELOPMENT.

BOTH THE 00Z ECMWF AND GFS HAVE BOTH SHIFTED THE VIGOROUS UPPER
LEVEL SHORTWAVE TRACK FURTHER TO THE NORTHWEST INTO ALBERTA AND
SASKATCHEWAN. THE TRACK IS AS SUCH THAT IT WOULD FAVOR THE BEST
CHANCES OF CONVECTION INTO THOSE LOCATIONS AND PERHAPS EXTENDING
INTO THE NORTHERN ZONES OF THE CWA. ANOTHER RIPPLE OF SHORTWAVE
ENERGY PASSES THROUGH THE CWA ON SATURDAY AFTERNOON. THE GFS IS A
BIT STRONGER THAN THE ECMWF AND GIVEN THE DIFFERENCES IN MODEL
SOLUTION HAVE ONLY MADE MINOR TWEAKS TO POPS IN THAT PERIOD.

SUNDAY INTO SUNDAY NIGHT...THE 00Z MODEL SUITE HAS SHOWN BOTH
CONSISTENT AGREEMENT AND EXCELLENT CONTINUITY THAT THIS PERIOD
COULD OFFER THE BEST POTENTIAL FOR THUNDERSTORM DEVELOPMENT
ACROSS THE FORECAST REGION...WITH THE POTENTIAL FOR SOME STRONG
THUNDERSTORMS CAPABLE OF HAIL AND GUSTY WINDS. ACROSS THE CWA IS
THE PRESENCE OF A NICE THETA-E RIDGE INDICATING ABUNDANCE OF WARM
LOW LEVEL MOISTURE. FORECAST SOUNDINGS IN THE MODELS DO SHOW
DRYING AT THE MID LEVELS. CONVECTIVE INDICIES ACROSS THE CWA ARE
ALSO FAVORABLE WITH LIFTED INDICIES SUNDAY AFTERNOON AND EVENING
RANGING BETWEEN -3 AND -7. ALSO NOTED THAT CAPE REACHES AROUND
1000 TO 1500 J/KG. SOUNDINGS FURTHERMORE ARE INDICATING A NICE
VEERING WIND PROFILE WITH A LOW LEVEL EASTERLY 850MB JET OF AROUND
40 KTS. WHILE NOT IMPRESSIVE...THIS DOES PROVIDE DECENT
DIRECTIONAL AND SPEED SHEAR ACROSS THE CWA. PWATS ALSO LOOK TO BE
OVER 1 INCH INDICATING ABUNDANT MOISTURE IN THE VERTICAL COLUMN.
UPPER LEVEL DYNAMICS COULD LINE UP VERY WELL WITH THESE
THERMODYNAMIC PARAMETERS AS MODELS ARE IN EXCELLENT AGREEMENT ON
GOOD DIFFLUENT FLOW ALOFT SUPPORTIVE OF FORCED VERTICAL ASCENT AND
LOWERING PRESSURES. WITH SHORTWAVE ENERGY APPROACHING THE AREA
DURING THE AFTERNOON AND EVENING HOURS...TIMING SHOULD BE
IDEAL...BEING COINCIDENT WITH MAXIMUM HEATING AND BEST
INSTABILITY. WILL NEED TO WATCH THIS CLOSELY OVER THE NEXT SEVERAL
DAYS...HOWEVER...CURRENT THINKING IS THAT GIVEN EXCELLENT MODEL
AGREEMENT...RUN TO RUN CONTINUITY...AND FAVORABLE UPPER LEVEL
DYNAMICS LINING UP IN BOTH IDEAL TIMING AND PLACEMENT WITH
THERMODYNAMIC VARIABLES...SUNDAY AFTERNOON AND EVENING COULD PROVE
TO BE A BUSY WEATHER DAY ACROSS NORTHEAST MONTANA. THIS IS STILL
OUT IN DAY 5 AND SO THERE IS UNCERTAINTY THIS FAR OUT...BUT AS IT
GETS CLOSER...MESOSCALE DETAILS WILL BECOME CLEARER AND SO WILL BE
ABLE TO HAVE A BETTER HANDLE ON THE MODE OF CONVECTION THAT WOULD
OCCUR AS WELL AS BETTER CONFIDENCE ON PRECISE TIMING AND LOCATION.

MONDAY AND BEYOND...LONG RANGE GUIDANCE CONTINUES TO KEEP NE MT IN
A SOUTHWEST FLOW ALOFT REGIME...WITH ADDITIONAL CHANCES FOR
SHOWERS/THUNDERSTORMS DEPENDENT ON EMBEDDED SHORTWAVE FEATURES
THAT ARE DIFFICULT TO PINPOINT THAT FAR IN ADVANCE...AND SO
PAINTED THE CWA WITH LOW END CHANCE POPS THROUGH MUCH OF THE EARLY
TO MIDDLE PORTION OF NEXT WEEK. WITH NOT MUCH CHANGE IN THE
OVERALL FLOW PATTERN...WOULD NOT EXPECT MANY FLUCTUATIONS IN
TEMPERATURES...AND SO DID NOT INTRODUCE MUCH IN THE WAY OF WARM
UPS OR COOL DOWNS IN THE EXTENDED PERIOD. MALIAWCO

&&

.AVIATION...
VFR. SCT-BKN MID AND HIGH CLOUDS WILL DECREASE THIS EVENING TO
SCT-SKC. THE BIG STORY OVER THE NEXT 24 HOURS WILL BE STRONG GUSTY
SOUTHEAST WINDS...ESPECIALLY AT KGGW WHICH WILL SEE AN ENHANCED
SURFACE FLOW THANKS TO LOCAL EFFECTS. GILCHRIST

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL MIDNIGHT MDT THURSDAY NIGHT FOR FORT
PECK LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND
SOUTHERN VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

$$

WEATHER.GOV/GLASGOW