Update Sun 8:51 AM— The clouds from that predicted upper air disturbance have started moving in. The cloudiness mid-day may be considerable and last into mid to late afternoon today.
Saturday Forecast Review —
HRRR 8 AM (12z) Saturday forecast for 11 AM Saturday -Hail parameter showing 0.9 inches (red/orange) (Click on image for a larger view.)
Stan in Collegeville had commented that he had some brief hail late Saturday morning. I was curious if the models had predicted this. Indeed, yes. Here’s the HRRR model “hail parameter” from Saturday’s 8 AM model run (12z).
FYI, NOAA’s Severe Storm Site defines hail as being greater than 0.2″ in diameter. Otherwise it’s still ‘sleet’ or ‘ice pellets’, even if it’s created from low level convective or thunderstorm activity.
Update Fri 10:49 PM— Based on tonight’s early models, HRRR, NAM-NEST, I’ve updated Saturday’s forecast below. It’s more optimistic about some sunny breaks. Sunday’s forecast unchanged.
This coming weekend will be influenced by an influx of colder air and a dip in the jet stream to form an upper air trough, pushing a cold front through. Disturbances rotating around an upper low will bring showers on Saturday.
GEFS upper air wind forecast (250 mb- jet stream level) for Saturday 8 PM. The dip in the jet winds and the upper air low in upper NY State will bring enough moisture and lift to create cloudiness and light showers on Saturday. The tropical jet (2) is just visible. (Click on image for a larger view.)
Saturday
A mix of sun and clouds early, then mostly cloudy with very light scattered showers starting mid to late morning. Showers should be light (about 0.08-0.15 inches). A mix of sun and low dark clouds in the afternoon, with another chance of scattered showers, especially 4-6 PM. Windy. High 52.7º ± 1.6º (NBM model Blue Bell)
This afternoons’s HREF 1 hour precipitation forecast for 2 PM Saturday. The HREF is similar to the ECMWF forecast. The NAM-NEST forecast (not shown) is more optimistic about some sun early and clearing after 3 PM. (Click on image for a larger view.)
Previously Posted Fri 4:56 PM —
Sunday
Mostly sunny, some periods of instability cloudiness late morning into early afternoon. WINDY and chilly. High 45.5º ± 2.6º NBM model Blue Bell)
Winds
NBM wind forecast (Click on image for a larger view.)
