AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 935 PM EST Mon Jan 9 2012 .UPDATE... 02Z Water vapor and H4 RUC analysis shows a complex upper level pattern in place across the CONUS this evening. Main northern stream FLOW arrives across the Pacific NW while ridging up into SC Canada. This flow then dives back to the southeast forming longwave troughing across the NE states and eastern Canadian Provinces. Other feature of note, and most important to our forecast is a large cut-off upper LOW spinning over TX. WV imagery shows abundant MID/upper level MOISTURE streaming east/NE ahead of this feature along the northern Gulf Coast. Synoptic support ahead of the low is combining with deep WAA pattern to produce a large area of showers and storms along and south of the LA coastline. This weather will enter our forecast later Tuesday and Tuesday NIGHT, however for the rest of the overnight, our weather will remain dry and QUIET, outside of areas of FOG. 00Z KTLH SOUNDING shows a fairly dry profile in the middle and lower levels this evening, however the upper level moisture mentioned above can be seen overriding the region above around 400mb. This moisture will be lowering with time overnight resulting in a mostly CLOUDY forecast for your Tuesday. Once again, fog will be the main forecast concern during the early morning hours. HI-res guidance is generally hinting toward better fog potential in the western zones associated with a developing weak southerly flow. While some fog is certainly possible overnight, the areal coverage and PERSISTENCE of the fog does not appear AS impressive as previous nights. This is especially true noting the amount of mid/HIGH level clouds overspreading the region which should have some influence in slowing the radiative process. Still a bit early in the evening to determine the degree to which this higher level moisture will impact the fog forecast, so will not make any significant changes with this update package. Temperatures appear on TRACK with lows generally dropping into the lower to middle 50s. Will expect a FEW mid/upper 40s over toward the SE big bend and Suwannee River Valley in closer proximity to the surface high. ...(TUESDAY THROUGH THURSDAY). The 12 UTC model suite remains on track, bringing a strong cold FRONT through our forecast area Wednesday morning. The NAM is still a little slower than the global models, but the global models are a bit slower than their previous runs so the timing differences are smaller than 24 hours ago. With strong Q-G forcing and ample deep layer moisture, there is almost no question as to whether or not it will RAIN here, it`s just a matter of when. Our POP for Tuesday night/Wednesday morning is about 80%, but this will probably come up to near 100% in subsequent forecast packages once the timing becomes more certain. Our STORM total QPF for this even is about an inch areawide, but of course a few locations could get double or triple this amount in the heavier storms. Temperatures behind this cold front will not be very cold, and lows Thursday morning will return to near average (lower to mid 40s) with mostly clear skies and a dry airmass in place. A stronger (but dry) cold front will pass through our forecast area Thursday afternoon and evening, but will not arrive in time to prevent high temperatures from reaching the upper 60s to lower 70s. Not much has changed with regard to the severe weather potential for Tuesday night and Wednesday morning. All indications continue to suggest another high-SHEAR/low CAPE environment for our region as the SQUALL line moves through. The SPC subjective Convective OUTLOOK the 09 UTC SREF, and our local objective severe weather PROBABILITY forecasts show the chances for severe storms at about 5% within 25 miles of a point. This looks reasonable based on our experience with such cases. There may have been a subtle change in the model forecast WIND profiles, which now suggest a less curved HODOGRAPH (but still strong shear magnitudes). This would indicate more of a threat for damaging wind gusts in LEWPs, and still possibly a weak, short-lived TORNADO. This is more LIKELY where the greatest SBCAPE coincided with the squall line, which right now appears to be the FL Panhandle (west of the Apalachicola River). By tomorrow the high-resolution NWP guidance will have the event within its forecast time, and we will be able to examine UPDRAFT speeds and HELICITY to confirm the overall severe weather threat.