Netweatherforecast...
Synopsis
BY 12Z FRIDAY, LOW PRESSURE OF 997MB IS EXPECTED CENTRED NEAR WESTERN ISLES TRACKING EAST THROUGH AFTERNOON, WARM FRONT AFFECTING NE SCOTLAND MOVES EAST INTO NORTH SEA, WHILE COLD FRONT STRETCHING FROM ELGIN SW THROUGH LONDONDERRY AT 12Z MOVES SE TO BE OVER NERN ENGLAND BY EVENING, MOST OF THE UK IN WARM SECTOR FRIDAY AFTERNOON, WITH TROUGH MOVING EAST IN WARM SECTOR ACROSS ENGLAND AND WALES. BY 00Z SATURDAY, LOW IS EXPECTED JUST EAST OF ORKNEY ISLANDS WITH COLD FRONT STRETCHING SW THROUGH EDINBURGH-ANGLESEY-ST. DAVID MOVING SE FOLLOWED BY TROUGH MOVING SOUTH ACROSS SCOTLAND.
...1200Z-2000Z FRI OVER SERN SCOTLAND, N. IRELAND, NERN, CENTRAL AND ERN ENGLAND...
STRENGTHENING CYCLONIC UPPER FLOW AND STEEPENING LAPSE RATES OVER NERN AND CENTRAL UK WILL SEE WARM SECTOR AIRMASS BECOME INCREASINGLY UNSTABLE HERE, IF SUFFICIENT INSOLATION OCCURS IN THE AFTERNOON - SCATTERED HEAVY SHOWERS AND ISOLATED THUNDERSTORMS ARE LIKELY TO DEVELOP ESPECIALLY INVOF OF SURFACE TROUGH MOVING EAST ACROSS ENGLAND DURING THE AFTERNOON ... ALTHOUGH 30-40 KTS OF DEEP LAYER SHEAR AND MODEST LOW-LEVEL SHEAR ARE FCST - INSTABILITY MAYBE LIMITED GIVEN RELATIVELY WARM MOIST PROFILES ALL THE WAY UP ON FCST SKEW-TS SO ANY CONVECTION IS UNLIKELY TO DEVELOP SEVERE POTENTIAL. NON SEVERE GUSTY WINDS AND HEAVY DOWNPOURS ARE MAIN THREAT.
...0000Z-0600Z SAT OVER N. IRELAND, SERN SCOTLAND AND NERN ENGLAND...
STRONG UPPER TROUGH MOVES IN ACROSS THE AREA FROM THE WNW OVERNIGHT INTO SATURDAY MORNING FOLLOWING BEHIND SFC COLD FRONT MOVING SE, UPLIFT OF FAIRLY MOIST MARITIME AIRMASS ALONG NERN END OF COLD FRONT WITH HELP OF FORCED ASCENT ON ARRIVAL OF UPPER TROUGH WILL LIKELY LEAD TO HEAVY CONVECTIVE RAINFALL OVER THIS AREA WITHIN THIS PERIOD, ISOLATED T-STORMS MAY POSSIBLY DEVELOP WITH THREAT OF HAIL AND GUSTY WINDS - AS DRY AIR INTRUSION ARRIVES ALOFT FROM THE WEST WITH ARRIVAL OF UPPER TROUGH AND MIXES DOWN IN ANY CONVECTIVE CELLS. DEEP LAYER SHEAR WILL TEND TO WEAKEN FROM THE NW DURING THE NIGHT BUT SOME ORGANISED CONVECTION MAY STILL DEVELOP, SOME MODERATE LOW LEVEL SHEAR IS ALSO INDICATED ... HOWEVER, LACK OF INSOLATION WILL TEND TO LIMIT INSTABILITY SO WILL NOT WARRANT A SLIGHT RISK OF SEVERE WEATHER FOR NOW. AN ISOLATED WEAK TORNADO CAN'T BE RULED OUT HOWEVER.
Issued by: Nick F - Senior Forecaster for Netweather
